I have a seized up conrod bearing and have a spare bearing that I could use. When you say the cank cant be rebuilt are you saying you cant put new bearings ie conrod bearings in? or is there other things you to rebuild?
So basicly what exactly is a crank re-build?
please can someone repond to this question as I am sure it will benefit alot of people.

Until recently, crank bearings for the NSR were even rarer that the proverbial rocking-horse sh!t, as neither Honda nor Koyo (the bearing manufacturer) would supply them!!!

Consequently, NSR cranks were labelled as non-rebuildable, and the only official answer to wear and tear and/or seizure, was to buy a complete crank assembly direct from the big "H".

Recently though a small stock of main bearings has become available from a supplier in Australia, and a link for them can be found on both the homepage and at the very top of the Classifieds page.

Needless to say then, the NSR crank CAN be pressed apart, and new bearings installed, but it MUST be done by a reputable engineering shop - preferably one with mucho 2-stroke experience! Tuners such as Bob Farnham and Terry Shepherd spring to mind! Only recently has one owner in the UK had his crank rebuilt with alternative (to the Koyo/Honda) bearings by Chris Appleby, but his motor has yet to be used in anger!

So, the latest word on the street is, "yes - the cranks CAN be rebuilt, and yes, you CAN get main bearings!", but... there is still no known supplier of big-end bearings although there must be something out there suitable as they most likely won't be unique to the NSR.

Andy.
NSR-WORLD.COM

Hi andy
I have 2 old seized nsr cranks (mc21), the seizers happend on different sider of the crank (conrod bearings), would it be possable, if 1 good conrod bearings from one crank could be transplaneted onto the other crank? this would save a hell of alot of money.thanks

In theory, yes, but the big-end crank pins would need measuring just to make sure.

This may present a big clearance issue between the crank pin/big-end from one crank and the web that it's pressed in to on the other.

I don't reckon big-end bearings will be much of a problem to replace. I bet something like TZ, RS, or even TZR bearings (something anyway - but you do need the speed rating of 13,000+rpm, which is why you can't just pop down to the local bearing factor on the trading estate!!) will be the same, and cheapish too.

For what you are intending, you will most definitely need to speak to a 2-stroke crank specialist. Go for one of the real reknowned proddy tuners like those mentioned in my first reply. Another well known name in 2-stroke tuning/racing circles is Graham File.

Andy.
NSR-WORLD.COM

This is one fo my favorite rants.

Bearings are $150, rebuild by a qualified guy will be $200 minimum. Don't
trust your rebuild to a hack. You will regret it. Ask for ALL runout and
dimensional measurements from your rebuilder and compare to spec. Can you
buy new rods and big ends? That's another maybe $150 with the washers, and
it would be nuts to install new mains without new big ends and rods. So now
we have a used crank for $500. Remember the crank pins will wear out at some
point (spec. is .05mm radial play) and no amount of new parts will fix that.

Why would one go through that headache when a new one is $700, unless of
course the parts are unobtanium.