who owns or have owened a 1998 KX250

[iracekx]

To all that owns or has owned a 1998 KX 250. Did you run race gas a mix of race gas and super unleaded or just straight Super-unleaded? If you run just straight super unleaded what jetting did you end up using and where did you put the clip on the needle. I have been running race and super to get 100 octane so it does not detonate. I have pro circuit pipe and silencer and pro circuit told me to run race gas and put the clip up one position which is one from the top. I have done that and the bike has always run good the only time that I had fouled plugs was when I was first learning to ride it and getting use to the power. I am going broke buying race gas since I ride twice a week I go through quite a bit of gas. I just want to get some feedback what you guys did and where you started off. I rode it one time back in the day just on super unleaded since they where out of race gas and I thought I heard it detonating. I could be wrong I might be over paraniod about the sound just don't want to tear it up and have to put new crank because of stupidity. Thanks for your info and help

[FPMXer]

I haven't owend a KX250 yet. But in my other 2smokers I run 92 octane with my oil and have never had any spark plugs foul. I find that jetting down from stock on the main from a 160 to a 155 gave me the best power output. I bought a hand full of mains and pilots and just changed them out after every ride until I got the best power output and plug color. I have never heard detonation or pinging beyond the normal pinging of a 2smoker. I also haven't had the topend blow either.

[motodemon172]

i had a 1997 kx250 with pro curcuit cylinder and head porting,pipe and silencer.i tried unleaded 92 octane and fouled plugs.so i ran 110 octane vp and it was a little lean on top so i went up one on main and raised clip position one (rich in mid).plug always looked perfect and never fouled another one.very fast.if u run race fuel u probably wont foul plugs and it will run sweet.i know $$$$$.lol

[don46]

Race gas typically runs richer than pump gas, you should be able to LEAN your main jet rather than richen it. I had a 98 KX 250, don't remember what I ran for jets, had an FMF pipe and silencer. For practice I ran pump gas and 50/50 pump and race gas on race day. Never fouled plugs or heard any detonation. The 98 was one of the most powerful 250's kawi built, in fact until probably 05 it had the meanest motor of all the kx 250's. Throw a Wiesco flat top piston and head combination and you've got a real animal.

[iracekx]

Originally Posted by don46

Race gas typically runs richer than pump gas, you should be able to LEAN your main jet rather than richen it. I had a 98 KX 250, don't remember what I ran for jets, had an FMF pipe and silencer. For practice I ran pump gas and 50/50 pump and race gas on race day. Never fouled plugs or heard any detonation. The 98 was one of the most powerful 250's kawi built, in fact until probably 05 it had the meanest motor of all the kx 250's. Throw a Wiesco flat top piston and head combination and you've got a real animal.

What do you mean by a head combination.

[don46]

To Run the flat top piston, the head must be modified to accomodate it. In stock form Kawi uses a domed piston, Wiesco makes a flat top piston for the 250. I've run a Suzuki flat top(stock) in my kawi 125, mean combination (head has to be modified as well). The flat top combo works great up to 2002, it didn't work in the 03.

[Giggs]

what about the 2001 model kx 250 different to 98 or same what are the exact mods to the head to get the wisco flat top