R100GS running rough

[Jaseone]

My 1988 R100gs is a bit poorly. It starts pretty well, will tick over beautifully,
pulls away well, but! Get up to 50-60-70 & it just feels rough, almost as if I have a REALLY nobly rear tyre causing a vibration through the bike. Also at a steady 60ish at around 4k rpm it will miss the odd beat & stutter a little. (Pull the clutch in & close the throttle, smoothe as).
Now I have replaced all 4 plugs (it's been twin sparked), caps & leads, checked the float bowls (clean fuel), made sure carbs are clean & needles are clear, carb diaphragm 's appear good. The only thing left I can think of are the coils, however I'm uneasy about changing these costly item's and then still having the problem of a rough running bike.
Anyone have any ideas, or know where I can get the coils tested. I'm in Monmouth, south Wales by the way.

Thanks Jase

 

[soiled]

coils

Hi, I can lend you my coils from my 100GS PD if you happen to be in Manchester

 

[SJRoome]

Hi

Is this vibration related to road speed or to engine revs?

Do you only get the missing at 60 or does it occur at speeds higher than this?

Steve

 

[Jaseone]

That's really good of you , but i'm not going to be anywhere near you any time soon.

 

[Jaseone]

Hi

Is this vibration related to road speed or to engine revs?

Do you only get the missing at 60 or does it occur at speeds higher than this?

Steve

Hi Steve, the vibration only seems to appear after 45 - 50ish mph. It's then there all the way up to 80. I'm sure it's engine however because as I say, if I get up to, let's say 60, then pull the clutch in & close the throttle the vibration goes away.
And the missing occurs at a steady 60 70 80.

Jase

 

[SJRoome]

Hi

What about if you are at the same speed but in two different gears? I just think you need to be really sure the vibration is not from the driveshaft. If you pull in the clutch there is no load on it.

Have you checked the valve clearances and the compression?

Steve

 

[Rob Farmer]

How many miles has the bike done?

Sounds like it could be worn valves. Got a similar issue with my pd and that's worn valves and guides.

Have you had vacuum gauges on it? If its a pain in the arse to setup it could be your valves.

 

[Jaseone]

I'm not sure about the vibration being there in 4th or 3rd. I think it was only there in top gear above a certain speed . I will get out on the bike & try it in lower gears & diff speeds & get back to you. We have checked the valves & clearances & they appeared perfect. I've not had vacuum gauges on it though, againI will try that & get back.

Thanks
Jason