New Member, first build. 80cc china girl on a fixie

GoldenMotor.com

jerrywelz

New Member
Aug 20, 2014
17
0
0
California
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!
 

jerrywelz

New Member
Aug 20, 2014
17
0
0
California
few more pictures, shameless bump on the question about the mixture!

I am running a stock NT jet, SHA carb, banana pipe, 36 tooth sprocket mounted to the fix gear with the rag joint (solid).

the Bike four strokes pretty bad, always at top speed WOT and sometimes through all RPM ranges. Once the engine is warmed up it 2 strokes in the mid range and always when climbing hills.

I've got the Champion CJY7 plug with 2 washers on it so it doesn't contact the piston. tried running the b7hs and it ran poorly i don't think the NGK sits far enough in the combustion chamber.

i'm running 12:1 2 cycle sport oil by masterpro with 91 octane. the engine is broke in but if run less oil the bike will bog even worse. do i need a smaller jet to run a leaner oil fuel mix and not four stroke at WOT?






 

AssembleThis

New Member
May 11, 2014
163
0
0
NC United States
Hi jerrywelz!

Welcome to the forum. This is the third time I'm trying to post to your thread. System is acting funny like there's a hack program in your post. Never seen a post act this way.
Anyways, I would recommend reading others posts. I've learned tons of information by doing that and found most of my questions answered before I even asked them. Saved me a lot of time and aggravation doing so.
Question? Were you texting on the phone when you crashed your bike?
Also nice air filter, looks like a black panty hose.

Dave
AssembleThis

.duh.