Steve_o1989

Member
Apr 27, 2008
1
0
I bought a '07 CRF250R a couple of weeks ago. It has been a hard starter from the get go, and I get a bog when coming off idle. I checked the valves, and the intake is well within' spec, but the exhaust is a little tight.

I was suspecting jetting issues so I tore the carb out today to check. I have a 178main, 45 pilot, and 68 leak. I am unsure where the needle sits. The bike has a FMF factory 4.1 dual exhaust, but appears to be pretty stock aside from that.

To me, the main jet seems too big, the pilot is too big (fuel screw has no effect) and I am unsure of the leak.

I dont have a jetting chart, but where would be a good baseline to start off of? I want to go down to a 42 pilot, but I am not sure what to try for the main, or if I should touch the leak?

I ride at ~2000' elevation and 60-86*F

I will also change the plug, air filter and fluids.
 

_JOE_

~SPONSOR~
May 10, 2007
4,697
3
I would start by getting the pilot circuit dialed in. My 06 was really sensitive to weather conditions. A half turn can make the difference between the bike being easy to start and responsive or difficult to start and laggy. Mine liked a couple twists of throttle to prime it through the accelerator pump when cold. After years of tuning the bike I found that when it was set up properly you needed the choke/throttle to start it cold and hot start to start it if it stalled mid ride.

Some people run their exhaust valves on the tight side. They don't tend to tighten up nearly as often as the intakes. If they're below minimum spec go ahead and shim them. Be sure to check the valves every few hours for a little while until you know they're staying put.

Accelerator pump tuning can improve throttle response. I tried a few different setups. The o-ring or wire mod, shaved diaphragm rivet and a 45 (I believe) leak jet worked best for me. The timing is also critical and should be set to just miss the slide as it rises.
 
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