My left cylinder won't run. I've got new spark plug and it has a good
spark. Havn't done compression test but compression seems good when I
try to kick start it. Right cylinder runs fine and I can't seem any
diffrence between the two. Any ideas? Thanks.

(E-Mail Removed) wrote:
> My left cylinder won't run. I've got new spark plug and it has a good
> spark. Havn't done compression test but compression seems good when I
> try to kick start it. Right cylinder runs fine and I can't seem any
> diffrence between the two. Any ideas? Thanks.
>
A weak coil can show spark when the plug it out of the engine, but won't
muster enough energy to spark in the engine. I'd switch coils if
possible. Also do the usual such as check the carb for clogs, water in
the bowl, etc.

Here are speciality boards for BMW airheads. Check there too.

(E-Mail Removed) wrote:
> My left cylinder won't run. I've got new spark plug and it has a good
> spark. Havn't done compression test but compression seems good when I
> try to kick start it. Right cylinder runs fine and I can't seem any
> diffrence between the two. Any ideas? Thanks.

Does it start running on two cylinders when you open the throttle past
1/4 turn? Clean your carburetor out. Especially the idle jet...

(E-Mail Removed) wrote:
> My left cylinder won't run. I've got new spark plug and it has a good
> spark. Havn't done compression test but compression seems good when I
> try to kick start it. Right cylinder runs fine and I can't seem any
> diffrence between the two. Any ideas? Thanks.

You ought to be able to swap the spark leads. Both cylinders fire
on each upstroke, so it doesn't matter which lead you connect
to a plug. Leave them plugged into the coils, swap at the plugs
and see what happens.

You probably could do the same for the carbs as well.

I think you can be fairly certain that it's an ignition,
carburation or compression problem.

A couple of candidates on my suspects list would be plug wires,
punctured carb diaphragm, clogged jets or stripped crankcase
threads (cylinder studs). What work was been done to the
bike most recently before the problem turned up ?

Hey guys thanks for the advice. I tried switchin spark plug cables, no
diffences. I then took off the bottom of the carb float bowl and it
was prety disgusting. had lots of white junk in it (aluminum
oxidation?) . Well, i cleaned it out, and gave it another try. It
started up, and i suddentl noticed it was running on both cylinders.
Revs up fine but idling is rough. left cylender randomly shuts down and
comes back to life while idling.
I guess my next step is gonna be to just try to clean the carb. I've
had this bike since '76 and never touched the carbs. Anyone recomend a
place to find good isntructions for cleaning the carbs?

(E-Mail Removed) wrote:
> Hey guys thanks for the advice. I tried switchin spark plug cables, no
> diffences. I then took off the bottom of the carb float bowl and it
> was prety disgusting. had lots of white junk in it (aluminum
> oxidation?) . Well, i cleaned it out, and gave it another try. It
> started up, and i suddentl noticed it was running on both cylinders.
> Revs up fine but idling is rough. left cylender randomly shuts down and
> comes back to life while idling.
> I guess my next step is gonna be to just try to clean the carb. I've
> had this bike since '76 and never touched the carbs. Anyone recomend a
> place to find good isntructions for cleaning the carbs?
>

Here's a link to a generally good site. http://www.dansmc.com/carbs.htm.

Charles

Well guys, I got it working! I took the carb off and found more white
junk. So i sprayed the whole thing with carb cleaner and wd-40.
Sprayed wd-40 right throught the idle and main jets, took a tooth brush
and scubbed all the white junk out of the main passagway. Put it back
together and the bike runs great. I while ago my center stand broke
off so i have been using the side kick stand. I think that leaving
that bike tipped at an angle for so long caused the left carb to clog
up with all that white junk. Well, thanks for all the help.

(E-Mail Removed) wrote:

> together and the bike runs great. I while ago my center stand broke
> off so i have been using the side kick stand. I think that leaving
> that bike tipped at an angle for so long caused the left carb to clog
> up with all that white junk. Well, thanks for all the help.

I expect that the left carb rested lower than the right but that they
were both tipped at the same angle.

mad scientist wrote:

> Here's a link to a generally good site. http://www.dansmc.com/carbs.htm.
>
> Charles

http://www.dansmc.com/MC_repaircourse.htm

Hey, there's a lot of good stuff at that site. E.g. see the photos of
spark plugs at http://www.dansmc.com/spark_plugs/sp...s_catalog.html

Thanks!

(E-Mail Removed) wrote:
> Anyone recomend a
> place to find good isntructions for cleaning the carbs?

http://www.bingcarburetor.com/
http://www.airheads.org/old/index.php?Technical%20Tips
http://ibmwr.org/r-tech/airheads/index.shtml