NSR250 rebuild - 'The ELF Special'

[Wil_K]

Thought I should share one of my current projects. I'm doing a build thread on another forum, but hopefully I can get some local expertise, and maybe a few parts sources here.

What I've got is a 1987 Honda NSR250R (MC16) with a 1989 MC18 engine. I picked it up just 100 bucks in a pretty sorry state. The plan is to do a full rebuild with some modifications.

I'll summarise the build so far:

This is basically what I'm aiming for:


And this is what I started with:

After pulling the engine:


The engine was seized so I decided to investigate by pulling it apart. The pistons weren't seized but the crank was. Water had gone inside and rusted up the right hand bearing.

[Wil_K]

Bottom cylinder was good


Top cylinder wasn't. Looks like it was running lean, as there's detonation marks on top of cylinder and head.


Heads are ok, but I've picked up another one in great condition to replace the top head that was slightly pitted.


Calipers were seized up


Down to the frame

[Wil_K]

Split the cases to investigate. Looks like water had entered the crankcase through a lubrication hole near the bearing.


After a good cleaning with de-greaser and a dremel:

[Wil_K]

De-rusted tank and expansion chambers. I used steel BB's in the tank. Swished them around to remove any flakey rust, then a phosphoric acid soak for the rest. Yeah there's a few spots remaining. The chambers were done with a wire cup brush.



Chambers painted:

[Wil_K]

Calipers re-painted and rebuilt:


Swingarm polished up to a satin finish. The frame is next and both will be clear coated.


Forks rebuilt with new seals. Form bottoms painted and finished with a nice Showa decal.


Polished up the triple clamp. Took ages as it was originally sand cast, and the casting marks had to be sanded down first.


Loosely assembled the front end to see what it will look like.

[Wil_K]

So right now I'm just getting it up to a rolling frame before I tackle the engine. Just need to do a bit more polishing and painting then I can get it assembled.

There's a fair bit more I haven't posted including lots of pics. It you want to see more of the build so far, check it out here: http://www.dotheton.com/forum/index.php?topic=39780.0

On another note, are there any NSR owners who have any spare parts available? I'm mainly after a crankshaft, in usable or rebuildable condition (my old one's not rebuildable). I'm also in need of a good barrel, re-plating them is hideously expensive ($575 quote from NZ cylinders, I think the only place that does it in NZ).

[ducatilover]

I'll be watching this, awesome little beasty

[Neal]

Hi there ,

if your crank pins are ok then you can get rods to rebuild the crank , there are some guys that can supply the main bearings but the centre crank seal is NLA if i am correct .

If you are not fussy , any nsr barrel with head can fit onto your casings .

[Kickaha]

I'm also in need of a good barrel, re-plating them is hideously expensive ($575 quote from NZ cylinders, I think the only place that does it in NZ).

Imdying had a place offshore that was considerably cheaper, think it's posted in one of the RS250 rebuild threads

[Sable]

Cool man. Bits hard to find?

[Wil_K]

Hi there ,

if your crank pins are ok then you can get rods to rebuild the crank , there are some guys that can supply the main bearings but the centre crank seal is NLA if i am correct .

If you are not fussy , any nsr barrel with head can fit onto your casings .

The old crank is pretty stuffed, there's pitting on the small end of the rods. Don't know the condition of the crank pins, but the rods were never made as a replacement part anyway so you can't get new ones (a guy in NZ has had custom ones made though). Bearings are somewhat hard to get, but this being a later model MC18, it uses the same bearings and seals as the MC21 and 28. Actually, an MC21 or 28 crank can be made to fit if you machine a few mm off the outside of the webs.

[Wil_K]

Cool man. Bits hard to find?

Yes very hard to find! Especially engine parts. It's a shame no one makes much aftermarket parts for these.

[gammaguy]

Yes very hard to find! Especially engine parts. It's a shame no one makes much aftermarket parts for these.

Not true

I have a warehouse in Japan full of parts for MC 11 16 18 21 28

[Neal]

You make a plan - if your pins are 24mm mc16 and early mc18 then you use rs125 rods .
If they are 25mm , you use the rods from Samarin ( Tucker ) or the crm125 with a yz small end bearing .

[Wil_K]

Not true

I have a warehouse in Japan full of parts for MC 11 16 18 21 28

Huh! Tell me more. Are there NOS parts? aftermarket? Do you sell parts?