NSR125 Forks to NS125 Forks

[Snorty]

My friend is picking up an NS125 at the weekend, and we have a fair few NSR bits, forks/calipers etc.

I was wondering if the forks could be swapped over (for the NSR's better forks and grimeca calipers). Would it be easy enough are they similar?

[Kickstart]

Hi

Not sure.

However I have a suspicion that the NSR forks are shorter than the NS forks (not certain, just a feeling that the NSR head stock is lower than the NS). The NS fork inners are longer (about an inch), but about half an inch of that will be compensated for by the 17" wheel on the NSR front end.

The calipers are pretty much the same on both bikes from memory. Although think they are on different sides of the wheel so you will need brake lines as well. You might gain a bit from the larger disk on the NSR (but for real fun, try and source one of the NS front ends which had twin disks, although they are pretty rare).

The NSR has a 17" front wheel and the NS a 16" front wheel.

The NS used 32mm forks while the NSR used 35mm forks. So you would need to use the NSR yokes. Not sure whether these would fit in directly or whether you would need to press out the stem from one set into the other. As the clocks mount on the yokes this would give you a load of hassle mounting the clocks (and assuming an NS125F, a load of hassle with the headlight and fairing as well).

Personally I would stick with the NS front end. No hassle, and avoids having non matching wheels that would look really rubbish (and fitting an NSR wheel would need an NSR swinging arm, and rigging up some way to mount a rear brake master cylinder).

All the best

Keith
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[Snorty]

Ahhh we'll just stick with standard then I reckon! Just asked on the off-chance they used similar components.

Had a little test go on it, it's quite nippy! These are essentially Honda's answer to the TZR 125 (RK model) aren't they?

Whereas the NSR125 is the TZR125R equivalent.

[Kickstart]

Hi

The NS pre dates the TZR by a few years. So more the TZR was the answer to the NS.

The TZR125R was sold at a very similar time to the TZR125. The Italian 125 market was large and the normal TZR was heavily built down to a price and wouldn't have been competitive. So Belgarda (the Italian Yamaha importer) built the TZR125R for sale while the normal TZR was still a pretty new and current model.

The NS was Hondas equivalent to the Aprilia AS1, Gilera KK/KZ125, Cagiva Alletta Rossa and the like. Aprilia came out with the early AF1, then replaced that with the alloy framed AF1 Sintesi, while Gilera moved on the MX1 and Cagiva launched the Freccia. The NSR was the equivalent to these.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Snorty]

Do you know how much power these (theoretically) will make?

I've got a TZR 125 which I've just pegged open the power valve on, will they top out around the same?

[Kickstart]

Hi

Err, difficult to know. Full power they were around a real 20hp I suspect (never seen actual figures for one, so that is a bit of a guess). However UK one didn't have the ATAC power valve system, but I have a feeling that the ATAC chamber was closed so in the high rpm / power position (unlike the MBX125).

The speedos seemed to quite often be pretty optimistic.

Personally I would expect a derestricted TZR to be a couple of mph faster than a derestricted NS (think the TZR in full power form managed a true 92~93, so 90ish for the NS).

The NS main actual restriction is in the expansion chamber, along with the missing ATAC system. Short of souring a full power engine there isn't anything you can do about the ATAC system, but the exhausts can be cut open and the internals of the expansion chamber removed.

Somewhere I have an article in PB on their attempts to tune and play with an NS125F.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing