After much research on this website today regarding rebuilding MC18 cranks, I understand there are sources for rebuilding these cranks with new bearings, seals and thrust washers, but without new connecting rods and crank pins. Seems a little risky.

And with no way of knowing if crank pins have brinneling or rust until it is taken apart, more risk with shipping and assessment cost.

I understand a new MC21 crank will fit in a MC18 with machining of webs, which seems to me to be the best solution. All new all the way around. Are there any other differences between MC21 and MC18 cranks that I have missed?

Is there anyone that has experience doing this milling? In the USA? Does the crank need to be taken apart to do the milling?
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MC21R9N track
MC18R2J track
CBR954
CR250

Talk to ****** at rgv spares in australia he may even have a rebuilt mc18 crank instock .

A mod'ed '21 crank will only fit 1989 MC18's. 1988 R2 MC18 still require a dedicated MC18 crank.
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If I have to take the carbs off once more...

How do you tell the difference betwen a 1988 MC18 engine and a 1989 MC18 engine?
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MC21R9N track
MC18R2J track
CBR954
CR250

The cranks different

There is no way to tell from the outside.

The '88 engine does use a different fly wheel to the 89 but unless you have both its hard to compair.

The '89 crank has an integral center seal, the 88 doean't.
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If I have to take the carbs off once more...

thanks.

cangus wrote:How do you tell the difference betwen a 1988 MC18 engine and a 1989 MC18 engine?

Hi i have checked my parts book for you and as RobH has said yours is a R2j Model motor. This will mean it will have the 1988 crank installed and will have a seperate center seal and bearing setup. Unfortunately you cant fit a modified later crank into these cases as the center seal and bearing are different so you will either have replace the whole bottom end for a later model where cranks are still available or find a very good machine/engineering shop to rebuild the crank for you. Using a late bottom end will be the best idea as cranks are available for these and hopefully will be for while yet but new cranks are no longer available for the R2j model. Hope this helps fella.

This crank was up for sale a few weeks ago. Looks like it didn't sell maybe Moriwakiman can find out if it's still available

http://www.microsofttranslator.com/BV.aspx?ref=IE8Activity&a=http%3A%2F%2Fpage18.auctions.yahoo.co.jp%2Fjp%2Fauction%2Fw56699968
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Why do things simply when you can complicate them

RobH and caboking,

If you can't tell the difference between 1988 and 1989 models from the outside, how do you know it is a 1988 R2J model? from the engine number alone? Is this information on the parts schematic on this website?

Thanks.

By the engine number in my parts guide
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Why do things simply when you can complicate them

thanks.