87-89 trx piston 5mm shorter than 86 ATC ???

[BC250R]

Is this correct?

[PWK39]

I think the wrist pin location is 5mm different.The pistons are the same size

[deathman53]

the pin is 5mm higher on the piston and there is some diference, as 87-89 cylinders had a bridged intake. Both the style pistons will work wtih 85-89 cylinders. If you have a short rod motor, your only choice is a 85/86 piston, long rod: 87-89 piston or 85/86 piston and 5mm spacer plate.

[rich250rracer]

I think the wrist pin location is 5mm different.The pistons are the same size

Yeah, the pin is 5mm higher on the 87-89 piston which requires the long rod 87-89 crank. I wouldn't use the later piston with an 85-86 cylinder though.

[Billy Golightly]

The overall piston height is also different. I've got an 85-86 piston next to an 87 right now and the 85 is noticeably higher. Both are wisecos by the way.

[BC250R]

Thanks for the help guys. Ive got an 86 motor that i've just ordered the a TRX250R 87-89 (5mm longer) Hotrod. So if i've got this right i can use an 86 piston with spacer (already have spacer on hand) and the 87-89 without? my cyclinder has no bridge on the intake.

[rich250rracer]

Thanks for the help guys. Ive got an 86 motor that i've just ordered the a TRX250R 87-89 (5mm longer) Hotrod. So if i've got this right i can use an 86 piston with spacer (already have spacer on hand) and the 87-89 without? my cyclinder has no bridge on the intake.

That will work fine. The reason that I don't recommend running the newer piston in the 85-86 cylinders is because of the lack of the bridge in them. The 87-89 piston is fully skirted, and since there is no bridge on the older cylinders, there's a chance that the skirt can snag on the intake port on the downward stroke.