GS750 Cam Timing

[KW]

Hi,

Can anyone tell me the cam timing settings for a 1977 GS750 fitted with stock cams. I want to check the current settings before deciding whether to have the cam sprockets slotted so I can degree them in.

Thanks

[KEITH KRAUSE]

On your bike, the cams are not degreed to a specific setting, they are degreed within a range. On the early GS's the range can be about 100-115+ degrees. This is the main reason two identical bikes will perform differently right out the door. If you have the cams degreed around 110, this will result in more top end/horsepower, but the low/midrange torque will suffer. If you degree the cams around 100-102 you will have more low end torque. I had both my intake and exhaust cams timed at 106 degrees for what I consider the perfect compromise between top end/horsepower and lower/midrange torque.
Higher degreed cams (112-115+) will result in slower warm ups, a hotter running engine, the carburetion is difficult to set correctly and a narrower powerband.
With your cams timed at 104-106 degrees, you'll have a broader powerband, better throttle response and the best compromise between peak and low rpm power, gas mileage will be at it's best too.

[KW]

Thanks for that Keith, at least now I have somewhere to start from.

On a similar topic, someone sugessted I fit GS1000 camshafts as they have a slightly higher lift. Do you know if this is true? And is there a downside to doing this?

Thanks

[Anonymous]

Is this also correct for GS550???

Great stuff im reading here 8O . Does somebody know if the same things apply to a GS550E. I feel a have a lot of horse power in high rpm?s but there?s absolutely nothing at low rpm?s. No torque and no power. I was just about to change the gears and put a bigger weel in the front when I read this.

[Don Lobacz]

According to my GS1000 Clymer manual, page 179, the GS1000 and the GS750 use the same intake camshaft. The GS750 exhaust camshaft must be slightly larger, since it is recommended for use in the GS1000 for more throttle response in the 6,000 - 8,000 rpm range. Bigger cams are definitely used in the 1980 and later 2 valve big bikes (GS850, GS1000E and G(L), and GS1100G(L)). 106 cam centers are the best setting, and you would think that we would have the Motorcyclist how-to article available for those people who want to adjust their cams (I have an original copy).

[KEITH KRAUSE]

Thanks for that Keith, at least now I have somewhere to start from.

On a similar topic, someone sugessted I fit GS1000 camshafts as they have a slightly higher lift. Do you know if this is true? And is there a downside to doing this?

Thanks

That's funny because someone here recently suggested installing 750 cams in a 1000 for more performance. I don't know the spec's of a 750 cam, so I can't compare it to the 1000's.
High lift cams can certainly increase power, but you need to make other mod's to take full advantage of them. A high lift long duration cam on a stock motor is generally a waste of time. You should also port the head for more air flow and install a less restrictive exhaust/intake system along with adequate carburetion.
Downsides are kept to a minimum if the mod's are done right, but whenever you increase the power like this you will have a motor that makes more heat and the valve train usually wears out faster. The remaining "stock'' parts in the motor will be forced to operate under conditions that they were not designed for. If you frequently use the extra power you've installed, the motor generally won't last as long. If you use it sparingly, you can expect a much longer life. An oil cooler is worth installing also. Also, use the highest octane fuel at the pump.