Having used a couple of tanks of fuel now, I am happy that all of the old fuel (probably 5 years old) is now gone.
I decided that it was time to investigate the poor running at low revs. After attaching the vacuum gauges I find that there is no way that the number two brass screw is going to adjust. It ended screwed all the way in. Removed the brass screws to clean and lube the seal with a little silicone grease with no luck.
Off with the throttle bodies. I can see that the butterfly valves are not all closed but the number two is a little open when all of the others are closed.
I suspect that a past owner has been messing with the sync using the grub screws. Is there a guide to check these out there somewhere?
The bike is a '91 16 valve K100RS.

I know that it's considered a heresy by many but I believe that the butterflies can be adjusted provided you have a decent set of gauges.

It's not something I routinely do but I've adjusted them on a few bikes when I've found that a previous owner has tweaked them.

I'd have to say that I am with you on that one. After 25 years in aircraft engineering there is very little that I would not attempt. Just ordered a set of 4 column carbtune gauges as the dial type are not as accurate in my opinion.

bikerboy wrote:Is there a guide to check these out there somewhere?
The bike is a '91 16 valve K100RS.

Don Eilenberger's helpful procedure for fixing a TB with mal-adjusted interbody linkages

Paul Glaves on the same subject

And if you had used the search function on this forum, you would have encountered a similar discussion on how to use a drill bit to set the linkage screws.

I have just set mine using 4 dial gauges but don't know how successful it is as it isn't back on the road yet. It was a very complicated jig I made to hold them and the gauges so its not for the feint of heart to try. I shall let you all know the outcome soon.

I managed to get my K1 out for a blast today after tinkering with them and I can only say that it's transformed it. It wasn't exactly rough before but it wasn't right. Now it's almost as smooth as a K75 and throttle response is better than any K I've ever ridden. Pick-up in fifth is so good that I tried finding sixth a couple of times!

Only problem, unconnected, is that a fork seal blew (again).

MikeP wrote:I managed to get my K1 out for a blast today after tinkering with them and I can only say that it's transformed it. It wasn't exactly rough before but it wasn't right. Now it's almost as smooth as a K75 and throttle response is better than any K I've ever ridden. Pick-up in fifth is so good that I tried finding sixth a couple of times!

Only problem, unconnected, is that a fork seal blew (again).

If you change the fork oil on one of them you only need to put 400 in one side and 350 in the other If you put 400 in the 350 side it will blow the seal. Maybe that is what happened, just trying to think of some reason for it happening.

RicK G wrote:

If you change the fork oil on one of them you only need to put 400 in one side and 350 in the other If you put 400 in the 350 side it will blow the seal. Maybe that is what happened, just trying to think of some reason for it happening.

Rick, thanks. I've started another thread on the topic:

https://www.k100-forum.com/t5687-16-valve-bike-fork-seal-change#64441

Rick G you say you used a dial gauge to set your TB's? that made me think How? did you set them up on a steal plate and use a dial gauge on a slide post to line up the butterflies in series? perhaps set at a predetermined step off fully home?????

I used two magnetic clamps to firmly attach it (TBs) to a big lump of plate and then mounted dial gauges on each TB and worked from there. This should be fairly easy for any home handyman to do as this sort of stuff is lying around everywhere .
I don't know if it has really worked yet as I have yet to go for a ride. It was supposed to happen today but I got waylaid with some other interesting project and didnt get to go. Joys of being retired.

last balance job I did was a mates kz650 so out of wack was it I ended up removing the carbs and set the float bowls 1st then used 4 x 1/8" drills to use as draw gauges same as we used to do with points and feeler gauges worked well enough for those old scoots. got back that famous Kwaka howl for him.