Sounds a bit choppy

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klapool

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Aug 29, 2011
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This is a new 66cc on the kids stingray. He said that while he was going down the road it started to slow down a bit and then it really started to pull.

I know this is a big no no with a brand new engine he was just to excited.

What do you think?

http://youtu.be/78eTt8zf9mU
 
Last edited:
Greg58

Greg58

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May 1, 2011
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Doesn't sound too bad for a new engine, which notch on the needle do you have the e-clip? The leanest is the top groove, if it runs fairly good I would run a couple of tanks of 24/1 mix then switch to 32/1 or maybe 40/1 with synthetic. The more time you get on it the better it will run.
 
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klapool

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Aug 29, 2011
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Wisconsin
Greg58 said:
Doesn't sound too bad for a new engine, which notch on the needle do you have the e-clip? The leanest is the top groove, if it runs fairly good I would run a couple of tanks of 24/1 mix then switch to 32/1 or maybe 40/1 with synthetic. The more time you get on it the better it will run.
Click to expand...
I never messed with the "E" clip and never looked at it. I'll look at it tomorrow and see which setting its on.

Thanks for the info! even though Ive done 3 bikes I still feel like a newby and dont know what Im doing!!!
 
tooljunkie

tooljunkie

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Apr 4, 2012
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yup,one notch up on the needle lowers it a little more into the jet,leans out the less than wide open part.
the lad is gonna have a blast.aggrivating the neighbours,lol.
 
2door

2door

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Sep 15, 2008
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It could be running a little lean due to a lacl of back pressure (no muffler)
You really might want to explore a quieter exhaust system. The little guy might like it but I can guarantee that someone in your neighborhood eventually won't. I think you'll find that the engine will perform better and you won't make any enemies.

Good looking build however and I'm proud of you for having him wear a helmet. Congratulations on a successful build and a father/son project.

Tom
 
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klapool

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Aug 29, 2011
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Wisconsin
I am kind of wondering if that might be the cause of the choppyness sound.

Someone posted on the you tube video that the bike was not missing but 4 stroking.

I found this video and it sounds the same.

http://www.youtube.com/watch?v=0wzph3hL6EE


So how do i stop the 4 stroking? do i fab a different muffler? I have the short stock muffler. looks like the same muffler that came with the 49cc kits but only about 5 inches long.

Would fabbing an expansion chamber help? or opening the intake to get more air?

Any ideas would surely help!!!!
 
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cmanns

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Jul 1, 2012
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Santa Cruz, California
Did you run stock exhaust before doing the custom one?

Put the stock muffler on would be my suggestion, see how it runs. If it runs a lot worse, the backpuressure is keeping the a/f mixture in, and its too much. So then tune your carb alil, then pop your other exhaust on. or start straight with the carb.

but yoru exhaust could also be causing a lean mixture, 4 stroking is sometimes too much fuel, not enough air (choke) can cause it as how the guy did it in the video.
 
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klapool

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Aug 29, 2011
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I didnt run the stock exhaust due to fitment issues. This was the reason I built the exhaust. What I will try is to build a exhaust pipe that is the same size as the stock and weld the stock muffler in place.

I noticed the exhaust port is about 1.5" X 3/4" but the exhaust flange has a 1/2" hole to the exhaust pipe. What happens if a flange is built to the dimensions of the exhaust port???
 
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cmanns

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Jul 1, 2012
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Santa Cruz, California
klapool said:
I didnt run the stock exhaust due to fitment issues. This was the reason I built the exhaust. What I will try is to build a exhaust pipe that is the same size as the stock and weld the stock muffler in place.

I noticed the exhaust port is about 1.5" X 3/4" but the exhaust flange has a 1/2" hole to the exhaust pipe. What happens if a flange is built to the dimensions of the exhaust port???
Click to expand...

Ah ok def try that, and yesyou can match the flanges that's fine, I'd put the muffler up close, then run th elong pipe you got off the muffler. Should help keep you more near stock flowability so you're not chasing an issue caused by near straight exhaust. My 2 stroke 33cc will barely run when the mufflers just a tad loose from the a/f mixture escaping out the exh port :)
 
Greg58

Greg58

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May 1, 2011
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All the parts I used were scrap conveyor roller parts, the muffler is half of a1.9 x 20 roller shell. The head pipe is 3/4 emt.
 
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