low speed miss

[koonta]

I've got an '83 that seems to run great when cold, but once it warms up it seems to drop a cyl.until you hit about 2500, then runs good, it seems to idle fine too. I've replaced the plugs and diaphragms. years ago I had a similar problem [i think] and it had a bad diaphragm. stumped now,think it might be valve adj? or electrical? If I just rev it up it sounds good, but on the road it doesn't matter how much I wash it, it looks like dung under 2500

[cimmer]

might want to check or just replace your plug wires and caps too if they havent been replaced. Plug wire could be back and not pass strong juice to the plugs when at low speeds. I know when I replaced mine, my low end response improved.

Just a thought.

Rick F.

[koonta]

Thanks, I checked the spark and it's yellow not blue, but they all were the same so I figured it was ok, maybe I figured wrong.

[jasonm.]

I've got an '83 that seems to run great when cold, but once it warms up it seems to drop a cyl.until you hit about 2500, then runs good, it seems to idle fine too. I've replaced the plugs and diaphragms. years ago I had a similar problem [i think] and it had a bad diaphragm. stumped now,think it might be valve adj? or electrical? If I just rev it up it sounds good, but on the road it doesn't matter how much I wash it, it looks like dung under 2500

Sounds like you have my issue. Warm and idling too long #3 drops out. But rev it for 5 seconds and it's good again. DO THIS TEST. Start it in the garage or driveway. Let it idle till it misses. Then listen for crackling or popping by the spark plug cap. When you think you found the one. Shade the area and use a long screwdriver against the head and slowly get it closer to the cap but still contacting the head. YOU NEED good 20/20 to see this. You will then see arcing from cap to screwdriver. NO your cap is not specifically bad. But that cylinder is likely rich for some reason. Float level too high or other oddity. Mine the cause to date has yet to be found. UPDATE: on mine I got another set of carbs and swapped #3 &4. Mine is now much better. I used to get a black spark plug when running non-hiway speeds. And the throttle was too sensetive. It was way rich. The 2 replacement carbs a a few new parts have seemed to get mine livable. Throttle is now linear. Next step is to EGA the bike at a local guy.

Edited June 27, 2010 by jasonm.