Is it an upgraded cam?

[Sammy_1101]

Hi everyone,

I'd say I'm about halfway through getting my '79 GS850G on the road when I had an interesting thought cross my mind. Compared to other GS850's I've seen on youtube (even ones also with a 4 in to 1 exhaust) mine has a rather lumpy idle. And also from what I've seen, they should accelerate through to red line relatively smoothly. Whereas mine takes off at around 7k.

Is there any possibility that my 850 has an upgraded cam? Is that a rather common mod to have been done to the bike. I'd rather not have to open up the engine just to have a look because all the internals seem to be performing fine but is there any other way of knowing?

Thanks in advance for your help

 

[GregT]

You're in Australia - we both know weird things happen there, LOL. Yes, it is possible a PO has changed the cam(s). Next time you check the valve clearances look for any markings on the cams - often on the ends if it's a regrind. Genuine Yosh ones have popY cast in close to the sprockets.

 

[Sammy_1101]

If it is an upgraded cam, or a regrind, would the clearances still be the same as factory or will it change the required adjustment?

 

[GregT]

If it is an upgraded cam, or a regrind, would the clearances still be the same as factory or will it change the required adjustment?

Generally the cam specs would call for a bit more clearance. If when you do look, you can ID the grinder by any marks engraved or cast on, it's not hard to search out the right running clearances. Most of the info is on line.

 

[Tom R]

Stock exhaust and airbox? More likely scenario is your carbs need to be gone through.

 

[Sammy_1101]

Stock exhaust and airbox? More likely scenario is your carbs need to be gone through.

Pod filters and a delkevic 4 in to 1. Carbs have been jetted, are pretty close, a few minor adjustments away from being perfect.