# 2-stroke bogging under WOT under full load



## michaelrlitt (Jun 6, 2008)

Hello, 

I'm new to this forum. I've used the search bar but have come to the conclusion that my problem is fairly unique.

A friend gave me a no name 23cc 2-stroke scooter.

At one point, he pulled off the muffler and used a dremmel tool to remove the restricting ring and that sound deadening mesh.

When I initially start the scooter, it runs fine under WOT. I take it to the end of the street and it starts to bog only when it's pinned. If I keep it pinned it will eventually die. 

I replaced the rubber gaskets (I assumed some kind of air leak) and flushed out the fuel lines. It appears as if the engine is running lean in the high end when warm (Engine seems to get overly hot).

So I assumed some issue with jetting. Why does this only happen when the engine is warm? The carb doesn't appear to have any mixture adjustment screws. 

When I pull the starter slowly it seems to be holding good compression.

Any ideas? I don't have manufacturer name or anything as it's a tad old. I use this scooter to get to work daily and I'm starting to pull my hair in frustration.

Thanks!

Michael


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## 30yearTech (Sep 14, 2006)

may have a small air leak, I would check the crankshaft seals to see if either one looks wet, if so this could be a leak that can possibly be the cause of your problem.


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## geogrubb (Jul 28, 2006)

While it is running spray some carb cleaner along all mating surfaces to see if the engine changes tempo, if it does you have found a leak. Have a good one. Geo


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## michaelrlitt (Jun 6, 2008)

Thanks guys!

Looks like this actually is the issue. 

What are your recommendations for an easy DIY fix?

Thanks again!

Mike


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## 30yearTech (Sep 14, 2006)

If it's an air leak causing your problem, then you have to determine where the leak is. One of the best, is the way geo described in his post.


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## michaelrlitt (Jun 6, 2008)

It's really intermittent which leads me to believe that it's a jetting issue.

Since there is no adjustment on my carb, I'll have to pull it apart and clean it all up, or get some new jets I suppose.


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## MrLarkins (Jun 16, 2008)

I am having this same issue (I think). My 80cc 2 cycle is strapped on my mountain bike. 

It starts easy, idles easy, and accelerates easy. When I get to the higher RPM's, it starts to bog down and won't accelerate no matter how much more gas is given.

If I use geo's method of finding an air leak, do I rev the motor to the trouble RPM and then spray the carb cleaner? or will his techique work when idling?


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## COMP (Jun 11, 2008)

MrLarkins said:


> I am having this same issue (I think). My 80cc 2 cycle is strapped on my mountain bike.
> 
> It starts easy, idles easy, and accelerates easy. When I get to the higher RPM's, it starts to bog down and won't accelerate no matter how much more gas is given.
> 
> If I use geo's method of finding an air leak, do I rev the motor to the trouble RPM and then spray the carb cleaner? or will his techique work when idling?


yes but be real carefull ,, 2 cycle's can scare a cky wall also fire,,,,could the ex. be clogged ?


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## MrLarkins (Jun 16, 2008)

I washed the muffler out with gasoline and let it completely dry, it had no effect on the problem.

I will go buy a new spark plug and replace the current plug (which only has a few hours of usage), but it is chinese, so you never know. :freak:


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## COMP (Jun 11, 2008)

MrLarkins said:


> I washed the muffler out with gasoline and let it completely dry, it had no effect on the problem.
> 
> I will go buy a new spark plug and replace the current plug (which only has a few hours of usage), but it is chinese, so you never know. :freak:


hmmmmmmm have you tried to add a little choke at RPM to see if its a lean problem ?


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## MrLarkins (Jun 16, 2008)

I do not have an air leak. I tried Geo's method, and nothing.

I have replaced the spark plug, and verified its gap.
I have cleaned the air filter.
I have cleaned the carborater and verified proper working.
I have replace the plug cap.
I have remixed and verified proper mixture of gas/oil (30:1).
I have 'bogged' it down in high rpm and applied a bit of choke, and it killed the moter and almost threw me over the handle bars. (I won't be doing that again!)

I have noticed that there is a massive vibration right before it bogs down. Once the vibration subsides (from lower rpm's), it will respond with a speed up in rpm.

Could the vibration be causing my problem? What could have come loose inside the motor?


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## COMP (Jun 11, 2008)

MrLarkins said:


> I do not have an air leak. I tried Geo's method, and nothing.
> 
> I have replaced the spark plug, and verified its gap.
> I have cleaned the air filter.
> ...



does your carb have a check-ball in it to act as a RPM limiter ,,i have seen those ??


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## mopar4u (Jul 14, 2006)

Did it ever run correctly after this was done?

"At one point, he pulled off the muffler and used a dremmel tool to remove the restricting ring and that sound deadening mesh."

I'm guessing your 2 stroke may be running lean at top end do to the modification to the muffler. From your description it almost sounds like the muffler has been gutted. Exhaust can play a critical role in the performance of 2 strokes.


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