engine swap questions

[whiteman350x]

Ok dealing with 85 250es Also have 86 trx250 . Is the 86 250 bottom end compatable with an 85 250es top end? Will the 86 trx250 engine be a direct drop in for the 85 25es?

[atc500x]

exact same thing,some difference in the Bottom,but same top

[fabiodriven]

exact same thing,some difference in the Bottom,but same top

Look what the cat dragged in!

[ps2fixer]

I'm pretty sure the wire harness hook ups changed on the atc vs trx engine too. I think the engine output drive shaft is the same. If you use the atc bottom end and trx top end you should be fine I'd think though. If you have the whole trx machine, the swing arm is an "upgrade" item for the atc250sx machine, +3in but requires welding up a new shock mount.