big bore?

[atver13]

i have a 2000 400ex and wanted a big bore kit but dont know how big to go.
i hear they have lots of problems with the 440s. dose any one have one wit ha 500 kit from four stroke tech?

[PaRedneckRiders]

If your on a stock bore/stroke/comp i wouldnt suggest going that big unless you plan on doing something special with it like a full drag bike or something because you will have to upgrade the cooling system if you plan on actually riding it over a distance or going slow at any times.
I run a 426 and i like it, i do a little bit of everything drag race, trail, ride MX race whatever else ends up in front of me.

I would go 416 then if you have problems later on you have one overbore to a 426.

BTW if your looking at the prices on the FST website there wrong, last time i talked to FST the prices hadn't been updated in the last 5 years so everything is more expensive now.

[atver13]

what is the 426 is that a stroke crank or piston? do u have any heating issues?

[honda400ex2003]

88mm piston. if it doesnt idle for a long time most people dont have over heat issues. alot of it depends on the rest of the setup also. 11:1 with 93 octane in hotter conditions could cause trouble but when stopped shut it down. I would say that it should be alright but some guys do have trouble with them occasionally. steve

[atver13]

how would that work with a stage 1 hot cam?

[honda400ex2003]

it would depend on where you want your power to be and what compression you choose but in some cases it is great, such as for low end with a 10 or 11:1 compression piston. 11:1 may be a bit much with the stage 1 but would be fun depending on the setup. :D steve

[atver13]

i want to keep the compression down so i can still run pump gas. and i would rather have the power down low if i can

[honda400ex2003]

you should be fine with 11:1 and a stage one if you can get 93. sometimes it is a tough call to determine if it will work or not with that compression. I guess to be safe i would go 10:1 with the stage 1 but it is really preference. I cant always get 93 so it can be tough for me.

There are quite a few guys that run 11:1 with a stage 1 and it would def be a great low end machine! I am interested to find out if anyone running 11 and stage 1 will chime in. :D I may run a stage 1 in my 440 for a while to see how i like it. I have both though so it will be a tough call and will probably go stage 2 instead cause it will still have low end with more top.

steve

[416racer]

Ive been running a 426 with 11:1 piston and a stage 1 hotcam and that thing is a beast low to mid range and equal to or a little better than stock on the top end. If you wanting to stick with pump gas then Id go with 10:1 just to be safe. The first time I ran mine on just pump gas it started pinging then popped the head gasket.

[CJM]

Specs are in my sig. I run that setup on 93 octane pump gas and have been super happy. Its peppy, it has lowend, mid and high and like I tell everyone it keeps up well with the 450's.

416 is nice cause if it does go belly up you can bore to 426 and then to 440 as a last resort before you either do a new sleeve or something else.

Im quite satisfied with mine.

[atver13]

what do u use the fan for?

[hocman123]

he uses the fan to help keep the engine cool a lot of people do it to there 400. u need i think a 3 or 4 in pull spal fan and u mount it to the oil cooler and wire it into a switch. so it will pull more air over the cooler and blow more air into the engine. some peole have said it keeps there engine 10 degress cooler when not moveing

[PaRedneckRiders]

I ran a stage one in my stock bore 11:1 motor i had in my last 400.
It definitely had some power behind it, I loved the low end but it did seem to lack on top.
It was still fun to just be able to cruise down the road at low rpm 5th gear and just grab a hand full of throttle and pull a wheelie.

[atver13]

dose anyone know if the oil cooler kit from four stroke tech is worth it or just put the fan on the stock cooler?

[DragonGunner]

I've yet to have a 11:1 that ran good on 93 octane, always had to add a little race gas. I had a 416 with JE piston that was just under 11:1 that ran on 93...but always added a little race gas anyway. I would suggest the 416........I ran the 426 with 11:1 an 100 octane an it was also very strong with a race Web cam. it was great midrange an top end but I lost on the bottom. I have read but haven't been able to do any comparisons...so maybe someone can chime in, but have read that a 440 with the heavier piston is actually slower on top end than say a 416 with a lighter weight piston. My old race motor is only a 406 , when it wears out I'll go to the 416....to be they seemed faster all round than the 440 I had in it.

[atver13]

so if i had 10 to 1 i should be ok on pump gas

[honda400ex2003]

10 OR 11:1 would be fine on 93 octane. steve

[PaRedneckRiders]

Yes you will definitely be fine on pump gas at 10:1. It all depends on how high your pump gas is like the premium around me is 93 octane and i run that in all my motors, they were all 11:1 expect one that was all stock and it worked fine.

[atver13]

ok thanks guys. i would really like to tear the thing down and build a mx racer out of it. but like most things now its too expensive.

[PaRedneckRiders]

Ya thats what my 426 turned into.
I bought it for 500$ then was gonna fix it and resell it but instead i turned it into and MX machine and have way to much money in it now.

[atver13]

ya its easy to spend too much. especially in shocks and a arms

[CJM]

Spal fan really does help cool it down good. It def dropped 10 degrees at least while poking around or sitting. Trick is to not let the quad idle forever (why would you, your wasting 3.50/gal in gas anyways lol) and keep the quad moving.

The fan is waterproof and took me all of an hour to install. If you go to the 400ex stick there is an install that shows you exactly how to do it.

As for 93 and 11:1, no issues here but Im right at sea level pretty much and usually run better premium gas, I could run 100 octane but its 8/gal.