hi-comp piston/cam questions

[Miami_Vice454]

ok if i did just a hi-comp piston and stg2 cam would i really notice a big difference or should i go and bore it then. Would it be more reliable with just hi-comp piston, i think so but lemme know what you guys think

[matt14c]

With just the cam alone you would notice quite a difference. I wouldnt bore unless you had to or really wanted to because of power reasons. It would be more reliable from the standpoint that it would run cooler because of the thicker sleeve other than that an engine is only as reliable as well as you take care of it! You would definitly notice a difference though. I would take your cylinder to whoever your taking or sending it too to make sure it doesnt need a bore before ordering a piston. Worst case scenario get a 406. That way there you have two bores left before a resleeve is needed.

[Miami_Vice454]

i get ya, do ya think that will be enough to beat a stock 450. i like everything about the 400 i wanna keep it, just wanna make it keep up with 450 and be reliable, so i may bore anyway cause i dont think that will be quite enough

[jasonwayne222]

Definetly not gonna keep up or beat a stock 450r. sorry but your gonna have to do a lot more. if u want to beat a 450 u have a couple of choices

1. Do a 416 11:1 with stage 2 cam, port and polish, 450r carb, aftermarket exhaust, monster coil, and run racin fuel. and then u will barely keep up.

2. do the same setup with a stroker crank and a 12.5:1 comp. with stage 3 cam hardened rockers, oversized valves. then you will probly beat a stock 450r, but not by a hole lot.

3. same as #2 but with the 440 big bore kit, "not off ebay" one that comes with a new jug with bigger cooling fins, this with a stroker crank will make it a 460. youll definetly beat a stock 450r, and hang with a modded one.

4. Turbo charge it with all of the above but you have to run a low comp. piston. youll have the 450rs eatin dirt.

5. Give up on spending all that money, sell ur 400ex and buy a 450r, u can get around 1500 for an average latet model ex and get a 04 or 05 450r for around 2500 if u look hard enough.

Just make a good trail bike with enough power and be happy. its a great trail bike but not so much for racing with 450's around.

And whatever u do to the 400ex, make sure u upgrade the oil system, install a spal fan at least and if u got the cash a bigger oil cooler or just add one. u can get a civic tranny cooler with lines for 60 bucks from most auto parts stores

[TRXRacer1]

Originally posted by jasonwayne222
Definetly not gonna keep up or beat a stock 450r. sorry but your gonna have to do a lot more. if u want to beat a 450 u have a couple of choices

1. Do a 416 11:1 with stage 2 cam, port and polish, 450r carb, aftermarket exhaust, monster coil, and run racin fuel. and then u will barely keep up.

2. do the same setup with a stroker crank and a 12.5:1 comp. with stage 3 cam hardened rockers, oversized valves. then you will probly beat a stock 450r, but not by a hole lot.

3. same as #2 but with the 440 big bore kit, "not off ebay" one that comes with a new jug with bigger cooling fins, this with a stroker crank will make it a 460. youll definetly beat a stock 450r, and hang with a modded one.

4. Turbo charge it with all of the above but you have to run a low comp. piston. youll have the 450rs eatin dirt.

5. Give up on spending all that money, sell ur 400ex and buy a 450r, u can get around 1500 for an average latet model ex and get a 04 or 05 450r for around 2500 if u look hard enough.

Just make a good trail bike with enough power and be happy. its a great trail bike but not so much for racing with 450's around.

And whatever u do to the 400ex, make sure u upgrade the oil system, install a spal fan at least and if u got the cash a bigger oil cooler or just add one. u can get a civic tranny cooler with lines for 60 bucks from most auto parts stores I'm guessing you have no experience racing stock 450's. You've gone way overkill here! Telling someone to get hardened rockers with a Hotcam is just dumb. The way you suggest racing fuel is a power adder is disturbing too.

[Miami_Vice454]

yea i think you are over estimating stock 450s, if i do a 440 and stg 2 cam i think that will be good enough

[jasonwayne222]

ok well first off lets think of the question. can i beat a stock 450r? hmm well i dont know about u guys but i know a lot of people with 450rs but not a one of them that is stock. ya sure u can go stage 2 on everything and keep up but once they put in even a cam or exhaust with jets ur gonna be right back where u started. do urself a favor and go all the way or get a 450 because theres not a hole lot of people out there that buy a sport quad and keep it stock.

And ya u have to get hardened rockers when u go stage 3 cams. if ur gonna go big bore ur stupid not to go all the way and get the stage 3 cam and hardened rockers. thats kinda part of the whole stage 3 thing.

u fi#%^ dumb azzzzz

[jasonwayne222]

also i suggested running the racing fuel to help with the cooling since ur pushing ur machine all the way and with bores ur gonna overheat without upgrading ur cooling system. the 450s are liquid cooled so they dont have that problem. ur gonna get hot keeping up with those machines

not suggested as a power adder but a maintainer.

try thinking about what i said next time before u shoot ur mouth off.

[Miami_Vice454]

ya i think ill probably be doin something like ur #2 and i kno for sure i will beat a stock 450, i dont do a whole lot or racing, most fast trails. i just said that cause thats about the amount of power im lookin for. and it would be cheaper do that than buy a whole new bike.

[Miami_Vice454]

thanks for ur help guys.

[katch26]

what "stg 3" requires hard faced rockers?

[jasonwayne222]

pretty much all stage 3 cams requires the hard faced rockers.

[katch26]

but who else calls it the "stage 3" other than hotcam? hotcam says it does not require anything other than stock....just curious


"Stage 3: single-cam motor. More top-end power. Designed specifically for Hot Rods big bore stroker kit. Uses stock valve springs and rockers. *Does not use auto-decompression mechanism."

[jasonwayne222]

hmmm you know i just checked and ur right about the hardened rockers. what was it that requires them? i cant remember now but it was one of the higher performance cams that goes well with a 440 that requires it. i could of swore ive read it several times about hotcams as well but sure enough i just checked and ur actually right

but enough talk about this its gettin to be a battle between us and not about the guy who started this thing

[katch26]

wasnt my intention just wanted all info to be on the same page........

on another note this thread turned into what it would take to beat a 450r but never once did it come up what kind of riding? if youre talking about drag racing youre probably chasing a dream but if youre talking trail riding/ woods racing theyre are quite a few people on here that do just fine running the 400ex. MX you might as well be speaking a different language so no help there.

[Miami_Vice454]

i do like open trails, and drag racing, but never aginst a 450 just aginst other 400s im not stupid, i just wanna get close to their power so i can WHOOP on any 400 out there and hopefully beat some stock 450s. if i dont thats ok as long as im close, cause my skill will take care of the rest lol:p

[killer400ex]

i manage to keep up and pass alot of 450's not the highly modded ones, and you have to remember that its the man not allways the machine, i know people with modded 450's that cant ride them for there life but somehow there "racers" just because they own one, and i wouldnt sell out right away for a 450 because if your riding a 450 and you beat someone on a 450 its no big deal but if your riding a 400ex and beat someone on a 450 then it shows the skill level of the rider. it all depends on how far your willing to go to win, and yeah if your talking about drag racing then im sorry but a 400ex is probly not your machine unless you have crap loads of money to throw around, but as farr as a track or trail quad i love my ex

[Chukkinsod]

I believe the only cams you need to run the hardface rockers are WEB 479 and 463. I learned the hard way and wrecked not only the stock rockers with the WEB 479, but also gouged the hell out of my cam.If you go with the WEB .....I recommend the hardface. Hotcam stage 3 is not a hardfaced cam, so I believe if you run hardfaced arms, it will wear out your cam. Cam decision is all yours, all perform totally different.

[Miami_Vice454]

whats the best for the 440 11:1. i will get a hotcam so i dont need to replace the rockers. i think stage 2 is right, stage 3 seems to much. i want to kno what you guys think.

[Muzzgit]

Sure, more power will help, but better suspension is just as important if you want to go faster.

Go with a high comp piston, hotcams, port & polish, and spend the rest on better front and rear shocks. (Try GT Thunder)

[F-16Guy]

Reground cams = hardened (reground) rockers

Billet cams = stock rockers


To answer the OP, you'll probably need to bore to at least a 86mm piston to clean up the cylinder. I always recommend HD studs with any build. The Hotcams stage 2 cam is a good, economical choice, but there are others. If you want a drop-in cam that uses the stock rockers, you may want to see if you can get an HRC copy cam from XR's Only. The original HRC cam was one of the best cams you could get for the XR/EX engine, but Honda quit making it. Al Baker's XRs Only then copied it and should still sell it; I think it's $189.99 on their website.

Assuming you have a pipe and filter, adding a high compression piston, cam, and possibly a 450R carb will get you up there with a bone-stock 450R. The 400ex is not going to be smoking any mildly built 450s unless you dump a lot of money in it, but if you just want to keep up a little better, a well built 406-426 will put you in the ballpark.

I would stay away from the 440 kit. Installing the sleeve and setting the deck height adds another layer of complexity that can end up in disaster unless you're willing to pay to have it done properly. A simple bore job is pretty straight forward, and most decent shops can do it without screwing anything up. There may be a little bit of a power difference between a properly built 440 and 416, but if you're looking for the most bang-for-the-buck and a simple build, a 406-426 is hard to beat.

[killer400ex]

Originally posted by F-16Guy
Reground cams = hardened (reground) rockers

Billet cams = stock rockers


To answer the OP, you'll probably need to bore to at least a 86mm piston to clean up the cylinder. I always recommend HD studs with any build. The Hotcams stage 2 cam is a good, economical choice, but there are others. If you want a drop-in cam that uses the stock rockers, you may want to see if you can get an HRC copy cam from XR's Only. The original HRC cam was one of the best cams you could get for the XR/EX engine, but Honda quit making it. Al Baker's XRs Only then copied it and should still sell it; I think it's $189.99 on their website.

Assuming you have a pipe and filter, adding a high compression piston, cam, and possibly a 450R carb will get you up there with a bone-stock 450R. The 400ex is not going to be smoking any mildly built 450s unless you dump a lot of money in it, but if you just want to keep up a little better, a well built 406-426 will put you in the ballpark.

I would stay away from the 440 kit. Installing the sleeve and setting the deck height adds another layer of complexity that can end up in disaster unless you're willing to pay to have it done properly. A simple bore job is pretty straight forward, and most decent shops can do it without screwing anything up. There may be a little bit of a power difference between a properly built 440 and 416, but if you're looking for the most bang-for-the-buck and a simple build, a 406-426 is hard to beat.

x2

[killer400ex]

remember that if you put a bigger piston in that your engine is going to need to breathe alil better than before, to really open it up and let it breathe good i would allways suggest a cam with a piston, you really wont notice much of a difference without the cam, and if you do decide to go up in bore size i also recommend having a port and polish job done to your head and putting on bigger headers, and a 450r carb to top it off