400ex engine build advise

[Mtndew99]

Well guys my last post I asked about what to setup for harescramble racing and I got all the suspension setup this winter I'm going to tear down my stock 400 to the frame and go from there I got elka shocks all around with long travel setup but I just wanted to know what to do on the motor i know I'm not doing no big bore or stroker but I'm thinking of a 416 or 426 with 11:1 comp and hc stage 1 and port and polish with hd head studs and new valve springs and going to try to get a revloc auto clutch. Any advise from others on there build just a mild motor build. O and what is best timing chain I've heard of putting a crf450 timing chain in it but what year and model

[hocman123]

well i would get a stage 2 hotcam i used a stage 1 with those same mods u are doing and i was never happy with it. now i got the stage 2 and i love it.

the timing chain is a crf 450 i ordered a 02. make sure ur tensioner is in good working order when u do the rebuild or replace it

[Mtndew99]

I've never really go into the motor I'm going to go over the bottom end to I get some vibration through the handlebars and all over idk what it would be tho

[CJM]

Vibration could be many things. COuld be bad piston slapping round in there, could be a bad crank that is just starting to go, could be loose motor mounts, etc, etc.

[Mtndew99]

I'm pretty sure the bottom end is all original I'm not sure tho it's a 2002

[hocman123]

i dont think the bottom end would cause a lot of vibration unless the crank is loose but thats vary unlikely and u could find out with just the top end off and see if u have any up and down movement on the rod, a little left to right movement is normal.

do u feel this vibration when it sitting still or only when u are on the gas? it might be bad wheel bearings, stering stem bearing, bent rim or there is nothing wrong and it just more vibration then u are used to and u should pick up a stearing stabilizer it does wonders

[Mtndew99]

It just happens when I'm on the gas as it revs higher the vibration gets worse

[hocman123]

well as cjm said it could be a number of things. ur rings just might be loose and the pistons moveing around

the cranks on the 400 allmost never go bad unless u run it way low on oil and burn it up. cjm 400 is a 2000 i think and he has the original crank and it has had a couple of top ends on it allready. the crank is still in great shape

[Mtndew99]

Well the 400 when I got it was smoking pretty bad and the guy beat the hell outta it and never put oil in it so when I got it I checked the oil there was none and the filter was straight black but since I got it I pretty much keep up on maintenance

[hocman123]

well maybe somthing is bad with the crank but i would test it before u take the bottom end apart or oder parts that stuff is expensive

[Mtndew99]

And what's ur guys opinion on double row bearing carrier for harescrambles?

[hocman123]

u cant go wrong with a dual row bearing for any type of rideing. u can get them on ebay for around 100 bucks

[Mtndew99]

And it seems like my quad when I first start it and gas it it has some puffs on black smoke or gray smoke what is that from

[CJM]

Could be possibly rich in the fuel (too much gas).

Could also be valve seals ar ebad when starting up cold they leak down the oil a bit.

[Mtndew99]

I adjusted the valves today because when the quad got hot and warmed up they started to tap so I got them to the right Clearence and started it up sounds great but when i has it past half throttle it just puffs out black smoke well not puff it's consistent but after it warms up a little it starts to go away and could anything bad happen from running it a little rich

[CJM]

Running rich wont do much harm except ruin your plug.
You should have approx a 155-160 main jet if your engine is mostly stock and you have an open airbox.

[dxcody]

On mine, a 152 is just a lair lean. About 155 is perfect w/o the airbox lid.

I have stock motor, Slip on exhaust, choke removed on the carb.. That is it for the engine mods.