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shutupnshift04
01-22-2005, 04:43 PM
i am going to be building a complet mx 400ex and i was wonderign which bore size would be best for mx racing. i want the best motocross engine avalible and also who would be able to build me the best motor i was thinking sparks or tc cause i had tc do my yfz and liked his work. i heard many different opinions and would like to hear from u gus cause you would know best. please tell me which would be the best.

shutupnshift04
01-23-2005, 10:14 AM
some one please respond i need help on making this decision please i dont no much abotu 400ex's i have a yfz this is for my younger brother

EvilJester400EX
01-23-2005, 10:24 AM
416. Fast revving, more reliable. I would not recommend doing a 425, most of my friends that had them blew up. Who knows, maybe they didn't take good care of them, but if I was going to do anything I'd send it to Tom Carlson and tell him 416 with everything. :macho

shutupnshift04
01-23-2005, 03:18 PM
i heard the 416's were great for motocross to but howcome the 440 isnt better for motocross wouldnt it make make more power and wouldnt a 425 make more power to? i dunno im new to ex's :D

400exrider707
01-23-2005, 03:25 PM
I hear a lot of people say that, but I think its cause most people dont properly build their 440's. It just doesnt make sense for a 416 to be faster than a 440. If you want ultimate reliability then do the smallest overbore possible and do a high compression piston to get the more power. If you do a cam and piston combo it will be a lot better than stock.

shutupnshift04
01-23-2005, 03:40 PM
o ya and iwant something that is gonna hang with 450's on the track to so he can try and keep up lol

NacsMXer
01-23-2005, 03:45 PM
Originally posted by shutupnshift04
o ya and iwant something that is gonna hang with 450's on the track to so he can try and keep up lol

All I can say to that is: GT Thunder 452 stroker kit! :devil:

JDiablo
01-23-2005, 03:52 PM
alot of people go with the 416 because they rev so much damn faster then the other ones,i researched this,and i was going to go with a 460 LRD kit,but now im going with a JE 10.8 -1 compression piston,hotcams stage two,ported and polished head,lighten freewheel,fcr carb,and full HMF exhaust

K_Fulk
01-23-2005, 05:43 PM
The 440's and 426 ive had seem to pull out of the corners a lot harder than the 416's ive rode.

Blastermax
01-23-2005, 05:52 PM
I know someone with a 400ex and he hasnt had any trouble with it or anything..:)

shutupnshift04
01-23-2005, 10:01 PM
ok so wait the 416 revs the quickest but the 426 have the best power? and what about the 440 where does that fall into place? and which one would i want that would make my lil bro keep up with the new 450's on the mx track. and if the 416 revs the quickest how can it have the least power? i would think the engine with the most hp would rev the quickest and what good is power if it doesnt rev as quick. o man i need 2 stick 2 my yfz lol so what im saying is which engine would make the bike the best it can be on a mx track and y? i want something that is gonna pull hard and make the fastest lap times

Crazy400EX
01-24-2005, 06:41 AM
im putting in right now a 426 with a stage two hotcam and i dont know what i want for a pipe yet.

416exduner
01-24-2005, 10:00 PM
The 416 is a good engine, I love it. One reason that hasn't been talked about is that the 416 is the first bore on the stock sleeve. If you do a 416 kit and sometime in the future have a problem with it or blow it up then you can do a 426 kit for fairly cheep, you wouldn't have to get a new sleeve put in yet. And the 416 kit doesn't always rev faster, if done correctly the 440 kit should rev just as fast as the 416 and so should the 426. This is a touchy subject with a lot of 400ex owners so you'll always have various opinions. The thing the made me decide to do the 416 kit though was that it would have the least stress on the starter and the oil cooler and all the other parts and also I could one day go up to a 426 if I want to.

400exrider707
01-25-2005, 10:46 AM
actully I'm pretty sure with aftermarket pistons the first overbore is a 406 not a 416. I went with a standard bore high compression piston for all out reliability, and its waaaay better than the stock setup.

countypark
03-06-2005, 11:40 AM
Is the bore in the 426 88mm?

K_Fulk
03-06-2005, 07:49 PM
Originally posted by countypark
Is the bore in the 426 88mm?

yup