Looking 4 Best Way To Increase Accel

[Rohr397]

Well I've basically got two options going into the local arenacross season. I can either stick with my 400, which I've been riding all year with plenty of good mods, or buy a nearly stock 450 and make a go of it that way. I'm leaning towards the 400ex since it doesn't look like a nice, newer 450 is financially possible right now for me (for some reason everyone in the area feels that $5000 for a stock 04 Trx450r is justifiable and that a stock Ltr or Kfx is worth over $6000, might as well buy new).

If I'm not going to go to a 450, I'm going to need better acceleration out of the ole girl, there's no way around it. I can tolerate the lack of upper RPM's, but the slow acceleration is driving me mad. When I hammer the throttle, it takes it's time chugging towards the upper RPM's. It takes quite a bit of time to go from bottom to top, rather than the instant hit I want. I don't think it's as much a gearing thing as it is a motor thing. The response is there but the motor just can't get going fast enough. I can ride it like a 2 stroke and just not let off, but we all know that doesn't suit the 400ex well. I'm looking for that aggressive snap out of the motor, any ideas?

[CJM]

Stage 2 hotcam and 450r carb. If you can modify the engine Id put in an 11:1 piston as well.

All of that will give you excellent torque (which is where you need the acceleration-down low!).

[cheater13]

Cam, 450r carb, exhaust, and maybe you could take your box off and get a "velocity intake" off eBay and stick a UNI filter on the end. But just rejet it.

I wanna do the velocity intake to mine when I get some extra money because I ran it with no box and just hooked my UNI onto the intake boot without rejetting and it pops alot.

Anything that increases airflow will give you the power you want. I'm sure a port and polish would benefit too, but that can be pricey.

[Stickman400]

Deff. a 450R carb., that will give you a huge power increase down low. The cam will comliment it quite well too if you put one in there. Also remove your airbox lid or get an EHS lid and jet for it if you haven't already. That will you give you a good power increase down low.

[Rohr397]

Got the airbox lid off, K&N w/ Outerwears and piped. I think it's time to go into the motor and do the carburetor. My carburetor is bored w/ choke removal mod but I know a 450r carb will be an upgrade regardless. Other than that, sounds like it's time to go into the motor.

[HondaRacing83]

im doing an 11:1 wiseco with a hotcam. im not sure of what bore yet. 416 or 426..

[ish416]

450R or FCR carb will help in the upper RPMs.

11:1 piston of whatever bore you decide.

Stg 2 hotcam and get the head ported.

Those combined should allow you to accelerate faster than a stock 450. However, if the 450 has anything done whatsoever to make more power, you lose.

If you are serious about racing and winning you will need to be on a 450 especially in arenacross.

The 400, even with those mods doesn't have the power to get you over some of those tight corner jumps.

[Rohr397]

:ermm: yeah that's what I figured. I'm still trying to see if there's a way I can get myself on a 450. The prices for used ATV's around here is just ridiculous. I can find brand new leftover KTM's for the same price as 04's and 05's which makes no sense to me. I'm still trying to workout a deal to switch to the Ltr or Yfz450r but it's pretty slim.

[beastlywarrior]

Lighten the flywheel

[Pittsburgh400ex]

Man where do you live? Lol. 5 grand for a stock 450r? i jut picked one up yesterday actually for 3200$ they average 3000-3500 in my area in PA and it's not stock, but it is a "bullet"

More accel you want? I'm not a JE fan, but the sparks 416 kit is a beast. I had it and blew it up, but it was nice while it ran. 12.5:1 compression on it and i belive they give you the X-4 cam, which is mean. Includes hardened rockers and springs.

Running 426 11:1 wiseco now and hotcam stage 2. It's close to what i had but i dont think it beats that 416 kit.

I've never ridden a stage 1 hotcam, but as i understand it, it's a torque cam, might be better for dumping the clutch trying to get a holeshot. Really depends on the class restrictions and your bank account.

The 450 i got was running a 14:1. It;s back to stock piston now simply because i dont want to spend a fortune on racegas. Hotcam stage 2, Fresh hotrods bottom end, ported and polished, old White Bros. header and pipe, powdered frame, new stem and bars, rath nerfs and bumpers oversized radiator, new lower arms and older stock tops, stainless brake lines, racecut fenders and stock set of originals, new rear tires and a few other odds and ends.

Might wanna look around pittsburgh area in PA and if not too far away come buy one lol. might be worth the 1500-2000$ in savings.

[Longdong]

Not trying to light a match Just an idea.... Have you thought of buying a 250r?

[JOHNDOE83]

well if he lit a match I brought the blow torch....lol

What about a cr250 motor swap, cheap easy and well worth the extra HP and speed.

Thats what I did...:D

[Duf6]

Shaving the flywheel would be a good start for the price, I really like mine. Cost me $55.

[ish416]

As far as a two-stroke, most race classes (at least for points) have stopped allowing two-strokes into any race classes above the 200cc two-stroke 300cc four-stroke class (sometimes referred to as Quad intermediate). Not all classes/events are like this. Just some. Most in my experience.

If the races are AMA/ATVA certified check this link. AMA/ATVA handbook. (http://www.americanmotorcyclist.com/asp/racing/2012/AMA_Racing_Rulebook_2012.pdf) Check page 169 for ATV engine rules/classes. The 250R would only be able to compete against other two-strokes up to either 265cc or 265cc+. The only class that mixes two and four-strokes is the 200-300cc class.

Honestly, a 450 is a better quad for racing than a 250R is. Better frames, and better engines. At least at the 250cc rule that some (usually non-sanctioned) classes/events have. Also, 250R's are still fairly close in price to a 450. By the time you go through the engine and get the porting it needs to be competitive with a mildly built 450 you are already over budget, not to mention that you need to gusset the frames on the 250R's as square steel tubing will crack or break very easily compared to tubular steel or aluminium. I know this because I have two busted 250R frames in my barn (gusseted 86 and a gusseted 88. Both cracked on the bottom frame rail, the 88 is directly underneath the front shocks and the 86 is at the footpegs. NO they are not for sale).

I have owned and raced them all, the EX is a great quad. No doubt. However, it and the 250R's were never designed as pure competition machines to the extent that the 450s are. I am telling you, if you are serious about racing anywhere except the desert get a 450 an don't look back.

[Rohr397]

The rules here are different because none of the events are AMA/ATVA. Anything under 450cc can race in all of the 450 classes except the pro class, where the quad must be a production 450, nothing else. Motor swaps are not allowed however, only in the open class which is not much of a class at all. I've definitely considered 250r's before but it's uncharted territory for me and I fear parts availability would be limited. Things break on me a lot and to lose a stock part with no replacement would be a bad. I'm saving to pick one up for a side project though... that or a stand up jet ski.