Normal throttle response?

What is normal throttle response? With my 78 650 SR on it's center stand and running, when I twist the throttle slowly, the rpms slowly climb accordingly. When the RPMs reach about 2500 they then jump up rapidly to about 5000 without any further twisting. Is this normal?

is the bike warmed up when you do this?

wireguy wrote:

is the bike warmed up when you do this?

Yes the bike is warmed up......

Before you go doing much with the carbs. Take the points cover off and check the centifugal advace for binding or looseness. It sounds like it may be binding and releasing suddenly and doing a quick timing advance. With a good light, not a timing light, you can watch it as you slowly rev the engine to see if it's operating smoothly.

The Milkman wrote:

Before you go doing much with the carbs. Take the points cover off and check the centifugal advace for binding or looseness. It sounds like it may be binding and releasing suddenly and doing a quick timing advance. With a good light, not a timing light, you can watch it as you slowly rev the engine to see if it's operating smoothly.

I opened up the points cover and observed the mechanical advaance. It appeared as if it was moving in sinc. with the before mentioned problem. I squirted some wd40 in there and things lossened up to the point of no problem now. Thanks for the advice. It got right to the problem.

A shop manual will explain that you are supposed to remove the mechanical advance and clean the end of the crank and the advance and lube them both periodically else they get sticky... The reason is that both are made out of steel and tend to oxidize. You might want to remove them and clean them up some to get rust off.