Can't seem to get much power out of my new 2 stroke.

OhLongJonson

New Member
Jan 19, 2020
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First time builder here. So I bought an un-upgraded chinagirl kit off gasbike.net and they advertise that the bike will go 25-35 mph. Im using the suggested ratio for the break-in period(16:1) and I never moved the clip that's on the needle in the carb. I'm still in the break-in period (only 20 miles at most) but I feel like I should be getting more power. I seem to go 15, maybe a little less than 20mph at best, but i certainly cant reach 25-35, even on a long stretch of flat road.

One thing to note; I had to put the top head on the motor and when doing so, I accidentally pulled the piston out of the top head. I had to carefully align the rings and I made sure the hole in the piston was aligned with the holes in the motor. There is an arrow on top of the piston and I'm not sure if it has any significance, so it's possible I didn't install it correctly. I'm thinking my chain tensioner might also be an issue because it seems to be too close to the sprocket because I've never seen another bike that has a chain tensioner wrap about 75% of the sprocket in chain.

Here's the kit. Thanks in advance, guys.

https://www.gasbike.net/products/silver-slant-66cc-80cc-bicycle-engine-kit
 

OhLongJonson

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Jan 19, 2020
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So I used a GPS speedometer that's very accurate. It said my top speed was 17mph while going slightly downhill for a few hundred feet. I bought an NGK B6HS spark plug and didn't see any noticeable difference.
 

BrandFord2140

New Member
Oct 19, 2019
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Just something I found out sometimes the CDI may not be working correctly if you want to try something buy another CDI like the one you have and put it on it might help I'm not sure I'm kind of in the same boat as you but been riding for about 7 months now
 

Greg58

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May 1, 2011
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Welcome to the forum, the first thing I would do is change the fuel ratio to 24/1, that's plenty of oil for break in. There are several things you can do to get more speed, most stock exhaust pipes are very restricted, improved muffler will help. Move the clip up to lean and down to richen the mixture up to mid range, after mid throttle the main jet controls the mixture.
 

gill vanderwerf

Active Member
Sep 9, 2019
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i had the same issue but trust me it will get better it takes a while to break in motor mine is now running great after putting about 250+ miles on it.
 

OhLongJonson

New Member
Jan 19, 2020
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Welcome to the forum, the first thing I would do is change the fuel ratio to 24/1, that's plenty of oil for break in. There are several things you can do to get more speed, most stock exhaust pipes are very restricted, improved muffler will help. Move the clip up to lean and down to richen the mixture up to mid range, after mid throttle the main jet controls the mixture.
I just found out that the arrow on the piston is supposed to face front, toward the exaust. I'm gonna turn that around and move the clip. I'll let ya know what happens. Could it also be a possible air leak? If so, should I put rtv gasket maker on all the joined parts(exhaust, carb, motor)?
 

Goergedave

Member
Oct 23, 2015
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I just found out that the arrow on the piston is supposed to face front, toward the exaust. I'm gonna turn that around and move the clip. I'll let ya know what happens. Could it also be a possible air leak? If so, should I put rtv gasket maker on all the joined parts(exhaust, carb, motor)?
I Think you may be expecting too much too soon from this young Chinagirl. She has not yet had time to mature and as such will have reduced speed. I didn't add a speedometer(69) to my phone until I had had the bike for maybe 2 weeks or so. I'm still seeing speed increases over the same 2 mile stretch of road. I started with a top speed of 28mph and now it's up to 35mph. And I've yet to go WOT the entire trip.
I agree with the air leak and would reseat my gaskets. I did that and also changed my carb from one NT to another NT spare and that solved my lower speed issue. Oh, try choking a little more and a little more because when my engine had a leak, power was be restored by lifting that little lever. When it was wide open it seemed to be suffocating and the sound from the muffler was all wrong. I also adjusted the arms on the float down a little. I also changed out my fuel line, petcock filter and fuel filter. Sledge met fly.
 

OhLongJonson

New Member
Jan 19, 2020
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I Think you may be expecting too much too soon from this young Chinagirl. She has not yet had time to mature and as such will have reduced speed. I didn't add a speedometer(69) to my phone until I had had the bike for maybe 2 weeks or so. I'm still seeing speed increases over the same 2 mile stretch of road. I started with a top speed of 28mph and now it's up to 35mph. And I've yet to go WOT the entire trip.
I agree with the air leak and would reseat my gaskets. I did that and also changed my carb from one NT to another NT spare and that solved my lower speed issue. Oh, try choking a little more and a little more because when my engine had a leak, power was be restored by lifting that little lever. When it was wide open it seemed to be suffocating and the sound from the muffler was all wrong. I also adjusted the arms on the float down a little. I also changed out my fuel line, petcock filter and fuel filter. Sledge met fly.
Thanks for the info! I'll try that out and give it some time to mature before i start buying a bunch of performance parts. Lol
 

Greg58

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May 1, 2011
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It’s always a good idea to check the head for flatness if you remove it, I tape sandpaper to a flat surface and sand the head in a circular motion. This will improve power if you had a uneven surface.
 

Venice Motor Bikes

Custom Builder / Dealer/Los Angeles
Mar 20, 2008
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Los Angeles, CA.
I think your problem is that something isn't installed correctly (& you should also use 32:1 for oil mixture).

I agree with Greg58... don't worry about the arrow, (the piston ring ends just need to be towards the rear of the engine), & also, if you didn't use a torque wrench to tighten down the head, It might be warped from over torquing. (sand it flat & torque it to 12 ft/lbs)
 

Ralph hop

Well-Known Member
Nov 14, 2019
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rtv silicone will desolve in gas, there is a case sealant made for chainsaws if you need a sealer.
 

Ralph hop

Well-Known Member
Nov 14, 2019
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Only use sealer on the case halves if needed. Gaskets everywhere else and an o-ring where the inside of the carb meets the intake. Make sure to seal up the magneto case with something also.
 

OhLongJonson

New Member
Jan 19, 2020
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So I bought a spring loaded chain tensioner that mounts to the clutch case. When taking one of the bolts out, a nut dropped out and it was covered in oil. Where does this go?
 

Greg58

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May 1, 2011
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It goes on the top rear bolt which is longer, that bolt goes through the case and the jam nut helps keep it from loosening. The nut will be on the outside of the case.
 
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OhLongJonson

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Jan 19, 2020
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It goes on the top rear bolt which is longer, that bolt goes through the case and the jam nut helps keep it from loosening. The nut will be on the outside of the case.
Hmmm. Still can't find where the nut goes. Would you happen to have a link to a diagram or video? Sorry. Im completely new to this and i cant find any comprehensive video on youtube.
 

Homer J.

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Feb 5, 2020
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If you are running the stock cdi coil the spark plug wire (at least on mine ) was garbage...I replaced mine with a Briggs coil wire and ran great. I did a bunch of research and apparently it's an issue with these Chinese kits...hope in some way this helps.