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Post by magoconnor on May 9, 2018 22:30:31 GMT -5
Hello. I'm trying to dial in my mean machine, but I've currently hit a road block tuning the carb. I've Checked for leaks, found none. The bike idles just fine. I've currently running with 115 main jet which seems a bit large for a 72cc with 18mm carb, don't you think? I've tried a whole range of jets: 90 MJ: Way too lean, could barely move. got a little better with some tape on the air fitler. 98 MJ: Better, well let's just say I could move now. still alot of popping in the exhaust. And the spark plug was bone white. 110 MJ: Better, but still no cake. Sort of the same story. Pictures: 115 MJ: The Best so far. Some hesitation upon accerleration. Top end could be better. Pictures: 120 MJ: The bike would idle just fine, but I could not touch the throttle without it just dying. A real headache.... I have never heard of a 72cc gy6 needing a 115 main jet or higher. What could be the cause? And what do you think I should do now? Could you tell what you think of the spark plugs ? lean/rich? MY Setup: Kymco super 8 (gy6) 72cc, Bvh 21in/19ex 47mm chamber Performance cam. Stock carb 18mm leovince exhaust Free flow cone filter with a 20 cm intake runner. Naraku high tension coil. Brand new spark plug ngk.
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Post by magoconnor on May 9, 2018 22:31:08 GMT -5
The first two pictures are of the 110 Mj. The second set are of the 115 Mj.
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Post by V90Performance on May 9, 2018 22:51:55 GMT -5
From experience, it's hard tuning with a open air filter. I always use the stock air box with the intake snorkel removed. It becomes very easy to tune that way.
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Post by magoconnor on May 9, 2018 22:58:23 GMT -5
I'm sorry to say I no longer have the stock airbox...
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Post by magoconnor on May 9, 2018 22:59:14 GMT -5
Is it not weird that it needs so high a main jet?
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Post by V90Performance on May 9, 2018 23:02:57 GMT -5
Is it not weird that it needs so high a main jet? Well it kinda is since my old 50mm bbk used a 95 with a open air filter andmy current 52.4mm bbk with a stock air filter uses a 108 jet.
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Post by magoconnor on May 9, 2018 23:03:39 GMT -5
Could it be the Bvh?
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Post by V90Performance on May 9, 2018 23:26:04 GMT -5
Yeah it is.
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derek420
Scoot Member
Ready to Ride!
Posts: 33
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Post by derek420 on May 10, 2018 0:25:05 GMT -5
Bad crank seals maybe? Leak don't is hidden behind engine cases makes most sense sometimes a bbk will blow them.
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Post by magoconnor on May 10, 2018 7:40:46 GMT -5
I really dont think there is any leaks. The bike idles just fine. But what do you think I should do?
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Post by magoconnor on May 10, 2018 7:41:17 GMT -5
What do you think about the spark plugs?
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Post by magoconnor on May 10, 2018 8:24:34 GMT -5
There is some hesitation when I accelerate, like its not getting enough air. Top end could be better, sometimes it feel like it has alot of torque other times not so much.
Well lets says it stumbles when I go 25% throttle. But if i go from stand still to full throttle, it walks right pass the bumpy part
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Post by benji on May 10, 2018 8:44:53 GMT -5
I really dont think there is any leaks. The bike idles just fine. But what do you think I should do? why don't you think it's got an airleak? Did you test it? Because it's acting like it has an airleak.
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Post by magoconnor on May 10, 2018 8:48:10 GMT -5
Yes I have tested it, I let it idle then sprayed carb cleaner all over with no drop in rpm.
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Post by scootnewb on May 10, 2018 9:35:22 GMT -5
What size is the pilot jet in your carb?
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