Need help Jetting a 02 Yz250f

I have a 02 Yz250f and it won't rev past a 1/4 throttle and it starts popping. (Almost sounds like a false rev limiter)    The bike has a fmf mega bomb header, stock slip-on and a twin air  air filter. 

The jets that are in it are a 42-pilot jet, 178- main jet, 4th clip on the needle and a 72- jet.  

Just need some help figuring out what's wrong with it and what jet may need to be changed.

If the jetting you have now was ever working well, then the problem you have is not a jetting problem.

Check to see that the main jet has not fallen out....as it would do just that.

Your problem is most likely a jumped cam timing (if you have not changed the cam chain and tensioner in 15 years, this is to be expected), or a bad plug cap, plug wire, plug, or stator (arcing).

As stated, a bit more history on the bike is needed for us to help. What changed? Did you change something then the issues happened or is this just out of the blue issue?

I just picked the bike up not to long ago but when I got it it was doing this. 

 If the timing was a tooth off would it start up first or second kick?  

And could the pilot jet be to small?

Edited by YamiLife

Don't think it would be the pilot. Maybe the main or or needle location.

Sent from my SM-G900T using ThumperTalk mobile app

But my first guess would be spark.

Sent from my SM-G900T using ThumperTalk mobile app

On 8/6/2017 at 11:33 AM, YamiLife said:

I have a 02 Yz250f and it won't rev past a 1/4 throttle and it starts popping. (Almost sounds like a false rev limiter)    The bike has a fmf mega bomb header, stock slip-on and a twin air  air filter. 

The jets that are in it are a 42-pilot jet, 178- main jet, 4th clip on the needle and a 72- jet.  

Just need some help figuring out what's wrong with it and what jet may need to be changed.

The 72 jet is what? The starter jet? If the starter jet, leave that alone.

Perform a fuel screw adjustment:

 

Check the AP pump timing and leak jet size:

 

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