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Spikers400
12-17-2004, 06:05 PM
First off, i have a 400ex with a high comp piston, stage 1 hotcam, hmf slip on with a powerbomb header. If i wanted to bore it to a 426 what else would i want to do first. I dont have a job yet, and i cant buy everything all at once. What should i do first. Porting? carb?

Does a bored stock carb help a lot, and are they any special bores, rifled, tapered?

And should i replace my cam with a stage 2 or a web cam?

Thanks

TC426EX
12-17-2004, 09:58 PM
Youll want to get a full exhaust and a more aggressive drop in cam at some point. Sticking with a drop in will save you money on getting hardened rockers, heavy valve springs, etc. I would put heavy duty head studs in there for sure no matter what... On a budget, I would get it ported and then just remove the choke on your stock carb and jet it accordingly. If you do those things you will see a big difference in your bike. Down the line you can add a FCR 39mm carb or see about getting oversize valves installed. Trust me, a High compression, built 426 rips man!! If you wanna step up and run high octane gas then go higher than 11:1 when you build it. If you DO decide to do that though youll NEED to get your head studs replaced and add a heavy duty rod as well. Its all a money game... the 400ex motor responds very well to modification, and will eat as much money as you wanna feed it...

Spikers400
12-18-2004, 06:54 AM
Hey, thanks a lot for the help.
What type of studs to you recomend? And where can i get them? For installation do i drill the hole bigger and retap them or heli coil them?

Is it really worth resleaving, someone said that it is better because it keeps the heat under control, but wouldnt the heat transfer through a thinner wall better than a thicker one?

TC426EX
12-18-2004, 12:37 PM
Dont worry about resleeving it, youll be fine. You can get a heavy duty head stud kit from East Coast Atv at the link below for like 95 bucks...
You dont heli coil them. You drill it out bigger but its best to have it done on a bridgeport so that the holes are 100% straight. Then you tap it out and install the studs. I also red loctited mine in place in the cylinder just to be safe. I had just plain heli coiled stock studs before I put the HD studs in mine and it was still blowing head gaskets, and actually got to the point where the front stud wouldnt torque past 20 lbs. Since Ive added the studs I have not blown one singe head gasket...East Coast ATV (http://www.eastcoastatv.com)

smith_400ex_213
12-18-2004, 11:21 PM
at the shop i work at the 426's we build have consists of:wiseco .120 over piston, web cam,rockers,top end gaskets, valve seals, porting and head work,carillo rod, bottom gaskets, valve springs, and guides....and we run stock intake w/ a uni filter, stock header adn we have ran the WB R4 and HMF pipe..

Spikers400
12-19-2004, 07:55 AM
Are oversized valves hard to do? Do you just cut the seat bigger? Can most machine shops do it? Or is there a specific place i should send my head to?