For those who have both: How difficult would it be to fit the RS straight cut primarys to the NSR SP's engine?

Specifically: Would it be possible to fit the one on the back of the clutch just by taking the rivets out, swapping them over, and re-riveting?

Making new rivets is no prob for me...
_________________
The Chopster

Two completely different setups. The RS gear isn't even rivetted to the basket like the NSR!

Best you do what we've had to, and that's lay all the bits out and measure and compare them.

The motors are so similar in some respects, but different enough to make a big pile of totally useless bits if you don't know what you are doing!
_________________
Andy.
NSR-WORLD.COM

Please keep all responses to Forum posts on the Forum so that others may benefit.

Please DO NOT PM me for technical advice. My time is precious, and you will probably receive a faster response on the Forum anyway.

Check us out on Facebook! Please "like" our page!

This post is now five and a half years old.
When searching the forum I found one other post about this topic here, but that seemed to get a bit off track.
Also there is a little bit of discussion here.
Has anyone got some details on fitting Honda RS250 (or other) straight cut primaries to MC18/21/28?
_________________
[color=#808080][size=9]Yes,.. I too know how to waste Time and Money,...

You want my 1987 HRC kit!

Seriously though, as I've already said, the two setups are completely different. You may as well buy a complete NF5 bottom-end/transmission and take it from there. The only thing that's a direct replacement is the pressure plate.



_________________
Andy.
NSR-WORLD.COM

Please keep all responses to Forum posts on the Forum so that others may benefit.

Please DO NOT PM me for technical advice. My time is precious, and you will probably receive a faster response on the Forum anyway.

Check us out on Facebook! Please "like" our page!

Maybe it is possible to machine some existing gears to fit?
Perhaps someone has looked into getting some custom made straight cut gears made?
Any tips or tricks appreciated before I look at possibly doing some custom made gears myself?

NF5 clutch (and transmission) fitted to an MC21.



Note there's no water pump or kickstart.

The 1987 HRC F-III kit is based on an NSR casing, although it's still not machined for a kickstart.
_________________
Andy.
NSR-WORLD.COM

Please keep all responses to Forum posts on the Forum so that others may benefit.

Please DO NOT PM me for technical advice. My time is precious, and you will probably receive a faster response on the Forum anyway.

Check us out on Facebook! Please "like" our page!

Ere.........
That's my engine!!!

This engine has the RS transmission, primaries, clutch etc all fitted. Quite a simple job to do it that way. But as you can see the RS cover doesn't have any casting for the kickstart so as this was a race engine (300) I welded on a plate to cover it up.

The mechanical waterpump has been removed and the case machined and welded up. This is running an electric waterpump. I've done this on 3 or 4 NSR's now.

If you want to fit the RS primaries but keep the NSR clutch, then I'm not sure of the exact method as never done it, but what I have done is keep the NSR helical primaries and fit the RS clutch to this. What I did was cut out the centre of the NSR basket (with the M7 bolt holes, and then cut out the middle of an RS basket after pulling the damper off. Then welded the NSR centre into the RS basket.

Trouble with this is that the RS and NSR main shafts are different lengths so I had to make up clutch lifter assy and push rod so that I could use the 3 ball system like the RS.

First attempt worked dimensionally, but I messed up when hardening the shaft and lifter. After first shakedown I could hear something "mechanical" so pulled it apart and the ends that I'd hardened had cracked. I hadn't tempered the part after hardening. I made another and this time tempered it after hardening, by looking on the net and finding a temper colour chart. Works like a charm.

Is it straight forward? No, not really. Is it worth it? Probably not much, but I did lighten all the stock components while I had it in pieces by thinning down the stock primary gears and also taking a bunch of weight off the stock NSR clutch assy.

I actually still have one of the NSR basket centres in the freezer. Found it the other day It's in the freezer as I made it a shrink fit into the RS basket to ensure a nice strong fit before welding.

Anyway, it looks cool so it must be worth doing.

Here's some special kit, like what Andy's talking about!
I've painted the exhausts and fitted a new seal behind the clutch basket since this pic' was taken.

Lot's of stock NSR bits left in there eh Roy? I see one hose that might be from a KV3 NSR.

It would probably be easier to have new straight cut primaries made than source that little lot!
_________________
Please do not PM me technical questions, if you can't find it on the Forum start a thread

fontyyy wrote:Lot's of stock NSR bits left in there eh Roy? I see one hose that might be from a KV3 NSR.

It would probably be easier to have new straight cut primaries made than source that little lot!

Quite right John!
You got me thinking. It's cost me a lot of time, effort and a small fortune to get it to this spec'. Less, than a supposed mint '21 or '28 from some dealers though.
You're wrong about the hose though! I won't say what bike it came from as Andy might ban me!
I think there's only the headstock and swinging arm bearings, screen brace and clocks/dash bracket that are KV3 parts. The clock bracket is modified too! Oh the front brakes are KV3 also, at the moment!

Getting back on topic, I'm not sure I'd bother with straight cut primary gears for a road bike. Along with loosing the kick start, you also loose the gearbox oil pump. Something I personally don't prefer. Probably better to get some primary gears made to suit the standard set up.
Then again, as Matt says, it's worth it if you think it makes the bike better for you.
Just can't help modifying these bikes really.