Eyeballing 78 550 cams

[Nessism]

Checking the cam specs shows the 550 uses a 104 cam centerline for both cams. The 650 uses 106 Intake and 103 exhaust. The lift is a positive thing so I'd use the 650 cams and then degree them both to 106, or higher even, if you want high rpm power. I think this will make a bigger difference than the small amount of extra overlap afforded by the 550 cams.

[mlinder]

Moving 550 cams to the same lobe centers as the 650 will keep dynamic compression up, while still giving me quite a bit more overlap. I know, everyone wants more low end throttle rsponse from their tiny metric inline 4's, but I like to accentuate their natural tendencies.

[Nessism]

Moving 550 cams to the same lobe centers as the 650 will keep dynamic compression up, while still giving me quite a bit more overlap. I know, everyone wants more low end throttle rsponse from their tiny metric inline 4's, but I like to accentuate their natural tendencies.

It's only 8 degrees more duration with the 550 cams, I doubt this will make up for the lower lift when all is considered.

[mlinder]

It's only 8 degrees more duration with the 550 cams, I doubt this will make up for the lower lift when all is considered.

Only 8 degrees, but the profile is important too, and the 550 cam has what appears to have a much less abrupt profile, with the valve open considerably more for the amount of time it's open. This is very important for an engine that will see 9 grand frequently.

[Nessism]

Only 8 degrees, but the profile is important too, and the 550 cam has what appears to have a much less abrupt profile, with the valve open considerably more for the amount of time it's open. This is very important for an engine that will see 9 grand frequently.

The 550 cams are lower lift and higher duration, so the ramps are shallower. This does nothing for you other than it's more gentle on the valve springs compared to the 650 cams. The important thing is the lift amount, cam centerline, and duration. More duration means less cranking pressure and less torque, you won't make this up with only 8 degrees more duration.

[Suzuki_Don]

Checking the cam specs shows the 550 uses a 104 cam centerline for both cams. The 650 uses 106 Intake and 103 exhaust. The lift is a positive thing so I'd use the 650 cams and then degree them both to 106, or higher even, if you want high rpm power. I think this will make a bigger difference than the small amount of extra overlap afforded by the 550 cams.

When I got to working out the CL numbers it was a little confusing with the 650 Intakes at 106 and the Exhaust at 103. This is the reverse of normal Suzuki GS practice which in all other motors has the exhaust with a bigger CL than the Intake. So I was not sure why the Suzuki engineers had gone against current practice on the 650 motor. And I was not sure what characteristics the motor would display if I timed it following conventional practice. My settings were 105 Intake and 107 Exhaust. I think maybe Suzuki set the timing back to front on these 650 motors for some environmental or emmissions reason.

Having said that I have been extremely impressed with the power this motor makes and it feels more like a 750 to ride than a 650, in fact this motor feels much stronger than my CB750K2 I had in times gone.