Reincarnation of a Rat

[bitsa]

Hi again all, I'm still alive! Been busy so not had time to tinker much less take pics or update on the damned bike.

Anyway, had a bit of free time this last couple of days so pulled everything apart once again, stripped out the hacked up wiring loom & all. Went back over the intake boots, damn sure no leaks there now. Re-hashed the tweaked TB's using the ball bearing method outlined above (thank you TMG), cleaned up a lot of other random bits & reassembled.

On reassembly I've now switched to the un-chopped loom which was, supposedly, from a K100 but there's only 3 coil plugs and 3 injector plugs on the (also different) EFI harness so it's evidently been misidentified by the PO.  Also swapped over to the other HES that came with the bike ... Anyone get the feeling this is an issue that was being chased prior to my ownership?  think    Although I did find an issue, the tone ring was loose on the crank?/balancer?  so tightened that with some blue goo on the bolts. Maybe that was it?

So onto one of the non duplicated parts in the basket of this case, I know a few cars around this era have issues with bad capacitors in their ECU/ECM so opened up the brain box.  Nothing doing in there. I only saw one electrolytic, a 220@40v which I've swapped for the sake of it even though it actually tests good ESR and capacitywise.

Since I now have the appropriate plugs, I got into the clocks & gave them a quick clean up to see what works/doesn't. They're full of corrosion but most of the warning lights and backlighting works as does the tach (speedo not tested yet).

BUT... After all of this I still have pretty much the same issue I ended up at when I gave up on the original harness, in that it'll now start pretty well cold, idle along nicely around 1300rpm & even responds to light blips of the throttle with only a little lean pop if I'm too eager. Then, as she warms up it's as if someone's flicked a switch & it just dies out lean. I can just about get it to idle if I hold the starter button (slight enrichment) or better so if I wedge something in the AFM to trick it into believing more air is entering hence more fuel. Kind pf stopping to think things through now, suggestions welcome lol

Oh, and I've also checked the coolant temp sensor, it's in spec and stays in spec when bike is acting up. If I install the ratty old AFM (which I've been tweaking on) then I can get better results than with the unmolested one, although that produces a hugely rich idle in exchange for enough juice to run on throttle & that results in fouled plugs after a few minutes playing.

I'm beginning to wonder if valve clearance is an issue although I did check by eye and they all have clearance, compression sounds exactly the same on cranking etc. I've even blocked off the PCV on the plenum and vented to atmosphere to rule out excessive blow by messing with the AFM (doesn't seem to be any more than I'd expect). other than that though it "feels" electrical to me & I'm wondering if an ECU or Ignition module fault might cause this sudden switch on warmup from running reasonably to just refusing to deliver enough fuel without manual intervention.

Edit- thinking a moment, I may as well pull the injectors and clean them up again & rig something to measure fuel pressure just in case the regulator or pump are crapping out as they warm up. Cheers all, will go scratch my head at it some more lol

[The Mighty Gryphon]

Have you tried swapping in a different Jetronic unit? 

You say you eyeballed the valve clearance, have you actually measured the clearance?  Tight valves have been known to cause running issues in hot engines. 

You have replaced the fuel filter and have it installed in the proper direction, is that correct?  All the fuel line connections i the tank are tight and have no leakage?

If you run the engine at idle for a few minutes until it warms up, what do the spark plugs look like when you pull them out?  Are the electrodes and the insulator nose clean and white? 

Have you done a warm engine compression check with all the spark plugs out and spinning the engine with wide open throttle?  Along with the valve clearance numbers this will confirm that everything is okay mechanically.

[bitsa]

Have you tried swapping in a different Jetronic unit? 
That's one of the bits I don't have a second one of, but it's getting to where I may seek one out

You say you eyeballed the valve clearance, have you actually measured the clearance?  Tight valves have been known to cause running issues in hot engines.  No, not measured as feeler gauges are AWOL but there was at least I'd call it 5 thou inlets & a bit more maybe 10 exhaust, engine probably around 40c as had been running already. Will recheck cold though when the feelers turn up, I fancy I saw them last night on a shelf...

You have replaced the fuel filter and have it installed in the proper direction, is that correct?  All the fuel line connections i the tank are tight and have no leakage?
Fuel tank is spotlessly clean internally, filter is new/correct orientation as are pump isolators/lines, nothing spraying around if I look in there but will be testing fuel pressure if I can find a spec.
If you run the engine at idle for a few minutes until it warms up, what do the spark plugs look like when you pull them out?  Are the electrodes and the insulator nose clean and white? 
Honestly, being an '86 hasn't helped the plugs stay clean but will check with a fresh set when I get some since the DR7's are pretty stained now even after I clean them. Considering D6EA for testing purposes (hotter plug = less fouly?) but the only times I've pulled the plugs (after fouling up) they've all been black sooty with only #1 having a hint of wetness/oil fouling too

Have you done a warm engine compression check with all the spark plugs out and spinning the engine with wide open throttle?  Along with the valve clearance numbers this will confirm that everything is okay mechanically.
I haven't. To be honest I don't have the right adapter but will make it my business to get some actual numbers since I owe it to you guys at least. My calibrated ear gauge tells of a healthy engine though nice even crank hot and cold

Thank you for bearing with me & my redneck ways lol, seeing as how it's getting deeper than just a wiring or sensor issue I'll collect some real numbers before picking your brains again. Will get valves checked out along with fuel pressure (if there's a spec I can find) and hot/cold comp readings once I make an adapter for the tester.

Cheers all, much appreciated

[The Mighty Gryphon]

I would stay with DR7EA plugs for a plug reading.  A different heat range will just confuse what you are dealing with.  If your engine is running lean you need to see that with the correct heat range plugs.

[Laitch]

Will get valves checked out along with fuel pressure (if there's a spec I can find) . . .Thank you for bearing with me & my redneck ways lol, 

Download the K100/K75 2V manual from Motobrick.com, bitsa. Specs start each chapter. Here's a link to the section on this site then click the link to the manual.
I don't see your ways as particularly redneck, bitsa; I've encountered similar throughout the social spectrum, if that's any comfort.  It's just difficult to get a Brick to respond well to them. 

[bitsa]

Good point on the heat range, running close to right ought not require playing. D7EA if I can find them, always hated resistor plugs since having endless issues with DR8ESL over D8ESL in Hondas years ago. (plus, I believe '86 specs non-resistor anyhow.)

Laitch, you quite evidently (and understandably, since we're some 3500+ miles and one ocean separated) don't know me at all haha. I take being called redneck as somewhat of a compliment TBH, since my take on "redneckery" is pretty much making things work the way one wants them to, using the resources at one's disposal & quite a lot of lateral thinking and perseverance in preference to spending money on things that can be made/repaired or made-do.  I do appreciate though that certain things need to be verified and actually measured, as opposed to going on prior experience & feel hence I will be returning with actual data once I get it.

Speaking of data, one thing I can share is my vacuum readings.  These do give me cause for concern that something may be amiss valve clearance/timing wise. Engine warm & idling at around 1300rpm the best I've seen has been 6" to 6 1/2" Hg column. Even across cylinders. I'd have expected much closer to double this, and there are zero intake leaks at this point.

Anyway, it's sweltering hot here today so my project of choice is the clocks. They look to have spent some portion of time upside down in a swamp judging from the corrosion (more likely just off a winter bike and got salt spray inside).  Got some photos at last so will upload in a sec if I can work the confuser.

[bitsa]

Got photos

The poor beast as it currently sits.

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The instrument cluster debacle...

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To be fair, I'm more surprised that as much of the cluster worked given how grungy the guts are.  Testament to the quality of the original product, also the serviceability is top notch & as long as I can clean up the contacts without damaging the film I'm confident I can restore functionality. Only bit I'm less than enamoured with is the way the pins are riveted through both the film & the plastic. Going to experiment with cleaning and soldering if any have flaky contact.

[Laitch]

Laitch, you quite evidently (and understandably, since we're some 3500+ miles and one ocean separated) don't know me at all haha.

Thanks for the photos. That's a bit more scrambled than scrambler but resurrection is entirely possible, likely even without divine intervention. 
I don't know you, bitsa, but I am familiar with your definition of redneck in context of approach to challenges—my being a cracker from the wilds of Florida and all, with its Cracker cattle pastureland doubling as landing zones for drug-laden aircraft. It's just that the German engineering of a Brick doesn't often respond to native genius unless its accompanied by submission to data and technique. 
Somehow though, I am certain that even though I don't know you, you're likely to wrangle with this critter until one of you taps out. 

[The Mighty Gryphon]

I must admit that the patina on your brick is impressive.  That is a good point as currently, heavy patina is very hip.

[bitsa]

Well, Laitch ,my good sir. This old beast may well be determined to be left to finish dying after the "coolification" perpetrated upon it, but I have great hope that I am the more determined of this pairing & with time it may even actually decide it wants to live after all...

I do think though, the rough sanded (looks to have been either 40 grit or a rock) almost bare metal tank (replete with JB weld "repairs" to the underside) is a little past the patina stage TMG...   However, I admit that I don't actively *hate* the look of it & it's certainly less likely to be stolen!  Long term, the plan was to go with maybe Estoril Blue for the tank but I'm also not against a shade of black from an E23 I owned back in the early '00s, Diamantschwarz Metallic. Time will tell anyway.  Instruments roughly reassembled for now & not any worse than they were before, still no GPI or clock action but I'm sure there will be if there ever can be ;)

[bitsa]

Having got further into diagnosing the clock I've come to the conclusion that along with being submerged aside the Titanic, these particular instruments also spent some years in the high desert. Aging less like a good wine and more like, well like a set of Brick instruments in the high desert, I believe the LCD displays have become completely baked & there's no longer any liquid crystal left to display anything...

Is this a common issue though? I've not really seen much about instrument cluster repair/refurb yet but will be plugging that into the search box in a moment or two. Hoping there's a reasonable solution to fix the displays since (being the strange animal that I am) having functional clock & gear indicator would be quite desirable to me. After all, I have the makings of them so why not try and have 'em do what they did back when this cluster was out racking up it's first 108k miles?

[bitsa]

Today's project is the ignition control unit, stripped down (on opening the lid I was hit by a heady aroma, reminiscent of 80's TV's that have gone pop) & after desoldering the output transistors and plug to be able to lift the board out I saw the culprit.  3 of West Germany's finest, stankiest, prone-to-smoke-iest 0.1uF RIFA film caps.  I recall these bad boys well from my playing with old electronics, known mainly for cracking & absorbing moisture then breaking down under voltage and, shorting and engaging "RIFA madness" mode.  I knew I recognised that smell (ain't no seven layers, sure as hell ain't no Taco Bell).

Ripped those out along with 2 electrolytics, a 47uF@50v which tests very good still and a 220 @10 which was a little high on ESR so will replace that with a Nichicon 220@25 as well as the smoke bombs for some modern equivalents (tested the old for craps n laughs, one measured at 0.001 so pretty much open while the other pair tipped the scales nearer to 0.4uF which in a simple low-voltage test indicates leakage/breakdown as expected).

Side note, the date codes inside the AFM, ECU and ICU indicate a very early bike if I'm not mistaken.  Anyone else ever seen casting dates of '85 or even '84 for K75 parts?  Will have to check the VIN and plug it into some form of decoder, but she could be an oldie...

Pics to follow if I CBA 

[The Mighty Gryphon]

Today's project is the ignition control unit, stripped down (on opening the lid I was hit by a heady aroma, reminiscent of 80's TV's that have gone pop) & after desoldering the output transistors and plug to be able to lift the board out I saw the culprit.  3 of West Germany's finest, stankiest, prone-to-smoke-iest 0.1uF RIFA film caps.  I recall these bad boys well from my playing with old electronics, known mainly for cracking & absorbing moisture then breaking down under voltage and, shorting and engaging "RIFA madness" mode.  I knew I recognised that smell (ain't no seven layers, sure as hell ain't no Taco Bell).

Ripped those out along with 2 electrolytics, a 47uF@50v which tests very good still and a 220 @10 which was a little high on ESR so will replace that with a Nichicon 220@25 as well as the smoke bombs for some modern equivalents (tested the old for craps n laughs, one measured at 0.001 so pretty much open while the other pair tipped the scales nearer to 0.4uF which in a simple low-voltage test indicates leakage/breakdown as expected).

Side note, the date codes inside the AFM, ECU and ICU indicate a very early bike if I'm not mistaken.  Anyone else ever seen casting dates of '85 or even '84 for K75 parts?  Will have to check the VIN and plug it into some form of decoder, but she could be an oldie...

Pics to follow if I CBA 

This is very interesting information.  Is there any chance that you might be able to write up a turorial on these caps with photos for the Lieberry here.  As these old beasts add years, I'm pretty sure there will be others seeing the same failures.

[bitsa]

I was surprised to find them in an automotive application to be honest. Not sure if they were causing any of my issue yet (gut feeling is no) as I think they were just part of the noise (EMI) filtering/flyback voltage protection on the coil primaries, but they certainly weren't good & had been smoking at some point, the smell is distinct.

It's currently ended up going back together and I got no photos but if you think there's a need for it (or if it magically cures my running issues) then I'll certainly pull the box apart again with camera handy & do a little write up on them.  Usually it's electrolytics that go bad but the ones specced in these Bosch brains have very much stood the test of time IMHO. The pair I replaced, one in EFI brain & one in Ignition brain, were still pretty reasonable ESR & capacity wise & I don't expect those to be a problem certainly in pre 1991 machines.

IIRC it was around this time that some electrolyte specs were copied and stolen in an act of industrial espionage, unfortunately there was an omission in the formula which led to most electrolytics from the early-mid '90s being exceedingly prone to leakage due to the electrolyte turning corrosive (This in turn then ruined, and continues to ruin, countless PCBs from this era due to eating traces.) Side note, this type of cap stinks like rotting fish when in failure because part of the electrolyte IS fish oil...

[bitsa]

Well, not much more to report as not had time to do any further testing yet but will try the ignition unit again whilst waiting on new correct 'plugs.

Only thing I have done is, considering it has a "Bates" style headlamp and already de-looped/bobbed is I figured I'd pull the rear shock & replace it with a shorter one from an old ATV (completely wrong spring rate & entirely too short to consider actually using it) to drop the ass end on the inner fender/mudguard piece, tied an old Alfa Romeo wheel trim onto the back wheel & pull the 'bars back to a more leisurely riding position.

The result is as ugly as the day is long, especially the way the 'bars sit. I actually quite enjoy how hideous it looks & am giving serious consideration to keeping it as a rat.



*There... Hopefully with that threat hanging over it the damn thing will want to play ball and run for more than 15minutes at a time haha 

[Laitch]

I actually quite enjoy how hideous it looks & am giving serious consideration to keeping it as a rat.

When life gives you rats, make ratatouille.

[bitsa]

Small update, CBA faffing with stupid phone to upload pics yet but it's still in it's lowered hardtail "taint grinder"? form.  Ignition unit works as well as it ever did, if anything spark is a little fatter so that's cool. D7EA plugs installed, still behaves as before.  I'm considering it has to be the ECU now (or I have 2 bad AFMs that both test OK) but seeing as the cost of a replacement, that may or may not be the solution, is going to be in the region of £200 (notwithstanding the one unknown quantity item in the UK starting at £20 which I may bid on) I'm much more inclined to purchase and refurb an SU HS2 carb as fitted to Reliant 750cc car engines (from about £30 +£30 for a kit), a few odds/ends of pipe and plugs to gut the throttle bodies of the butterflies (probably in the region of another £30 tops) and just go caveman with it since I know I can make a carb behave consistently the way I want it to using screwdrivers, drills and feeler gauges.

This is just thoughts currently, I would rather get the EFI working the way it should but I think the carb would be a more time-friendly solution than properly diagnosing the thing and more budget friendly than parts-cannoning the thing (not an approach I savour anyhow).

To be honest I do like getting into chewy problems like this bitch & working through until I find the true cause, but it's summer and I just wanna go for a ride while it's dry (relatively, bear in mind UK!!!) and fix it right when the nights are long and the sky is heavy.

Will check back in when I can, hopefully with better news. Till then 73s out

[bitsa]

Well, I'm alive still & the Scrambled(tm) has followed me through a house move. Now the weather's less pissy I'm starting to get the urge to play bikes again so have re-resurrected the bike after it sitting under the naughty-blanket all winter.

All it took was a charge of the battery, plug the brains back in & force the now-jammed fuel cap to open in order to add some dinosaurs & we're back to where we were last year, runs dandy until it's warm and then drops either pig rich or leaner than the great depression.

Proper diagnosis to start soon, feeler gauges never turned up last year so got new on their way. Just opened the cam cover again to check timing and something doesn't look *quite* right with the cam phasing but will get into the tech data shortly just quickly letting anyone who gives half a damn, that it's not beat me yet! :D

[bitsa]

Ooh, feelers arrived whilst I typed that! :)  Looks like my redneck eyeball calibration was pretty well on last year. Inlets all at .005"/.13mm so on the tight side but not horribly so.

Exhausts were .24/.26/.23mm (.0095 / .0015 / .009") so middle cylinder OK other pair just on the tight end.

Now, they're not hugely out but they obvs ain't right so now out come the cams because I don't have a bucket tool & I'm not super-enamoured with the way the cams sit at TDC overlap so want to check them out & how they locate on the gears, then can calculate what I need for shims/if I can swap them round to make things better.

Big question is, could inlets .001" tight (and 2 exhausts .001 & .0005 tight) cause such a sudden reluctance to run right as soon as things warm up? My gut says this ain't "IT" per-se but probably one of a few issues to straighten out and the cumulative effect ought to have her purring.

[bitsa]

Ooh, feelers arrived whilst I typed that! :)  Looks like my redneck eyeball calibration was pretty well on last year. Inlets all at .005"/.13mm so on the tight side but not horribly so.

Exhausts were .24/.26/.23mm (.0095 / .0015 / .009") so middle cylinder OK other pair just on the tight end.

Now, they're not hugely out but they obvs ain't right so now out come the cams because I don't have a bucket tool & I'm not super-enamoured with the way the cams sit at TDC overlap so want to check them out & how they locate on the gears, then can calculate what I need for shims/if I can swap them round to make things better.

Big question is, could inlets .001" tight (and 2 exhausts .001 & .0005 tight) cause such a sudden reluctance to run right as soon as things warm up? My gut says this ain't "IT" per-se but probably one of a few issues to straighten out and the cumulative effect ought to have her purring.

Also, fuel injectors have been cleaned as well as can be expected, tested for pattern (decent) and leakage (good) at 40psi just for good measure. Regulator pops off at about 36psi and will check again hot/acting up assuming valves don't sort it.

[bitsa]

And as a fall-back (cop out) I did find a mostly complete Zenith CV carb laying round, from one bank of a 3.5 Buick/Rover V8 which by my reckoning ought to be close enough to run if a little on the lean side & could certainly be brought in.

[bitsa]

Well, valve clearances weren't the "magic bullet" as I suspected. What WAS however, was simply adding a longer length of intake tube pre-AFM... 

Rolls eyes... This was kinda on the radar from the get-go as, if you recall, the bike came with no airbox & a 3D printed air filter stub on the end of the AFM. I had previously tried with an extra bit of pipe, filter on, filter off and various ways of mounting the AFM to the plenum chamber but nothing seemed to have an effect. Also, seeing as it came with the filter adaptor & pod filter this led me to mistakenly assume it'd previously been running OK like this.

Should've known better, to assume is to make an ASS of U and ME, but like I say previous experimentation with intake configs seemed to yield no change. Only thing different this time is the bit of extra tubing I added is about 18" long with 2 90* bends in it (an intercooler pipe borrowed from a car build I'm working on). 

Anyhoo, net result is that yesterday the damned thing ran for as long as it's ever ran & as well as it's ever ran. The previous symptom seemed to be that it'd run OK till warm and then just go either richer than Oprah or leaner than Jack Spratt.  This time, it just sat and idled nicely, blipping it no lean pops or stumbling, no crackling on overrun, no dieing out lean, revving cleanly through to the limiter & coming back down to idle with no glitching and I ran it until the fan kicked on & back off again so as hot as I've ever got the thing.

Half of me pleased at the result, was never gonna let the bastard beat me but was starting to clutch at straws. Other half of me pissed at myself for not "getting it" sooner.

So, maybe she can have her rear suspension back after all. Though I am kinda liking the ratty-bob hardtail Scrambled-Scrambler look, next thing is to sort the wiring and get some actual lights on it though and see what it feels like. (You'll love the lighting choice, pure rat since the tail is going to be a unit off an old Cagiva or Ducati I've had kicking around for years, headlamp is staying Bates style & turn signals whatever I find in the shed. Probably some old Honda Vision ones and/or LED bullet style jobbers from god knows what.

Bitch lives though, sounds decent :)

[Past-my-Prime]

When you DO get it on the road (note I did not write IF) you will probably have taken the gawdawfulest pile of marginally useful scrap BMW and turned it into something. Keep up the photos, maybe there's a book in there somewhere.

I'm very curious about your electronics technologist work with the various mysterious black boxes that the bike has. I know I'd just be springing for a replacement of the whole box, if it were lazy me!

Keep up the posting!

[bitsa]

When you DO get it on the road (note I did not write IF) you will probably have taken the gawdawfulest pile of marginally useful scrap BMW and turned it into something.

Turned it into a gadawful pile of marginally useful scrap BMW that screams down the road looking full well like it just fell out of satan's ass? 

As far as the electronics goes, it's a combination of not having the liquid funds to throw at "possible" fixes & a perverted desire to fix anything/everything down to component level where vaguely practical.  The RIFA cap replacement in the ICU obviously wasn't the fix, although anecdotally/subjectively the spark seems a little hotter with them done it's more than likely placebo.

Will attempt to remember photos later on, it's still ugly as a bag of verruca-ridden feet that just walked across hot coals and dog turd though just vaguely more roadworthy-looking than it was before.

When there's time to get it done, I think it's earned an oil change and real coolant then possibly test-ride as it is & see if the hardtail idea is a goer or not. Cheers

[bitsa]

HAH! The slimy, scummy, two-timing, low-down double-crossing Kraut bastard tricked me! Started fine this morning, acted a little cold blooded for 5 minutes before settling into the rhythm of yesterday taking blips & full throttle like it should.

So I gave it the benefit of the doubt & spent the best part of the day treating it to nice fresh oil, couple of gallons of new unleaded & hours of tacking together wiring for tail/brake turn signals & horn. All working nicely now and looking half like a usable rig, fire it back up and....  F*ck off ya pr!ck not playing ball she says.

I'm 99.99% sure it's electrical now at least, probably a broken wire in the loom/bad connection but same symptom across two completely separate harnesses? I suppose it could be the coolant sensor acting up although I have previously ruled that out, whatever, it's time to get the multimeter out again & check inputs to the brain box.  If everything looks good there then I suppose the only thing left is a bad solder joint/flakey semiconductor in the ECU.

Bitch knows how to keep me on my toes, runs so sweet when it behaves too!