Hi Guys;

I have a mc21 but don't know the exact model or engine I have in the bike. Reason I need to know is I have done a crank seal and I have leaking oil out of the top of the engine case just below the carbs. I want to replace crank seals and need to know how to identify my engine to get the right seals. The bike has HRC heads and barrels not stock ones.

Thank You

Edd

From the 1989 MC18 R5/6k onwards the crankshaft bearings and seals are the same for all models I believe.
So that's all MC21 and all MC28 as well.

LH crank seal 91205-KV3-771 25x38x6
RH crank seal 91203-KV3-681 36x68x8 (also 91203-KV3-831?)

The inner central crank seal is an integral part of the centre main bearing of course.
The inner central crank seal/bearing does not have Honda part number as it is part of the crankshaft assembly.

The outer central crank seal is an O-ring. It has Honda part number 91301-KV3-771
Big end bearings are the same as for a 2012 Honda CRF150R being 25mm ID x 32mm OD x 16mm wide. Pro-X and Wiseco part number 22.253216F

For more info see this picture.

These parts are becoming harder to come by as time goes by, it seems.
Hope that helps.
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[color=#808080][size=9]Yes,.. I too know how to waste Time and Money,...

Hi Tuckerbag;

Thank you for the info I just received news on my model engine it is a mc 18 r2j crank. According to Mario (part supplier) centre seal is no longer available and big end bearings. I will have to replace the crank and engine casings if centre seal is damaged. Please say this is not the case I need good news.

Edd

If the centre seal is shot, you are completely out of luck. They are not available, full-stop. Your only alternative is to find a crank with a good seal, even if the rest of the crank is shot, and have one rebuilt.

We have to reuse centre seals (although we have some alternative seals to try, but the manufacturer won't rate them to 12,000rpm like the Honda ones), but we are not prepared to use them in customer cranks that we put our name and reputation on.

We've rebuild 87~88 NSR, HRC F3, and HRC RS250 NF5 cranks reusing [good] centre seals (the customer is always informed that we reuse the seal), and we've never had a failure. The seal must be perfect though, or we write the crank off.
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Andy.
NSR-WORLD.COM

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