400ex

[JW450R1]

so,1 of my riding buddies has a 400ex.he wants to rebuild the motor and hop it up a little.it also smkoes a little bit too.i was thinking 440,cam,piston and ring (stock compresion)and maybe even port out the head while it;s off.does any-one have any opinions?.how is the other kits.and is it worth like a 416 ,or should he just go with a 440 kit stage 2 hot cam

[jrm03]

416, Stage Two. Seems to be great power, and reliable, while still leaving a few bores left on the cylinder

[JW450R1]

is the 440 not reliable?

[Old Head]

Originally posted by JW450R1
is the 440 not reliable?

Only if its built right without cutting any corners.

[JW450R1]

what would those corners be.?

[Old Head]

Not putting in HD studs ,using cheap gaskets, not putting in hd cam chain. not doing a valve job, as stated by mr dunlap "make sure there is play between the sleeve and case"How to tips for boring & resleeving your 400ex ( 1 2 ).

[JW450R1]

ok,thanks thats all good stuff to know.i can ask when we drop it off.....

[Old Head]

Who's gonna do the work for you? Since we are in the same area i'd like to know who does nice work. I usually use Dags.

[JW450R1]

well,i usually have east coast atv do my involved motor work.
i also have a freind who has a machine shop,i was thinking about giving him a call

[northwest Texas]

Why not just bore it out the next size and get a different cam? Maybe have it ported and polished too. That would give him a definate improvement over stock.

[monstergt88]

I just did some work to mine. I did a 440 wiseco stock compression, cosmetic gaskets, hotcam stage 2, changed the rod and bearings, changed cam bearings, did the kibblewhite valves and valve springs, port and polished the head.

[j450rking]

you should put in a 416 with a hot cam port and polish with 11.1 piston that way you can still use pump gas

[monstergt88]

u can still use pump gas with a 440ex put it has to be stock compression.. 11:1 not 12:1. If you do 12:1 then you need to use racing fuel.

[j450rking]

relly i thought you could use a 11.1 pistone in the 440 and still use pump gas

[JW450R1]

so what is stock compression for an ex

[monstergt88]

you can use 93 octane in a 11:1. I went through this when i had a decision to go either high compression or low compression. If you go high compression(12:1) u need to use different head bolts and 110 octane fuel. My friend on his 2 stroke lt 250 bored it out and he went high compression. He had a lot of problems and it was a pain since he needed to use 110. Over here its also 8 dollars a gallon for 110. The guy at diggin racing said he recommends going low compression since it will be more reliable.

[JW450R1]

ok,thanks for the info every-one