Bike stalls mid throttle

[bike man needs help]

Hi so I recently installed an expansion chamber and silencer on my 2 stroke motorized bike. I run stock jets and 32:1 fuel ratio. Ever since the first 20 minutes of riding it, the bike would jerk back as if it were to stall. However this would happen mid throttle when I'm going at decent speeds. I don't know if it has to do with the clutch, cdi or expansion chamber. It may be a carberator issue but it is strange considering the bike cuts power so aggressively. Anyone know or suspect what it might be? Thanks.

 

[DAMIEN1307]

Don't run it !!!...take the entire jug off of it and find out what broke, snapped off, or whatever...You should also take the bottom half of the motor off the bike as well, flush it several times and shake it up, etc. several times and maybe pour it out over some sort of screening to see what floats out in the way of metal...You got a problem here that needs to be found before doing further damage.

Also check the wrist pin, the C clips and the needle bearing on the crank to piston connection as well.

 

[bike man needs help]

After about 20 days of thinking. I finally took the jug off inspected the piston, rings, c clip, wrist pin, etc. It all seems fine but this is what I found:
- crank arm has about 1cm of side to side play
- the piston is able to move from side to side (not freely) in the area where the crank arm meets the piston.
- I used a magnet to pick up any debris in the crank case and found a very little amout of metal shavings (less than a pinch)
- the top of the piston has carbon deposits
- there are no gouges or scratch marks inside of the jug
- I keep my spark plugs hand tightened and head torqued snug and tight

Is it a head gasket issue? Crank/piston issue? What are your thoughts. Thanks and sorry for the long delay.

 

[Nickt919]

After about 20 days of thinking. I finally took the jug off inspected the piston, rings, c clip, wrist pin, etc. It all seems fine but this is what I found:
- crank arm has about 1cm of side to side play
- the piston is able to move from side to side (not freely) in the area where the crank arm meets the piston.
- I used a magnet to pick up any debris in the crank case and found a very little amout of metal shavings (less than a pinch)
- the top of the piston has carbon deposits
- there are no gouges or scratch marks inside of the jug
- I keep my spark plugs hand tightened and head torqued snug and tight

Is it a head gasket issue? Crank/piston issue? What are your thoughts. Thanks and sorry for the long delay.

All of the above seems like typical engine conditions to me....at least the free play on the rod top and bottom.

My guess is the expansion chamber/tune is the most likely culprit.

Try going richer on the needle....as in raising the needle or lowering the e-clip... and see if it helps.

Go richer and see if it helps any. If not..., you can always go back....

 

[bike man needs help]

All of the above seems like typical engine conditions to me....at least the free play on the rod top and bottom.

My guess is the expansion chamber/tune is the most likely culprit.

Try going richer on the needle....as in raising the needle or lowering the e-clip... and see if it helps.

Go richer and see if it helps any. If not..., you can always go back....

Alright thanks man. I'll try it out

 

[Whitewill1412]

After about 20 days of thinking. I finally took the jug off inspected the piston, rings, c clip, wrist pin, etc. It all seems fine but this is what I found:
- crank arm has about 1cm of side to side play
- the piston is able to move from side to side (not freely) in the area where the crank arm meets the piston.
- I used a magnet to pick up any debris in the crank case and found a very little amout of metal shavings (less than a pinch)
- the top of the piston has carbon deposits
- there are no gouges or scratch marks inside of the jug
- I keep my spark plugs hand tightened and head torqued snug and tight

Is it a head gasket issue? Crank/piston issue? What are your thoughts. Thanks and sorry for the long delay.

You don't use a wrench to tighten your spark plug?

 

[bike man needs help]

I dont have the specific wrench for spark plugs so I just use my hands lol

 

[Whitewill1412]

I dont have the specific wrench for spark plugs so I just use my hands lol

That can't be good