Hi,
I am weighing up my options at the moment and I wondered what ownership and riding the RS250 NF5 is like?
I plan to do track days and the odd parade etc.
What is parts availability like? does anyone do a rebuild for the crank or is it new one every time? can you even get new cranks?
Can the cylinders be successfully re-plated or just go for new?
Any pitfalls that I need to look out for?

Any and all advice gladly received.

Cheers
Max

Hi again Max, new cranks and barrels are unavailable, unless you can find NOS, as of yet we haven't found anybody to rebuild the NF5 cranks, if you can find a bike with a good solid motor you shouldn't have any problems just with the occasional outing, I have owned my one for about 6 or 7 years now with no problems, admittedly I have a spare motor and lots of consumables plus a one or two used cranks and barrels, but what I will say is, I have had as much fun on my HRC kitted 21 as on the RS, more relaxed and less chance of being hurled into orbit.
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Lesviffer750 wrote:Hi again Max, new cranks and barrels are unavailable, unless you can find NOS, as of yet we haven't found anybody to rebuild the NF5 cranks, if you can find a bike with a good solid motor you shouldn't have any problems just with the occasional outing, I have owned my one for about 6 or 7 years now with no problems, admittedly I have a spare motor and lots of consumables plus a one or two used cranks and barrels, but what I will say is, I have had as much fun on my HRC kitted 21 as on the RS, more relaxed and less chance of being hurled into orbit.

Hurled in to orbit, I love it!

Did I see that someone was rebuilding NX5/NXA cranks? Where did they get their spares from to do that...
Maybe get a batch of bearings and seals made up, it could be an NSR-WORLD exclusive kit - maybe you have some kicking around in the bottom of a drawer somewhere!

I think Andy Sawford at St Neots Motorcycles is rebuilding Nx5 and Nxa cranks, I do know that they rebuilt a 92 NF5 with a NX5 crank , but that involved a fair bit of work if I remember. The main problem with the NF5 is getting the main bearings, and I have often wondered if the early MC18 ones are the same, over the years I have got hold of crank seals, but never the bearings, one of which has what looks like some form of nylon strip around the outer of the bearing, I suspect it is no more than a form of damping. If anyone knows of anybody who could find the bearings and rebuild one, I have a used one to donate to the plight of NF5 owners. Such a shame as they are a beautiful piece of kit, and the CRMC have just announced they are opening up regulations for " PARADE " machines, for bikes registered before Dec 31st 94, where as before it was Dec 86, this also will allow 93 - 94 NX5 in. Would also be good to get all our NF5's together sometime in the future.
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My NF5 crank was rebuilt by SEP http://www.sep-kegworth.co.uk/page1.htm
There bloody slow but when i checked my crank after the rebuild it was well within tolerance for run out.
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NSR250 MC18 SP, KR1S, TZR250 3MA, RGV250 VJ22P

With regards to the cranks I bought a stripped U/S crank and have some old NSR cranks of various years to compare. The NF5 cranks are very similar to the MC18 mk1 cranks with the separate centre seal (later NSR cranks have the centre main seal integral to the centre main bearing) The centre seal is exactly the same dimension as the mc18, pattern ones of these are readily available from Japan. The main bearings are identical except for the right hand bearing which Les pointed out has a nylon damper ring around the outer race but dimensionally is the same, the big ends are the same pre 91. The 91 and 92 have the conrod support type crank with no thrust washers in the big end and a wider con rod and big end bearing.

The Koyo NSR main bearings are available from various sources, the Big end I believe is the same dimension as the CR250 big end and the centre seal is available as a pattern part. The left hand main seal is still available form Honda, the right side main seal is an MC18 part and is available as a pattern part from Japan or can be replaced with a later NSR part.

Like the NSR cranks they are rebuildable dependant on the condition of the big end pins and conrods. I was planning to have one rebuilt at some point but I need to finish my current projects first

daz680 wrote:My NF5 crank was rebuilt by SEP http://www.sep-kegworth.co.uk/page1.htm
There bloody slow but when i checked my crank after the rebuild it was well within tolerance for run out.

Hi Daz do you know where they sourced the bearings and seals?

What pistons are you currently using in yours?

Lesviffer750 wrote:I think Andy Sawford at St Neots Motorcycles is rebuilding Nx5 and Nxa cranks, I do know that they rebuilt a 92 NF5 with a NX5 crank , but that involved a fair bit of work if I remember. .

I did ask Andy about this. They used the VHM NX5 con rod kits and NX5 pistons (15mm small end as opposed to 14mm on the NF5) and machined the barrels to correct the deck height, the crank builder they use is in Holland.

It would be pretty cool to get a bunch of 250 gp bike out on track

I rebuilt my engine with original Honda pistons but when the time comes I will probably put VHM pistons in as they are long out of production.

Some consumables are still available from Honda, .4mm and .6mm base gaskets are still available and the NSR base gaskets are .5mm and available, I bought pattern head O-rings from a place in Germany called gp-u-moto. They also sell Barnett clutch plates for the NF5, I plan to order a set of those so will let you know if they are any good.

Gasket guru in the UK makes all the gaskets as well but I prefer to use the Honda base gaskets for consistency.

Regarding riding them, the difference I found was night and day. I owned a 92 NF5 and rode it fairly regularly. I was lucky enough to have a go on Steve A’lee’s F3 MC21 at Llandow and did a back to back session on it and my NF5. His bike is almost certainly the fastest NSR250 out there but still ‘felt’ slow compared to the NF5. The NF5 is raw, hard, sharp. The NSR softer, more forgiving, not so alive. That said if you timed me I was probably quicker on the NSR. It’s more relaxing so you probably feel able to push for longer.

The other benefit of owning an NF5 is they are a joy to work on. Everything is designed to come apart easily. Changing jets is a doddle.

Probably the biggest factor is cost. When I got mine a decent NF5 with spares could be had for £1800. About the same price as a well sorted NSR250. Now it’s a different story. NF5s are a collectors piece and so cost big bucks. Much much more than a tidy track NSR.

Hows that NXA shaping up Tom.
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racer38 wrote:Regarding riding them, the difference I found was night and day. I owned a 92 NF5 and rode it fairly regularly. I was lucky enough to have a go on Steve A’lee’s F3 MC21 at Llandow and did a back to back session on it and my NF5. His bike is almost certainly the fastest NSR250 out there but still ‘felt’ slow compared to the NF5. The NF5 is raw, hard, sharp. The NSR softer, more forgiving, not so alive. That said if you timed me I was probably quicker on the NSR. It’s more relaxing so you probably feel able to push for longer.

Remember, when you rode the F3 at Llandow it was only just edging 70hp, and needed to go on a diet! When it went up against the NX5s at Donington a few years ago, it took the long straights for the RSs to pull any lead on it. It's making 75rwhp, and as light as an NF5, so I think you'd find it quite different now Tom. It still makes bags more bottom-end than an RS though, and doesn't rev as high, so the NX5 (and NF5) would still outrun it on a long straight.

PJ/PWK carbs would even things up a bit more... in that it would lose the bottom-end and gain some top, but big carbs ruin an NSR! Been there, tried that!
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Hi Paul
I'm using VHM NF5 pistons ( from SP125) and i supplied the centre seal. It is a T2 racing one that i bought from Japan along with genuine outer seals also purchased from japan. I do not know where they sourced the bearings from but it is fitted with a standard MC18 bearing on the RH side rather than the NF5 one with the seal built in.
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NSR250 MC18 SP, KR1S, TZR250 3MA, RGV250 VJ22P

The RHS bearing is a special 9-ball NTN bearing, and current availability is very much like the Koyos were back in the day... non-existent! As Daz says though, an NSR bearing can be used.

daz680 wrote:
My NF5 crank was rebuilt by SEP http://www.sep-kegworth.co.uk/page1.htm
There bloody slow but when i checked my crank after the rebuild it was well within tolerance for run out.

We had to (re)rebuild a client supplied NSR250 newly "rebuilt" crank from SEP as it was atrocious! Maybe it was a one-off, or had been dropped in transit, or they've just tightened their act up, but we certainly saw why the rebuild was cheap compared to GTPE at the time! Glad your NF5 crank was good.

I expect VHM are doing St. Neots' NF5 cranks.
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Andy.
NSR-WORLD.COM

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Andy wrote:

I expect VHM are doing St. Neots' NF5 cranks.

Andy told me that their crank man is called Frank, "Frank the Crank" I presume.