YZ400F jetting??? water??? bog???

I have a yz400f 99 and i just purchesed a second hand white brothers e series pro meg and im also putting a 13.5:1 comp piston in it, im looking for more top end and i have 9 plates for the pipe, i have to repack it should i pack it really tight?. I have herd the pipe dose not require jetting. Should i jet it cus there is bog from idle when i snap it on quick. I mostly ride around sea level & i have not done any carby mods, should i ???? im doing the head gasket cus it was chewn about 100ml of water every hour. ive put on a 1.4 cap and it slowed the loss of water a bit but then i spotted some oil in the radiator!!!!!!!!!!!!!! will the higher comp piston make it run hotter???? if so whats the best solution. ive herd about some additives ( water wetter, some sort of crystals ) do they work or are the radiators just to small. i would like to keep the same radiators cus they are quiet expensive.

the water looks like it flows well so i think the water impellor is fine. I do some 3 to 5 hour trail rides and i want to stop worring about running it dry and cooking it in the middle of the bush!!!

I would check the water pump and make sure all of the seal are replaced (so what happened to me does not happen to you). the parts are pretty cheap (about $30).

How is the White bros exhaust??? I was looking into buying one but i was not sure if it was any better than the FMF Q muffler I have.

can I ask how much you paid for your 400F???

Patrick M.

i have just brought the exhaust and the motor is apart (spare time from broken collar bone) so i havent run the pipe yet. just got the head done up so i dont know what to expect. was running the stock pipe but it got mangeled in the stack. im expecting the wb to be louder. louder the better for me!!!

i paid au $2200 off a mate who lost intrest. it did need a little tiding up but its all good now apart from the water issue.

what happened to the water seals??? was it the seals or the impellor???

the water pump seals went out and it would leak out the entire contents of the radiator. I figured that since i was already going to have to take apart the entire water pump to get to the seals, I decided to change the impellor shaft and the water pump bearing. The old shaft had a pretty deep groove that was worn into it and the bearing was so old that it did not roll freely.

All in all... I think I spent about $100 in parts (including the right crankcase gasket).

it took me about one hour to complete this fix (after I read the shop manual about 5 times).

it was an easy fix and my bike does not leak any radiator fluid. just make sure to change your radiator cap because the springs in it are most likely going to be shot.

If you need a list of exactly what parts I changed (with part numbers) just let me know and i can post it for you...

Patrick M.

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