Stock jeting and race fuel

I pulled my plug a while ago and it was sheet white. I am running 110 octane low lead (76 brand). I was runing the stock jetting (03 bike). Looks way to lean to me but it seems to run great. Changed the pilot jet to 45 (42 stock) main jet from a 170 to a 172 and put the needle in the 5th position (4th stock). After that it idles like crap and died when I gassed it so I went back to stock on the pilot. Everything seems ok now but havent ridden it yet. I know the "proper" way to jet your bike by reading the plug is to kill the engine and pull the clutch at different trottle settings then pull the plug and take a reading but no way am I going to take my tank off on the side of the track to check my plug.

Anyone else have to richen their bike up when running race gas?

I run VP with stock jetting and have had no problems. Whats your elavation and average temperature where you ride?


Im at about 400-500 feet (at track locations) and it has been 60-70 deg.

Your elevation may be a factor, I run at 2500 feet .


I run 1/2 110 76 and 1/2 91 pump. I have had no jetting problems at 1000 Ft

Leaded fuels leave white deposits more so than unleaded fuels. You need to do some research on the oxygen content and specific gravity, etc. of the fuel your trying to use. Some race gas requires leaner jetting, while some (oxygenated fuels) require richer jetting. Four-strokes are better jetted from feel than plug color anyway. Go a little richer or leaner and decide for yourself wether or not it was better or worse. Very simple, but time consuming. Oh yeah, don't forget that race fuels are each developed for very specific applications. They have varying burn rates and evaporation qualities that may work great for a high-compression engine turning 6,000 RPM, but work poorly at 11,000 RPM. Starting is also usually adversely affected, usually due to the evaporation rates. Tell me again why you want 110 octane race gas when most guys are happy with 92? Also, be sure your race gas is unleaded before you leftovers into your car or truck equipped with a catalytic converter. Lead will destroy them very quickly.


I am not running the race gas for the octane (that is just an extra) in my CRF. I am running it because it has lead and that cusions the valve seats and it is more consistant than pump gas. Cleaner too. I may just be wasting money but it gives me piece of mind.

Oh, and because my YZ250 will detonate if I run 92 so why not put it in both?


I wonder too if leaded fuel would extend the life of the Ti intake valves. I've got all of 1.5 hours on my '03, so I have no idea how mine are wearing. My '01 YZ250F required 1 adjustment in 15 hours of abuse, and my YZ400's never needed adjustment. Only time will tell. But think of it this way, would you rather buy 3 valves at $80 ea(YZF), or 2 at $40 ea(CRF). Parts cost were a deciding factor in my switch to Red. I can get Honda parts for 50% less than the equivalent Yamaha parts!


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