NSR250 rebuild - 'The ELF Special'

[al.ramsay]

Well, its been 5 and a half months since my last confession... ooops, sorry, wrong forum

I finally got my hands on a MC21 that as reportedly working fine apart from a few bent/broken parts on the left hand side from a drop. When I got my hands on it, I stripped the fairings off as I didn't want the Repsol paint job (will get this stripped back and repainted) and started about finding out what needed doing. The bike wouldn't start due to the kickstart being locked up, so it was off to the doctor for diagnosis. Once the engine was completely stripped (parts then ordered) we discovered the crank was seized in one of the bearings. We are going to have a crack at replacing all the bearings (told by a motorbike engine builder that they can do the job) and got in contact with a crowd in the UK that can supply the bearings - certainly the koyo bearings listed for an mc18.

What I am actually leading to in this longwinded message is, is the bearings in the mc18 the same as the 21? if that is the case I can replace them. Otherwise, I will have to pull them out and see if there are numbers or something on them. If anyone has the bearing numbers, please yell out, just so I can check my information.

EDIT; Further to this message, I have found out that these can be sourced locally, well locally in Australia... thanks to Neal for pointing me in the right direction

Cheers

[gammaguy]

Well, its been 5 and a half months since my last confession... ooops, sorry, wrong forum

I finally got my hands on a MC21 that as reportedly working fine apart from a few bent/broken parts on the left hand side from a drop. When I got my hands on it, I stripped the fairings off as I didn't want the Repsol paint job (will get this stripped back and repainted) and started about finding out what needed doing. The bike wouldn't start due to the kickstart being locked up, so it was off to the doctor for diagnosis. Once the engine was completely stripped (parts then ordered) we discovered the crank was seized in one of the bearings. We are going to have a crack at replacing all the bearings (told by a motorbike engine builder that they can do the job) and got in contact with a crowd in the UK that can supply the bearings - certainly the koyo bearings listed for an mc18.

What I am actually leading to in this longwinded message is, is the bearings in the mc18 the same as the 21? if that is the case I can replace them. Otherwise, I will have to pull them out and see if there are numbers or something on them.

If anyone has the bearing numbers, please yell out.

Cheers

I have parts manuals for all the NSR250,s let me know if you need the bearings decoded

[al.ramsay]

I have parts manuals for all the NSR250,s let me know if you need the bearings decoded

Do you have a parts list for the MC21 that you have in stock? I could be interested in buying some parts for future projects - certainly interested in pricing for a new crank if you have one?

I would like to know what the part number is for the big end bearings if possible? Wiseco B1059 bearings

Al

[gammaguy]

Do you have a parts list for the MC21 that you have in stock? I could be interested in buying some parts for future projects - certainly interested in pricing for a new crank if you have one?

I would like to know what the part number is for the big end bearings if possible? Wiseco B1059 bearings

Al

Got heaps of parts for them in Japan

Send me a list of your requirements also what part numbers you need

[al.ramsay]

Got heaps of parts for them in Japan

Send me a list of your requirements also what part numbers you need

My big one t the moment are the big end bearings for the conrods. I have the wiseco number but would help to have the Honda number if possible.

Do you have anything in terms of fairings? Decals to suit a '92? Complete lock set?

Cheers

Al

[Neal]

There is a guy selling cheap rod kits on ebay but I don't know anybody that has used them yet .
The big end bearing is the same as the crf150 . ProX sell them .

[Angreal]

Been following this thread since I went to the Isle of Man TT last year, stumbled across a stunning MC28 and decided that I needed another bike (previous one got stolen years ago). Picked up one from Japan, got it shipped here and gave it some TLC and just need new rotors to pass the brake declaration.

Anyway, keen to see your bike continue to progress Something about the smell of two strokes just seems right.

On a side note since it seems everyone who is knowledgeable about NSRs is here, I've been told that the cranks on the NSRs can't be rebuilt etc but it seems they can? Also, does the HRC RS250 crank swap into our bikes easily enough and does it offer anything? Sadly I have a lot to learn but I do know that I'm glad I picked up a tidy NSR while they still kinda exist

[Wil_K]

Feel free to hijack this thread while I procrastinate on the NSR project.

Angreal, the RS250 cranks will not drop in any of the NSR cases unfortunately. I think the RS conrods are a touch shorter as well. And yes cranks can be rebuilt. The biggest problem is the crank pins can't be replaced as they are a part of the webs. And OEM conrods were never made available. So whether a rebuild is possible will depend on the condition of your pins and rods. There is one place in Spain I think that does custom rods for the NSR though.

Anyway, keen to see your bike continue to progress Something about the smell of two strokes just seems right.

Saw a TDR250 take off from the lights a few days ago blowing a nice cloud of blue smoke. Got me exited to get back into the NSR soon.

[koba]

Saw a TDR250 take off from the lights a few days ago blowing a nice cloud of blue smoke. Got me exited to get back into the NSR soon.

Yum!

[Neal]

Glad to hear about another nsr being revived !
The RS crank can fit into the older casings but not the mc21 or 28 , there is nothing to gain from the crank .
All the bearings can be replaced on the mc21/8 cranks and you have 2 options for rods , Samarin or unknown quality ones on ebay . I have not seen anyone use them yet .

Did that nsr race at the Isle of Man ?

[Angreal]

No. The only bikes that raced on the IOM TT were 600s, 1000s, 650 twins and electric bikes (oh and sidecars but those guys are proper crazy). It was one of the many bikes fans take to the island I was oogling over. Also saw a v4 desmo but it wasn't as nice in real life as I thought it would've been... I guess I just have my heart set on one day owning a NSR500 The other bikes I quite liked there were all the old BSA bikes as they had a massive following but all the owners said the same thing which was along the lines of "rubbish bikes but we love them"

So I guess if my bike looks/runs decently it's one of those "it aint broke, don't touch it" moments then. Well a summer with a few decent rides and I've struck an oil leak and a fuel leak that I'll deal to over winter.

[Arronduke]

Just read the whole thread.
Keep working on this it is going to be cool when its done.

I had an 86 NS250R and loved it, it was the faring on the side stand that was soooooo cool.

Also enjoying the hours your putting in to getting the engine running right, long frustrating hours.
But in the end its worth the effort.

Will keep following this thread!

[Wil_K]

Cheers Arronduke. I love your RG, that would be a dream bike for me, though I think I'd prefer to have an RGV500 special!

I should really get back into this bike soon. It's just sitting in my Dads garage at the moment still ridable but I suspect something still isn't right with the engine. I've done a quick crankcase leakdown test which seems to suggest that either I have a massive centre seal leak or I just have air leaking across the read cages. If I test only one half of the engine I can't hold any crankcase pressure at all. But blocking off both sides and it seems to hold it's pressure ok. My sealing methods were a bit rough so I was expecting a few leaks. I'll take it into the workshop one day and fashion up a much better pressure testing jig.

Seems odd that there would be such a large leak since it idles very nicely. It is quite hard to start however.

I haven't given up on this, just procrastinating with a couple of other projects.

[koba]

I haven't given up on this, just procrastinating with a couple of other projects.

As we all do!

[Wil_K]

Probably going to have to sell the NSR If anyone is interested, make me an offer. Comes with lots of parts: wider MC18 front and rear wheels, MC18 swingarm, shock, front forks, brakes, radiator, new crank bearings and many other parts that I can't remember.