Bike has been sitting , appx. 1 yr. Replaced valves and gaskets , intake was bent , hit piston , probably over reved .. carb cleaned , tank , new plug , starts perfectly , runs well but has intermittint misfire . Tried different plug , same result .. spark plug gapped , spark tester jumps fire 1/4" or more but skips appx. 2500 - 3000. Rpm . Does small condensor have anything to do with this ???? Manual doesn't mention it .. Any thoughts ?????
ttr90. ignition
- Thread starter bweighmaster
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What I should have said , runs great at low speed and has good power but misses after 2500 3000. Rpm !,,
When I got my kids CR80 I was fairly sure there was no spark. It was recommended to clean/sand the coil ground/mounting bolt surfaces, and after I did that I had spark and it runs. Not sure if it really didn't have spark or if maybe I was out in too bright of sunlight to see a spark when I bought it, but after sanding down the mounting points it had spark and I knew I could eliminate that. So definitely eliminate that out of the equation, and all other possible problem areas.
All 4 strokes need 4 things to run; Compression, a combustible fuel mixture, spark, and ignition timing.
Probably wouldn't hurt to clean your carb again.
All 4 strokes need 4 things to run; Compression, a combustible fuel mixture, spark, and ignition timing.
Probably wouldn't hurt to clean your carb again.
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I've had problems like that with old lawn boy mowers , and other small engines . That jogs the memory , I'll try that . A proper ground sometimes makes all the difference . THanks ....
Is 1/4" gap all the coil can jump? If so that's pretty weak, you should have a good spark at 3/8 to maybe 1/2" gap.
It may jump more , thats just where my tester is set at , I have another that is appx. 1/2 " but pretty sure it will jump that also. ! also noticed that when it misfires it emits some black smoke . Won't hurt to re clean carb , already set slide needle to leanest setting , mabey float is leaking a little . Haven't worked on motorcycles much but have extensive experiance with small engines , weed eaters , chainsaws ect. I'll catch back up !!!
Ok, so the black smoke is a dead giveaway, sounds like zeroing in on the fuel system as you indicated would be a good direction.