I have a 1275 that is currently being worked on before being installed. It's got new valve springs and seats, and the bores and crank are being checked to see if they need attention. My question for you experts has to do with the carb. The one I've cleaned up has a 1.5 inch throat. Is that going to be big enough for the 1275? I plan to put a K&N type air filter on it with a big bore exhaust. Right now the cam is stock, but if it turns out to be bad I might opt for something with just a little more kick. I'd prefer to stick with a single SU, but do I need to move up to something like a 1.75? Thanks for any advice you can offer.

 

An 1 3/4" would be suitable for most any road going 1275 to 1380. If you want good torque, I was pleased with a Kent 266 cam.