Rough running

monkeybikegirl · Post by **monkeybikegirl** » Sun Jan 28, 2018 11:10 pm

Thanks for the tips. The weird thing is that it was running great and then a quick stop and it was acting up. No change other then stopping the bike and starting it up 10 minutes later. Well till the next weekend.

Twocams · Post by **Twocams** » Mon Jan 29, 2018 12:39 am

Are you using a good premium grade gas. If it has ethanol in your gas you may have to much water to run right. When I have to use ethanol gas I use an additive.

twocams

monkeybikegirl · Post by **monkeybikegirl** » Mon Jan 29, 2018 10:36 am

94 Octane from Chevron is the best I can get here in BC.

monkeybikegirl · Post by **monkeybikegirl** » Sat Feb 03, 2018 5:59 pm

I just replaced the conderser. It had no effect. It seems that it is only running on one cyclinder or just barely on one side.

Carott · Post by **Carott** » Sun Feb 04, 2018 10:44 am

A simple test to determine if you have a fuel problem or a spark problem is to connect a timing light and look at the light as the bike runs. Switch the pickup between plug wires to check both cylinders. If the light flashes continuously when the motor stumbles it is likely a fuel problem. If the light flashes intermittently or not at all you have an ignition issue and comparing the two sides can further help the diagnosis. The timing light gives a nice bright light to check for spark and provides information while the engine is running.

Good Luck

Brett

khittner · Post by **khittner** » Sun Feb 04, 2018 11:40 am

Not to throw parts at it, but if your spark plug leads/caps are older, they lose resistance and cause rough running. Not sure that it explains your symptoms' sudden onset, but I'd check them. Snowbum's treatises will have the correct resistance spec for that vintage; I'm pretty sure that the 5K ohms resistance that's necessary for my post-'81 electronic ignition bike is too high for the /6 bikes.

monkeybikegirl · Post by **monkeybikegirl** » Sun Feb 04, 2018 1:46 pm

I will try that, thanks.

monkeybikegirl · Post by **monkeybikegirl** » Sun Feb 04, 2018 1:52 pm

I believe the wires and caps are new. It wont hurt to check though. This bike was sitting for over 30 years and only has about 3000 miles on it. the major overhaul was done by a mechanic I trust, but he lives an expensive ferry ride away. I also need to learn to do this myself. I am encouraged by my success with an old r69, but the r90s seems more complicated so far.

monkeybikegirl · Post by **monkeybikegirl** » Sun Feb 04, 2018 11:19 pm

Getting closer to the problem. I checked spark from the plugs and one was not sparking as much. New plug which seems to have failed. Bike started much better and ran better after replacing the plugs with the older ones I still had around the shop.. I was able to take it for a ride and it runs great, except when starting out it bogs a bit and needs to be reved higher to get going. It does not do this all the time either. I will test the spark further this week.

monkeybikegirl · Post by **monkeybikegirl** » Wed Feb 07, 2018 7:10 pm

Back to the drawing board. Weak spark and rough running again. At least I know now which direction I have go in.

Vintage BMW Motorcycle Owners

Rough running

Thanks for the tips. The

Are you using a good premium

94 Octane from Chevron is the

I just replaced the

Ignition or Carburetor Problem?

Not to throw parts at it, but

I will try that, thanks.

I believe the wires and caps

Getting closer to the

Back to the drawing board.