hey guys, I rebuilt a 2000 400EX a few months back, and went with the wiseco 11:1 426 kit, stage 2 cam, port and polish, uni filter, and HMF exhaust, and for some reason this thing will keep up with a 450 any day of the week... but if its a modified 450, i lose by a bike length or 2... but anyways, i put on a used base gasket as kinda of a middle of the night temporary fix cause i needed it for the next mornin, so it leaks a lil now and i cant stand a leaky bike. so ima tear it down to chane the gasket since i got my new one in,. but would it be worth it to go with a 12:1 or even 13:1 ?? i went with the 11 for reliability purposes cause i sometimes ride the forest, and no one likes to get stuck 18 miles from the truck with a blown head gasket.........so how reliable would a 12 or 13 be as far as head gaskets and horror stories of strippin studs and head bolts ??? I have no problem upgrading the studs, so if yall know where i can get some good ones, please let me know. but any input on the subject of reliabilty or studs would be greatly appreciated. Thanks

 

IMHO you should stick with the 11 to 1 for many reasons.

It will be close but you should be able to get away with pump gas with an 11 to 1. With a 13 to 1; no way will pump gas work.

Performance it not that much better going from an 11 to 1 to a 13 to 1. From 9 to 1 to 11 to 1 you pick up a bunch but not so much at you go to a 13 to 1.

Heat will go WAY up with a 13 to 1 and with an air cooled engine that is not good on the trails.

Studs are the way to go if you put a lot of stress on the bolts. But like I said, you should stay with what you have IMHO.

 

I think that I mentioned before that we went from a stock piston to a CP 12:1 and absolutly love it. We mx this and went with the 400 because of a certain class we want to try to qualify for the Amatuer Championships so we are stock bore. In our district we have to run the production c class which is all 450's except ours. We can run 2-3 out of the hole shot unless it is a longer one and then the 450's shine, maybe because of one more gear not sure. But no regrets on the 12:1 and we run the Turbo Blue fuel.

 

highest you will be able to run with 92 octane is 12.5 my 13.2 is 100 minimum but you can go as high as 14.1 and run 110 octane and this would make a sizable difference just gotta figure how much you want to spend on gas the new honda 450 come 12.0 stock with 91 minimum so i think 12.5 would get away with 92 and a little octane boost

But trying to keep up with the 450s is harder my buddy has a 440 with a stage two hot cam and it is very fast but just doesn't quite have the zip of the 450s

 

thanks for the info guys, im already running about 100 octane as it is. I mix AV gas with 92 pump at a certain ratio and come out with about 100 octane. I know a lot of guys talk trash about AV gas, but I have always ran this in all my bikes with a noticable power gain and burns a lot cleaner. so mixing isnt a problem for me. and about the 440 not keeping up with the 450's,... a 440 has never taken me in a race.(not yet anyways) a 426 revs a lil faster and is just all around "quicker" in my openion.... im just leary about going higher than 11:1 for reliability purposes.... i dont know though,.. any more input is welcome. Thanks.