Hello

I'm new here so please try to be gentle!
I'm currently trying to work out a solid plan for marrying an RG 500 engine with a more nimble chassis for a classic GP replica with a modern twist.

I know the Aprilia RS250 chassis is the common choice for these hybrids, but I'm strongly biased towards an MC28 Chassis with ProArm swingarm, simply because of my love for RC30/45s. Bit of nostatlgia going on there.

But from a practical point of view: You guys would know best. I know NSRs can be a nightmare to derestrict and such, but in this case a rolling chassis is the only thing that matters.

Engine performance aside: How does the handling of an MC28 compare to the RS250? As far as I know both bikes were designed using GP technology so neither should be bad, but I want to achieve the best possible handling and lowest possible overall weight.

That also leads me to ask: would any of you have a rough idea of the weight of an MC28 frame and swingarm? And of an RS, for that matter?

Thanks kindly for any advice!

Have you considered a Honda RS250 GP frame and forks, you certainly wont find anything that handles better, plus you have the choice of the early nf5 , and the later nx5 93 0n proarm frame, these do come up for sale quite often, in fact i think Dan at gecko imports has both types for sale. i'm not sure how you would go about registering it for the road, as these were out and out grand prix frames and were never registered for road use, but where theres a will theres a way, just a thought instead of going the road based way. cheers Les.
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Proud Father of , 05 ktm 400exc supermoto 2018 honda crf rx supermoto

Thanks for the reply, Les.
I looked into it, doesn't the RS250 have the chain on the wrong side though? I don't have much experience with the ProArm, so I'm not sure whether I'd be able to use the swingarm from another model to suit the RG500 engine. It sure looks like a sweet frame, bet it's better than standard MC28 too, but it's the matter of rear end now.

The NF5 and NX5 chain are on opposite sides so you could pick which one suits...

I'm just looking at it now. The NF indeed has the chain on the correct side, but that one has a more old fashioned swingarm. Considering that I would want to use the ProArm for the bike if I went the Honda way instead of using Aprilia chassis, I''d have to adapt the MC28 arm into the chassis. Probably easier and cheaper to go with a complete NSR.

Hello "Helmheid", and welcome to NSR-WORLD.

Have you considered an NC30 or NC35 (VFR/RVF400) chassis? It may be better with a little more room. The NSR frame is quite narrow. That way you still get the Pro-Arm, and frame looks very similar to the NSR250 too.

Several people have used the NC chassis to fit NS400 triples into.
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Andy.
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Thanks, Andy.
How do you see the weight of the actual chassis? Do you think there would be much of a difference between NSR and VFR?

I wouldn't say there is a great deal of difference between them really.

We've got an NC30 and an MC28 in the workshop at the moment. I will try and get some comparison photos when work starts on them.
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Andy.
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That's great, I'd really appreciate it. If this goes ahead, I'll want to keep the weight to the absolute minimum, so there will be a lot of carbon/titanium/magnesium going about - but even with that in mind I'm sort of in love with the Pro-Arm system. 750 superbike nostalgia never dies once you've been a part of that!

Id agree with Andy on this. The NSR and Honda RS frames are too narrow and tight for an RG500 engine. The NC30/35 was the first bike I thought of with a SS Swingarm that would be a good option.

Ive seen an NC30 frame used to work with a 650 twin engine and have good room to fit it in.

if you really want to go all out, I am sure Harris would have something that could incorporate a SS swing arm no problem and be perfect for the RG500 engine.

It doesn't have to be a single sided swingarm - as said - Aprilia RS250 chassis with its original swingarm can accommodate the RG with light modifications. I'd only bother with a single sided arm if I went for a Honda frame. This project will be expensive enough without bespoke frames!

Watfordhorn from this form had an NC30 framed RG500. Went like stink and was what convinced me to buy a 4 cylinder 2stroke (YZR500 rep unfinished)

There is a guy who specialises building in them and doesn't live a million miles from London. His name escapes me, but a google search is bound to find him.

The trouble with an NSR frame is the top of rear shock mount is too high and getting those pipes over the top is difficult. The nc30 has a lower mount from recollection.

Wondering which is the preferred 500cc among the membership here.. the obvious answer is a Honda, but not easy to come by at a reasonable price. So is it an RG or RZ. I suspect there are lots of opinions, but the members here seem to be more factual. Not trying to hijack the thread, just interested in the general idea..

Jetting four carbs....good grief. At least on the RG they are easy to get too.

Having talked to a few professionals and done a fair deal of research, somehow everything keeps pointing back to the Aprilia 250 chassis... It's the easiest fit, has the reputation to handle inhumanly good and having riddden one over the weekend I must agree. Not to mention that you can still get just about any exotic magnesium/titanium/carbon parts for them that simply bolt on and are in production.

As for the engine...it has to be RG. Lighter, sexier... And Nova racing makes it even sexier with a dry clutch kit!

The chap racer38 is thinking of who lives near London, is Darren Lane, ex national 125cc racer, he has actually built a couple of tasty rs250 Aprillia framed 500's, and from what i have seen of them he seems to be quite a competent engineer, i believe he is in the Herts area somewhere.
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Proud Father of , 05 ktm 400exc supermoto 2018 honda crf rx supermoto