Hello,
I am buying a 90' MC21 which was stored for about 3-4 years. The bike is rather clean, started without problem before storage but I think it will now need some servicing.
Apart from usual replacement (fluids, brake hose line, cables, tires), what would you advise me to verify and do ?
Then, as I never had an NSR, what type of oil should I use (gearbox and 2 stroke), and what is the best petrol to use ?
I do not intend to race with it, but have some fun on the road.
These may seems basic questions but I hope you will excuse a newbie for asking. Better ask something dumb than break something for lack of care.
Sincerely

First thing I would do is make sure the RC Valve parts are all clean and free to operate, with zero resistance. Remove the cables and oil them if there are any signs of sticking. You want to protect the PGM-III as they're getting extremely expensive and difficult to replace!

Make sure the brake calipers/master cylinders are well serviced!

Use fully synthetic 2T oil, such as Rock Oil Synthesis 2, Castrol TTS, or Silkolene Pro2. We use Rock Oil GRO in all of our NSR transmissions.

Put the best fuel you can afford in it, with the least amount of ethanol content you can find! The NSR will actually run with pretty crap [low octane] fuel, but just because it will, doesn't mean you should! Besides, the ethanol content definitely effects the jetting, and almost certainly a major contributing factor to the poor longevity of the centre crank seal.

And don't forget to post some picture and update us later on!
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Andy.
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Hello Andy,
Thanks for the advice. I didn't think about the valves.
Do you think I should clean the carbs ?
It will be a while before I get the bike (January 2020), but when I get if I will post some pictures.

Sorry, I misread the post and thought it just said "started without a problem".

Definitely a good idea to clean and check the carbs. Pay close attention to the tiny holes in the slow jets, and the small power jets. Be very careful when removing the alloy screws to access the power jets, and use a good size close-fitting screwdriver, as the screws are easily damaged.
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Andy.
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Hello Andy,
Finally, no bike, it was a scam. I am still looking.
Anyway, as it may help someone, what are the symptoms of a defect central bearing seal ?
I saw it was one of the main problems that could occur, but I did not find how you could detect it without opening everything.
Sincerely.
Pierre

Sorry to hear it was a scam, Pierre.

There are a number of clues to a bad MC21/28 centre seal, but the two most common are a difficulty to start, and a poor/erratic idle.

When riding, the RPM will often "race" when the engine is at normal operating temperature too, and won't settle down unless a little load is put on the motor. They generally run very poorly lower down the rev-range, and sometimes struggle to pull through the RC Valve transition range (around 7000-8000rpm). They can however appear to run very well at high RPM, so don't let a seller try and fob you off by saying "the bottom end just needs a bit of a tune"!

Of course all the above depends on everything else being in absolutely tip-top condition. I.e. battery/charging system, fuel system (fresh/clean fuel), air filter, top-end (piston/rings), and last but not least, correct jetting. There is no reason whatsoever for any NSR not to pull right from the bottom-end all the way to 11,500+ without a single hiccup, regardless of tune. Even a full-on 70hp+ HRC spec F3 will pull flawlessly to the redline if it's in top condition.

The above also applies to the 1989 MC18 R5/6K, as it uses a similar crank/centre bearing.
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Andy.
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Hi Andy,
Thank you. I think it could help other people too.
Is the problem the same with the MC18 R2J with the seal outside the bearing ?
Sincerely

The symptoms can be similar for the MC16 and MC18 R2/4J MkI, but are notably rarer, even though they are older models. The 1987 and 1988 centre seals are of similar design, but are different in size.

There's a replacement offered by T2 Racing for the 1988 MC18, but no known replacement for the MC16 seal [with the correct speed rating and construction] that I know of.
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Andy.
NSR-WORLD.COM

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Thank you Andy !