A few years ago I picked up a cheap MC21r in pieces, the plan being to build a cheap track bike. Since then its pretty much stayed in pieces.

I picked up a MC16 F3 engine a while ago with the idea of using this in the track bike, http://nsr250.net/forums/viewtopic.php?t=11230

The plan is to get her up and running for the Donnington track day in July so I have finally got my arse into gear and made a proper start.

I stripped the engine some time ago so all the bits went for vapour blasting and plating.

If you read the previous thread on the F3 engine you will see I had a couple of issues to sort out. After a tip from Andy I sourced a set of MC18r2j engine cases from Johnymac. These fit the mc21 chassis and the mc16 crank but needed a bit of machining to accept the F3 ignition.

I had the corroded hose spigots on the cylinders replaced with some nice stainless ones.

And had an mc21 water pump drive shaft re-ground to accept the mc16f3 drive gear.

I had a set of mc21 f3 carbs tucked away for a rainy day so I gave these a clean up and rebuild with new seals. I bought one of those cheapo sandblasters from that auction site and used baking soda to blast the carb bodies. Heres a before and after shot.

I thought the result was alright. Gave everything a damn good clean and reassembled with new seals.

Nearly finished rebuilding the engine, just waiting for some bits to come back from the platers. New seals all the way through the engine....well not quite, the R/H main seal is no longer available and the centre seal needs the crank stripping to replace it so I have had to reuse them. Not ideal but i will do a leak check when its all together and fingers crossed it will be okay

Engine is only a temp fit at the moment so I could measure up for some spacers to be made for the F3 carb supports. Once I get those welded up I can start the build proper.

I have used a mc28 carb manifold to accomodate the 21 carbs which are larger than the 16 ones. The f3 kit deletes the boost bootles and has plugs for the holes in the manifold, mc28 manifolds dont have boost bottle attachments so is a bit of a neater solution.

In the meantime I have stripped, cleaned and rebuilt the set of NX5 forks I'm fitting and been cleaning a few other bits and bobs.I cant wait to get the frame welded and start the build so I can get some proper progress. I'm at that place in a project where I seem to have put a lot of work in with nothing much to show!

The whole thing looks good and like you say once the frame is sorted it will come together quickly,
It will make an impressive little bike when finished,
looking forward to seeing it in paint,
goodluck PG
jonmac
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John

About time I updated this. Dropped the engine out and had the F3 carb support mounts welded to the frame.


Got some nice shiny bits from the plater, finished the engine rebuild, threw the engine back in and installed the f3 carbs and carbon HRC replica air box.


Fitted a set of RS250 NF5 yokes using a Tyga stem conversion, NX5 forks and mudguard, 91/92 NF5 wheels and disks from Yakama, RS125 rear shock and Tyga rear sets.



I also scored a set of original fitment HRC RS250 Brembo calipers from Racer38



I

coming along nicely paul
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ive seen more tarts than mr kipling

Another quality build Paul. Must chat to you about the sand blaster and how it worked out.

Cheers guys, the blaster works okay on smaller stuff. I have only used it with baking soda which gives a nice finish, not as good as vapour blasting though.

Thanks for the lend of the RS sprocket carrier as well Tom. I have had a new one made so I must get that back to you.

It's looking great so far Paul, nice job
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Rich
MC21 Track Bike / RS250 NF5 'Spencer', NX5 'Cadalora' & NXA 'Aoyama' / RS500 / Two Brothers Racing RC30

About time I added an update to this. I hit a bit of a brick wall with it last year when I found the unobtainable centre crank seal was leaking but I have been making some slow progress on it. Also the fact that I'm using a mix of MC16,18 & 21 standard, F3 and aftermarket, RS250 and RS125 parts means nothing is a straight forward bolt on part and I need to fabricate and modify everything as I go.

I had a stroke of luck last year when forum member paul nw uk posted an ad in the classified selling a spare centre crank seal, What a result! I dropped and striped the engine for about the third (and probably not the last) time and the crank is away having the new seal and main bearings installed.

The other good result I had last year was finding a HRC MC18 F3 radiator with HRC temp gauge and RS125 rear brake on Yahoo Japan, a quick email to Moriwaki man and the parts where bought and posted to the UK. Excellent service again from Drew!





Unfotunately it does have a dented header tank on one side, its not to drastic but another job on the "to do" list! It also needs the two upper mounting lugs relocating to suit the 21 frame and a broken lower support lug replacing.



I also had this piece of non NSR 2 stroke filth arrive in the same package from Drew

I mentioned in an earlier post I sourced a pair of 92 RS250 NF5 wheels from Yakama, these of course arent a straight bolt on although they use the same spindle size so not a total nightmare. Big thanks to Tom aka racer38 who kindly lent me a NF5 rear sprocket carrier/left hand wheel spacer which I had a friend copy for me.



With this spacer installed The front/rear sprocket alignment is spot on so I have measured up the right hand spacer which also carries the RS125 brake caliper carrier. I'm waiting on this and a bunch of other parts which are in the process of being machined and will complete the F3 style rear brake set up. Another top tip from racer38 was The shiny brand new rear disc, this is an ATC250 rear disc which is the exact size and bolt pattern of the no longer available NF5 disc. The rear caliper has been blasted painted and rebuilt with new seals.



I have also stripped, blasted, painted and rebuilt the RS125 rear master cylinder. I didnt like the way it mounted on the Tyga rear sets, so I fabricated a spacer/heel plate/guard type thing to reposition it.





I'm not 100% sure if I like the way it looks so I might redo this at a later date.

I bought a Nissin radial front master cylinder from Watfordhorn, this was a tacky bronze fake magnesium finish, I personally feel that sort of thing is best left to gixxer owners and has no place on an NSR so I stripped and soda blasted it back to a more tastefull natural finish



The fluid reservoir is a standard NSR part, the hose is a new RS125 part and the reservoir bracket was fabricated by myself. The Goodrich hoses were on my mc21 before I replaced them with a set of HEL's.

I plan to use a set of Dogfight exhausts which have been kicking around my garage for years. They are a little bit used so need some repairs, the first issue being the worn manifolds which rattle around in the exhausts like a P**** in a bucket!



Had these nice shiny tight fitting new ones machined up with o-ring grooves.



Issue number two is the silencer mounting flanges which had been drilled and redrilled to accept various silencers with different hole mounting patterns. I ground these off and have had a pair machined to suit Tyga silencers, these are cheap and readily available as I will crash this bike at some point






Issue number three is the standard dent to the right hand exhaust.



I cut out the damaged area and formed a replacement section.



These are now away being welded.

Really good update, Paul. I hope we will see you and the bike at Donington this summer!

I guess with that rear shock you are going with an aftermarket seat unit. Have you decided what yet?
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Andy.
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Andy wrote:Really good update, Paul. I hope we will see you and the bike at Donington this summer!

Thanks Andy, If I dont get it up and running this year I will dump it in a skip! I couldnt take the embaresment of having the second oldest project on the internet The plan is to have it running by Donnington at the latest. One of the sticking points I have at the moment is with the F3 electrics, I think I have everything I need apart from a tacho convertor. I do have a plan "B" if I cant source one, build a stock 21 motor and use stock electrics and the HRC harness and delimiter but I really want to use the F3 stuff.

Andy wrote:I guess with that rear shock you are going with an aftermarket seat unit. Have you decided what yet?

I have a standard mc21 shape Tyga fibreglass race seat unit, I was originally going to go with RS bodywork but decided to go with the standard shape bodywork. I plan to fabricate my own alluminium subframe, but time constraints mean I might end up using a modified stock or Tyga subframe.

Its all these "little problems" which really soak up your time, the fact that I have to rely on other people to do stuff like machining and welding means I spend to much time waiting as well. I shouldnt moan though, I expect my issues are a walk in the park compared to building a pair os NSR500's from scratch!

Thats looking the dogs danglies Paul, i was about to jump in and say you could have used an RS125 rear disc, as i have, but then realised you have NF5 wheels, and they are 4 bolt disc fitting not 3. Be good to see it out this year.
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