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Old 08-20-2014, 02:22 AM
jerrywelz jerrywelz is offline
Motorized Bicycle Newbie
Join Date: Aug 2014
Location: California
Posts: 17
Default New Member, first build. 80cc china girl on a fixie

Hello everyone!

Here is a quick introduction, then onto the pictures =). I'm jeremiah, lived in southern California for most of my life. I spent four years traveling the world in the USAF doing fuel systems repair. I'm out now and currently working for the grocery store. this is my work commuter bicycle. 8 miles one way every day.

I bought a kent fixed gear from walmart for $120 and ordered the 80cc 44t china girl kit from ebay.

Originally i tried to run the 18t fixed gear and it barely ran. I had to pedal up the most minor of hill to keep the engine from stalling out. she was also four stroking badly all through the RPM's with the C clip on the leanest setting on the NT carb needle.

Couldn't get to work like this so i swapped the 44tooth and it was ride-able.

After i adjusting the float to the proper 21mm, opened up the obstructed steel intake and exhaust manifolds, she ran even better but was still four stroking.

I decided more oil would help with the overly rich engine. My understanding is that the main jet is too large and causes the engine to bog at almost all throttle settings. adding oil makes the fuel more dense therefore less can flow through the main jet leaning out the engine.

Anyways i mixed some 12:1 tcw3 and did some minor port work. i thinned out the transfer ports and took a few mm off the top of the exhaust. Also cleaned and slightly enlarged all the ports. in hindsight i probablly lost torque. I also polished the exhaust port and abraded the intake.

The bike ran so damn good like this until i crashed it. hit a curb head on and bent the frame and rear wheel. I decided to just get a new identical bike from Walmart because this is how i get to work.

Engine ran so good i decided to try the 18tooth again. the bike is slow off the start but can still climb hills. I hit 39 tonight on a small downhill road.

I need a permanent air filter solution and would like to jet smaller so i don't have to run sooo much oil.

I'd imagine the manic mechanic sprocket adapter with a 30tooth sprocket would be scary fast. thanks for reading guys. all input is appreciated. looking for tuning advice or tips. however i am constantly searching the forum and reading about areas i want to improve on and i', headed in the right direction =) thanks guys!
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