2003 RM250 head mod

[02'Cr Rider]

Eric,

Whats your turn around time for head mods.I need to have it checked out.I have it running on Avgas but it still pings bad under load.I had the head milled .010 to tighten up the squish band and it works great, but I get some bad pinging in sand or big hill climbs.I think it need to reshaped or something.I can provide more info if you like.

Thanks,

 

[Eric Gorr]

Opening up the combustion chamber may not matter. The ignition maps on late model 250s are real aggressive and it can't even be compensated for by retarding the stator plate. Have you tried a richer needle or bigger power jet? That may be all you need. The power jet is active in the mid-range. Another potential problem is that the solenoid that drives the power jet may not be working. You can test it with a multi-tester, it should show 5VAC when the throttle position sensor clicks on at about 1/3 throttle. You can also remove the sub-frame, start the engine and just look to see that fuel squirts out of the jet when you roll on and off the throttle.
Remember AV gas is low octane (87-89MON) but the lead content should reduce detonation but maybe not enough. That fuel was made for 4-stroke engines that run at high altitude which also implies lower air density and cranking compression.

 

[02'Cr Rider]

Eric,

Now that you mention the power jet,I do recall leaning out the power jet awhile back ago per procircuit recommendations.I will check out the solenoid,and wiring as you described.Per your comments above, I will try them out and see what happens.Thanks for your time....