Seized NSR250 - Opinions?

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Atesz792

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Sooo, family has an NSR 250.

Long story short:
Bought around 2000, we threw a bunch of money at it, then it seized under Dad, and he tossed it in the back of the garage.

Fast forward to 2010, we threw a whole other bunch of money at it. Shop said break-in would be 1000 km's and until that we should be gentle with the beast.
At exactly 997 km's while passing a car, it seized under me pretty far away from home. Not far enough to call a trailer so pushed it for an hour or two. Being a tall guy, my smile was not sincere while doing that.
I knew what one should do in that kind of a situation so pulled in the clutch when the rear wheel stopped. Stupid me just didn't believe what happened (could not, would not...) and dropped the clutch a second later. Some noise followed, but engine remained seized. Pulled lever back in.
After about an hour of pushing I tried kick starting it. It DID turn over at that time, but didn't start.
Pulled the spark plug at home and noticed that the ground electrode had disappeared (it melted completely). I should add that coolant temp was pretty high during the whole ride, but I was inexperienced and didn't know s*it was going to happen. I know I should have.
Considering that all available funds have already been pumped into it, it got tossed into the back of the garage - again.

A few years later I bought the GS500F and I love that bike reaaaally much.

The 2 stroke bug has started biting me again. This time, if I want to put it back on the road, I will have to do the labor.
Opinions? Worth it? What do you all think I would I find if I opened it up?
 
it was probably running lean - carb dirty or air leak.
as you have seen first-hand; two cycle engines can be reliable; or they can be troublesome. none as reliable as a four cycle.
 
You need to learn to read plugs and change jetting - basic 2-stroke survival skills. A well tuned 2-stroke will go 10's of thousands of miles w/o incident. A badly tuned one will either quit or throw you into the dirt.

With 2-strokes you have to pay attention to all possible air sources. Crank seals, all gaskets, carb boots, etc. I even had a porous case casting kill a Yamaha MX400 motor twice before we found it. Once we sand blasted the case, soaked the casting with penetrating epoxy and repainted with black epoxy paint, never another issue. AFAIK that bike is still running 20 years later ...

If you like the bike, do the work and learn ...
 
My way of dealing with crank seals is to wipe on a thin dose of Permatex RTV around the outside edge and then a coat of vasoline (petroleum jelly) around the inside and on the shaft. Old racer boys taught me this one. The vasoline hangs on quite well and lubes the seal lip until there is enough new oil from running to keep it wet.

This is especially true with double lip seals. I try to fill the void between the lips with vasoline. I have torn down engines after races with seals done this way and they were still immaculate with vasoline in the void.

I use vasoline as a light assembly lube during critical work, unless the job specifically calls for other lube like cam shaft moly paste, etc. Seems to work well
smile.gif
 
it most definitely leaned out.
this problem existed from before the first rebuild.
lots of causes and you must find it before you kill yet another rebuild.
 
Originally Posted By: Atesz792

Pulled the spark plug at home and noticed that the ground electrode had disappeared (it melted completely).


This one statement tells an entire story.

Should've paid more attention to the tune (or vacuum leaks, something 2-strokes are VERY VERY sensitive to!)
 
I have rode many 2 strokes and still have a mower with 2 stroke along with handful of chainsaws and the plug will quickly help with finding the issue of to lean.
 
It's an NSR250, it has to be kept in running order, it's not allowed to disappear. My last 2 stroke, a DT230 did a left main because of the oil seal. I didn't pick up the symptoms fast enough - it leaned out enough to be going like a cut cat, it just didn't want to cruise, on and off only. Some of the older 2 strokes had the right hand main bearing lubed by the gearbox, when that seal leaked they would suck in gearbox oil and smoke...more than usual.
 
Originally Posted By: Atesz792
Sooo, family has an NSR 250.

Long story short:
Bought around 2000, we threw a bunch of money at it, then it seized under Dad, and he tossed it in the back of the garage.

Fast forward to 2010, we threw a whole other bunch of money at it. Shop said break-in would be 1000 km's and until that we should be gentle with the beast.
At exactly 997 km's while passing a car, it seized under me pretty far away from home. Not far enough to call a trailer so pushed it for an hour or two. Being a tall guy, my smile was not sincere while doing that.
I knew what one should do in that kind of a situation so pulled in the clutch when the rear wheel stopped. Stupid me just didn't believe what happened (could not, would not...) and dropped the clutch a second later. Some noise followed, but engine remained seized. Pulled lever back in.
After about an hour of pushing I tried kick starting it. It DID turn over at that time, but didn't start.
Pulled the spark plug at home and noticed that the ground electrode had disappeared (it melted completely). I should add that coolant temp was pretty high during the whole ride, but I was inexperienced and didn't know s*it was going to happen. I know I should have.
Considering that all available funds have already been pumped into it, it got tossed into the back of the garage - again.

A few years later I bought the GS500F and I love that bike reaaaally much.

The 2 stroke bug has started biting me again. This time, if I want to put it back on the road, I will have to do the labor.
Opinions? Worth it? What do you all think I would I find if I opened it up?


It's worth it as they are a blast to ride, a collectors item and cheap to maintain.:)
 
Thanks guys.. I share your opinion (well.. except for the cheap to maintain part.. obviously never owned one or has much more money than I do ATM.. cheap is subjective), that is why it's a hard choice.
Thanks for the tips about possible causes. How do I start searching for the leak? Though I seem to remember that it was smoking so much it resembled a steam locomotive.
 
Plug the exhaust port, remove the carb and pull a vacuum on the engine through the intake. If it will hold a vacuum the bottom end is good. If not then pressurize through the intake and look for leaks.
When I did 2 strokes this was the fastest and most efficient method for leak issues.
YMMV

Smoky
 
Originally Posted By: Smoky14
Plug the exhaust port, remove the carb and pull a vacuum on the engine through the intake. If it will hold a vacuum the bottom end is good. If not then pressurize through the intake and look for leaks.
When I did 2 strokes this was the fastest and most efficient method for leak issues.
YMMV

Smoky


That's the way it's always been done. Get some rubber stoppers that will fit the various port flanges and have at it
smile.gif
 
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