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2 stroke tuning issues... Please help

Joined
Jul 21, 2007
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#1
I have a 2001 CR 125 and it’s not running well. The bottom 1/4 to 1/2 of the throttle runs like a champ. When I get on it trying to accelerate and pull to over half throttle instead of screaming like it should zzzaaaAAAAAAAA...

I get a zzzaaaa..aaa..aa..aaa..aa..aaa like it is cutting out and it never really reaches it's top end. This is my first dirt bike so I’m relatively new to tuning these things, but I was thinking this meant it was running to rich? So I should try a smaller main jet (larger main juet number) and/or moving the needle clip position up. Any other thoughts or suggestions?

Thanks.
 
Joined
Jun 20, 2007
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#2
hi, i think the first thing you should do is cleaning your carb and filter (if you do not)...
and yes, try a bigger main jet, should cure the problem...
if not, may be a weak ignition- try to get the gap of the spark plug a little closer.....
 

BSWIFT

Sponsoring Member<BR>Club Moderator
N. Texas SP
Joined
Nov 25, 1999
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#3
Several possibilities. As stated, insure that your air filter is clean and oiled. Clean the carb and insure that it is seated properly when you remount it on the bike.
Jetting is the most likely issue but you may have a gunked up power valve or acutator mechanism. Do a search in the CR/KX/RM/YZ forum under honda power valve. Also read the jetting thread that is at the top of that forum.
The best thing about doing the search and troubleshooting this issue is how much you will understand your bike when it is done. It sometimes helps not to search real specific, eg:2001 CR 125 power valve. General searches bring up lots of information that is very helpful but not model specific. If you find an old thread that has more info but doesn't address your problem exactly, post in that thread and it will be bumped to the top of the forum. Other members can review the thread and likely narrow down your problem quickly because you have eleminated other possible issues.
I've been on this board for many years and have learned a great deal in general about bikes but specifics are more related to yz's. A few searches will reveal tons of info and lots of insight. Good luck.