The difference between an NSR125 and an old HRC RS125?

[eunos20b]

Hi all,

Enjoying learning about bikes and I love that stripped down, white racer look of the HRC machines when they're unstickered... and they sure do go well...

I was watching a couple videos of the various HRC machines in Japan (if you've seen the videos you'll know). More in question, the HRC RS125, the old 2-stroke one, 80s/90's up to circa-2004.

How different is it to an NSR 125 of similar age? I assume obviously the necessary tender to make it road legal like lights and non-slick tyres are not there but would it really be that much faster round a track or B-road to necessitate paying like £6k more for one over an NSR that you could fiddle with and strip back?
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'90 Honda H100SII (SJ)
Learning something new everyday

[MarJay]

They are completely different bikes. the RS is a racing prototype, the NSR is a road bike. To compare them would be like comparing a Mondeo to a F1 car.
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[Teflon-Mike]

I would doubt that they share any more interchangeable parts than an M6 bolt or two!

The 'over the counter' RS GP bike, made aprox 45bhp, and has pistons and cylinders and cranks that are all service replaceable, with replacement intervals measured in hours! It has nothing that isn't required to either make it work, fast or comply with FIM race regulations. The generator wont even have bolt holes to take a stator that will make electric for 'equipment'.

The NSR, was a street bike. As stock, it barely made half the power that the RS did.. had more useful service intervals, but still. It was physically larger; heavier and the variouse derivatives over the years had all the equipment required to make it a viable, a marketeable road bike, and one that could make the company profit, where buyers wanted 'cheap' and make believe big-bikes.

As has been said, it's like asking the difference between a Renault Clio and a Williams Renault F1 car.. as different as a Boeing 747 passenger airliner is to a Typhoon yet fighter!!

As to the how quick round a track connundrum?

Well... there's a question...

Few years ago, there was a track shoot-out done by one of the mags; they put some of the latest 600 & 1000 super-sports round both Donnington, and I think Cadwell, may have been Mallory, and for comparison put round a British Superbike, a championship 600super-Sport and I think it was one of Haslam's team Britain's RS125 GP bikes.

The RS125 was consistantly quicker than any of the road bikes every where, and was as fast as the production racers, if not faster, depending on track & conditions. It consistently beat them at the tighter track.

It's miniscule weight, was sited as signitificant advantage; along with it running 'full' GP slicks, where even the Super-Stocks were compromised by running 'regulation' (cheating!) limited-production 'molded' tread tyres.

Take an NSR125... strip it of all road gear, add lightweight race fairings, and then start tuning it... IF you were good at the job, you would maybe get it down to under 100Kg, and if you were very very good, perhaps up to 30bhp.... that'd still 30% down on power and up on weight.. even if you gave it the advantage of race slicks and suspension, it would be WAY off the pace compared to an over the counter RS... let aslone one loaded with the HRC 'special parts' given to the supported riders in GP or national.

Crickey, it would barely be on pace with the RS's ancestor, the late 70's Honda MT125... which was Honda's first forrey into two-stroke GP bikes, developed in the US at the Elsinor factory to compete with the Yamaha over the counter TZ's.

Developed behind sociro Honda's back,the MT designation is actually derived from Honda Agri--Plant project codings! So sochiro didn't see what they were up to with 2T's in the board room!

That used a derivative of the two-stroke 'Elsinor' engine used in the 'scramblers' that were quite significantly 'productionised' to be sold through the US Farm shops as field bikes.... and won dirt bike races in the US mainly on reliability and popularity, marketing over merit!

MT, though, with a minimalist steel frame, highly tuned 'MX' motor, and a lot of component substitutions, many to magnesium to pare down weight, tipped in at around 80Kg and 25bhp.. before they offered a water-cooling kit and some HRC 'special parts' that got the last of them up to near 30bhp. A decade past thier sell by date, they were still some of the quickest things round a track, with laps times that frequently bettered those of the supersport 400's that included the last of the 2T 250's as well as the 4T 400's, and the 600's!

Interesting to note, that at the time 'Mini-stock' for 125 road bikes was being dominated by MK1 Yamaha TZR's... the NSR's were critasised for being too heavy, too bulky, and too under-powered and hard to tune to get them on the pace.... which for the class, as far as lap times went was only about as quick as the shoe-string classes, things like the Bantam/MZ's, or the scooters!

SORT of puts it into context.... the road based NSR's struggled to cut it in a class for 'tuned-production' 125's, that didn't, then, even have things like the Aprillias or Cagiva's to cope with, and they could only just about cut the mustard with an old, air cooled, east german, pressed steel frame, piston ported MZ250...utility commuter with a bit of port-play?!?!

Yeah... do you REALLY think you have a cats in hades chance of making one even remotely quick as an HRC GP contender that could shame almost anything you could buy with a numberplate... even ones tuned and prepped for proddy racing?

Good luck!

You would have more chance, of making something more RS 'like', taking a steel framed CR125, MX bike, that as stock probably delivers more bhp than you could hope to get from the NSR lump... and messing with that.... then it would be a question of how far your money would take you, before it would have been cheaper to buy a genuine RS....

And to what end?

For super tuned lightweights, folk take old 500MX motors and chuck them into Mito chassis, which makes for something pretty potent for the road, and is nominally more affordable than a genuine RS, but even that only just about matches RS power, still exceeds its weight, and the only real advantage is service intervals that give it a chance to get from Manchester to Mansfield without needing a new set of piston rings, before the petrol tank needs topping up!
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[eunos20b]

Bloody hell! That's incredible I wasn't aware there was THAT much of a difference even in basic specs. 45hp is absolutely barmy from a 125 2t in any sense. I can't believe it would be that quick against such bigger stuff. There's that little idea packed back in a box and thrown out the window

Thanks Mike, hit the nail right on the head.
____________________
'90 Honda H100SII (SJ)
Learning something new everyday

[jjdugen]

Hmmmm...... It took Yamaha four cylinders and watercooling to get 35 bhp and Honda 5 cylinders and 18000 (!) RPM to get roughly the same output in their GP racers.
I do find it a bit difficult to believe only a few years later you could get that and more from a single cylinder 2T...... Just sayin'.
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[redeem ouzzer]

[Teflon-Mike]

[Kickstart]

[331X2]

My Mrs was talking to William Dunlop at the Gold Cup last year and his RS was running around (I think) 56hp, Ron at Fahron was talking similar figures when I spoke to him recently as he's got one he still runs.

[jjdugen]

Tef, you cite the Elsinore of the mid 70's, the V four Yams raced in 1968 before, as you rightly say, the FIM banned development. That's as many years difference as I have fingers, after ten I have problems adding up.
What did change in the intervening years was tyre and frame technology, I very much doubt that a single lunger MX derived AIR-COOLED engine could hope to match the power of a 4 or 5 cylinder engine. All depends where you measure it I suppose.
I don't actually give a damn, I HEARD them, nothing like it before, certainly not since!
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The CBR900RR has been sold. Aprilia Falco worms its way into my heart.
Try Soi 23 on Amazon for a good read.... Self promotion? Moi?