How Many Teeth????

Diehard · Trackday Trickster Joined: 18 Jan 2004 Karma :

Ok I've tryed everything! And now this is the last thing I can think of. With my NSR125RK (1989) only hitting 60, in 4th gear, at 9,000 revs (then won't go anymore), I have adjusted mixture (very lean now), checked float level, everything! It has a whole new top end and still won't go past 60-65! So at a last ditch effort, sprockets! Out of interest how many teeth should there be on the front + back sprocket on my bike? Anyone know? This is really bugging me, the only good thing is 0 - 60 is in seconds! Very fast, but then it chugs along! Embarrassing! Want the speed at max so it will sell easier in the future, any help?

P.S. thanx for all replys to my last post about this

Diehard
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McJamweasel · BCF Junkie Joined: 22 Mar 2002 Karma :

If the mixture is too lean then you will damage the engine, so becareful with that.

If I remember right, if should be a 13 tooth on the front and a 35 on the rear.

Have you done a compression test?
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Diehard · Trackday Trickster Joined: 18 Jan 2004 Karma :

Cheers for that I'll count them tomorrow. Erm on the compression test... No because some people say, yes do one, then some say no it isn't relevent on my bike. How would I go about it, and if it was"incorrect" whatever that refers to, how would I fix it?
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Hex · Party Boy Joined: 04 Feb 2002 Karma :

A compression test is relevant on engine with pistons really, if it isn't producing the right amount of compression (ie too low) it won't be producing as much power as it should.

If the compression is low then its normally a replacement ring job (unless theres scores in the bore or the pistons the wrong size etc etc etc), But basically if it's low the compression is escaping somewhere where it shouldn't be.
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Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

A compression test is probably the first thing to do. It is quite easy to damage the rings when putting the barrel on, and that will reduce compression. A compression tester will cost under £20 from Halfords. The result should be 143psi, give or take 28psi.

Standard gearing on an early NSR is 13 tooth front sprocket and 35 tooth rear sprocket.

The bike should happily go past 9000rpm in 4th gear. Can you take the cover off the power valve and check that it is operating. As the revs rise it should turn clockwise (about 30 degrees I think). Ignore what it is doing at very low revs as I am not sure whether it has some self cleaning functions which might to some strange things around idle.

Also check the air filter is clean and take the exhaust off and check there is nothing stuck down there.

All the best

Keith
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Diehard · Trackday Trickster Joined: 18 Jan 2004 Karma :

Well as I said b4 the power valve is jammed fully open, all the time, cos it was going in reverse! as for the compression test, I have an MOT this month so I'll get one done then, can't hurt I suppose + rings are only £20. Bugger putting them in the barrel though! Also it is a new exhaust, so that is ok. Someone sugested I may have the piston the wrong way round??? Not likely cos I can read, but you never know.
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R1stu · Shrek! Joined: 12 Mar 2003 Karma :

When thing I noticed when I had my 2 stroke was that the exshust system needed to be decoked on occasions.

When My RD and FR50 wouldn't go past 30 without a struggle I decoked the system and the power just came back!

Why don't you try that!
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Diehard · Trackday Trickster Joined: 18 Jan 2004 Karma :

Go on then I'll get the potato and the hot causic soda out and give it a try. Any idea how long I should leave it in the exhaust before I have nothing left?
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R1stu · Shrek! Joined: 12 Mar 2003 Karma :

Like you said! Block up the small end with whatever you can use (I used a rubber wine bung) and mix up the caustic soda until the bucket gets very warm!

Make sure you use gloves!

Then pour into the system until is comes over the top. Leave for 5 minutes to soak in and then top up the system.

I used to leave the setup overnight and all was ok, pour down the drain and rinse well with cold water.

Leave vertical for an hour or two and then put back on!

you should find it helps alot, after a hundred miles or so the baffles and padding should be all dry as well.
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Diehard · Trackday Trickster Joined: 18 Jan 2004 Karma :

Cheers for that will try. I'm a walking disaster though so should be fun! If no one hears from me in a while you know I've burned me fingers off!
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