Topic: 550/650 valve sizes?

[kayaker43]

I've been searching this forum and the web for a half hour but can't seem to find some easy info. Does anyone know the valve sizes for both CB550 and CB650 SOHC heads?

I must not be picking the right search terms and I'm away from home or I would just measure them.

[Soos]

not sure on the size of a 550's valve, but a 650's has a 5.5mm stem, and the exhaust head is 26mm at the biggest diameter, the intake head diameter is 31.5mm, overall length of exhaust valve is 88.7mm.
Would measure the length of the intake valves, but they are still in the head.

Are you thinking of a valve upgrade for a 550 head?


l8r

[kayaker43]

Thanks, just gathering info for a later motor build up. I'll start with a 650 motor with big bore but not sure how big yet, don't know how much the rods can handle? It will have a pretty hot cam and I was wondering what size carbs to use? The old rule is 88-90 percent of the intake valve diameter. Don't know if that's good info but just wanted to see what it comes out to?

I was hoping it could handle Keihin CR 29's or Mikuni 29 smoothbores because there's not so many choices smaller except CR26's which are too small. I have used KZ1000 carbs on a full race CB590 and I think they were 27-28's??

Also the cast in place manifolds on the 650 are an issue.