crf250/trx hybrid build

[fish-d-fish]

currently in the process of making an 08 crf 250/ 06 trx 450 hybrid and had a couple of questions for those that might have done this combo or could help me out. Has anyone tried moving the motor forward about 1-1-1/2" and not mounted the rear of the engine directly onto the swingarm? I was wondering if tabs could be welded onto a solid bushing in the swinger and through bolted onto the rear motor mounts. This would allow for much better clearance on the upper frame/shock mount. We are also using the stock trx 450rear shock, if the resi is facing the carb its just about impossible to get to the airbox. Thoughts? Also, what have you found to be the best intake tube design to work? I was looking at some 2-1/4" radiator tubing to a modified airbox? Finally, I noticed in another post that the 99-01 yz 250 kicker might be shorter and fir on the Crf 450..will it work on the 250? Let me know your thoughts

[Vern Forenpohar]

That is how we mounted the kx250f motor in Clay's LTR chaissis, worked fine the only issue is you have to run the chain a little looser than I would like to because of the added distance between the swinger pivot point and the drive sprocket, it has never been a problem. Here is a link to some pictures, http://s1042.photobucket.com/user/redline121/library/LTR250f

[9matt2]

i would try and mount the engine into the swing arm pivot, when the bike is under load i could see it causing the rear suspension to go stiff and cause traction issues, and there would be unnecesary drag on the chain slider that would cause pre mature wear.

[fish-d-fish]

I learned today, which i forgot, that the old 250r quads had the rear bolt through a mount like i am describing. This should fix the trx notorious problem of a trx having chain tension issues as well. Moving it forward will allow the head to clear the tank better as well. I will post some pics as we go

[JOHNDOE83]

How much of a weight difference is there between the trx motor and the 250 motor?

Is the crf250 motor still faster then most 400cc atvs?

I know its built to race specifications, so if its faster then a 400 is irrelevant but I would still like to know, thanks in advance.

I switched to a 2 stroke cr250 motor from a 400ex motor, there is a 50lb difference between the 2 motors.

Currently wanting to build a cr80/400ex mx hybrid.

[fish-d-fish]

The crf motor is approx 53 lbs and an 06 trx 450 is 73 lbs. approx stock hp of the trx is 39 and a crf 250 is about 35.. So, i would say the crf is the best power to weight option, much over the 400 ex

[Logan #34's Dad]

Just use a CanAm DS450 chassis.... :blah: :blah: :blah:

[fish-d-fish]

Originally posted by Logan #34's Dad
Just use a CanAm DS450 chassis.... :blah: :blah: :blah:

Rock, does anyone ride can ams still? I thought they were kind of outdated?:devil: :p

[laeger400]

I used a yfz450 intake boot. I also put the pivot bolt through the engine. I have pics of everything ive done on the build. Maybe that will help with some ideas.

Thanks Jerry