head mods and pump gas on new bikes.

[Nevada Sixx]

ok,, i was on the other board talking about rm 250's in the woods, and someone said a 03 rm 250 needs race gas to run properly and that you have to have a head mod to run pump gas... i dont have access to race gas,, so is it really necessary to do the head mod for a new rm,, and what about a kdx?

it wouldnt be hard to send it off, but do i need to do it?

 

[luvtolean]

It was widely reported in the mags that the RM needs race fuel or risk pinging.

 

[luvtolean]

My 03 CR250 pinged on pump gas too with the stock jetting as well. Adding C12 to pump 50/50 cured the problem. I don't know if I could've jetted it away as I have decided to run race fuel and just jet to it anyway.

 

[Nevada Sixx]

will a simple head mod cure the pinging?

 

[luvtolean]

Originally posted by Nevada Sixx
will a simple head mod cure the pinging?

I dunno for sure, but I'm willing to wager Eric Gorr could help you out there.

 

[Studboy]

Or for a temporary fix you could go to a thicker head gasket or double up on them.

 

[Nevada Sixx]

does that mean the pinging is caused by high compression,, and high compression ignites the fuel too fast?

 

[marcusgunby]

Head mids will stop the problem.So will 2 head gaskets but its not as good a fix.

 

[cujet]

Have you tried octane booster? There are a couple of good ones available. I had success with ones that contain MMT. The use of super unleaded and booster with MMT often will be enough to eliminate mild detonation. I find adding booster as easy as mixing oil, and far less than the price of race gas.

Chris

 

[gwcrim]

I don't have any experience w/modifying 2 strokes but in a 4 stroke cylinder head mods sure do fight pinging. I know one shop that turns out 11:1 Harley heads that will run pump gas. Of course the ignition needs to be spot on.

What they do is machine the squish band to perfectly match the piston top and then set clearance around 0.032. I believe squish bands were first used in 2 strokes so this is probably a real easy fix.

 

[Studboy]

Cujet, MMT octane boost will cause serious deposits in your engine.

 

[Mxrracer973]

All I know is I dont run pump gas for the simple fact Ive almost blew up my new stock 03 yz125 the piston was so bad when I did a top end it pre detonated so bad I could have lost the whole cylinder now Ive started running 100 from rebel/76 with much better results . Also the guy that bought my old bike ran pump gas in it when I told him the cylinder and head had been worked and he melted the ring to the piston then started running c-12 again with good results .

 

[Chief]

My 01' RM250 needed race gas. Eric reduced the compression and it runs fine on amoco 93. It pinged badly before the mods.

Joe Chief