TOPIC:

Hi all,
I understand that the subject of carb tuning crops up fairly often when fitting an after market exhaust, filter or perhaps both.
Has anyone experience of actually fitting a different type of carb to overcome the associated poblems?
Thanks
Stephen

Twin Keihin CR33 Smoothbores is what you want. The simplest and most effective tuning mod for a Nordwest. If you get them on Yamaha 600 'centres' they fit straight on. Well if you junk the standard air filter box, swing the battery box round and grind a smigeon off the frame.

Allens carburettors used to supply them. Still do I think if the SRX600 kit is suitable - they will know as they sold several pairs to Nordie tuners.

www.allensperformance.co.uk/products-kits-crs.html

Hi 72,
Thanks for the reply, have sent a note to Allens to check out the situation.
But just to be clear please. The carbs have to be on a SRX 600 mounting plate in order to fit the centres on the Nordie ?
Forgive my ignorance but is this a plate from a standard SXSR or specially made to accomodate the KH's ?
Ditto on jets, are they jetted to suit the SRX600 and therefore suit the Nordie
Also whats the sitch with the choke cable. Lots of questions so sorry for that but would really like to learn more, is there fee i will have to pay you?
Thanks
Stephen

No mounting plate as such but the pair of carbs are fixed together by brackets so that the stubs align with the intakes on the Nordwest manifold. This luckily is the same as on the Yamaha so kits designed for them will fit.

Allens will jet to your requirments which will not be the same as a Yamaha. With luck they may have a note of what people have used on Nordwests before. It's a long time since I set up my Nordie with a pair so I don't remember the details. I think Kano Nordi's Norturno has still got CR33s on so he might be able to help. Though if I remember correctly the bottom end carburation wasn't perfect on that. The back presssure of a road legal exhaust sytem can make a big difference. I got my 604cc big bore Nordwest motor running very nicely with them, but with a Frigerio race can.

A standard Nordwest has no choke cable. The push-pull throttle cables need careful routing for a Kehin set up. The CRs have a 'toggle' for the enrichment jets so no choke cable needed for them.

No charge

If John doesn't spot this thread I'll give him a nudge as he is the only person I know these days using the Keihins - unless he reverted to a standard Teiki dual choke unit.

Hi Stephen,
I have 35CR's on the Norturno and I also have a set of 33CR's that used to be fitted to 72degrees 604 hill climb bike I'll grope the 33's and see what jetting is inside at the weekend and post you back
John

Thanks John, though I think you will find that the Norturno carbs are also 33s. Paul (who bought it off me) even borrowed my 33s because he was having trouble with carburation and we thought the 35s might be just too big, only to discover that they were the same bore as on the Norturno.

When I quizzed John Rushworth about it he told me he had intended to use 35s when he wrote about building the beast in 'The GeN' but decided they would be over the top and put in 33s instead.

How does it go in the heat of Africa?

Thanks for having a look at the jetting. It would at least be a starting point, though as I said mine may well still be jetted rich for a race can and no air filters at all as when I was hillclimbing it.