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Post by mrbensteele on Oct 5, 2021 15:03:50 GMT -5
Last year I rode my moped 40 miles through back roads with lots of unfriendly dirt roads, it performed well until I rode at max speed on paved roads.
My engine is 50cc modified to 70cc so it gets to a max of roughly 42 mph according to the gauge. Once it reaches between 35 and 42 mph it began to hiccup. Every time since its done the same and stutters but runs just fine 35 mph and under.
Recently I took my moped out for the first street trip this year, about 3 miles to the store not far and just like before it stuttered and hesitated once I reached max speed.
I've done some research and there seems to be several possible causes, clogged or gunked up carb, bad fuel, bad spark plug, oil, etc.
I sprayed the car with carb cleaner. My fuel is 91 super unleaded dosed with carb cleaner (recommended by a mechanic), oil was changed earlier this year, gear oil was changed a few weeks ago. Air intake is clean as is the air filter. Previous owner modified the air box to increase air flow as well.
I dont know much mechanically speaking about mopeds, just basic maintenance so if possible please be descriptive or link me to videos or resources.
Could the hiccups be the product of hitting max speeds and why? Have any of you experienced the same issue?
Any suggestions are welcome and appreciated,
Thanks.
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Post by 90GTVert on Oct 5, 2021 15:17:52 GMT -5
It's got a BBK and a modified airbox so my first thought is; has anyone made sure it has a good main jet in it? Test passes with different jets and recording results is how I do it. Could just be that the mix is off at high throttle openings.
If it's always the same speed/RPM, then there's a possibility that you are experiencing a speed/rev limiter. If speed and RPM vary when it happens, that's not likely what's up.
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Post by mrbensteele on Oct 5, 2021 15:26:45 GMT -5
I'll have to look into that, im not experienced in swapping jets. I will watch some videos to see what it entails. Thanks.
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Post by scooter7878 on Oct 5, 2021 21:39:18 GMT -5
Did the bike run well previously to the dirt road trip? Or was the bbk installed than only driven on the dirt road trip? Issues at wot are generally fuel related either wrong/clogged main jet or a fuel supply issue like the vacuum petcock or fuel filter or the carburetor float adjustment is incorrect and the bowl is not filling with enough fuel to supply at wot and ur running the bowl dry at wot. Or a limiter like said above. If it was running well for a long time before the dirt ride I'd just remove the air filter for shits and take a brief wot run if ur issue is gone it's something with the filter most likely unless it's new I'd try that to be sure it's not restricted from dust. But only take a breif rude as running with filter off it will be in the lean side so don't run long just enough to see if issue is gone or better
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