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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: E30_Crazy on May 12, 2017, 05:53:41 PM

Title: Stuttering under part-throttle
Post by: E30_Crazy on May 12, 2017, 05:53:41 PM
Brick in question is an 85 K100 2V.


Usually fine up to around 4k RPM, then I get some hesitation under part throttle if cruising or slightly accelerating. Can most of the time power through it, on up the RPM range at full throttle. Every once in a while, it will stutter all the way up.


Just looking for the next logical step.


I've changed the plugs and wires, and coil checks good to specs. Taken a torch fuel bottle and sprayed around the throttles and other rubber to check for a rise in idle (none).


I have recently replaced the FI computer and the AFM.


Next on my mind is the fuel filter. But other possibilities I can think of, and/or read about are injector reconditioning, FPR and lines, coolant temp sensor (may be getting rich/lean mix if this is putting out wrong resistance, I believe), and possibly attempt a TB sync.


Anything else I might be forgetting, or other opinions on what to tackle next?
Title: Re: Stuttering under part-throttle
Post by: Scott_ on May 13, 2017, 09:33:40 AM
I'd suggest you check valve clearances before a TB sync if you haven't recently.
Title: Re: Stuttering under part-throttle
Post by: The Mighty Gryphon on May 13, 2017, 10:11:55 AM
Are you using made in India Bosch plugs?  Someone on another forum had starting problems that went away when the made in India Bosch were replaced with NGK.   Your stuttering sounds like intermittent spark, and could be one or more plugs.

If you go NGK, you will need the terminal nuts at the top to get a correct connection to the OEM plug wires.  You can get them from NGK customer service.  Just email them, and they will send them to you, no charge.
Title: Re: Stuttering under part-throttle
Post by: E30_Crazy on May 13, 2017, 04:52:45 PM
I'm already running NGKs with the terminal nut on top. Guess I need to get some feeler gauges and check valves. I did recently change out a cam that had snapped on me. But it ran fine for a while after that.
Title: Re: Stuttering under part-throttle
Post by: E30_Crazy on May 13, 2017, 07:35:14 PM
Pulled the fuel filter today. Cleaned it out best I could, shook it up with some fuel inside, drained, hooked it up backwards and ran the fuel pump (fuel into a jar, of course). Repeated several times until mostly clear. Thought I might have fixes it, but after a few miles the stuttering came back. So either, the inside of the filter is falling apart and I just need to be patient and wait for a new one, or it's temperature related. Gonna try and test the temp sensor without burning myself on the radiator tonight. Or it could be a by-product of heat on an undiscovered cracked vacuum hose (once warmed up, more flexible, hole/crack then allows air in)
Title: Re: Stuttering under part-throttle
Post by: The Mighty Gryphon on May 13, 2017, 07:41:07 PM
Why are you messing with the fuel filter?   The crap that stops the flow is trapped in the paper and can't be flushed out.  Back flushing also messes up the element.

Go to NAPA and get a #3032 NAPA Gold.  5/16" line, steel can inline filter.  Less than $5.
Title: Re: Stuttering under part-throttle
Post by: Elipten on May 13, 2017, 08:58:19 PM
My thought exactly. Too cheap to do anything but replace.


Sent from my iPhone using Tapatalk Pro
Title: Re: Stuttering under part-throttle
Post by: E30_Crazy on May 15, 2017, 05:24:29 AM
I'll have to do that... After I get a new injector. I had some seals, tips, and microfilters to do a soft-rebuild. And not thinking too clearly, when seating one of the microfilters in the top, I had the tip on the counter.... Without the yellow tip on... I mashed over the little pimple that protrudes out the end of the injector... So now gotta buy a new one...


On that note, should I just go ahead and buy a set of the 4-pintle injectors? The ad claims better throttle response and MPG. Remanned from standard, of course.
Title: Re: Stuttering under part-throttle
Post by: Motorhobo on May 15, 2017, 06:26:53 AM
Which 4-pintle ones are you talking about? I'm looking at the ones here:

For my K75:

http://www.jt-c.com/product_info.php?info=p35_k75---4-holes-injector-upgrade.html

For your K100:

http://www.jt-c.com/product_info.php?info=p4_k-upgrade-2v-and-4v---4-pcs.html

Then there's this:

http://www.jt-c.com/product_info.php?info=p40_k100---k1100---k1200-tuning--25-.html

Let me know if you've got something better cheaper in domestic production...


Title: Re: Stuttering under part-throttle
Post by: E30_Crazy on May 15, 2017, 07:54:38 AM

These are the ones caught my attention. And on sale currently. Much cheaper than ~130EUR.

http://www.ebay.com/itm/BEST-UPGRADE-Genuine-BOSCH-Fuel-Injector-Set-of-4-Update-4-Nozzle-Tip/281435347207?_trksid=p2481888.c100675.m4236&_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20160908105057%26meid%3D6b4f69d9087a4894bd698d14b8cd877c%26pid%3D100675%26rk%3D1%26rkt%3D15%26sd%3D281435347207&_trkparms=pageci%253Aa79fa650-3964-11e7-a692-74dbd1804fea%257Cparentrq%253A0bf1c4a215c0ac8077b255fcfffe1311%257Ciid%253A1

Title: Re: Stuttering under part-throttle
Post by: Motorhobo on May 15, 2017, 09:00:02 AM
Cool -- thanks, I think I'll join you on that!
Title: Re: Stuttering under part-throttle
Post by: Filmcamera on May 15, 2017, 09:08:00 AM
If you do I would be very interested to hear how they are different and what performance gains you get.
Title: Re: Stuttering under part-throttle
Post by: The Mighty Gryphon on May 15, 2017, 09:34:46 AM
I too, would be interested in hearing what improvements are gained. 

The listing claims smoother idle, better atomization(how does a user determine that?), better throttle response(MAF lag is the problem there), and easier starts.

Probably no improvement to be had on my bikes.  They start instantly and purr right from the start.  Can't tell how they atomize, but judging from the way my bikes run and the 45-48mpg I am getting the old injectors are getting the job done. 

Throttle response on Jetronic equipped engines is determined by the inertial lag of the MAF sensor's "barn door".  Removing it in favor of a throttle position sensor in the Motronic system is the reason for the MUCH crisper throttle response of the 4 valve engines.

Downside of the four hole injectors is that the injector orifice diameters are 1/2 that of the single hole injectors.  In my book, being the mechanical pessimist I am, that means they will be at least twice as likely to plug and create problems with fuel delivery.

Title: Re: Stuttering under part-throttle
Post by: Motorhobo on May 15, 2017, 09:51:53 AM
I just ordered them -- we'll see. The injectors on my current rider are 178k miles old it's either have these cleaned or get new ones, so new ones it is, at that price can't be worse than what I've got.

Well see about the green, though...
Title: Re: Stuttering under part-throttle
Post by: E30_Crazy on May 19, 2017, 08:12:56 PM
I procrastinated too long and just ordered mine the other day. So now they won't be here for the weekend. Oh well. Have you gotten yours yet? I wouldn't mind seeing pictures of the actual injectors, since the eBay store seemed to use stock photos.
Title: Re: Stuttering under part-throttle
Post by: jakgieger on May 20, 2017, 12:00:00 AM
These look to be the same injectors I got from Osidetiger on Ebay...I saw 10+ mpg and 20 more hp  :hehehe :hehehe .  No, seriously, I never ran the pintle injectors (bike had sat for 10+ yrs.).  I will say that power and throttle response are good.  Don't have any reading on efficiency.  Replacement is direct...MG, you're right about hole size, BUT, change your filter regularly with a quality product.
Title: Re: Stuttering under part-throttle
Post by: Motorhobo on May 20, 2017, 07:44:36 AM
I procrastinated too long and just ordered mine the other day. So now they won't be here for the weekend. Oh well. Have you gotten yours yet? I wouldn't mind seeing pictures of the actual injectors, since the eBay store seemed to use stock photos.

They look as advertised -- but are considerably heavier than the OEM ones, from what I remember. Looks like there is actual metal to these, where I remember the OEM ones to be 100% plastic.

These are the ones at the eBay link above:


http://www.ebay.com/itm/BEST-UPGRADE-Genuine-BOSCH-Fuel-Injector-Set-of-4-Update-4-Nozzle-Tip/281435347207?_trksid=p2481888.c100675.m4236&_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20160908105057%26meid%3D6b4f69d9087a4894bd698d14b8cd877c%26pid%3D100675%26rk%3D1%26rkt%3D15%26sd%3D281435347207&_trkparms=pageci%253Aa79fa650-3964-11e7-a692-74dbd1804fea%257Cparentrq%253A0bf1c4a215c0ac8077b255fcfffe1311%257Ciid%253A1 (http://www.ebay.com/itm/BEST-UPGRADE-Genuine-BOSCH-Fuel-Injector-Set-of-4-Update-4-Nozzle-Tip/281435347207?_trksid=p2481888.c100675.m4236&_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20160908105057%26meid%3D6b4f69d9087a4894bd698d14b8cd877c%26pid%3D100675%26rk%3D1%26rkt%3D15%26sd%3D281435347207&_trkparms=pageci%253Aa79fa650-3964-11e7-a692-74dbd1804fea%257Cparentrq%253A0bf1c4a215c0ac8077b255fcfffe1311%257Ciid%253A1)

I'm going to ride a bit this morning, do the install, sync the throttle bodies, ride a bit more and will report back...
Title: Re: Stuttering under part-throttle
Post by: E30_Crazy on May 20, 2017, 09:04:04 PM
Oh wow. Just got mine today. Didn't think they'd be here for the weekend. I'll have to go grab one of those replacement fuel filters tomorrow. It's very tempting to throw them in tonight, but no sense in gumming up new injectors if my filter has failed.
Title: Re: Stuttering under part-throttle
Post by: E30_Crazy on May 21, 2017, 12:31:01 PM
Also, after reading about syncing the throttles, I noticed that my caps for the vacuum ports have been switched out for vacuum lines and T-fittings, connecting all of the throttles together. Logic says this wouldn't cause a problem, since it was running fine before (unless there's a split in one, obviously) I mean just in theory of operation.
Title: Re: Stuttering under part-throttle
Post by: Motorhobo on May 21, 2017, 03:15:36 PM
Just installed mine and first impression is: awesome. I rode it before the throttle sync and it seemed to be a great improvement -- am going to ride it again now after the sync...of course, the mind plays tricks but...that appears to be $79 very well spent.

BTW they are no heavier than the original ones, my earlier comment was false.

I don't see how replacing the caps and the vacuum hose with t-fittings can be a good thing. If it were me, I'd drop the few pennies on the caps and get that one vacuum hose on the far right with the protector coil around it and do it the way the Krauts designed it -- that is unless someone has a really, really good reason to not do it that way.
Title: Re: Stuttering under part-throttle
Post by: Scott_ on May 21, 2017, 07:20:07 PM
I have all of my sync ports connected together with "T"'s to feed vacuum to my Cruise control setups. I've not noticed any performance issues with this setup.
Title: Re: Stuttering under part-throttle
Post by: E30_Crazy on May 21, 2017, 07:37:21 PM
Well, no change in the stuttering... Almost feels a little worse now. Can really power through it now. Stutters even with full throttle, and gets hung up around 5 or 6k. Almost starting to remind me of when the ECU failed. Hope it's not that, since that'll make me think there's a bad wire somewhere frying them. Or maybe just got unlucky twice? Still gotta finish checking the rubbers. Haven't got the intake manifold off yet to check the throttle rubbers. Can't very well see the back side of them. Fronts don't look too bad.

Next only list is the FPR and associated lines I guess.
Title: Re: Stuttering under part-throttle
Post by: Laitch on May 21, 2017, 07:57:32 PM
Well, no change in the stuttering...
You haven't mentioned whether you changed the fuel filter. You stated on May 20 that you intended to change it today.
Title: Re: Stuttering under part-throttle
Post by: Motorhobo on May 22, 2017, 05:50:16 AM
I have all of my sync ports connected together with "T"'s to feed vacuum to my Cruise control setups. I've not noticed any performance issues with this setup.

Thanks --  I didn't know there was a practical use for that. Is that cruise control documented here? I'd like to check it out if it's K75 applicable -- a search for 'cruise control' turned up a number of hits, not sure which is the one that applies.
Title: Re: Stuttering under part-throttle
Post by: Scott_ on May 22, 2017, 07:00:01 AM
Thanks --  I didn't know there was a practical use for that. Is that cruise control documented here? I'd like to check it out if it's K75 applicable -- a search for 'cruise control' turned up a number of hits, not sure which is the one that applies.
http://www.motobrick.com/index.php/topic,434.0.html

I have the older vacuum version that you may or may not be able to find new any longer. They have gone full electronic/electric actuator in leu of vacuum.
Title: Re: Stuttering under part-throttle
Post by: johnny on May 22, 2017, 07:13:44 AM
greetings...

murph has the ccs100 whole and parts...

https://www.murphskits.com/product_info.php?manufacturers_id=6&products_id=422

j o
Title: Re: Stuttering under part-throttle
Post by: Scott_ on May 22, 2017, 07:32:22 AM
Thanks for the link JO.
I'm debating replacing the unit on my '97, nice to see I can just purchase the canister/cable assy that's bad and not the entire kit....
Title: Re: Stuttering under part-throttle
Post by: The Mighty Gryphon on May 22, 2017, 09:47:43 AM
Be aware that the giant airboxes on Jetronic bricks make it difficult if not impossible to install the throttle cable without messing up the throttle action.  The Motronic units with the hoses to the throttle bodies make for a much easier install. 

I was very lucky to find a "cable interface unit" from Motorcycle Setup PTY to connect all the cables to the throttle body. 
Title: Re: Stuttering under part-throttle
Post by: Martin on May 22, 2017, 01:56:27 PM

E30  have you checked your fuel hoses for deterioration, have you checked your valve clearances. And you might want to give running a couple of doses of Techron through the system.
Regards Martin
Title: Re: Stuttering under part-throttle
Post by: E30_Crazy on May 23, 2017, 07:58:51 AM
Laitch, yes filter was changed, pulled the pump out and cleaned the screen and tank.


Fuel hoses are still looking good. Believe they were changed just a couple years ago.


Gonna change the FPR, and if that doesn't fix it I'm gonna look for another ECU, since it seems to be slowly getting worse, and in the same way last time when it was the ecu
Title: Re: Stuttering under part-throttle
Post by: Laitch on May 23, 2017, 02:33:15 PM
Gonna change the FPR, and if that doesn't fix it I'm gonna look for another ECU, since it seems to be slowly getting worse, and in the same way last time when it was the ecu
That isn't a productive way to go about solving this problem although it does keep parts suppliers in business. We all want that.

Have you checked your valve clearances, air filter, vacuum leaks then done a throttle body balance? You've already change the plugs and fuel filter. The other elements I've described would complete what is called a tuneup. When was that last done?
Title: Re: Stuttering under part-throttle
Post by: E30_Crazy on May 28, 2017, 03:19:04 PM
No definite date or even surety as to when it was last all done. I was all over this and other sites reading up on the K100 before buying mine, so I knew what questions to ask and what to look for. IIRC, most anything maintenance and tuneup was done by PO. Splines, filters, plugs, etc.


I have a spare FPR, so might as well try. Gotta dig down to it to check the vacuum lines anyways. Air filter is good. Was gonna replace all the vacuum lines last night, but got sidetracked making a new key pin post for the makeshift lid of the alternate relay box, AKA lower half of stock airbox. After new vacuum lines are in, I'll try an adjustment. Weird how it could just fall out of adjustment suddenly.


Oh, and I just found a vacuum test kit on sale at the local Harbor Freight, so I'll try the TB sync as well, after the vacuum lines are all set
Title: Re: Stuttering under part-throttle
Post by: E30_Crazy on May 28, 2017, 03:21:46 PM
Or TB balance, rather? The TB sync is the mechanical adjustment? The one that can be a PITA?
Title: Re: Stuttering under part-throttle
Post by: Laitch on May 28, 2017, 03:41:29 PM
Weird how it could just fall out of adjustment suddenly.
I don't think it has been determined whether something is out of adjustment, obstructed or disconnecting intermittently. The goal is to work in an orderly way toward understanding what is happening.
Title: Re: Stuttering under part-throttle
Post by: E30_Crazy on May 29, 2017, 09:31:03 PM
So, on my way under the lower airbox half to check out fuel and vacuum lines, I stumbled across a spade connector that had it's stem/crimp poking out of a relatively long rubber boot. Long enough of a boot that it seemed highly unlikely for it to still be connected under the boot ar the top. Pull the boot off, lo and behold a loose spade connector.


It's connection is to a thingy just forward of the FPR on the back side of the throttles (I'll be looking up said thingy and function after this post).


Some of the vacuum likes around the front of the throttles have hardened and begun to crack around the T-fittings, so I won't be ignoring those either. Fuel lines all look good enough for now. Think I'll leave the FPR alone for now. That was I can determine the effect of "thingy" (has an electrical connector, but I'm thinking a vacuum like out the top.... We'll see)




EDIT


Took a wild guess at Google, and nailed it. The vacuum switch. Claims are abound about it not doing anything... But only because BMW removed it after '85. BMW would have then tailored out any requirement for it to be there. On a bike that should have it, I'll go ahead and reconnect it and go for a quick ride.
Title: Re: Stuttering under part-throttle
Post by: E30_Crazy on June 02, 2017, 02:50:45 PM
Still no change. I may be experiencing some very bad mileage aswell. Was pretty sure I had a couple gallons left, fuel pump was fully submerged. Made it about 5 or 10 miles all together after changing fuel filter and checking the pump. Ran out of gas at a stop light. Luckily it was at the turnoff for my sidestreet.


My compound pressure/vacuum gauge only reads 10psi, so I'll need to get another one to test the fuel pump output, and fuel rail regulated pressure.
Title: Re: Stuttering under part-throttle
Post by: E30_Crazy on June 09, 2017, 04:07:31 PM
While checking fuel pressure, is it just during idle that you're expecting around 36psi? I gave some revs and it was down around 20-25 psu at points. Couldn't tell much on the stuttering, since it wasn't in gear/under load.
Title: Re: Stuttering under part-throttle
Post by: E30_Crazy on July 02, 2017, 06:55:58 PM
Just another tidbit.... I seem to have the symptoms of a bad/out of adjustment TPS. But the TPS and wiring all check good, and I've made sure to double-check the adjustment. However, it seems to be when rolling onto throttle slowly from off throttle, when over the 2k RPM fuel-cut. That would tell me the TPS is doing its job (fuel on and off above 2k RPM according to throttle position) albeit possibly on the rich side.


Valve shims are good, vacuum line replaced, TB balance done, new/clean injectors and fuel filter, air and water temp sensors are good, hall sensor good, compression test done. Along with everything I could check with a multi meter on the connectors to the EFI and Ignition ECUs.


I'm going to redo my fuel pressure test. My gauge was leaking all over. Got it traded out at Harbor Freight.
Title: Re: Stuttering under part-throttle
Post by: Martin on July 03, 2017, 06:19:29 PM

There are a couple of signs that there could be a problem with the FPR. One is leaking fuel in the vacuum line, and another is when revving  the motor hard ( NOT TO REDLINE) while stationary, it will blow black smoke  which is excess fuelling. I don't know whether this is your problem but it did cure a mates bike.
Regards Martin.
Title: Re: Stuttering under part-throttle
Post by: E30_Crazy on November 05, 2017, 06:16:39 PM
That's an assumption. It was removed because it interfered with performance. Eliminate it and shield its spade connector with electrical tape. Setting the throttle bodies and setting the correct idle will do, according to many riders' outcomes.

Are you asserting that you checked all values in the troubleshooting guide pertaining to the fuel injection control unit and the ignition control unit and that they conformed to what is presented in their respective charts?


Yes, all values were measured/verified IAW the Vogel troubleshooting guide.


Was riding it around tonight, after a hiatus for a while. Noticed the low voltage light making a dim appearance. It gets a little bit brighter the higher I go in RPMs. Down lower, or at idle, it seems to go away, or at least much dimmer. I have a digital voltage meter wired up in the triple tree, and get sporadic drops in voltage down to low 12s, sometimes high 11s at higher RPMs. But it's not consistent. Starter and wires have been cleaned a couple times now. Battery ground in clean. Grounds under tank are clean. I may try a different alternator. It or the voltage regulator may be acting up... This may be its own problem however. I don't know for sure if a slightly low voltage would cause a stutter? Maybe the coil can't draw enough power off the battery alone (new battery just today, too) without a strong output from the alternator...
Title: Re: Stuttering under part-throttle
Post by: Filmcamera on November 05, 2017, 06:32:00 PM
I had a similar issue in reverse when my alternator was giving out.  I got a nice clean 12.8 V or so at idle but when I revved the bike to 4000+ that voltage went up into the 15 V range.  The engine began running rough after a while at the higher, cruising type revs, I am not sure exactly why but guess that the ECU did not appreciate the higher voltage.  ANyway I had the alternator rebuilt and have never had a problem since.

So I would certainly take a close look at your alternator
Title: Re: Stuttering under part-throttle
Post by: Laitch on November 05, 2017, 10:36:53 PM
Was riding it around tonight, after a hiatus for a while. Noticed the low voltage light making a dim appearance. It gets a little bit brighter the higher I go in RPMs. Down lower, or at idle, it seems to go away, or at least much dimmer. I have a digital voltage meter wired up in the triple tree, and get sporadic drops in voltage down to low 12s, sometimes high 11s at higher RPMs. But it's not consistent. Starter and wires have been cleaned a couple times now.
How are the regulator brushes looking? (http://k-bike-knowledge.000webhostapp.com/electrical/alternator/Replacing_brushes.htm)
If your bike hasn't been upgraded to a 50 amp, you could try this (http://www.euromotoelectrics.com/product-p/boalt-reg286.htm) or these (http://www.euromotoelectrics.com/Alternator-Brush-Kit-BMW-K-BOALT-286Brush-p/boalt-286brush.htm) if you need a change.
Title: Re: Stuttering under part-throttle
Post by: E30_Crazy on November 08, 2017, 04:46:57 PM
Just researched/performed some alternator testing. Cold/warm and idle/revving and stuttering returned good values on the battery, and both the red and blue leads off the alternator. Makes me think the alternator, regulator, and brushes are OK. My on-board voltmeter and/or it's source or wiring must be giving me a false low-voltage.


I was able to snag a video this time around. It usually doesn't act this bad just sitting and revving. Usually only out and riding, under a load. Not that it can tell you much, other than its stuttering, haha. https://youtu.be/NzhNqq6NCO0 (https://youtu.be/NzhNqq6NCO0)


Oh, and my clutch cable just snapped at the little knurl/tophat that slips into the keeper pin of the lever, so disregard that in the video... It never ends! Haha.


Back to the plan of the FPR next, when I have time to dig to it.



Title: Re: Stuttering under part-throttle
Post by: lmiklosy on November 08, 2017, 05:43:51 PM
E30 how were the injectors tested?  The impedance should read 16.5 Ohms but that isn't a sufficient test. Have you listened to them 'tick' at idle?   If you don't have a stethoscope, try the long screwdriver test up to your ear, do at low rpms when the muffler noise is least. At idle you should hear a soft 450cpm tick sound.  Failing a screwdriver test try start a cold engine and run for 30 seconds then shut off. Then starting at the 4 into 1 header feel each header pipe with your fingers to find the cold one(s), there's is your suspect injector.  From the audio I hear a cylinder(s) missing a heartbeat altogether.   Hope that helps.
Title: Re: Stuttering under part-throttle
Post by: E30_Crazy on November 11, 2017, 02:33:10 PM
E30 how were the injectors tested?  The impedance should read 16.5 Ohms but that isn't a sufficient test. Have you listened to them 'tick' at idle?   If you don't have a stethoscope, try the long screwdriver test up to your ear, do at low rpms when the muffler noise is least. At idle you should hear a soft 450cpm tick sound.  Failing a screwdriver test try start a cold engine and run for 30 seconds then shut off. Then starting at the 4 into 1 header feel each header pipe with your fingers to find the cold one(s), there's is your suspect injector.  From the audio I hear a cylinder(s) missing a heartbeat altogether.   Hope that helps.
Injectors tested good as far ad ohms could take me. Brand new injectors also. Tested each one from the ECU plug as well, making sure the ohms changed correspondingly to how many injectors were plugged in.


I can try the idle tick, but the issue doesn't really present itself at idle, especially cold
Title: Re: Stuttering under part-throttle
Post by: Laitch on November 11, 2017, 02:50:38 PM
Consider performing the Hall sensor test in the troubleshooting guide.
Title: Re: Stuttering under part-throttle
Post by: E30_Crazy on November 11, 2017, 05:47:32 PM
Consider performing the Hall sensor test in the troubleshooting guide.




I built the DIY LED tester lead, hall sensor seems to work as advertised.


Got the FPR replaces today. Wasn't as bad as in the video, but couldn't tell for sure if it was gone. And couldn't get it under a load very easily without a clutch cable. Gotta wait for that to get here
Title: Re: Stuttering under part-throttle
Post by: E30_Crazy on November 25, 2017, 05:12:43 PM
Still spitting and sputtering around 4k after the FPR swap. Does seem to get worse the brighter the battery light illuminates. I bought a batter charger/tender/jump box on black Friday, and it's alternator check function calls the alternator bad, even though I couldn't really see anything wrong with a multimeter. Think read somewhere about phases going dead or something, and hard to tell with just a basic multimeter. I will try a voltage regulator, then move on to getting it rebuilt or replaced with a different one.
Title: Re: Stuttering under part-throttle
Post by: E30_Crazy on May 18, 2018, 02:47:41 AM
Got my clutch cable replaced, so now I can do more testing than just revving it in neutral in the garage. I had put some heat on the hall sensor while running, and it seemed to affect the running a little. Think I even had it die once. Put a new hall sensor in today. Idled out of the garage just fine (it was almost midnight, so no revving up to 4 or 6k rpm). Went to pull off, and it lost all acceleration and died after about 10mph. It then would no longer start and/or idle. Seems very similar to the "bad temp sensor no start" scenario. I have checked the temp sensor several times throughout this ordeal, and checked it yet again tonight. Numbers for resistance and temp seem spot on.


So, my next question; looking at the wiring diagram and troubleshooting guide, I see the temp sensor goes to the temp sensing switching unit, and the FI relay. Do these symptoms point more so to one of these than the other?
Title: Re: Stuttering under part-throttle
Post by: Martin on May 18, 2018, 04:19:46 AM
When my sensor played up, it was the connection not the sensor.
Regards Martin.
Title: Re: Stuttering under part-throttle
Post by: E30_Crazy on May 18, 2018, 10:50:19 PM
The cutting off and not starting while hot presents a temp issue. Just looked more carefully at a more detailed wiring diagram. I had only checked my temp sensor and wiring at the FI computer plug. Gonna check the other signal and wiring going to the temp switching unit, the unit itself if I can, and the fuel injection relay. I can bear the pump running while cranking, and it sometimes want to start (when hot) but then dies. Pump or injectors may be cutting off as a result of bad temp input somsomewhere.


If these all check out, I'm back to the FI computer being shot (for a second time)
Title: Re: Stuttering under part-throttle
Post by: Martin on May 18, 2018, 11:46:40 PM
If the sensor is playing up the spark plugs will be wet. With the plugs out and earthed ( failure to earth the s/plugs can result in damage to ignition module) the check the spark, but be careful not to ignite the excess fuel. Remove the fuel pump fuse #6 while doing the test.
Regards Martin.
Title: Re: Stuttering under part-throttle
Post by: E30_Crazy on May 19, 2018, 01:56:56 AM
Temp sensor checks good at the temp switching unit. Wiring from temp sensor plug to the unit it good as well. Nothing burnt up inside the unit. Wiring from Temp switching unit to the FI relay checks good. I may try and pick up a new FI relay. Wondering if something inside is failing after carrying the power load for an amount of time.... And I may have the wrong one anyways. The part number returns as a BMW car relay. Reading around here and other forums, the K100 (or at least early ones like mine) had points reversed, and that the double 87 shouldn't have an "A" and/or "B" attached (double output vs alternating output IIRC).
Title: Re: Stuttering under part-throttle
Post by: E30_Crazy on May 19, 2018, 08:30:07 PM
Tested the fuel injection relay, and it turns out that it is a dual output relay.


Bike starts and idles fine. But after warming up a bit, if I try to rev past 4 or 5k rpm, and it stutters too much, or I try to ride it, it shuts off and won't start again until it cools off some. Temp sensor, and all wiring after it on both paths checks good. I'm thinking the FI computer has failed for a second time. If the signals and sensors are all correct, it must be the interpretation part that is bad.
Title: Re: Stuttering under part-throttle
Post by: Laitch on May 20, 2018, 07:08:47 AM
Test the coils according to the method within this guide (http://hrsbstaff.ednet.ns.ca/bvogel/K100/download/bike-wont-start1.htm). It's located just after the Hall sensor test. Have you done that yet?
Title: Re: Stuttering under part-throttle
Post by: E30_Crazy on May 22, 2018, 04:44:32 AM
Yes, that was done near the beginning of this whole debacle. Along with going up and down the troubleshooting guide several times now. Very informative, and I've used it on several occasions trying to trace the source of the issue. Nothing seems to present as "bad" or "broken" on all testable components and/or circuits. All voltages, resistances, and continuities are checking as the guide describes.


I have another ECU on the way. From there, the only thing I haven't changed is the ignition control module.
Title: Re: Stuttering under part-throttle
Post by: rbm on May 22, 2018, 07:48:18 AM
The purpose of the temp relay is to turn on/off the cooling fan, so it has no effect on your stuttering at 4K. Ignore that 1/2 of the temp sensor and that line of inquiry.  However, the other 1/2 of the temp sensor in the stand tube feeds the ECU, and that can be a problem for you if the temp sensor is acting up, or the wiring or mounting in the stand tube is corroded. Have you ever had that part out of the motorcycle for an inspection?
Title: Re: Stuttering under part-throttle
Post by: E30_Crazy on May 22, 2018, 01:46:16 PM
Yeah, had it out to make sure threads of the housing and the temp sensor weren't corroded, and to boil the sensor checking that it gave the proper readout to the ECU. Wiring to pin 10 on the plug checks good, too.
Title: Re: Stuttering under part-throttle
Post by: E30_Crazy on May 28, 2018, 01:38:53 AM
Finally gave in and bought another ECU. Ran great, been riding for 3 days now. Just tonight, however, it started down the same progressive path of failure as before. A little sputter here and there just around 4k, but will accelerate up to and past 4k no problem. Its just the cruising at 4k affected. Then it gets a little worse, not wanting anywhere from 3.5-6k rpm while cruising . Still runs and idles for now. I have already checked basically the whole bike for shorts and continuity.... But it very well seems like a short somewhere in the wiring harness, and its frying my ECUs (and wallet )
Title: Re: Stuttering under part-throttle
Post by: Laitch on May 28, 2018, 06:13:57 AM
I have already checked basically the whole bike for shorts and continuity.... But it very well seems like a short somewhere in the wiring harness, and its frying my ECUs (and wallet )
Have you disconnected, dismantled and inspected the ignition switch for dirty contacts or other faulty parts? That's been a fault of many used or neglected K-bikes recorded here many times. http://www.eilenberger.net/K75S/IgnitionSwitch/ (http://www.eilenberger.net/K75S/IgnitionSwitch/)

 
Title: Re: Stuttering under part-throttle
Post by: alexg on May 28, 2018, 03:37:28 PM
Just a thought if you are frying Computers: have you checked the system voltage while running? Could it be too high?


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Title: Re: Stuttering under part-throttle
Post by: E30_Crazy on May 29, 2018, 12:02:41 AM
Have you disconnected, dismantled and inspected the ignition switch for dirty contacts or other faulty parts? That's been a fault of many used or neglected K-bikes recorded here many times. [size=78%]http://www.eilenberger.net/K75S/IgnitionSwitch/ (http://www.eilenberger.net/K75S/IgnitionSwitch/)[/size]


Actually yes. As just some inquisitive/preventative maintenance, I did have it apart just the other week. All seemed in good order. I still freshened up there contacts a bit before reassembling.
Title: Re: Stuttering under part-throttle
Post by: E30_Crazy on May 29, 2018, 12:09:22 AM
Just a thought if you are frying Computers: have you checked the system voltage while running? Could it be too high?


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It runs right around 13v at idle, and drops a little with headlight on and upper RPM range. I had planned on changing out the brushes and voltage regulator in an earlier post, until I thought I fixed the problem with the ECU. It was still in the  plans in the close future. However, it was more so to see if it would keep the voltage from dropping, not having an overvoltage.


The bike does seem to run fairly rich now, in its current half-dead state. Either just a side effect of the failing ECU, or it could be receiving/sending an incorrect signal due to a short (I.e. the signal from the AFM is getting juiced up, and the ECU is sending too much fuel)
Title: Re: Stuttering under part-throttle
Post by: timewolf on May 29, 2018, 01:36:42 PM
Well, no change in the stuttering... Almost feels a little worse now. Can really power through it now. Stutters even with full throttle, and gets hung up around 5 or 6k. Almost starting to remind me of when the ECU failed. Hope it's not that, since that'll make me think there's a bad wire somewhere frying them. Or maybe just got unlucky twice? Still gotta finish checking the rubbers. Haven't got the intake manifold off yet to check the throttle rubbers. Can't very well see the back side of them. Fronts don't look too bad.

Next only list is the FPR and associated lines I guess.


slow down your check and changing to many things at once.
you ever mentioned how she idles ? steady? fluctuation ? popping ? smoking? white or black smoke present? these are tell tail signs


make a check list and eliminate as you go ! air , fuel , spark.
1. did you do the valve adjustment ? if you have a tight valve that could cause all kinds of problems
2. make sure your fuel flow is clean and steady! new filter and pump and is working right.
3. now if she idles right after valves are check / correctly shimmed.... you can move onto timing and throttle body sync.


you said you did the gas check for leaks and it didnt show leaks. leave that alone for a sec. just work on idle .
once thats right you can chase down the other issue.
1. mass airflow sensor ( could be stuck or a faulty unit) or just needs to be adjusted . there are articles here that walk you thought it . 
2.ECU maybe a bad unit or a short  ( probably not )
3.throttle position switch could be a culprit .


most important!!! only work on your bike on a full stomach !   
one thing at a time . make sure they are good. before you move on

Title: Re: Stuttering under part-throttle
Post by: timewolf on May 29, 2018, 03:15:58 PM

slow down your check and changing to many things at once.
you ever mentioned how she idles ? steady? fluctuation ? popping ? smoking? white or black smoke present? these are tell tail signs


make a check list and eliminate as you go ! air , fuel , spark.
1. did you do the valve adjustment ? if you have a tight valve that could cause all kinds of problems
2. make sure your fuel flow is clean and steady! new filter and pump and is working right.
3. now if she idles right after valves are check / correctly shimmed.... you can move onto timing and throttle body sync.


you said you did the gas check for leaks and it didnt show leaks. leave that alone for a sec. just work on idle .
once thats right you can chase down the other issue.
1. mass airflow sensor ( could be stuck or a faulty unit) or just needs to be adjusted . there are articles here that walk you thought it . 
2.ECU maybe a bad unit or a short  ( probably not )
3.throttle position switch could be a culprit .


most important!!! only work on your bike on a full stomach !   
one thing at a time . make sure they are good. before you move on




SOrry i didnt realize this threat was three pages deep and you guys where way past this point.  :dunno2:

Title: Re: Stuttering under part-throttle
Post by: johnny on May 29, 2018, 04:45:11 PM
greetings...

its the 4 pin... trust me on this... i have never been wrong... check my credentials...

j o
Title: Re: Stuttering under part-throttle
Post by: E30_Crazy on June 01, 2018, 12:35:58 PM
Wouldn't that just cause the pump to stop? Not over-fuel to the point of stalling? Or are you meaning there is a short frying ECUs possibly in the 4-pin and/or associated wires?
Title: Re: Stuttering under part-throttle
Post by: E30_Crazy on June 15, 2018, 01:27:44 AM
greetings...

its the 4 pin... trust me on this... i have never been wrong... check my credentials...

j o

Still not sure if you're just yanking the ol' chain?? Could the 4 pin cause the FI computer to over-voltage or short the system out enough to damage it?