Hi all,

Just got myself a 92 MC21 SE. Very happy with it bar it doesn't run too cleanly.

Admittedly it's done only 20 miles since being imported into UK. The dealer told me the carbs had been cleaned out, etc but fuelling seems quite "wooly" as in doesn't seem to pull cleanly. A bit like it's running out of fuel. Happens at about 8k but clears by 9k. Although it's not always consistently at this rev range. Sometimes lower but occasionally higher.

Anyone got any ideas? It's been 9 years since I last owned a 2 stroke so my knowledge has kinda dropped a bit. Could it just be it needs a good run to help clear it out? Obviously no bike likes sitting around for long periods of time and I really don't know how long this one sat in Japan before it was imported.

Regards,

Dave.

Has the bike been serviced - to YOUR satisfaction?
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There are 3 things you want to do with any new NSR (or any 2-stroke really);

1. Pull the carbs, and check what the settings are
   
2. Clean the air filter(s)
   
3. Fit new plugs.

You never know how it was previously set up before it was sold. It could've had race pipes on before, open carbs, even an HRC jet kit... some of which may still be fitted, if you're lucky!

Before you know the base settings there is no way to know where to start looking.
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Andy.
NSR-WORLD.COM

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Andy wrote:Pull the carbs, and check what the settings are

Pal of mine, mc28se, the one reviewed in MCN, they raved about how well it went;

HRC card (good)
JHA pipes (good)
Stock airbox (not so good)
Stock jetting apart from the biggest pilot jets you can buy (bad)
RC valve marks lined with the TPS plugged in (very bad, and I've seen that one on three different bikes)

And yes, this was a big money dealer bike/box of bits...........

Probably quite lucky it ran so badly it wouldn't rev past about 9500 rpm (and didn't work at all below about 7000)! I doubt it'd have survivied otherwise, the funny thing was he thought that might be how it was supposed to be AND he'd taken it to a dyno, paid to have it setup and they said it was OK.
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I think a more appropriate quote of my post would've been:

Before you know the base settings there is no way to know where to start looking.

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Andy.
NSR-WORLD.COM

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You're right, if the bike is stock make sure everything in the carbs is stock, clean them up and check the RC valves are set correctly.
While the carbs are off have a peer inside and make sure the reeds are OK.

Then if it doesn't work on clean plugs something is actually wrong.

Check the plug caps are well attached to the leads. I chased a random spluttery missfire for a couple of weeks before the cap and lead actually parted company.
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Please do not PM me technical questions, if you can't find it on the Forum start a thread

Basically, a totally stock NSR250 works perfectly... far better than most "tuned" 2-strokes!

MC18, MC21, and even MC28 restriction is only really noticeable in 4th, 5th, and 6th, at the very top-end, or when riding with quick guys on full-power UK 250's fast!

If a stock one isn't a dream to ride, then it has issues. Put it all back to completely stock and work from there, because we know how good the setup is. It's a fault-proof test!
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Andy.
NSR-WORLD.COM

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Thanks for the suggestions guys.

I'll strip it down once I get a day off and see how she's set up.

If need be I've a friend who's a mechanic but he lives a distance away.

Thanks again,

Dave.