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Thread: Overheating/electronics on a r69s & oil breather

  1. #1
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    Overheating/electronics on a r69s & oil breather

    OK, so probably the last sunny day in fall today, go on a ride to a restaurant that has a history for me - years ago, I ran out of gas on my R50/2 on this road. Damned if I didn't run out of gas today in the exact same place! I felt it getting low, so I switched to reserved, it got me maybe 2 miles before it was bone dry.

    Turns out a fellow BMW rider lived about 300 yards from where I stopped, so he set me right.

    But then, about 40 minutes later, I'm on a main drag, and the bike just dies.

    Acted like no spark, no fuel.

    The bike cooled off for about 30 mintes, push started, got it running again.

    I remember hearing something about overheating coils. Can anyone fill me in on this?

    I also have a question about the oil breather. This bike tends to burp up a nice mist from the breather tube. What does this signal?

    Thanks for all the help and advice, and I hope all of you had weather like I did today (but better luck!)

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    The situation with the lack of spark on the older coils, especially when hot, is due to the breakdown of the winding when hot. There should be one long winding which results in the most energy when the field coils are saturated and collapse (slightly different with the magneto setup). Once the winding becomes sets of multiple shorter sets, the energy drops off. That's why the bike will usually start OK cold, but be much harder when hot. Solid state coils are available that are form/fit/function and do a great job.

    Oil/mist coming out the breather pipe might be a signal of crankcase overpressure, likely caused by worn rings and excess blowby. The breather is trying to relieve the pressure bring some mist with it. Engine seals also take a beating in this situation.

    You're not overfilling the bike with oil are you? Sometimes that could cause windage and more churning of the oil, creating excess mist. Too much oil also decreases the internal air volume in the case, further creating more overpressure.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

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    Breather & spark

    No, definitely not overfilled with oil. And I'm pretty sure that I'm not over-revving, simply becuase I can't get the bike to go over 70 on a good day. I'll have it up to 60-65 in Third, then once in 4th, I can barely maintain that speed. I pretty much rode in 3rd today anyway, as I didn't go on any highways.

    I'm thinking that all of these things are somehow connected. I haven't pulled the carbs yet and I haven't re-checked is the valve clearances.

    The Coil seems to be a new black one from the Emerald Isles, or something like that. It looks new to me.

    Remember, I bought this bike fully restored, got it from a reputable place, was given a list of what was done, and who did what, and i've been finding things that were simply not right on it, that don't make sense in light of the work that was done on the bike that cost some serious coin...

    Appreciate your help!

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    Quote Originally Posted by 166926 View Post
    The Coil seems to be a new black one from the Emerald Isles, or something like that. It looks new to me.
    Emerald Island, I think is what it is. I recall that the first series of these coils had an issue with proper grounding. The second series added another grounding wire which took care of the problem. I bought one from Vech maybe in 2009 and it had the second wire. No problems to date.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

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    There may not be any problem there. Something is happening that kills the motor got a good 30 min...hmm...what are some of the more common things to look for? Btw, the misting isn't constant, it usually happens before the shutdown. Is there someone in the Detroit area who wants to have a look? Coffee is on me!

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    Next time you begin to loose power, try slightly unscrewing the gas cap. It should vent. Maybe you're getting a vacuum that prevents fuel flow.

    When this happens again, quickly shut off the petcock and safely coast to a safe area on the side of the road. Pop the top off the float bowls. Is there fuel in there?

    Do you have the brass floats? They can crack and fill with gas, thus sinking. This would be a permanent problem, though, and not necessarily cure itself in 30 minutes.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

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    I'll check; but if they do sink, wouldn't that result in more gas coming in to the float bowl? I thought that they floated up to push up the fuel cut off valve.

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    Yes you're right...I was just pointing out issues which can make for a poor running bike...but you're bike is stopping. If you do have the brass floats, give them a shake the next time you have them out. Vech sells plastic replacement floats which don't crack or sink like the brass ones do.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

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    I'll bet I solved part of the problem...

    Gotta love the internet. I'm going to check the the intake and exhaust valves. I'll bet that the exhaust valves are too loose. That being the case, they don't open enough to fully vent the exhaust, and that means that the only way out for the gasses to escape are past the rings, hence the oil barfing. The faster I go, the worse it gets.

    This would also result in a poor mixture in the combustion chamber.

    If the exhaust valves are out of spec, I'll bet that the intakes are probably off as well, and that too can effect my top end performance.

    I don't know what role any of that would have in killing the motor, other than choking it, but I'll let you all know.

  10. #10
    1960R100S 46211's Avatar
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    Torque the heads first, then check your valve lash.Also grabe the timing light and check your timing.

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    Finally got a chance to fiddle with the motorcycle; just before it started to snow. The valves were actually pretty tight; not bad on riders left, but definitely tight on the right. I understand that tight valves equal hard starts and loss of top end and dying at higher speed. Unfortunately, didn't get a chance to start or ride. Did wash it off, got it ready for storage. I guess we will know more this spring! Any bets?

    All this does ruin my theory on the oil barfing. Any thoughts?

  12. #12
    Rally Rat
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    Generally, anything more than oil misting from the breather indicates poor ring sealing, which could require ring replacement or cylinder reboring. This could also explain a lack of power.

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    Oh !@&#

    So I couldn't resist, and I tried to start it today. Zilch.

    My father in law is a mechanic, and he lent me his compression tester. 30 psi left, 60 right, and leaks down immediately. Oil in the cylender was of little help.

    I'm going to seriously loosen the valves and give it a shot, but I'm thinking i've got a problem here....

    I'll do a photo log. Let's look at the damage together...

  14. #14
    longridgebuilder
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    Was the engine rebuilt ? If so, how many miles on the rebuild ? You must get the engine up to operating temperature and test compression when hot. Testing a cold engine is meaningless.

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    I will totally own up to this. I bought this bike without even starting it. It had no gas, but I took one look at it, and it was the bike of my dreams. I was only a few miles from my house, so I figured that it was a sign. It was so clean, and the guy had a whole history as to what was done to it, including a rebuilt crankshaft, new cylinder heads with new springs, valves, and seats, overbore pistons, etc.

    I don't know the mileage, I was in love.

    I'm beginning to think that what happened here was that the work was done as represented, but the new bits were assembled by someone who works on bikes, but not BMWs. I say that because some of the things that I have found on the motorcycle are not consistent with what I'd expect if the main players had finished the bikes.

    So I have this beautiful bike, represented as fully restored, and I'm so taken with this thing that I ride it for a few hundred miles total. To be 100% honest, all I did was check all fluids to make sure that we were good, and off I went. I never did the timing, never did the valves, etc. After all, the thing is restored!

    So, I'm going to check a few more things with the compression test, and then, I guess I'm digging in to the top end...

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