I have just bought my first nsr 250. It's a mc 16 and done about 22000 km. Hard to know how accurate the speedo is but it is very tidy albeit with a new paint job, black.

I have a couple of questions for the experts about the engine condition .

I have a rough patch at about 5000 but I am wondering if this is the transition of the power valves, once through this she pulls well and have got ore 160 kph before buttoning off and there was plenty of go left.

In the process I have noticed that once I remove the air box cover when running the carbs, particularly the left ( rear) carb , I noted an oil residue in that side of the air box. I note at idle the front cylinder idles stronger than the rear. I note when I rev the engine up when the rear cylinder fires up in earnest the carb starts spitting fuel back, the right carb does it but not so strongly.

I have cleaned out and synchronized the carbs. I borrowed a compression gauge and both cylinder topped out at 90 psi.

I note the specs of the mc 16 are comp ratio of 6.2 to 1 . My calculation, possibly flawed , is that if atmospheric pressure is 14 psi then at this ratio I would expect about 90 psi but the consensus seems to be they should be much higher? I Note that older 2 stroke bikes often had these low comp ratios? A discussion with a local 2 stroke mechanic/ racer revealed he thought if the engine was tired it would be hard to start of idle poorly or be mechanically noisy.

My engine is none of these . But I am feeling now that it may be time to replace the reeds and freshen up the top end with either rings or if worn the pistons as well?

Interested in expert opinions of some or all problems. I can live with the faults as she goes well above 6000 and handles great.

Thanks

Hi buddy
Tha answer is simple:just replace your reeds,reeds is a one way valve,it opens to let the air and fuel/oil mixture in,and is suppose to close after that,if the reed is leaking,once your pistons is under compressoin,it will put pressure against reeds,now if the reeds doesn't seal,it will only spit the mixture back again(atleast some of it,had same problem.new reeds,runs like a bomb

you have low compression i would recommend a top end rebuild.

you should have around 120-150psi on a fresh engine.

my nsr 125 needs a new top end and has compression of 80psi and it no longer runs

Thanks 2 stroke maniac,, hey you were unlucky with the rugby btw.

The problem here is parts availability since the nsr , as far as I know , was never sold here new.

Nsr jb. Thanks good info also. I guess if I have the barrels off I may as well replace pistons and rings rather than jut rings, what would you say?

Any idea how to determine which pistons are required for mc 16 or is it matter of removing barrels and measuring them ?

Thanks again.

We still have a month or so till the better weather arrives

FWIW the R5k in SEED livery was sold new in NZ.
It was sold unrestricted: no wire splice necessary.
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[color=#808080][size=9]Yes,.. I too know how to waste Time and Money,...

Thanks. , I see you're in nz also, any ideas whom to deal with for parts. In particular reed petals ? Are mc18 petals compatible with mc 16 cages , I see a set of mc 18 petals on eBay. Can't find new mc 16 reeds anywhere so far.