cb125 re-jet?

B

BeerRules420

666
went to a straight pipe and new air filter so i know i need to get a bigger main jet i'm just not sure how to go about this. is there anything i need to buy? a new needle? or do i just drill out the current jet a mm or so bigger? bike idles fine and runs good low, but theres just no power left even at 1/2 throttle. thx in advance.
 
Pipe is killing any chance of power, fit a long reverse cone silencer.
Start with a 105 main jet and work things out from there
Don't be drilling jets if you have no clue where your going ::)
 
ok ok i feel ya. in my service manual it says theres an 88 main jet. you suggest 105? to stick with the look i have going with the exhaust right now, could i just weld a big washer to the inside of the pipe to create more back pressure? or huge waste of time? totally crazy? stupid even? thx for the help.
 
Pipe length is the important thing.
Using just front pipe puts working range in the 15~18,000rpm range
You will still need about a 3/4"~1" hole in washer
you'll need about 10% bigger jet for 'pod' filter and a bit more for short open pipe.
I built a couple of 90+mph XL125's back in the day
 
Forgot to mention, (only just remembered , sorry) the XL's used a modified left carb from Suzuki GT250 two stroke twin
The stock Kei-Hin is a good carb though and will push 125 to 70+ (as long as you don't hit a headwind)
 
These engines HATE straight pipes and pods.
Buy a few different jets and see. No magic "install this" as there are way to many variables
Dont do things that decrease performance just for a look

Did the bike ever run right or did you "mod" it with no base line?
 
sorry my dog just posted that. but the bike didnt run when i got it. i opened it up and there was pieces of the piston missing and the valves were beat to hell etc. i rebuilt it and stripped everything off the bike in the process. it had also been wrecked before i got it so it was just ugly, which is why i decided to change so much. would it be in my best interest to just go back to the stock pipe? wish i could post a pic of it, alls i'm rockin is a flip fone tho.
 
BeerRules420 said:
when i got he bike it didnt run there was w324444444w
Click to expand...

You got lucky,the kitten usually manages to shut down computer for me (still haven't figured out how she can hit single key and shut down, usually takes a couple of mins for me, even when I hit power button it takes 5 sec????)
 
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