1967 R69S rough running between 40 - 55mph

[jimstravlin]

Just a quick query to the group. I have been riding this 67 R69S for many years. Motor has been rebuilt and the carb slides are bronze covered and done by Titan Machine shop in Canada, works nice and smooth all the correct jets are installed. The bike has a rough patch between 40 and 55 MPH. At 55 the motor settles out and runs great, smooth and very powerful. I have rebuilt the advance mechanism, both static and dynamic timing have been set, no problem with the carbs and from the block out the cylinders, pistons, and heads are 1967 NOS, what a find that was. The problem was present before the change in the top end so I do not attribute it to that work. I am a bit stumped here and thought I would reach out and see if anyone has a clue what it might be... Jim

[Slash2]

15Mph seems like a broad rough patch. Have your wheels been verified as straight and true? Particularly the front. Does it matter what great you’re in? Are you silent blocs original up front?

[Daves79x]

Possibly a too-lean or a too-rich carburation issue? I'd say lean if you want a guess. Try raising the needle one notch and see what happens. If worse, go the other way one notch.

Dave

[808Airhead]

I was going to say the same,everything else being "right",play with the needle position. Bringing the needle "up" will enrichen it and bring the main jet earlier. If it gets "worse" then go "down" on the needle. Make sure carb flanges are flat.

[niall4473]

Describe your "rough patch", is it misfiring, vibration, hesitancy, flatness?, give us a clue.
Just for clarity, what rear drive ratio are you using?