Engine rebuild

[mr jamez]

Hi

I have basically stripped the whole of the NSR down now, and I thought it may be a worthwhile job to rebuild the engine, as I don't know the history of it and the previous owner didn't do any work on it. First of all what causes a 2 stroke to seize? is it just the piston rings? or the piston as well?. I guess that it will all need cleaning out, not to sure what to use really. Oh and what parts am I going to need, I guess new piston rings, head gasket and mabey a piston?

Can anyone think of some problems that I *may* encounter also

Or is this just a total waste of time and money

ta

[Robby]

when I rebuilt danny's NSR we used the following bits:

Pattern piston and rings
Gudgeon pin
small end bearing
head gasket
base gasket
oh shit clips

I would recommend taking the engine out of the frame, space is a little tight. The gudgeon pin may also be rather tight, I forced Danny's one out with a long bolt, a nut, and lots of spacers to slowly squeeze it out.

Use the manual, do it slowly, and its easy. The only bastard part of the job is setting up the powervalve at the end.

[mr jamez]

Right ok thanks, the engine is ready to come out now so I will do that tomorow. Think I will just replace the whole lot, don't really want to be doing this again. If I get stuck I will just have to drag one of you down here or something

[Kickstart]

Hi

Once you have enough off the NSR to take off the top end of the engine it is quite easy to remove the engine (far easier than the RS125 or the Mito).

Siezures are normally caused from lack of oil. However running lean can do the same (causes the bike to overheat), as can running hot for any other reason (no coolant, blown head gasket, knackered water pump, etc).

If it has seized then the piston will almost certainly be knackered.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[mr jamez]

Well I dragged it out today, had a bit of a mishap with the gear box oil staining my legs but otherwise it went fine

Just to clarify, I will need:

Cylinder head gasket
Cylinder base gasket
Piston
Piston rings
gudgeon pin
Small end bearing
left + right crank case gaskets

Also I had a few problems with the clutch, but whether that was with it not being used that much I dunno. Are they hard to fit, do you need any special tools etc? the front sprocket also looks a bit funny, some teeth look *sharper* than others?

ta

[Kickstart]

Hi

You will also need some circlips (sometimes known as "oh shit" clips, as that is what you say when they ping across the garage).

I am not sure with the NSR, but clutches can sometimes be a pain to fit, depending on how they are located (eg, FZ750 it is a doddle to change the clutch, but G had quite fun fitting one to a Hornet at the drag strip).

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[mr jamez]

Right nearly there now, although there seems to be a small mark/crack in the plating on the cylinder wall It is very small, the engine seemed to run ok with it like that.

[jimbo]

UH-OH! I wouldn't risk putting that cylinder back in. If u can feel the crack with your finger nail, then it's a baddie.
I had a similar thing on an NSR80, which doesn't have a plated cylinder. Thought it would be ok with a tiny little notch, and after 3 days it ate the piston.
The problem is that that small area between the ports is under higher stress than the rest of the cylinder-it runs hotter and bears a higher load, so it's only going to get worse.
I'd check to see if the barrel can be honed back and replated. You never know if there's a hairline crack running into the casting though. A bike shop should be able to tell you.
Even a clean second-hand cylinder would be a better option.
I just remember all those shillings i had to spend again-another piston, another set of rings, another set of gaskets, another rebuild....

[mr jamez]

Well I have already decided to get a new barrel and I think your post has made me certain, about £90 with a piston so not that bad really. I can feel it with my nail and I don't want all the parts I am putting in now to get broken because I didn't spend a little bit more.

Better safe than sorry

How much is it to get it replated?

[cagiva gezzer]

www.stanstephens.com

Not saying go there, but the prices that he charges are about normal.
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"because one stroke isnt enough and four strokes waste two"

[Git]

[Kickstart]