Author Topic: Possible engine flooding issue  (Read 311 times)

Offline kod81

  • Motobrick Curious
  • Posts: 17
Possible engine flooding issue
« on: August 19, 2019, 11:37:33 AM »
Hello,

New member here.

A little background story:
I have acquired a '93 K75 RT as a project in 2018, which was a non runner at the time of my purchase.
The previous owner was adamant the bike did run with no issues, then he started the cafe project and never got to finishing it. When I purchased the bike, it looked complete (all fairing came separately as he's removed them ) and without the wiring loom attached, but again it came separately. I did the usual checks, changed the oil, the fuel and attempted to start it, but was not successful. When I checked the compression, there was none on cylinder one which led me to taking the engine apart and discovering nearly half exhaust valve on cylinder 1 was  burned off and was missing.
Long story short...  I've rebuild that engine. Had the cylinder head tested, cleaned. All valve guides replaced and new valves restated. I've put it all back together following the Haynes manual and other online sources. Not done the valve clearance yet just used the previous shims in the same order as pre rebuild. All gaskets, bolts, washers are new, etc. I have experience building several BMW car engines (I own a e30 car - old 3 series from the late 80s) and yes I have never build a K75 engine before but I understand the principle and would like to believe that I am competent enough to do it.


Here's the current issue:

First of all, I've put it all together and there was no fuel coming from the injectors (this wasn't the case pre engine rebuild).
Following the advises I've found on this forum, I did some troubleshooting with the multi-meter and came to conclusion that my injectors are stuck. I've borrowed another set of injectors from my mate and these do fire fuel. I've sent my injectors of in the mean time to have them cleaned.

The bike does not want to start though. It cranks, but does not start. If I crank it for a long time, there's eventually a big bang (usually supported by a fire) of the unburned fuel being eventually burned. It may also some have a little bit of fuel coming out by the exhaust manifold at this stage, so it appears like the engine is being flooded. I've tried starting with the throttle fully open, but no luck.

Upon removal, the Spark plugs are wet (they are not dark, but they are new spark plugs). Each spark plug produces a nice, white, spark when tested against the cylinder head.  That suggests to me that the Coils and HT leads are fine.

The condition of the temp sensor, that's on the same part of the loom as injectors, is unknown. I've tried starting the bike with it unplugged but it made no difference. I don't know if it would have an impact on the bike's ability to start. I guess it could if the bike thinks the ambient temp is too low? When I measure across the pins on the plug, I get 2,5V going to 4V when I crank the engine.

Fuel pump works and there's fuel pressure in the lines as the fuel does squirt through the injectors. I've not measured the value of the fuel pressure though. The bike did not come with the vacuum hose between the FPR and the Throttle Body (the one inside the spring). I've ordered the spring but not the hose, so currently running a transparent plastic hose as a replacement in there.

I've not checked the engine compression after the rebuild. I can't find the adapter to fit K75 for my compression tester, so had to order a new one.

I've not installed any cooling system back on the bike, so it currently has no radiator, not fan plugged in, no pipes and obviously no fluid. I can't imagine this is needed, but perhaps bikes are different ?

I have no dashboard. I've jumped pin 5 and 6 on the dash plug to crank the engine. Again, I don't know if this would have an impact of my ability to start it. I have no fairings, no lights, no horn, no indicators plugged in. Again, I can't see this having an impact, but it's worth mentioning.

I've tried another ECU and Timing Module which I borrowed from my mate from a working K75 RT. No change.

Throttle Position Sensor was removed and reinstalled in the same position.

I've not tested the AFM, but the flap is shut and moves freely when I use my finger on it, so I assume air gets in the engine. My plan was going to focus on this element next.

Throttle bodies are original just cleaned, with new intake boots top and bottom ones.

Vacuum hose is new (the one linking the throttle body and cylinder head)

Side stand is attached, neutral gear engine and choke connected. The engine does crank without me pressing the clutch lever.

Battery is a small car battery (45Ah). The bike came with a small bike battery, which seems to run out of juice after few cranking attempts.

I have no exhaust, only the exhaust manifold.

Oil level sender is plugged in, but the temp sensor gauge is not (I can't find where do I plug it into?)

Hall Sensor was removed and reinstalled. I've made marks to reinstall in the same position, which were pretty much the default setting. I have not tested the sensor, but I understand it's not straight forward to do so.


Am I missing something obvious here please? Like not meeting a certain criteria for starting the bike?
Any advise would be appreciated as I got a bit stuck.
Thank you,











  • UK
  • K75 RT
1993 BMW K75 RT

Offline Laitch

  • ^ Quintessential Motobricker
  • Posts: 6932
Re: Possible engine flooding issue
« Reply #1 on: August 19, 2019, 12:06:32 PM »
One obvious thing you missed is checking the valve clearances to verify that they are correctly set. You had engine failure from a burned valve. That you used the previous shims in the same order without checking the results is not good practice. Check the clearances then report back with the results before you do anything else.
  • Along the Ridley in Vermont.
  • 1995 K75 72,000 miles
I wept because I had no radials until I met a man who had no splines.
http://www.motobrick.com/index.php/topic,296.msg53303.html#msg53303

Offline kod81

  • Motobrick Curious
  • Posts: 17
Re: Possible engine flooding issue
« Reply #2 on: August 19, 2019, 12:42:33 PM »
Thank you. This makes sense.
I will drain the oil, remove the head cover and measure the gaps.
  • UK
  • K75 RT
1993 BMW K75 RT

Offline Martin

  • ^ Quintessential Motobricker
  • Posts: 3872
Re: Possible engine flooding issue
« Reply #3 on: August 19, 2019, 04:39:23 PM »
You don't need to drain the oil to set the valves. Once you have done the valves check that the temperature sensor connection is clean and firm. The values of the temperature sensor at various temperatures should also be checked.
Regards Martin.
  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

Offline The Mighty Gryphon

  • ^ Quintessential Motobricker
  • Posts: 4596
Re: Possible engine flooding issue
« Reply #4 on: August 19, 2019, 04:53:10 PM »
Giving the engine ANY throttle when starting will flood it.  Just use the "choke" control on the left handlebar.
  • In my garage in Marilla, NY
  • '94 K75RT Mystic Red, '91K100RS White/Blue, '89 K100RS Special edition White/Blue
Current:
'94 K75RT "Ilsa, She Wolf of the SS"
'91 K100RS "Moby Brick Too
'89 K100RS SE

Offline Laitch

  • ^ Quintessential Motobricker
  • Posts: 6932
Re: Possible engine flooding issue
« Reply #5 on: August 19, 2019, 05:21:01 PM »
The condition of the temp sensor, that's on the same part of the loom as injectors, is unknown. . . . ? When I measure across the pins on the plug, I get 2,5V going to 4V when I crank the engine.
What are the pin numbers of the plug and which plug is it? What do those numbers mean to you? With what are you comparing them? What are you doing trying to start an engine with no coolant in it? That is unwise. Slow down and check one system at a time. You are proceeding randomly and that isn't good strategy.
  • Along the Ridley in Vermont.
  • 1995 K75 72,000 miles
I wept because I had no radials until I met a man who had no splines.
http://www.motobrick.com/index.php/topic,296.msg53303.html#msg53303

Offline stokester

  • ^ SuperNatural Motobricker
  • Posts: 578
Re: Possible engine flooding issue
« Reply #6 on: August 19, 2019, 06:20:25 PM »
I may have read past it but are you trying to bring this Brick back to original specs?

If so, I'm one who would ensure all the lights light and everything looks normal before depressing the starter button.  It may be an indication of a missing connection or input.

  • Yorktown, Virginia
  • '94 K75S Dakar Yellow - '93 K75S Seiden Blau - '91 R100RT Dark Blue- '78 R100S Smoke Red

Offline kod81

  • Motobrick Curious
  • Posts: 17
Re: Possible engine flooding issue
« Reply #7 on: August 20, 2019, 04:48:23 AM »
Hello,

Thank you all for your feedback.

I didn't want to go on for too long in my first post as it seemed long enough.
I should have mentioned that my aim at the moment is to just have the engine started, as I've never seen it doing. To recap... when I bid on the bike I was told it was a runner but the wiring loom was on it at the time, as it was a kicked off project, so I it could have not been confirmed. It was a heart/impuls driven purchase at a local auction (they did a lot of vintage bikes on and two K75's came up one after another) that I ended up running into. The previous owner was at the auction as well.  I always knew this was going to be a project, but the price for super low.

As it stands, I have no intention to run the engine for any prolonged period, just to start it. It can run rough or stall straight after and I still would be very happy with that. I just want to ensure that the engine itself is fine and that I've built it correctly before I start throwing any more money at other components it as it would need new brakes, new parts in the cooling system, new lights, seat, etc, etc.
I have just installed... what I though was... the bare minimum to start the engine on a K75.

Laitch made a good point about the valve clearance. I've omitted it at the stage of installing the crankshaft as I wasn't confident not doing it with the shims before (I've done it on a engine that has rocker arms). I am looking forward to checking checking it.

Martin,
I was going to drain the oil as I might just put the engine back on the stand so I can flip it by 90 degrees to make my life easier when working on it. I am not as young as I used to be;)

The Mighty Gryphon,
I've tried with the choke only, no choke full throttle, no choke no throttle, etc. I did breaks in between, sparks out, injectors out to let it dry. I was doing it over the course of days. Same results each time.

Laitch,
I've not tested the sensor itself yet. I believe this is done via pin 10 and ground, but I've not done it yet. I wasn't sure what impact this sensor has on getting the engine to start and if it can be started without it or with it being faulty. I've measured across the two pins on the temp sensor plug that's on the same loom as the injectors just to see if I get any readings at all. I don't feel like I am proceeding too randomly. I have explained the areas I've checked, things I have fixed (like the broken valve) or replaced and checks I did in order to attempt to start the bike. I had the entire engine apart and then methodically put it together.  This isn't me doing it all in one day by the way. The components were checked, cleaned or replaced if visually broken:) I was then looking at each major system separately first before I tried to start the bike... oil in, fuel in, timing set to default, cables plugged in... then got fuel, got spark, got air, cooling system is off the bike. Is it required to start the bike please? (I not planning to let it warm up though, I understand the risks of doing so)

Stokester,
I'd like to achieve the original mechanical spec. I am a bit OCD about it and I go through the lengths of even buying bolts or washers directly from my local BMW. All parts on this engine are BMW original parts. Cosmetics wise, I think it's past the stage where its financially feasible to restore to orignal RT spec. The frame's loop has been cut, tank sprayed with rattle can, lamps replaced with some street fighter style ones, some fairings are broke, etc. The lamps and indicators did work, and so did the horn. I've also had an access to a dashboard at some stage (borrowed from the same mate as injectors) and had the Neutral Gear light on, ABS light on, Oil Check light on. I could lit the backlight on the dash and flick the indicators left and right.


I should have also mentioned that both the alternator and the starter have not been touched (I've only replaced the rubber bushes for the alternator as they were in pieces). I do get the correct voltage readings at the alternator so presumed it's good enough to achieve what I want to achieve at this stage.
I've also cleared the two ground points on the frame and replaced the nuts.
I've cleared the wiring loom with a spray electric cleaner and checked cables for continuity when I first purchased the bike and tried to start it, pre broken valve discovery.
I removed all ABS and brake system too and none it's currently not on the bike.
I've not plugged in... what I think is the temp gauge sensor... It's at the bottom of the water pump, next to the oil sender. It has a one pin wire in a blue square plug and I cant' locate where do I plug it into.

Like I said, my aim was to just have the engine started with the minimum required before I invest any more into the bike, but perhaps I am yet to achieve that minimum. Stokester has a good point and I may have a connection missing somewhere that I am not aware of. It is possible that I've not plugged something in yet as I have put the wiring loom myself not having a reference of how it was all connected before, however most sockets seemed fairly logical to be identified. The cables that are not being used, like those for the lights, are isolated and put out of the way. I am confident they don't touch on anything.

I can start by checking the clearance on valves, as that's an obvious thing I have not yet done and go from there.

Once again, I appreciate everyones response. Regards,


  • UK
  • K75 RT
1993 BMW K75 RT

Offline John Lang

  • ^ Proficient Motobricker
  • Posts: 162
  • John Lang
Re: Possible engine flooding issue
« Reply #8 on: August 20, 2019, 06:59:09 AM »
The sensor at the bottom of the oil/water pump is for oil pressure, not temperature. The square clip on its wire slides onto the small flange on the sensor end. Nothing to do with your problem.
  • Ottawa, ON Canada
  • 1987 K75C

Offline Laitch

  • ^ Quintessential Motobricker
  • Posts: 6932
Re: Possible engine flooding issue
« Reply #9 on: August 20, 2019, 09:34:56 AM »
. . . I should have mentioned that my aim at the moment is to just have the engine started . . .
This is a case for the Five Boroughs Sisyphean Society's intervention team.

Adiós.
  • Along the Ridley in Vermont.
  • 1995 K75 72,000 miles
I wept because I had no radials until I met a man who had no splines.
http://www.motobrick.com/index.php/topic,296.msg53303.html#msg53303

Offline Martin

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  • Posts: 3872
Re: Possible engine flooding issue
« Reply #10 on: August 20, 2019, 04:35:18 PM »
Temperature sensor is located in the lower part of the stand pipe under the hose. This sensor is a known cause of flooding. After removal it can be tested using a thermometer and a multimeter.
Regards Martin.

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  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

Offline kod81

  • Motobrick Curious
  • Posts: 17
Re: Possible engine flooding issue
« Reply #11 on: August 29, 2019, 07:55:53 AM »
Hello,

Just as an update...

All valve clearance have been checked and they are all too tight...

I cannot literally squeeze the 0.05mm feeler gauge in intake or exhaust, so I have either messed something up when I was putting the cams or I need all new shims.
When I rotate the enginge, everything seems fine... I can see the camshaft moving and the valves closing/opening, etc, but it does make me worried.

I've just ordered a tool to remove shims, so will get them out in a few days or so to see what values they are.
Regards,
  • UK
  • K75 RT
1993 BMW K75 RT

Offline Laitch

  • ^ Quintessential Motobricker
  • Posts: 6932
Re: Possible engine flooding issue
« Reply #12 on: August 29, 2019, 08:09:47 AM »
Once you have verified that the timing marks on the camshaft sprockets and crankshaft are in correct alignment and the valve clearances are correctly set, don't do another task until you do a compression test. Your failure to do an initial valve clearance adjustment coupled with rotating the crankshaft might have damaged valve components again.
  • Along the Ridley in Vermont.
  • 1995 K75 72,000 miles
I wept because I had no radials until I met a man who had no splines.
http://www.motobrick.com/index.php/topic,296.msg53303.html#msg53303

Offline kod81

  • Motobrick Curious
  • Posts: 17
Re: Possible engine flooding issue
« Reply #13 on: August 29, 2019, 08:21:15 AM »
It might be instructive for others involved in rebuilding if you clarify one point. You assert that you rebuilt this engine. When you assembled the camshafts into the cylinder head, aligned the timing marks and put the cover on the timing chest, when did you adjust the valve clearances?

I have not adjusted the valve clearance at all following me putting the cylinder head back on, following the valve guides being replaced and some replacement valves being re seated by a 3rd party.
I have only aligned the timing marks, installed the cam followers then put the shims in the order I've removed them (This is not really relevant as some valves were actually replaced and put in back in the same order)... and that was it. I haven then completely forgotten about me not checking the valve clearance until I've been reminded about it on this forum.

I also do not know what was the valve clearance before, as when I have originally took the head off back in 2018, one of the exhaust valves was burned out so that was an obvious issue to me at that point.

Regards
  • UK
  • K75 RT
1993 BMW K75 RT

Offline Laitch

  • ^ Quintessential Motobricker
  • Posts: 6932
Re: Possible engine flooding issue
« Reply #14 on: August 29, 2019, 08:40:33 AM »
I revised my previous post after I read that you had failed to adjust the valves at all previously in this thread. I'll repeat it in this one and include an observation. Is there oil in the engine? Don't fail to add some now. You're forgetful. When you verify the camshaft timing marks are in alignment with the crankshaft and all the valve clearances are adjusted, do a compression test because you might have damaged the new components by rotating the crankshaft.
  • Along the Ridley in Vermont.
  • 1995 K75 72,000 miles
I wept because I had no radials until I met a man who had no splines.
http://www.motobrick.com/index.php/topic,296.msg53303.html#msg53303

Offline kod81

  • Motobrick Curious
  • Posts: 17
Re: Possible engine flooding issue
« Reply #15 on: August 29, 2019, 08:58:04 AM »
Good shout Laitch. I still haven't found the attachment for my engine compressor tester, good job you've reminded me as I need to get one/

Yup, there's brand new oil in the engine.

  • UK
  • K75 RT
1993 BMW K75 RT

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