Author Topic: 90cc sport does not run :(  (Read 2250 times)

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90cc sport does not run :(
« on: April 11, 2011, 04:57:29 PM »
my bike will run only after being push started and only stays running if you keep it in high RPMs. I have cleaned the carb and the engine is getting spark and the timing seems to be correct and it is getting good compression. Do you think it could be the condenser or the points? Any suggestions?
« Last Edit: April 13, 2011, 02:40:32 AM by Sean1965 »

Dave K

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Re: 90cc sport does not run :(
« Reply #1 on: April 12, 2011, 11:04:38 AM »
If everything is clean like the carb. and the timing is correct. I would suspect either the crankcase seals and of course check the compression.

Offline reed

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Re: 90cc sport does not run :(
« Reply #2 on: April 12, 2011, 11:41:49 PM »
Remove the fly wheel and check the crankshaft seal and while you are there check  i if there is any up and down play on the
Crankshaft, if every thing is OK look at the points ,i had a baffle blocked in the exhaust the other day on a Yamaha i cleaned
It out and it ran well.

Offline old smokey

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Re: 90cc sport does not run :(
« Reply #3 on: April 13, 2011, 09:00:16 PM »
I don't know about the 90 carb, but that sounds like the same problems I had getting my Honda MB5 to run 2 years ago.
I had already cleaned the carb (or so I thought) and then an MB5 guru told me there was a small hole running thru the carb that had to be open.
Once I tried that it was up and running.
Do you get different (better results) if you try a shot of model airplane fuel in the carb (I use 15% nitro variety)?
'67 350 GTR undergoing repairs with a '75 Yamaha TX500 front end


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Re: 90cc sport does not run :(
« Reply #4 on: April 16, 2011, 01:24:03 AM »
I got it running once I realized the spark was inconsistent. Then I narrowed it down to the gap on the points. Thanks for the help.



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