Slow to lose revs - Trolle

[trolle]

Thank you for the info.

After the last long trips, 90 miles at an average speed of 75 mph, the right carb has a tendency to "hang". The engine revs at appr. 2-3000 rpm and if I yank the throttle cable of the right carb. the revs settles down at a normal (800 rpm) idle level. I have not found the cause yet, but suspect that the butterfly spindle sticks. Any comments?

greetings from a sunny and showery north

[nhmaf]

I thought that you had relatively recently rebuilt the carbs on your bike, is this true ?
Maybe the throttle cable itself is sticking or is frayed on the inside, which can cause it to drag sometimes ?

Can you get this to occur when the bike is warmed up but sitting in the garage ?   I wonder if sustained riding
at a particular speed has anything to do with it, or just opening up the throttle by the same amount for 30 secs or so
while at rest would do the same thing ?

[tagordon]

Trolle
I had this happen repeatedly on the 81 R65.
First check the free play in the throttle cables.
If you have free play in the cable at closed throttle.
Next check the levers on the carb.
Road grime can cause the levers on the carbs to get sticky.
If you use the choke/enrichener that lever can stick and cause the problem.
You won't notice it at speed, only when you slow down and the idle speed is high. This you can see when twisting the throttle then letting it return, the lever will jump instead of smoothly returning to the stop.
And if all this does not reveal the cause, check the valve clearances.
Yes, I said check the valves. It happened once to me, that the valves adjustment had moved.
I did the valves in a hurry and one slipped later. Rpm's usually are erratic as well with the valve issue.
It also happens at times on the 91 R100 when I remove the tank for working on the bike then somehow change the cable routing.
It don't take much to cause the cable to bind.
Try moving the handlebars around when it does this. If the rpm's change then its a cabel routing issue.
Another check is to get out the carb cleaner and spray around the clamps and carbs watching/listening for any anomolies.
Extra air intake can cause same problem.
HTH
Troy

[trolle]

Thank you very much for your input.

Yes, I have just done a complete rebuild of the carbs and that is why it irks me. The problem only arises after a prolonged (appr. 20 to 30  minutes at least) drive at the same high rpm (5500 to 6500 rpm). Then the right carb has a tendency to stick at 2500-3000 rpm but a short yank at the throttle cable normally makes the revs fall back to normal. The problem never shows it self when driving around in town or when driving with revs below 4000.

I'll install my new stainless throttle springs and see if that solves the issue.

I have experienced faulty valvesetting and I do not think that this is the cause. A too tight exhaust valve setting will make the idling very high but this high idling can be forced down by putting load on the engine and not by yanking the cables. This time it is the other way round: Load does not make the revs go down but yanking does.

greetings from a quiet north