Jump to content
Sign in to follow this  

07 yz265f Stroker

Recommended Posts

My daughter rides 07 yz250f, we recently put a Cylinder Works 265 kit with a Hot Rods Stroker Crank. I was wondering if there are any recomended jetting mods that could made to help with some idling problems. Maybe even run a mix of race gas and premium.

Share this post


Link to post
Share on other sites

No need for any fuel more than premium unless you experience pinging. Fuel (other than being fresh) has little bearing on idle. The correct pilot jet and fuel screw setting however does.

Fuel Screw/Pilot Jet

Fuel screw settings in the 'book' are recommended starting points. Every bike is different, as is the temp and altitude. Set the screw according to this method. Do it with the bike fully heated up.

Gently turn the screw all the way in. Now back it out two turns. Start the bike and fully warm it up, go for a 10 minute ride. Set the idle to speed to 1,500~1,800 RPM as best you can (I know, without a tach this is tough, just set it to were it idles relatively smoothly). Once warmed, slow the idle to the lowest possible speed.

*** When turning the fuel screw, keep an accurate 'count' of the amount you are turning it and record it in case you have to reset it for some reason. Makes life easier when you can just set it from notes Vs. going through the procedure again.***

Turn the screw in until the idle becomes rough or the bike stalls.

if it stalled, open the screw about 1/4 more turn. Restart it and slowly screw it in till you can just perceive a change.

If the screw can be turned all the way in and the bike still idles perfectly and does not stall, then you need to go down a size in pilot jet.

Now very slowly, open the fuel screw till the idle is smooth. Blip the throttle, let the bike return to an idle, wait say ten seconds. Confirm it is the same smooth idle.

If the screw has to be opened more than 3 turns to get a smooth idle, you need to go up a size in pilot jet.

If you find it does not stall with the larger jet but has to be open more than three turns with the smaller pilot jet, put the larger one in and set the fuel screw at 1/2 turn.

If the idle speed increased, adjust the idle speed knob to return the bike to a real slow idle speed. You must then re-visit the fuel screw. Keep doing this till the fuel screw is opened just enough to provide a nice steady idle at the lowest possible RPM. Once this is done, increase the idle speed to the normal one for your bike, typically about 1,800 rpm, but go by the spec in your manual.

I bet your current pilot is slightly clogged, Try a new jet (not just cleaned).

Share this post


Link to post
Share on other sites

a few years back i built a 08 250f yammie that was done in the stealth form.it was a 269.i used a cp piston with a comp ratio of 14:1.i ended up with this jetting,and it was done using renegade mx4 leaded/oxygenated fuel.main 165 pilot 45 leak 55.a red needle from jd jet kit in the 5th pos.also ran a filter cage from a 250 2stroke.good luck and keep us posted.

Share this post


Link to post
Share on other sites

what is the idle problem if the pilot circuit does not cure it check you plug for propper gap and consistent spark may be time for a new plug the longer stroke will make it more sensitive to the spark. If your not getting a complete burn every stroke then it will idle very rough and backfire a little simular to the symptoms of a lean pilot circuit.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×