Sick 83' R100RT

[oldowan]

Hello,
I have a very sick 83' R100RT.
Brief History: I bought this bike less than 6 months ago. The previous owner was a very meticulous guy and when I went to pick up the bike it looked as though it was just rolling off the showroom floor in 83'. The bike had 56k miles on it.
I just completed a six week (6000 mi.) trip from Denver to Key West and back, this is when the bike started acting up.
When I was down in FL the bike started to stall on me, and run very rough at idle. Not wanting to tear into things too much on the road, I just changed out the plugs, took off the air intakes and sprayed carb/choke cleaner into the carbs. I played with the floats to make sure I was getting gas and they seemed to be working OK. They only thing I tweaked was the idle screws to bring the idle up to 1k rpm to try to get the bike not to stall on me at every light. I did not touch the mixture screws.
SYMPTOMS: As I already mentioned, the bike stalls and runs very rough at idle. But one other thing is that it seems to "cough" or "hiccup" violently below 2k. Also, it is a bit reluctant to start.
CURRENTLY: I put in new spark plug wires because they old ones were showing signs of age.
No change in the symptom.
I drained the tank and put in new gas. No change.
Rechecked the plugs, the looked OK, gap OK.
I took off the top covers on both carbs and checked the diaphragms, they looked ok.
Inspected the vacuum hoses, they all look pretty good.
Yesterday, I took off the top of the right carb removed the diaphragm, throttle slide and the float bowl. Everything looked very clean. When I looked down into the carb I could see right through the main jet and it looked clear. The jet needle looked pretty good to me, but then again, what do I know.
I'm not sure where to go from here or even if I am on the right track or just chasing my tail.
My next thought was to remove the carbs and check the idle jets.
I would greatly appreciate any advice any of you folks might care to give me.
Thanks and Best Regards,
Mark Reidy
Denver
720.256.7552

[sgborgstrom]

I didn't see any mention of checking the valves. Not idling is a classic symptom of not enough clearance.

Steve

[oldowan]

Hey Steve,
I will check the the valves, is this something that can all of a sudden change?

[Braddog]

I'm not sure if your symptoms would show up all of a sudden, but if you've put on 6000 miles, and haven't checked your valve clearances, you're definitely due.

Plugs and wires are now OK, your carbs are probably OK as well, so the valves are the obvious choice.

Good Luck, and let us know if this fixes your issues.

[20774]

The '81-'84 models had the poor metallurgy for the valve seats...they didn't conduct heat well which resulted in slow damage to the valve itself. Over time and left unattended, the clearance can close up and in a short period of time. Definitely check your valves...they've probably closed up some. If so, then recheck them in 1000 miles or so. If they begin to close rapidly, you should consider having a top end done to include new seats, guides, and valves. Parts produced by BMW from '85-on should be fine.

[ccolwell]

I'm not sure if your symptoms would show up all of a sudden, but if you've put on 6000 miles, and haven't checked your valve clearances, you're definitely due.

+2 6k is a long way between valve clearance checks for these. I used to my '84 R100 every 1800 and the exhaust valves always needed adjustment. And that was when it was relatively young at 20-25k. I had the valve seats changed and it didn't need checking near as much. Not a cheap job though.

[brickrider]

As others have mentioned, valves are a real serious issue on this model bike. I went through 3 complete sets of valves in 117,000 miles on an 83 R100RT. So these need your immediate attention.

That being said, I suggest you also go back to the carb diaphragms. These critters often develop a split too small to see, but which expands upon stretching pressure. There are numerous threads on checking diaphragm / slide action while the motor is running.

A sudden appearance of the symptoms you describe would lend itself to carb issues, while slower onset of problems would be the valve recession coming on. I never got more than 40,000 miles on a valve job (all new stuff). The last valve job also required a new head, as the valve guides were at the max limit by the second job.

It's time to go through the bike in a methodical manner for maintenance.

Ride Safely,
Brickrider

[BuddingGeezer]

I met a guy on an extended (FL to OK to NC to FL) trip on a '77 R100RS. 150 miles later he calls me and says his bike lost power and won't run and doesn't know what to do. He says his valves have closed up. I go and get him (300 round trip) and put him up in the extra room.

Next day he checks his valves. Good. His problem??? His points had closed up. He reset the point gap and finished his vacation.

Another buddy with a '86 R80RT. He's restoring. rebuilt the carbs, bike won't hardly start and idles like crap. The coils on these bikes are called "Crackamatics". He ordered a new Dyna coil from Motoelecteik. Problem solved.

It may very well be your valves. Just don't get locked in on a problem.

I came out on the guy with the problem. His wife does upholstery and she upholstered my Bill Mayer seat in goatskin leather. It's beautiful and smooth as a baby's but. Also I stayed 2 nights with him on a trip to Key west.

Ralph Sims