am i right in thinking the nf model gearbox's go in the nsr? if so is it worth doing or just a waste of money and time? cheers _________________ ive seen more tarts than mr kipling
No, they do not fit. The input shaft is different and can not work with the standard NSR clutch. The out put shaft bearing and seal is also different, an area where the NF5 crank cases are also differnet. _________________ If I have to take the carbs off once more...
i have justified it by thinking dan was building/tuning my engine anyway,so would be a shame to see the gearbox sat in his garage.ive saved it from the spiders and should say dans done me a good price as always _________________ ive seen more tarts than mr kipling
Ok then, what parts are compatible with an MC21? I have read that cylinders can be used, with some appropriate modification to the cases.
If someone is prepared to modify cases, what other RS bits could be used, or combinations of parts be used? I've read that the crank tapers are different, but could RS pickups be used with a lightened NSR flywheel?
For example, could the standard 21 kickstart mechanism be removed & plated over allowing for the RS clutch side cover etc?
How close could you make the 21 bottom end like an NF5?
RS cylinders just bolt on, the volume may be slightly tight with NSR pistons, it's way too loose with RM125 (single ring) pistons but if you're using RS bits you'll be checking such stuff anyway, a badly assembled RS would be beaten by a well assembled stock ported NSR every day of the week.
Obviously stock RS pistons have a 14mm piston pin and thus can't be used.
You will need all the RS RC valve pulley mech.
You'll have to do something about the pipes, the RS has a three bolt flange.
The RS crank (of the correct age?) fits the early mc18 cases.
If you machine the cases you can use the RS adjustable flyweel and tiny stator, details of what to machine are in the mc18 f3 manual but if you've got the flywheel, stator and it's backplate it's obvious.
The flywheel fits the NSR crank.
There is no reason an engine like the one above won't run very well on the RS pipes, carbs and all electrics.
It's been my finding (only from 2 bikes so this may not be conclusive) that the RS PGM-II works OK on a stock NSR motor if that NSR is running RS pipes. It's rubbish on NSR pipes, the KV3 (mc18) PGM-II is 5 bhp better at the top and stronger all the way up too.
Be aware that the RS loom and CDI does not have any provision for the air solenoids or TPS. Likewise the RS carbs don't have a TPS on so if you run the RS carbs and a stock NSR PGM the RC valves don't work as they just sit in the "set" position.
It's a shame I can't mod this forum as this topic wants splitting now. _________________ Please do not PM me technical questions, if you can't find it on the Forum start a thread
Thanks Fontyyy - just the sort of information I am after, from someone who has first hand experience.
I wanted to build a track only bike - and with 2 '21's in the shed, another one seemed a bit ho-hum. Time for something a little different.
So, I now have much of the late model NF5 parts, mostly stuff that involves little engineering should it need to be changed out, if you get my drift. The bottom end is where I thought the incompatibility issues would be the greatest.
I'm not too keen on a complete NF5 motor, solely due to the crank availability and service life issues - I know they're closer to MC18's - but MC21/28 cranks are still available.
Still planning, hunting and hoarding at this stage. I definitely don't want to slap it together, but just make sure I'm on the right track.
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