Help - CR250 82 / 83

[Digga]

I have an 82 CR250 that I am rebuilding to race & have now completley stripped it down to restore.

Have since found that the motor is actually an 83 serial number but the head & barrell appear to be from an 82 model.

Engine # is ME03E-2502491
Head is stamped HF-1 & 1Y2 (maybe? bit hard to read)
Barrell is stamped HF-1 & 1219 (again hard to read the numbers) with 82 stamped on the underside

According to schematics on the web, it looks to be an 82 head & barrell so wondering if this is going to be OK if I rebuild it as is or will there be issues that I need to be aware of & will need to be rectified.

Appreciate any advice please & can send pics if anyone needs to see what I have got, thanks

[oldyzman]

if its 83 it will have 7 head studs...

[Digga]

There are definitely only 6

[oldyzman]

Maybe 82 then

[Digga]

Yes, so it is definietly an 82 barrell/head then, so what I need to know is will it still be OK to use on the 83 motor bottom?

[Digga]

Yes, so it is definietly an 82 barrell/head then, so what I need to know is will it still be OK to use on the 83 motor bottom?

Anybody able to clarify this one for me?

82 barrell/head onto an 83 motor? Will it be OK or is it going to self destruct on me???

[oldyzman]

Well they do take the same piston 81 82 83...

[Digga]

OK, well I suppose my concern comes from the Clymer manual where they quote:

Compression ratio
1981 - 7.5:1
1982 - 7.6:1
1983 - 8.4:1

Hence my query as the 82 & 83 cylinders look different in the pics I have seen 

[oldyzman]

Where are you located?

[Digga]

Adelaide

[oldyzman]

If you were in sydney, i would offer you to see mine to compare..
Brett

[Digga]

Thx Brett, I will just have to wait patiently in case someone else on the forum can help out, cheers

[GMC]

Seems that the crank, rod, piston & base gasket are common to both the 82 & 83 models so I doubt they are too far different.

When the piston is installed just check that it comes level with the top of the cylinder at TDC
If it sits too low or too high then you will have a problem, I doubt this will be the case and this is the only thing that I can foresee that might stuff an engine.
For the most part the cylinder will have changed for minor things, different porting and it seems an extra headstud

[Digga]

Thx Geoff
I will get back out into the shed later in the week to check as you suggest. If these parts are all the same (or near enough to), then  how did they bump the compression ratio up so high between the 82 & 83 models? Is not important really but just curious?

[oldyzman]

FYI
The height from base to head is 134mm on My 83 cr250RD.