Hey guys, new member here! I am 54, been riding for over 30 years and been dreaming of owning a 2 stroke for a LONG time. Well, I am finally in a position where I can pull the trigger on one and I am working a deal on a 1990 MC21 NSR250R from moto2 imports. I am a decent wrench but I have a lot to learn on this bike! That being said, this bike will be ridden on the street occasionally and most likely never be tracked but I was wondering if there are any issues with these or things to be aware of?

I am pretty damn stoked about getting it!

Expect to replace all the rubber. It's a 29 year old bike. The biggest item to pay attention to are the crankcase seals. Once they start leaking, you're splitting the cases.

I've replaced every hose, o ring and seal on my 1994 mc28.

Good advice and something I will be paying attention to. Hoping the crank seals are something I won't need to mess with for a while but i completetly understand. Any good shops in the U.S. that can do a total rebuild when needed?

If the bikes been used on a regular basis you might be lucky with the crank seals for a while, but if it's one just out the crate and been stood a long time you might not be so lucky as they tend to dry and go brittle, also make sure you use a good quality 2 stroke oil.
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Lesviffer750 wrote:If the bikes been used on a regular basis you might be lucky with the crank seals for a while, but if it's one just out the crate and been stood a long time you might not be so lucky as they tend to dry and go brittle, also make sure you use a good quality 2 stroke oil.

Thanks....the bike has like 2700 miles and that does sort of worry me (lack of use) but the Moto2 folks (Tim Hope is a really nice guy) assured me they would be checking it over well. Me getting the bike and month later having to do a bottom end/seals would not be good for their business, haha.

Any tell tale signs of bad seals (I know the bike will run lean)?

Do a leak test. You can search the site here on how to do it. I made blanking plates and plugs you can borrow if its something you want to take on. I'm in Texas so mailing the stuff is not trouble.

ericandchi wrote:Do a leak test. You can search the site here on how to do it. I made blanking plates and plugs you can borrow if its something you want to take on. I'm in Texas so mailing the stuff is not trouble.

Thanks and I will let you know! Going to be a few weeks before I get the bike. It is being de-restricted and getting tyga pipes/jetting, new chain, Samco hoses, etc.

Just a question also....if i HAD to have a bottom end done at some point (if it needs seals I would probably just have the motor rebuilt).....are there any options for a good rebuilder in the US? Can i ship the motor to NSR-world performance in the UK? Just looking for options when the time comes.....

All the hard stuff is pulling the engine out. Once its on the bench doing the bottom end is easy. I would think shipping overseas will be expensive. I'll be retired next summer, until then I have plenty of side projects. I am curious how much folks would charge you.

For me, if you get to that point you will want to vapor blast everything and install all new bearings. The hardest one is the upper clutch arm which is a small needle bearing way up in the case. Took me a while and some surgery but i got it out. Much less work if all you want are new end seals on the crank.

If its the center crank seal that's bad things get expensive.

ericandchi wrote:All the hard stuff is pulling the engine out. Once its on the bench doing the bottom end is easy. I would think shipping overseas will be expensive. I'll be retired next summer, until then I have plenty of side projects. I am curious how much folks would charge you.

For me, if you get to that point you will want to vapor blast everything and install all new bearings. The hardest one is the upper clutch arm which is a small needle bearing way up in the case. Took me a while and some surgery but i got it out. Much less work if all you want are new end seals on the crank.

If its the center crank seal that's bad things get expensive.

All good info. If I had to to take it apart, I think it would be getting a new bottom and top end kit, including crank. In any case, I am overthinking it at this point and hopefully I don't have to worry about it for a while. We will see.

Hello CRFan1, and welcome to NSR-WORLD!

Looking forwards to seeing your thoughts once the bike arrives.
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Andy wrote:Hello CRFan1, and welcome to NSR-WORLD!

Looking forwards to seeing your thoughts once the bike arrives.

Thanks Andy! To say I am stoked about getting this bike is an understatement! Look forward to hanging out for sure!

When you do get it, ensure the RC Valve operation is smooth, and there are no tight/kinked/sticky cables. If there's any resistance to the RC Valve servo, it can blow the PGM (ECU). That and the centre crank seal are the two weak points of the 89 to 97 NSR250s.

Don't let that put you off at all though, they are unquestionably the most reliable and well laid out 250cc 80s/90s race rep available.
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Andy.
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Andy wrote:When you do get it, ensure the RC Valve operation is smooth, and there are no tight/kinked/sticky cables. If there's any resistance to the RC Valve servo, it can blow the PGM (ECU). That and the centre crank seal are the two weak points of the 89 to 97 NSR250s.

Don't let that put you off at all though, they are unquestionably the most reliable and well laid out 250cc 80s/90s race rep available.

Great info. thank you! I will be going over it with a fine tooth comb for sure.......

Do you know the particular model on the way?

NSR250R - Base model.
NSR250R-SE - Adjustable Fr/Rr suspension & dry clutch.
NSR250R-SP - Adjustable Fr/Rr suspension, dry clutch, Magtek wheels.
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Andy.
NSR-WORLD.COM

Please keep all responses to Forum posts on the Forum so that others may benefit.

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