How to tell which year my motor is?

[ZSK]

I have an 86 250R and I need to put a fresh piston in it but I don't know what year the motor is.

[Dave83]

Look at the rod and see what # it has on it.HA2 is the long rod requiring the 87-89 piston.HA4 orKA4 is the short rod requiring the 86 style piston.This is all assuming there is not a spacer plate between the cylinder and bottom end.

[ZSK]

I'll have to check that out, thanks. There is no spacer plate between the case and cylinder.

[ZSK]

The rod is aftermarket. Markings include:

Hot rods CK 103

Piston Markings are: 9502E 526MO6750

I'm asuming this is a 67.5mm piston but it is measuring ø67.25mm

[marksuttonjr]

It does not matter what year engine you have. Measure the bore. If it can be made clean with 69mm or unde5r use the CR piston instead of the TRX and it will bump your compression up a bit. Another recomendation to bump the compression up is to split the new head gasket and only usy the metal portion of the gasket. Throw away the fiber portions. Also only use gasket sealer on the base with no gasket. That will get you around 11:1 to 11.5:1 compression. You will have to run race fuel, but it is well worth the extra $.

[marksuttonjr]

Originally posted by ZSK
The rod is aftermarket. Markings include:

Hot rods CK 103

Piston Markings are: 9502E 526MO6750

I'm asuming this is a 67.5mm piston but it is measuring ø67.25mm



For some reason this post was not showing up beore I made my last post. You are good to go with a CR pistom, only the metal part of the head gasket, and only gasket sealer for the base.


Throw a Curtis Sparks MX pipe on that beast and watch just how much you wake up that 2 smoke power. Forget about the 4 jokes, because they aint $#it

[ZSK]

I won't run race fuel again. I did that before with my built 400ex and it's just not worth it for me. The cost is about double what 94 is simply because I have to drive 30 miles to get it.

I just want to know what style piston/rod combo I have so I can get a new one.