Worth it? Honda NS125 engine in RS50 frame .....

[Jamie S]

I have an old Honda NS125 sat in storage, it needs a load of work doing, has no tax or test, all bearings nackerd, tyres shagged, C&S shagged...... The list goes on.... but , it does have a great running engine.
So , I had a thought, I have a 2001 RS50 rolling chassis sat here, sold the engine ect a while back, So I'm considering fitting the NS engine to the RS chassis.
What do you think ? I'm considering having it for messing about at trackdays, or might even try and flog it on to some 16 year old edjit ...... ?
I never got to ride the RS, so ive no idea what it handled like, should of thought that with a 125 engine it would be good fun though ?
Any one know what power an NS125 engine puts out ?
Jamie

[Kickstart]

Hi

Stock NS UK engine puts out about 12hp. Derestricted probably high teens power.

How old is the RS? Alloy frame or steel frame? If alloy then frame mods are likely to be far more difficult.

Getting the exhaust to fit will be difficult, and if it is a decent unscuffed exhaust then please don't wreck it!

Suspect the RS chain will stretch like an elastic band with the NS engine.

Doesn't the RS50 6V electrics.

No idea how much space there would be for the NS engine.

All the best

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

[Jamie S]

Was hoping you would reply ....
Is that all,12 bhp....
The RS has an Ally Frame with Steel lower cradle, the exhaust thats on the NS is a chrome "allspeed" if i rememeber correct.
Didn't think about the electics , will have to check what the RS wiring runs on.....
Space wise it seems ok.
TBH if it's only going to be 12hp then maybe it's not even worth it...

[Kickstart]

Hi

If it has an Allspeed exhaust then it will be derestricted, so probably high teens power. Honda were very keen on complying with the old 9kW / 12hp learner law. Not much you can do about the lack of ATAC power valve.

However even more so, do not trash a decent Allspeed on the NS.

All the best

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

[Jamie S]

Ok, I might look at using a diffirent engine then, and selling the NS on, I know I will never get what I payed for it though, which is why I was considering the transplant, then sell on whats left of the NS.
Jamie

[Kickstart]

Hi

Advantage of the NS engine is that there is no external power valve electrics or anything.

All the best

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

[Jamie S]

True, suppose it all hinges on the RS electrics being 12 volts.....
Will have a look tomorrow.
Jamie

[chris-red]

Just replace the entire RS loom with the NS one, use the NS clocks worse comes to worse you need new bulbs/indicators to fit. That way the tacho, idiot lights etc. will work instantly if you use the NS clocks and loom on the RS. The speedo maybe more difficult.
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[Jamie S]

The NS isn't worth spending a penny on, it already owes me £300, ive since lost the key, it needs two new tyres, swing arm bearings, front and rear wheel bearings, new front disk and pads, chain and sprockets, headstock bearings replacing/adjusting, fork seals, and would need a new set of farings which are hard to find, not forgeting painting the frame, tank not to mention an mot tax ect...... the list goes on ,it's a nail thats worth nothing even when done tbh.

Jamie

[nsr_J22_FOXEYE]

Yes it is worth doing:

Source of information: I'm the ejit that would be interested in buying it from you


So long as you keep the labour down below £1000 and parts and the bikes don't owe you much then do it... and have fun. I can see many hours of smoking and coffee drinking but the end result would be fun for a track bike.
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[Jamie S]

Might look at somthing equaly as compact and simple, but more power, maybe along the lines of an old CR250 engine.....

[stirlinggaz]

personally wouldnt bother trying to transplant the ns engine into the rs...........
although you dont want to spend any time/money on the ns, (i can understand why, when your never going to get much over £500 for a complete bike) i would consider selling the ns parts.
there are plenty of people out there who would pay for the 18bhp ns lump, with a good exhaust (like the allspeed) & set up carb.
i know, i had an old ns which i bought for £300 & then sold it some time later........which i still regret.
i could have sold the engine & exhaust (micron, or gibson iirc) a hundered times over. (they can be fitted to other bikes but no idea about the rs)
great little bikes when looked after, even if they arent the most "trendy", sought after or fastest. the parts are cheap s/h & its a very easy bike to work on, with parts from other hondas from that era which are interchangeable..
mines was good for 80mph, done the 40 mile commute day in/out, no complicated pv's etc to worry about, very reliable 2t 125, not many of those around nowadays.
the rs 50? plenty of s/h engines around that would cost less than you would make from the ns parts...........
cheers,
GAZ

[Pol Anorl]

if the barel is in good-ish condition ill give you £50 for it ? got to be better than mine which is now ruined
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[Jamie S]

Haha! I'm not stripping a complete running bike for just a 50 quid barrel..... Also, why bother sending me a pm if you have asked in this thread???

[ms51ves3]

[Jamie S]

No but it's almost as shocking as his !

[stevo as b4]

The NS125 in full power form was supposed to be 22bhp at the crankshaft, so figure on 18-19bhp r/w. That's a decent amount for a 125cc even today, and i think that it would make for a very interesting and nippy conversion into the RS50 frame, which is possibly a stronger and more rigid design than the NS chassis. The brakes will probably cope ok, with the power and 85mph potential, but you might need to uprate the suspension to cope with the added weight.

Seeing as you already have a running NS125 engine and a Rolling RS50 chassis, then you should at least offer the engine up to the frame and see how it looks for size, and what needs moving and modifying to allow it to fit before you make a final decision.

[Jamie S]

Going to go ahead with this now I'm unemployed and have a bit of time on my hands!
Will start a thread in show and tell in the next week or two!
Jamie

[alains]

RIDICULOUS !!!!!!!
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[Frost]

Stick the engine on some blocks and put the chassis on top of it. If it looks like it'll fit i'd give it a go.
An RS50 frame is worth nothing, the wheels and stuff could be sold, but that remains true even if you attempt it and fail. The same goes for the NS motor. So get a mate who knows how to fabricate to give you a hand and see what you can do.

[mysterious_rider]

to be fair, im still halfway going through a two stroke enging convertsion with a pitbike.

engine swaps are HARD.


Lining up of the sprockets, sorting of the electrics, fitting it actually into the frame,

and you still have to sort an exhaust.

IMO bearings cost F ALL, go and fix the ns up. It won't cost that much, and at least at the end of it you will have a nice old school bike.