Engine Bore Help?

[trailrider894]

Hey guys, I am building a 426 Engine out of a 2000 400EX. I am ordering the piston kit from Vertex Pistons. I would like to know everything i will need to know about what all i will need to get. I also have a a good deal with Hotcams and I would like to know what cam I should get? Or what else should i need to know about clearances or other parts I will need?

I really don't know anything about the process.Â_SoÂ_iÂ_wouldÂ_takeÂ_evenÂ_stepÂ_byÂ_step Â_inÂ_instructions.

[CJM]

88mm piston is what you need, I would suggest 10:1 or 11:1 compression. I would order a JE piston or a Wiseco, never used or have heard of vertex.

-Need to have the cylinder bored to size by a machine shop
-Need all new gaskets, you can either buy them from the dealer or cometic (cometics cheaper)
-Do a stg 2 cam, will have all the power you need.
-Need to rejet the carb, might as well eliminate the airbox lid to boot

Not much else too it, gonna need metric tools and a torque wrench and some time.

[dalejiw25]

CJM pretty much nailed it for you. I would throw in a CRF450 Cam chain while I was in there too (Honda Part # 14401-MEB-671). Also, Take your piston with you to the machine shop so they can correctly fit it to your cylinder. If you don't already have a service manual, Get one. When you've decided for sure what you're gonna do, Post up and we'll help you as far as what Jets to pick up. Take you're time and if possible take pics as you go to make the assembly easier if you get confused. Not really difficult if you take your time and pay attention. Break-in is also critical, Do as you would a new motor, Using straight oil - No Synthetics. Good Luck. And don't forget to remove the Plunger and spring used for the old Decompressor style Cam, You won't need them with the aftermarket Cam.

[CJM]

dales right, get a crf 450 chain (think its 02 and up fit) and replace the timing chain tensioners (the plastic things int he block) and the actual tensioner spring on the outside of the head. All of these parts are usually quite worn.

[trailrider894]

Already have the CRF chain installed on my atv from my last rebuild. I have heard all kinds of things about the clearence between the top of the piston and the head? what is this about?

[togup]

there are several tricks to bring up your compression by decreasing the combustion chamber ,example ; an 11.1 in a stock ex is closer to a 9.1 or 9.5.1 because the piston sits " low " .