Hi all.

Im having a bit of a problem with my nsr 250 mc 21.

Its not burning all the fuel on the bottom cylinder, the result is that it is wrecking plugs flat out and there is sh*t coming out the exhaust.

I've been told that it could be that the crank bearing has shitted itself and taken out the seal and is sucking in gear box oil that's stuffing it. It doesn't look or smell like there is any petrol in the gear box sump.

Is there anyway of checking to see if the seal and bearing has shitted itself?

Any help would be great as it looks like Im going to be up for a bit of cash.

Cheers

Welcome to the site Joe, shame yor first post is about a bad NSR!

Firstly, it sounds like the jetting may be out on the lower cylinder, and it's runnin rich. Either that or for some reason the plug is not firng properly and it's not burning all the fuel.

You need to do a compression check to see if he cylinders are in good condition.
_________________
MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

Hi, i did a compression check about 1-2 months ago when it first started playing up, it came out both cylinders 130.

It still has standard jets in it, i thought that about the spark, would you say that it could/would be a ignition coil??

Cheers

Could be yes. We've had a few instances of bad supply to the coils, so check the spade connectors for pitting and security of fit.
_________________
MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

We've found dirty pins in the PGM connector too which can drop one cylinder. I think the lower cylinder is a black/yellow wire (of the top of my head though).
_________________
If I have to take the carbs off once more...

StephenRC45 wrote:
We've found dirty pins in the PGM connector too which can drop one cylinder. I think the lower cylinder is a black/yellow wire (of the top of my head though).

That yellow and black wire off the top of your head Steve, is where we plug you in at the lab!
_________________
Andy.
NSR-WORLD.COM

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

Please DO NOT PM me for technical advice. My time is precious, and you will probably receive a faster response on the Forum anyway.

Check us out on Facebook! Please "like" our page!

When my centre crank seal died, the mixture still burned OK as long as the revs were kept up. It was the part throttle and bottom-end rpm that suffered the most. It still made 60hp though!!

You can check the centre crank seal with the motor in place. Take the barrels off (keep the heads in place to save on gaskets) and mix up some pre-mix at 50:50. Fill the upper (left) side crank case with the pre-mix, and put a drip tray under the lower cylinder. You'll soon see if the seal is buggered!

I imagine there may be a very slight/slow amount of transfer between the cases over an extended time, but if the seal is shot, the level in the top case will drop noticeably in a very short time.

If the seal between the transmission and the crank has gone, it would be given away by white smoke from the RHS exhaust and the transmission oil level dopping as it is burned off.

Oh, and welcome to the Forum!
_________________
Andy.
NSR-WORLD.COM

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

Please DO NOT PM me for technical advice. My time is precious, and you will probably receive a faster response on the Forum anyway.

Check us out on Facebook! Please "like" our page!

Andy wrote:

StephenRC45 wrote:
We've found dirty pins in the PGM connector too which can drop one cylinder. I think the lower cylinder is a black/yellow wire (of the top of my head though).

That yellow and black wire off the top of your head Steve, is where we plug you in at the lab!

I did wonder why I had them
_________________
If I have to take the carbs off once more...

"It's ALIVE!!!"
_________________
Andy.
NSR-WORLD.COM

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

Please DO NOT PM me for technical advice. My time is precious, and you will probably receive a faster response on the Forum anyway.

Check us out on Facebook! Please "like" our page!

Come on Andy....now you're just getting carried away. The only time I saw Suh-teve move at any sort of pace was when the whisky was flowing.

Another whisk.........oh, help yourself mate

How dare you!

At least I could still move Mr Matt!

Andy knows I like a touch of whisky, and he saw the state I get into when I have a tad to much..... oh make that a double hey!?

Anyway back to this black and yellow wire off my head......
_________________
If I have to take the carbs off once more...

Hi, thanks for that so far guys, ill check em out and see how it turns out, also any ideas that are more simple than pulling the motor to bits would probably be better too.

Thanks

They'd be better in that they're easier, but sadly they wouldn't tell you if the seal is gone.

There really isn't much pressure built up between the two haves of the crankcase, so as Andy has pointed out, you're only likely to notice it at low RPM.

Have the exhaust off and take a good look up t the piston with a bright light.

Are the powervalves working properly?

Is there a good blue spark?
_________________
MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball