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Performance downgrade?

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Hi all,

 

I have recently purchased a 2003 CRF150F for my son. I suspect that there have been a number of improvements made by the previous owner. Among them are a new exhaust pipe, 26mm carb upgrade (up from 24), performance cam, 175cc big bore kit (probably, I found paperwork).

 

I haven't been able to get the thing to run at all with the choke fully open, the engine bogs when coming on the throttle quickly, and there is a lot of popping through the exhaust on deceleration while in gear.

 

All of this adds up to a pretty finicky bike for a rider that is just learning. Plus, we meant for this to be a trail bike, not a racer. I'd like to go back to the more docile factory setup. I have all the original parts, but wonder if the bigger piston that is installed will cause trouble if everything else (except exhaust) is returned to stock.

 

Thanks 

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choke fully open

 

Not to forget:

 

Choke lever up = choke on = cold start

Choke lever down = choke off = ride setting

 

 

:ride:

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Sounds like a clogged idle jet possibly?

Has the bike been sitting before you got it?

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A good carb cleaning should help. Even with all the performance stuff done on this bike it should be pretty docile if running correctly.

You could swap back to the 24mm carb if you get the correct jetting specs for it.

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Conn110,

 

It appears nobody mentioned the exhaust.  If there is an air leak in the carb or exhaust, that would throw off the carb settings and that could create your issue.  Do all the carb things everyone mentioned above, but first make sure the exhaust doesn't have any air leaks.

 

Now that doesn't mean to wrench that thing down as hard as you can.  Brains over muscle here.  Where the header exhaust enters the engine, it's supposed to have a hollow copper ring.  It's a $2 part and it's a one time part.  If you change the exhaust, you are supposed to install a new one.  I bought a bunch of them so I'd always have one.

 

Then there's the area where the exhaust header meets the silencer.  I use silicone from your local auto shop to seal that.  It's messy, but I'd recommend to add some of that.  Now that end of the bike should be good.

 

P.S.  No need to go back to the stock pipe for this issue.  

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Conn110,

It appears nobody mentioned the exhaust. If there is an air leak in the carb or exhaust, that would throw off the carb settings and that could create your issue. Do all the carb things everyone mentioned above, but first make sure the exhaust doesn't have any air leaks.

Now that doesn't mean to wrench that thing down as hard as you can. Brains over muscle here. Where the header exhaust enters the engine, it's supposed to have a hollow copper ring. It's a $2 part and it's a one time part. If you change the exhaust, you are supposed to install a new one. I bought a bunch of them so I'd always have one.

Then there's the area where the exhaust header meets the silencer. I use silicone from your local auto shop to seal that. It's messy, but I'd recommend to add some of that. Now that end of the bike should be good.

P.S. No need to go back to the stock pipe for this issue.

But the stock pipe will be much quieter and will not take away or change performance in any way.

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