Help identifying motor and internals

[BULLET99Z28]

I'm pretty sure the motor out of my parts bike is an 86-no spacer plate. Cast into the lower left case-TB063, and tagged right below that is 1011508. The cylinder is the 85(bottom of sleeve has HA2 stamped, and 85 on opposite side) - open intake, not bridged, and has some decent porting.

Also it has a replacement piston, marked at the fron-55010, and in the middle-525M06900. Any ideas on brand? I'm pretty sure that means its a 69mm piston, correct? How many more bores can I go on this sleeve, max bore size/piston size?

And it has a HotRods lower end- Rod casting- CK103 B. The motor looked like it had the cases split by the nice clean green gaskets. I just wanted to pull the jug to inspect everything before I stuff it in my frame for my build. Thanks for any help guys

Sorry for all the questions, this is my first R, and first honda 2 stroke since I owned my Pilot and Fl350 ody about 15 years ago.

[C-LEIGH RACING]

For sure an 1985 cylinder.
The piston, you sure it is 525MO ??.
It should be 526MO6900 for the 85/86 year TRX250R.
Yes it is a 69.00mm for sure & a 69.50mm is the last size in the TRX pistons.

The piston number is indicating it is a Wiseco piston.

On the crank, with the year cylinder & you indicated it has no base spacer plate & then with the part number on the piston, just about sure it is a Hot Rods short rod crankshaft.
I would say you have either an 85 or 86 year ATC or TRX engine.
Neil

[BULLET99Z28]

After some digging around, I believe I have a Wiseco piston, .120 over-69mm piston. Not sure what size that makes the motor, but that is a 3 mil overbore.

I see that wisco has a 69.5 piston, but how big can I go on this sleeve? 4 mil? And what size pston would that be?

Also, how can I tell if I have an entire HotRods lower end, or just the rod itself? Thanks guys

[C-LEIGH RACING]

Just a little over 269.2cc.
In the Wiseco TRX pistons, 69.50mm is the last piston offered.
After the 69.50mm TRX piston, once you've worn that out, you can go to the 70.00mm YZ250 piston.

Now I've never done a 70.00mm YZ piston on a short rod crank before so dont know if you would need a spacer plate or not.
I'm guessing that you wouldnt, but not 100% sure.


Just by looking at the crank down in the cases, theres no way to tell if it is a complete Hot Rods crank or just a rod kit.
Neil

[BULLET99Z28]

Thanks Neil, I must have been typing my last post when you reponded:) The piston looks darn near brand new, I guess Ill take the cylinder to work and measure it to see what it measures for proper piston/cylinder fit. What is an acceptable tolerance with the wiseco forged piston? I'm guessing its a good fit and has good compression because when I bought the bike it kicked over pretty tough(either that or I'm a wuss, not owning a kick start for a log time)

[BULLET99Z28]

Neil- what years of Yz piston would I use, and what are the over-bores on the 69.5 and 70.0yz setup? What steps would I take to determine if I needed a spacer plate(measuring wristpin locations?) How far can I bore this sleeve? I'd like to get max life out of this cylinder. Whover did the port-work matched the sleeve really well.

[C-LEIGH RACING]

It needs at least 0.0030 piston to cylinder bore clearance & warm it up real good before you blast off or you'll cold seize it.

No way to tell on the crank other than the rod.
Machining is so close to the same as an OEM Honda crank, you can hardly see any difference.

A Hot Rods, once you've handled quite a few, theres just a we slite difference in the tint of the metal on them compaired to the OEM Honda. Honda is just a tad darker.
Neil