Will a 350 big red motor fit on a 250?

[roach1upkennels]

I just picked up another 250es big red, I am trying to talk a guy out of his mint 350 motor sitting in his barn. I'm fairly confident it will bolt right in....anyone know for sure? Thanks for any input

[dougspcs]

I think there are other threads on this subject and though I don't know from personal experience, I believe there are issues related to this. Driveshaft connections are what I recall..

The one that pops to mind having pulled several engines from the SX/ES series machines is the extremely tight fit..it the 350 motor is even a 1/4 taller I'd have to say no go without frame adjustments. The clearance to remove then engine is unbelievably tight..

Careful measurement of the engines mounting points..especially at the top mount is crucial.

[TheRealFatShady]

The only 350 Honda motors that are similar are the 350x which is chain driven and the trx350 (aka 350d/foreman 86-94, later years only in Canada).

The trx350 motor will not bolt in easily, one it has a front driveshaft and is full time 4wd, and also the driveshaft/output shaft for the rear doesn't line up to my knowledge.

If you really want a 350, the best bet is using a trx350 crank in your big red or trx250/300 engine. Then you can use the full top end but will need a custom made reverse cam as the engines turn opposite ways. Or you can use a big red head and cam, without a custom cam. Not sure if you need to enlarge the head for the larger cylinder sleeve.

You can either turn down the 350 crank flywheel side to the size of the 250, or attempt to cut two flywheels and make one out of the two. The only guy I heard of that did this didn't get it 100% perfect so it was never as good as it could have been, and he used a stock TRX300 (same as big red) head.

[roach1upkennels]

I was referring to a Honda 1985 atc250es rolling chassis and installing a1985 Honda atc350es motor. I'll measure the mounting points tomorrow, but everything looks exactly the same. Thanks for the input.

[Cave Rider]

Atc 350ES ??? Did I miss something ???

[roach1upkennels]

Well I just assumed it was an atc I guess maybe it is a four trax? Came off of a 3 Wheeler, shaft drive and is 349 cc

[TheRealFatShady]

Got pics? Could be a custom build

[Larry T Moore]

Hell Im curious now

[ps2fixer]

subbed for photos :)