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hot cylinder
- schrader7032
- Posts: 9062
- Joined: Fri Oct 27, 2006 3:00 am
- Location: San Antonio, TX
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hot cylinder
The cylinders should run about the same temp as you suggest. Most likely you have a difference in the carbs that's causing this...I would think the left one is running leaner than the right. Or maybe the right side is running too cool. You say the left plug was greyish (light tan is the color you're shooting for) while the right was black. Grey is not too bad but black would indicate too rich...or possibly oil fouled.
Did you confirm the settings in the carb, such as jet sizes and especially the position of the needle that sticks out below the slide? Do the floats actually float? You should measure how much of the needle sticks below the slide...it should be the same on both sides. The needles should be held in position by a small clip on top of the slide. You'll see a number of holes...these are used to position the needle up or down. If you see many holes above the slide, that's a rich condition. If you don't see any holes, that's a lean condition.
This website is a good one to consult for the /2...Duane has some good insight on these bikes.
http://w6rec.com/duane/bmw/index.htm
Type carb into the search engine and look into how to balance the carbs. This is an important step to getting the bike running right.
How's the timing? You'll need to go through the steps to set the magneto timing, the static timing, and then to check how the timing is under higher RPMs. Also be sure the valve clearances are set correctly.
How many miles on the bike? What do you know about any of the previous maintenance history? The no-filter episode doesn't bode well. If there are significant miles on the bike and the slingers haven't been cleaned, this will be something to consider in the future. The bike has no filter system and the slingers are a way of settling out the larger particulates. If the slingers get too full, they can starve the bearings for oil. This type of work requires that the bottom end of the engine come out...it takes a certain amount of skill, knowledge, and tools to do this. Most people can disassembly the top end, but for my money, the bottom end should be left to skilled mechanics.
Unless there's some real nasty deep problem, these bikes will run fairly well even though they are not tuned within an inch of their life. But keep working at it...you should be able to do most things yourself with help like the above website and people on various forums.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.
hot cylinder
one other thing you may wish to consider
retarded ignition timing will reduce chamber temp but increase exhaust temp
advanced ignition timing will increase chamber temp but lower exhaust temp
it is possible for the timing to be incorrect from one cylinder to the other
it would also be somewhat possible for one side to have it's valves opening much more than the other
so checking both valve adjustment clearance, as well as max lift at least, wouldn't be a bad idea
maybe somebody ran one side loose and ended up knocking a lobe or two down
will you need a "qualified mechanic" ???
that depends on you, these things are about as simple as any
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Re: hot cylinder
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- Posts: 59
- Joined: Fri Oct 27, 2006 3:00 am
hot cylinder
"I like new stuff... especially after it gets old"
- Bruce Frey
- Posts: 536
- Joined: Fri Oct 27, 2006 3:00 am
hot cylinder
If you have one cylinder that does not warm up as quickly as the other or runs cooler, try swapping the plugs wires and caps from one side to the other.
Do a compression test.
If the compression is close to the same in both cylinders and the plugs, wires and caps do not make a difference, I think you are down to carbs or differential timing.
Good luck,
Bruce
hot cylinder
After reading the manual and looking at the spark plugs. the left side was grey in color and the right side was black. ( I dont know if that helps.)
I replaced the plugs. cleaned the carbs. replaced the gaskets. tried to tune in the carbs.( much better idle after that) but still the left side seemed to heat up faster and hotter than the right.
I also think the previous owner was running with no air filter. since it took me over an hour to dislodge the cover, which was rusted shut. and no filter.
I dont know if this will require a qualified mechanic, or if this is something I may be able to fix myself or if this is normal. I knew the engine would get hot tuning the carbs since we were stationary, and air cooled is air cooled, it just didnt seem correct.
This is a new realm for me, so please forgive my ignorance.
Any help would be greatly appreciated.
Thank you. bewildered BMW in mass.
a.k.a Kevin.