Need help identifying NSR cylinders

[centaurus]

Hi all!

I am currently preparing to do a top-end rebuild on my NSR 250 MC18. One of my cylinders has interior surface damage and needs to be replaced.

I've bought a broken down NSR (car accident). I don't know the history of this bike, I don't have any papers, but based on it's physical characteristics it's obviously an MC18. I stripped down and cleaned it's cylinders, and now I'm just about to order the top-end kit.

The problem is that there are different marking on the "new" cylinders - they are not the same as the ones on my old cylinders. I know that there are some NSR specialists out there that have helped me before and I'm hoping they will help me again this time.

I've photographed one of the old cylinders and one of the new ones and compared the codes:

The old cylinder:
one one side, at the base of the cylinder, cast in the cylinder (below the "249cm3"mark) an "F"
on another side, at the base a "B" stamped (I'm assuming this is the bore??
on another side, at the base is stamped: 9MQ1 231 and another markings cast into the cylinder: 14 and 02
the cylinder head has: KV3GF E1 cast into the material and a 5 and 4 the same

The new cylinder:
F2 instead of the F above
B stapmed on the base like the one above
8NY1 098 stamped and ??? and 15 (can't make the first number
the head had KV 3GRE2 and 12 and 10 cast into the material

I will attach pictures for further clarification:
first picture: old cylinder - 3 pictures concatenated
second picture: old cylinder head - 2 pictures concatenated
third picture: new cylinder - 3 pictures concatenated
fourth picture: new cilynder head - 2 pictures concatenated

Any help would be really appreciated. I would hate to buy the wrong top-end kit all the way from UK, just to realise that it's not the good one.

[Wheeliemonsta]

Gidday Centaurus,
Take the chassis & engine #'s from both bikes down to your local Honda shop & have them I.D the models...

It's the only real way to be certain... (The Dealer will most likely have to get hold of Blue Wing, they'll probably have to e-mail Japan & that may take a day our two...)

I'm picking you'll find that they may well both be MC 18's but from different "Original Markets" & therefore could have different porting specs on the barrels...

Make sure you use the barrels as a matched pair - i.e not on from one engine & the other from another

Cheers

[vagrant]

You could have a look on here,

http://www.nsr250.net/forums/index.php

They have a huge parts catalog, for cross checking your numbers, and tonnes of experience.

[centaurus]

Thanks a log guys for your answers.

I went to the bike shop and they verified the frame numbers from both bikes (I still don't know where the engine number sits for this bike model).

Honda japan says that both of them are NSR250 MC18 R6K.

Couldn't find any of the codes in the parts manual as part numbers. I still don't know what they are but I guess it doesn't really matter, as long as it's confirmed that they are both for the same model.

I also measured them with a Vernier calliper and they seem to have the same dimensions.

One more question though: being B cylinders (both pairs) it means I need to order a B size top end kit, right?

[centaurus]

I've looked over the tyga-performance online shop and ended up asking them questions about the top-end rebuild kit.

Problem is they only have a "no mark" piston (mc21/28). The guy says this is what I need (my cylinder being B). Should I believe him? Don't I need B mark piston or something like that?

I'm not quite familiar with the cylinder/piston sizes/marks. I searched the forums but I can only find partial info on cylinder - piston compabibility marks-wise.

[zxcvbnm]

Go's like this.

A Cylinder - B Piston
B Cylinder - No mark Piston
C Cylinder - D Piston

I've got A cylinders with no mark pistons (bit tighter). I think thats all there is left now.

Check the barrel heights are the same to.

[centaurus]

Cheers everybody for your comments. You've been very helpful.

I finally ordered the top end kit and I'm expecting it to arrive at the end of this week

Hopefully I'll be riding again soon