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Post by paydem on Aug 18, 2019 8:28:40 GMT -5
minarelli horizontal 70cc air-cooled engine. when the top end was new it would max out at about 50mph. now it barely tops out at 43mph when the engine is relatively cold, and about 38mph when hot. I guess it's because I need a new piston.
Other problem which I couldn't figure out is, when I lift the wheel off the ground, and give it full throttle, the engine tops out at about 7000rpm (when top rpm should be around 10k), it other words, starts trailing, sounds like it cuts ignition (and at the moment when it cuts ignition, it puffs out smoke out of the exhaust) which I guess is unburnt fuel.
I've changed the ignition coil, spark plug, and the problem is still there. I would love to know if it's electrical or I need a top end refresh. Opinions?
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Post by geoffh on Aug 18, 2019 15:20:52 GMT -5
Errmkk,are you sure it,s engine related ?it could be the CVT overheating ?
Geoff
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Post by paydem on Aug 19, 2019 9:37:41 GMT -5
Errmkk,are you sure it,s engine related ?it could be the CVT overheating ? Geoff I'm pretty sure it's the engine. And when the engine is cold, it starts first kick everytime, but when it's hot I have to give it full throttle and kick it a few times to start it (doesn't matter how I set up the carb) so I guess it's the lack of compression. But why it wouldn't build rpm's is unknown. |
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Post by paydem on Aug 21, 2019 14:15:33 GMT -5
Weird. Went today on a ride, it was a cold day. Could go WOT for as much as I wanted, the engine ran fine and didn't "misfire" - built rpm's all the way. I guess it's carburetor's settings that I got wrong, correct?
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Post by geoffh on Aug 21, 2019 14:52:30 GMT -5
That,s you sorted,no more summer rides though!!
Geoff
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Post by paydem on Aug 22, 2019 13:01:08 GMT -5
Changed main jet from 90 to 80. Top speed increased, rpm's now build all the way. Only at about top speed (50mph) it starts cutting down when I give it full throttle. I guess dropping down main jet size would help, but I don't have different jets. And yes, tuning that way will probably seize the piston, though I don't really care
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Post by 190mech on Aug 22, 2019 17:34:57 GMT -5
I have a CDI box that signs off at 6900 rpm in my pile,perhaps yours is restricted also?
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Post by paydem on Aug 24, 2019 10:49:51 GMT -5
I have a CDI box that signs off at 6900 rpm in my pile,perhaps yours is restricted also? No, mine's not restricted. My only good guess as to what's happening is that my case is not hermetic (or leak-proof), because I've dropped the main jet by 10 and it still is rich up top. Probably crank seals, which I've installed, are leaking pressure and forcing a rich-mixture. |
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