hello everybody

my name is pierre, i'm new on this site, i live in france
i've got a yamaha 350 rd aircooled year 1973 and a yamaha 500 rdlc year 1984.
i would like to give to my 500 rdlc a new life and install the engine in a good aluminium frame, so i think the 250 nsr frame is the frame i'm looking for, especially because of the shape of this frame near the kick starter.
i found a frame on this site, but the owner tell me there's difference between mc18 and mc21 frame.
can anybody tell me what are the main differences between this two frame?
it will help me for buying

thanks

The MC21 frame is a little more substantial. Rails are larger, I beleive head stock is larger, etc..

The swing arm is also much different. MC21 has a "gull arm" on the right side, where the MC18 is straight on both sides.

As for the engine mounting, they are both about the same since the engine cases are basically the same between the two models.

The mc21 is also considerably wider.
_________________
Please do not PM me technical questions, if you can't find it on the Forum start a thread

The possibly wiser choice would be a VFR400R NC30 frame, as it's slightly wider again. Not sure if there's suitable recess for the kickstart though, but there are a number of NC30/NS400 conversions already done, so there must be some room there.

May be a little awkward to fit a Gull-Arm to an NC30 frame due to the shock mount, but hardly an insurmountable problem if you are capable of fitting an RD500 motor into it in the first place!

Having said that, there's at least on RG500 motored MC21 chassis floating about, so a 4-cylinder will go in with enough thought. Rear expansion chambers look a bit of a job though!
_________________
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!

thank you very much for the answers .

i've got some more questions:

the fuel tank, is it the same on mc 18 and mc 21 (size) ?

is it possible to fit in the mc 21 frame, the "standard" mc 18 swingarm without big modifications?

pierre

Fuel tank is not the same. Due to the difference in width between the frame rails, the tanks are different sizes.

I have seen people fit MC21 swing arms into MC18 frames, so Can't see why one cant go the other direction. Just a question of how much work needs to be done to make it work

I don't understand why you would want to fit an MC18 swingarm to an MC21. The MC21 Gull-Arm is (a) significantly stiffer, and (b) gives significantly more room under it to run expansion chambers... something you will surely need to consider if you are thinking of running "GP style" pipes on the conversion.

Go search "Wyn Belorusky" on Google and have a look at his RZ500. Although he uses a modified RZ frame and a TZ (or maybe 3XV, I can't remember... it was 10 years ago I last saw him and the bike!) swingarm, you can see the benefit of plenty of clearance under a "gull-style" arm that an MC18 arm won't give you.
_________________
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!

I know of at least two NC30 frames with a RG500 motor in it

Personally if I was building a special with an RD motor I would be looking at the TZR 3ma frame, its been done before and you wont have such a problem with the top two exhausts.

As to the gullarm...anyone know of someone who as ever fitted a CBR400 gullarm to a NC30 frame...I have one ready for the 500 but am also a little concerned about the offset rear shock, cant see it being a massive task though.

I'd be interested to know too Leigh, so if you start work on it can you start a thread on it in the Members Area please. (NC30 frame, NC29 swingarm, and RG500 motor isn't very NSR, is it?! )
_________________
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!

Your right, there isnt much NSR on it, wheels and fairing stays are all I can think of, the fairing is MC28 style but not genuine, maybe thats a good thing in your eyes as all my NSR spare parts are for the MC28...now how can I get a PGMIV to fit it???????

No worries about the thread, not sure it will happen any time soon but I dont think it would be a massive task....I hope not anyway!

I'd say try fit your engine within an RGV vj22 chassis,its stronger,wider and most importand with a much "slower" caster angle which is good thing for a road bike with too many horses under the hood.

Kostas Dee wrote:
...an RGV vj22 chassis,its stronger...

I'd like to know where you got this info!
_________________
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!

made me laugh as well
_________________
ive seen more tarts than mr kipling

Andy wrote:

Kostas Dee wrote:
...an RGV vj22 chassis,its stronger...

I'd like to know where you got this info!

Ιnfo?Nah i'm not an internet or whatever info seeker mate,only know things by personal exp.

I dont want to start a debate or something,i said something that i highly believe its right,take or leave it,no reason for poking or laughs.

Its nice when we have an opposite opinion to try just agree to disagree

PS Aprilia RS has an even stronger chassis btw


_________________
Addicted to that Rush..

NSR 250 MC18 '88 JHA pipes
NSR 250 MC28 R Tyga pipes
Aprilia RS250 MKII Arrow pipes

me and andy have personel experience of owning rgv's hence our responses
_________________
ive seen more tarts than mr kipling