NSR50 siezed---help

OK guys...thank you so much for your input. I'm taking your advice and splitting her up. Oh, i forgot....i've never done that before. I can handle a top end, but a bottom?

Does anyone have a service manual they could email me or possibly some step by step? I've seen a bottom end done on youtube on a yz but that looked quite complicated...case splitters, flywheel pullers, etc.

 

From all the MX bike's I've done and all the ones I've blown up, it looks alot like just too many hours between rebuilds. The piston wears and starts to wobble inside the bore causing the skirts to slap the cylinder wall. Eventually this will cause cracks, then the skirt comes off. You can flush it, its been done thousands of times by many people, works 90% of the time. Seeings how its winter though and not much riding to be done, I'd split the case just to be sure. If you do flush it, gas works, and blow it out with a blow gun really good.

 

And you come up with this figure how??? I have done many, many rebuilds that were required just because of people following that kind of advise. If the piston was left in long enough to stress and break, what does that say about the lower end maintenance schedule?? Tdub

 

Shit.....I've been racing my NSR since 04 (probably around 75 track days and I'm pushing 200lbs in gear) and have done "nothing" to it except change the oil and put gas in the bugger.

 

Well I for one have done it several times. Go hang out at any MX track (well, probably not anymore) where the 2 strokes run, and you'll see it being done at the track, as well as people doing it at home. Not every one who smokes a top end rips the bottom half apart. Is it the 100% right way to do it?? No, probably not, but when time is a factor (you have a moto in 20 minutes) then right or wrong is out the window.

 

On the picture with the rod sticking up, it looks like there is bluing on the crank which is usually caused when the big end rod bearing overheats. It appears to me the crank got hot enough you need to replace it.

 

I know one thing,if my Honda RS 125 seizes good,out comes the crank!BuT then again I have 2 bikes and a spare motor I've tried your way and it may work once in a while but for a few hours work its worth th epiece of mind knowing it won't make a mess!

 

The NSRs are built proof, look at this thing...

http://minigpx.com/news/article/?article=25346

 

Knowing this is for his son, there is no way I would chance it.

Split the cases put a new crank assy, oversized piston and rings, bore the cylinder and have a nice fresh engine.

 

Yeah I really doubt he overrev'd the lil bugger! I've got a stock nsr motor for sale if ur interested

 

I ordered the tools to split the cases, and got a deal on a new engine. Think I'll just put the engine in for now, and pimp the old one out with new crank, big bore, etc. Might be fun to have both.

Thanks to all of you for your help and advice on this.