crf 450 or trx 450

[eganracing]

I'm pretty serious about mx racing and my 440ex engine is havin a hard time keeping up with the big 450's so i have been thinking about upgrading. The thing is i dont want to spend all the money i have on a new quad because my 400 ex frame has all the suspension stuff already. So im debating if i should slame a crf 450 dirtbike engine into my 400 frame or should i just start with a 450r? o and how much modification would i have to do to my 400 to make a crf 450 engine fit?

Any input is appreciated.

[h400exrydr]

i would keep the 400ex frame and stuff a crf motor in it, i am pretty sure the CRF motor has more hp. then you wouldnt have to do too much to it and u would have a very fast quad. There is a thing on this site that tells what u have to do to put a crf motor in the frame. i was going to but.....a new motor is alot of money. good luck

[eganracing]

i know a new motor is alot of money but i think if i get a used dirt bike and rip the engine out of it it will be cheaper. if u could post how to make the engine fit that would be awesome.

I think go with the new 450. Handling will be better once upgraded. crf engine does not have the gear ratios suited best for atv. IMO

[ZeroLogic]

i would put the crf 450 engine in there

[ill_lil_romey]

I would put the dirt bike engine in. The 400ex chassis has an excellent geometry, I still prefer it over todays quads. The problem with the dirt bike engine is the gear ratios.Like rawdeal stated a dirt bike it not suited for a quad. It would definately work and be a very fast quad, but a dirt bike motor is geared to pull one very skinny tire, not two wide quad tires. I always wonder if anyone has experimented with changing the gears inside the dirt bike motor to fit a quad application. Hybrids are the sh*t man go for it you wont be dissapointed. The resale value of hybrids is through the roof too

[deathman53]

I have a crf conversion, yes the gear ratio's are a little wierd, but you get used to them.

[h400exrydr]

http://www.exriders.com/vbb/showthread.php?s=&threadid=90605&highlight=400ex+to+crf450 here is the link that shows all of the steps to make a hybrid. good luck

[eganracing]

those instructions look like a lot of work. i was wondering if i could get a frame already set up for the crf 450 engine.

[h400exrydr]

you could probably have one made, but they cost like 2000 dollars.

[Rich250RRacer]

While I give this guy alot of credit, a few things turn me off to this right away. The biggest being chain alignment. If you cut down the seal collar on the axle , you shift the whole axle to the right. This means you're moving the hubs, tires, etc over which means the front will not track in line with the rear. By the time you get done with this conversion, you could probably get a 450R and get started on the suspension with the money you have invested.

[eganracing]

2000 dollars? thats way to much. So i end up paying 2000 for the frame and 3000 for the engine. i think i might just sell my 440 then and buy a 450 and mod it. i got sponsors which will make it cheap. yeah i dont know about shifting the entire axle. that sounds a little crazy.

[balls2da-wall]

Send your frame to ATV FOUR PLAY and they will convert it to a CRF motor application for 650$ plus they will also gusset your frame...sending mine out the first week in Jan. Go will the CRF motor thats what im doing...im using mine for XC too and have had people tell me not to do it because its for a dirt bike and blah blah blah but I feel I want to prove them wrong and I know its a good match because all the big pros used to run this set up in MX