I just purchased a 1986 yz 490. I have an extra complete 1984 atc 250r rolling chassis. I am wanting to put the 490 motor in it. I know that it doesn't have a counterbalancer. What things do I need to do to get this to work? I know people have used rubber engine mounts. Where can i get these? I'm not sure if the exhaust will work off the 490. Where can i get exhaust made for this conversion? I know this dirtbike really is fast and I think it would make my trike fly. Thanks for the help.

 

i know of a similar conversion with a atc250r and cr500 motor............it hauls!

but haven't had a good look at it

i like your way of thinking thou!!

i hope to go down this avenue in the future/.........i am thinking xr500 head and barrel on my 350x [img]i/expressions/face-icon-small-happy.gif[/img] yeaha

good luck

pudding

 

a counter balancer isn't too big of a deal for a trike. in fact (correct me if i'm wrong) most trikes don't even have em. the front end is set up like a dirtbike and thats why its not too big of a deal. the bigger engine will cause more vibration tho and rubber engine mounts would be a good idea. also you might wanna invest in a longer swingarm and maybe frame reinforcing. it will haul *** when its done! also the engine won't just bolt right in your going to have to come up with some custom engine mounts but i say do the conversion when your done you'll have one of the fastest trikes around. [img]i/expressions/face-icon-small-smile.gif[/img]

 

hey pudding, I saw where you said somthing about an xr500 head on a 350x, whats the deal with this?? can this be done? also have another question you might be able to answer, I have a 250x quad with a 350x motor in it, I still have the 250X carb though. I have heard that this carb works just as good as the old stock 350 carb, do you know? think I may benifit from a bigger carb? sorry for the pounding of questions, so thanks in advance

l8r
91 TRX350X
85 ATC250R
86 ATC200X

 

ya

the 350x has a 34mm carb

250x ain't much different..........in fact the carb on the 250x is a 36mm throttle bore (QB01B type)

the 350x was a very 'lazy' motor

gotta fly man

the xr500 deal?

i am told it is possible

people on this forum have done something like it i think?!

i haven't done my homework completely to see if its possible

hmmm.......i think the xr500 would be a dual carb too........it was kinda popular before the trx400ex turned up on the scene

more carb?...........friend here in NZ has just bored out a 300ex carb.........he reckons its a good idea.........removes the choke and stuff or something

i suffer from a lack of detail

i will do more home work and get back to you

laters

pudding

 

If it is not already done to the 490, you need to shave .5mm off the carb slide cutaway. The needle jet needs to be changed too, but I don't know what it is off the top of my head. This will get rid of a very rich 1/4 throttle causing low end blubbering. Another thing that is beneficial is to get the head recut. The angle between the squish band and piston dome is not optimal. Forward Motion Racing has done a lot of these.