1985 ATC250R engine

[rooster300ex]

I have a 1985 atc250r engine that needs to be rebuilt and thats it. I'm wondering which trx250r frames that this thing will bolt right into???

[Master LTR450]

all

[2muchquad]

all of them,the 86 and 87 frames have a rear motor mount that goes through the swingarm.

[rooster300ex]

How do the rest of em mount up on the back of the motor?

[Master LTR450]

the 86-87 have the mount through the swingarm like stated above, and the 88-89 have the mount built into the frame.

[wilkin250r]

There are internal differences from year to year, but externally, they are all the same. As stated above, the 86-87 frames are different than the 88-89 frames at the rear swinger, but th engine mounting bolts are all the same location. Any year motor will bolt directly into any year frame.

This also includes the liquid cooled ATC motors, like your 85. Same thing, same external dimensions and mounts. The air-cooled ATC250r motors are entirely different.

[brandonpeake]

hows the power comparison, will a trx pipe fit the 85 motor ? there was a cate 85 motor on ebay the other day but had heard only use the 86 atc motor but the guy telling me had an 86 atc in his trx so i had no idea

[deathman53]

any liquid cooled 250r motor will work in any year 85-89, exhaust flanges are the same also. As others said external the same, there differences inside the motor, nothing to really be concerned about. I have 85 atc motors and some 86 motors, all atc motors. Everything is perfect in my 88 trx. I have a 88 trx motor also. The earlier the year motor, the harder of it hit it has(if any are stock now). I believe stock the 88 motor had the most power, while smoother. There aren't too many stock out there now, I wouldn't be concerned.