NSR 250 swop out to Rz 350

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Granto
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NSR 250 swop out to Rz 350

#1 Post by Granto » Tue May 03, 2016 4:41 pm

Hi all

I have the opportunity to buy a NSR 250 mc 18 full rolling chassis (sans engine) and would like to swop out the front and rear of my spare '83 Rz 350 project. I have hunted through the forum and can't find any real reference as to whether it will fit or not. Some individual sites mention that the front end is nearly a bolt on, but wondering about the rear.

Anyone have experience doing this kind of conversion or could possibly point me in the direction of a post that covers this?

Thanks
Grant

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vespaman1
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Re: NSR 250 swop out to Rz 350

#2 Post by vespaman1 » Tue May 03, 2016 5:26 pm

No experience personally, but unless it's just completely undo-able due to size I'd go the other way and put the RZ motor in the 250 unless there are registration problems. Probably a much better frame

evan_calgary
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Re: NSR 250 swop out to Rz 350

#3 Post by evan_calgary » Tue May 03, 2016 5:56 pm

No clue fitting the swinger, its a matter of sizing it up. As vespaman said though, why would you not try and put the 350 motor right in the NSR roller? It would be a much better chassis package. If you see one of my other posts I am looking to do something similar to that.

If you do decide not to use the main frame, please shoot me a message, I would be happy to take it off your hands.

Cheers,
Evan.

Granto
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Re: NSR 250 swop out to Rz 350

#4 Post by Granto » Tue May 03, 2016 6:04 pm

I certainly have considered it, it's going to be a pure track bike, so registration is not an issue. I am fairly tall and have heard the NSR is quite a small frame whereas the Rz is a nice size for me.

I read somewhere that the Rz engine is too long for the NSR frame, but yes would defo consider this as well

evan_calgary
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Re: NSR 250 swop out to Rz 350

#5 Post by evan_calgary » Tue May 03, 2016 6:07 pm

Gotcha. Well let me know on that frame Granto! I have a spare NSR swinger sitting around over here... :)

Granto
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Re: NSR 250 swop out to Rz 350

#6 Post by Granto » Wed May 04, 2016 6:21 am

Sorry man, would be happy to sell the frame to you, but am based in South Africa, so I think courier fees alone would be outrageous :)

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gammaguy21
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Re: NSR 250 swop out to Rz 350

#7 Post by gammaguy21 » Wed May 04, 2016 10:35 am

I've recently seen a picture of a rz350 with a nsr250 mc21 swingarm.
I know that the nsr mc18 r2j/k is about 7 mm shorter at the pivot (198 mm)... so my guess is it should fit.

For the front, the steering stem on the mc18 is almost the same dimensions as a rgv250 vj22. It's a couple of mm taller and about 7mm wider at the top of the stem where the top bearing would sit.
Fork wise, the mc18 is about 1/4 inch shorter than the rgv vj22 forks. Seen lots of rgv vj22 front end swaps on the rz, so I think the nsr front end could possibly work.

Back about 2007, martin77 (2 stroke pipe builder) put a rz350 engine in a nsr250 mc21 chasis.
He said that the nsr front mounts need to be cut off and a cradle fabricated for the rz engine. Also the rear engine mounts needed to be relocated.
However the mc21 is slightly bigger than the mc18. The mc18 is a narrower frame, so the rz engine would be a tighter fit in the mc18 frame and may not work.

Here's martin77 nsrd350
Image

Image

Hope this helps.

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Questo vecchio rz
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Re: NSR 250 swop out to Rz 350

#8 Post by Questo vecchio rz » Wed May 04, 2016 1:42 pm

Ive viewed 2 NSR250s with RZ YPVS engines in their frame, it can be done.
I understand your notion of a 250 being quite small..they are tiny bikes. I'm 6'1" and 198 lbs look & feel utterly ridiculous riding one...lol.
As far as front end swapping out, the NSR250 is almost a bolt on affair from what Ive seen. Here is a basic "copy & pasted" primer. Honda NSR250 (MC21 or MC18) complete front-end and calipers, almost a bolt on! You will need a 1/8" spacer below the bottom bearing to clear the frame. Ream out your top RZ bearing 1mm to adapt it to the larger NSR stem, add a upper spacer between top crown and bearing. Done! NOTE: You must use RZ tapered bearings.The rear is unkown to me, but Probably doable with some fabrication. Im sure someones tried it.
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Granto
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Re: NSR 250 swop out to Rz 350

#9 Post by Granto » Fri May 06, 2016 2:37 pm

Tx guys, going to possibly pick the NSR frame up tomorrow morning, will do some basic measurements before pulling the trigger, will let you know how it goes

Granto
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Re: NSR 250 swop out to Rz 350

#10 Post by Granto » Mon May 09, 2016 6:05 pm

So checked out the frame over the weekend and all preliminary measurements looked like it would work, so I bought the chassis. Took it and the rz apart, fitted the pieces up in a rough mockup and everything seems to fit for the most part. Still have to check alignment for the chain, but it's looking very promising. Will start up a project thread this weekend and let you guys know how I get on.

evan_calgary
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Re: NSR 250 swop out to Rz 350

#11 Post by evan_calgary » Mon May 09, 2016 11:11 pm

Awesome! Make sure to post pictures and hopefully some direction for anyone giving it a shot in the future!

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