Idling problem

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Red Thunder
New Member
New Member
Posts: 13
Joined: Thu Apr 29, 2021 3:17 pm
Year: 2011
Color: red

Idling problem

Post by Red Thunder »

I just installed the Yuminashi 164 cc kit, piston ,cam, springs, and a 31mm throttle body with the 31mm intake and A type fuel injector, larger fuel line etc. All the parts from the Yuminashi Kit and suggested upgraded parts. STOCK 125 head and valves (ported the runners for both intake and exhaust. Just enough to take out the casting roughness and enlarge it to the gasket size. The bike starts and runs just fine under power. It will not idle below 15-20mph ( bike on the center stand not the ground ). It will only idle at lower speed if I manually give it gas by turning the throttle grip to keep it running. I have adjusted the idle screw on the throttle body and tried positioning the throttle cable. I am assuming the stock Idle Air Sensor is not calibrated for the larger 31mm throttle body. I tried the stock throttle body and manifold with better but similar results.
Is their any advice on getting a better idle? I put @ 18 miles on the bike while on the center stand ..making sure no leaks and it works like it should before I put all the body panels back on.
Red Thunder
New Member
New Member
Posts: 13
Joined: Thu Apr 29, 2021 3:17 pm
Year: 2011
Color: red

Re: Idling problem

Post by Red Thunder »

Well I figured it out. I took it for a ride and it felt like it lacked power so I figured the timing must be off a tooth. I re-set the timing and it solved the issue. Now it starts and idles fine and runs good. I am " breaking it in " so time will tell how well it actually performs. I have read a lot of the others 164cc conversions on here so hopefully it will perform as theirs did. I followed Maddie Dogs posts and it was smooth as could be to do the kit change. I also changed out the gears for a 15/45 and 54 tooth high gear from Yuminashi, Yuminashi Variator, 12 gram rollers, new belt, and speed sensor.
I had about 8000 miles on it before the build. I started noticing the top speed loosing about 3 or 4 mph so that's why I went ahead and did the rebuild.
I have had the parts sitting around sense 2017 and finally got around to swap everything. I have been reading this forum since about 2016 and finally decided to actually join. So thanks to all who post here your information is awesome a has helped me with my PCX.
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