Revs slow to come down.

[Padmei]

As bit of a follow up to my similar problems.
I disassembled my LHS carb, checked the mian jet, needle etc, float levels recleaned the mixture screw & jet, made sure the choke was the right way around & buttoned up.
I found the spring missing from the mixture screw so put in a substitute spring. I siliconed the outside of the choke assembly & rubbers to the head (already been told off for that but the silicon is on the outside & not in contact with petrol).

I then opened up the beancan & sprayed liberal amounts of CRC inside.

I went for a long ride the other day & am happy to say the revs now drop & I have engine braking back. The carbs are horribly out of synch & the mixture all wrong but I won't worry about that for now as there is more work to be done.

I personally think the problem was the weights in the bean can sticking however it was good to eliminate the other issues

 

[lockyv7]

I picked up a 1989 R100GS last weekend and it has the same problem and i have worked my way through new trottle cables, set the valve clearances and adjusted the floats and have it starting like a treat when cold and idles from startup in the morning. But the revs climbing when hot is still there and also no engine breaking so i am guessing its the bean can weights that are sticking. Thats my next thing to look at. Think it may be a good bike flew to Sydney and rode 1200K in 14 hours home in one hit without a problem, no oil weeps or other problems.

 

[Captain Black]

As bit of a follow up to my similar problems.
I disassembled my LHS carb, checked the mian jet, needle etc, float levels recleaned the mixture screw & jet, made sure the choke was the right way around & buttoned up.
I found the spring missing from the mixture screw so put in a substitute spring. I siliconed the outside of the choke assembly & rubbers to the head (already been told off for that but the silicon is on the outside & not in contact with petrol).

I then opened up the beancan & sprayed liberal amounts of CRC inside.

I went for a long ride the other day & am happy to say the revs now drop & I have engine braking back. The carbs are horribly out of synch & the mixture all wrong but I won't worry about that for now as there is more work to be done.



Sorry messed up my text a bit.



Can you lube the weight's with the bean can in situ ? and what's CRC ? Would spray grease do the job, or better still motorcycle chain lube ? I've got that PJ1 I think Its called, goes on like liquid but then is ultra sticky. Did you put plenty In or use sparingly ?
I personally think the problem was the weights in the bean can sticking however it was good to eliminate the other issues

 

[Captain Black]

I picked up a 1989 R100GS last weekend and it has the same problem and i have worked my way through new trottle cables, set the valve clearances and adjusted the floats and have it starting like a treat when cold and idles from startup in the morning. But the revs climbing when hot is still there and also no engine breaking so i am guessing its the bean can weights that are sticking. Thats my next thing to look at. Think it may be a good bike flew to Sydney and rode 1200K in 14 hours home in one hit without a problem, no oil weeps or other problems.

Back up the Bruce Highway ?

Nice bike mate, and a good shake down test for sure!

 

[Padmei]

Crc is similar to wd40 & isn't the correct stuff to use however it's all I had at the time. I think you are sposed to use spray grease but i've never come across anything like that over here.
The bean can was left as is & I disconnected the battery, opened the front up & just unscrewed the 2 screws on the front of the beancan- one was on the verge of being stripped. I would use some CRC or what you use to free screws the day before.
Under the cover of the bean can was some manky looking foam which was peeling away. I got rid of the bits hanging off.
There is nothing you can really see in the bean can so I just put the long straw in & sprayed lots around. I went had dinner then came back & buttoned her up.

It went good.

 

[oldenoughtoknowbetter]

Nightmare journey

...back home from the Stafford Classic bike show last night on my 1990 Bumblebee. Similar symptoms to above except that the revs red-lined on a closed throttle. Would only slow down with the engine under load or by using the brakes. Torrential rain didn't help either. All cables are running free as are all levers on the carbs and no obvious air inlet leaks. Mixture and vacuum plugs are all present. Bike ran well on the way up there except that the revs took slightly longer than normal to drop back on a closed throttle. Then the revs got progressively higher on the way back. I've recently acquired the bike after being standing unused for quite some time. It's done around 19K miles. Suspected the carbs but now wondering that the bean can might be responsible. Before I pull everything apart does the bean can seem to be the likely problem? If so, would it be obvious that the weights are stuck on removing the aformentioned cover?
Many thanks.

 

[ken brooks]

i've copied this for you from snowbums site....... Hope it helps "High Idle RPM

High idling rpm, perhaps it came on slowly worsening, is often the cause of one of two problems. Occasionally from both.
One of these problems is a sticky automatic timing unit in the ignition canister at the front of the engine.
The other problem is leaking intake manifolds or mis-adjusted carburetors (usually the idle mixture screw) or, no slack in one or both throttle cables.

Perhaps THE most common problem, is a sticky automatic advance unit, that results in a high idle speed, typically after a full warm-up of the entire engine. A full warmup takes at least 10 miles, often 20. You must have the ENGINE CASE fully hot, NOT JUST THE CYLINDERS. The PROPER fix is to disassemble the canister and very carefully clean and re-lubricate it. This project is not easy for the novice. Sometimes removing the oval side plate and squirting in a cleaner and then a fine oil (NOT EVER WD40!) will help, but may or may not hold up over time. When disassembling the canister, some of the ATU parts may need to be burnished (sort of a more complete polishing) which DOES help, when necessary. Typically a careful cleaning and light lubrication is enough; but a judgment call is needed about burnishing, which removes a minute amount of metal, to enable smoother operation. I try to do what is necessary, so when the ATU is HOT, it does not bind in the slightest.

There are several TESTS for proving that the ATU is at fault for a high idle rpm after warmup (rare, before warmup) (and not, say, a vacuum leak at the intake rubber hoses, no free play in the throttle cables; or a mal-adjusted idle mixture screw).
In some instances, just turning off the engine and restarting it after it was already hot and exhibiting the very high idle, is enough to reset a stuck ATU from the inertia of beginning ATU rotation, so try that. If that then shows a normal idle, it is likely a ATU problem. A few repeats, and if this is the situation, you can be nearly 100% sure it IS the ATU needing attention. YOU CAN DO THIS YOURSELF.


If restarting doesn't show up the problem, then DO get a friend's help. First take the bike for a 10-20 miloe ride, and if the idle rpm went quite high after a FULL WARMUP of the ENGINE CASE, then pull the bike up to a nice big object, like a brick building. You could also just use the front brake.
With the bike in gear, let out the clutch very slowly, loading the engine, and thus slowing the engine to about 900 rpm. Have a friend use a timing light, triggered from the left spark plug, point the light at the timing hole. If the timing is well-advanced and not where it should be (~S mark), then the ATU IS THE PROBLEM. Prove it by pulling in the clutch...you have a high idle rpm again, yes? Try several times to be sure.

If the increase from the ~900 rpm test is SLOW, and the timing is OK, then try tightening the intake rubber hoses at carburetor and at cylinder head, and then start the engine and let it idle, and spray brake cleaner at that hose and its ends...no rpm change should be noted. If OK, re-synch the carbs (don't even think about doing this unless you KNOW the valves are properly set, as tight valves will mask all your analysis and work). During the resynchronization, pay especial attention to the idle mixture screw, idle balance, and ending idle rpm (1000-1100). Go back and forth until all adjustments are OK. If you take more than a few minutes for all this, either ride the bike to cool the engine a bit; or use fans blowing on the cylinders. My website describes how to get an appropriate squirrel cage fan for nothing."

 

[Beemerboff]

As Snowbum says, to get direct access to the bob weights it is only necessary to lever of the small oval tin lid on the side of the bean can.

The original lube is grease, which hardens with age and heat, so a blast of a cleaning solvent like WD 40 might loosen the old grease up a little, giving a temporary fix, but you still want some new lube in there too, and something like a chain lube which is high in solvent and will penetrate well in before stiffening would seem ideal.

I used Wurth spray grease, but just remember that the solvent in this grease is highly inflammable, so it is best to give it plenty of time to evaporate off, particularly if you have points in the bean can - DAKIK

 

[oldenoughtoknowbetter]

Very many thanks for your help. It seems that this may well be the culprit given the history of this bike. I'll give this a try tomorrow and see how I get on. Thanks again.

 

[Damien]

The fly weights are sticking on my bean can after following the above advice.

I had a go at levering the small oval cover on the side of the can off but it is really tight so not going to try again.

Can I take out the 2 screws on the front and remove the front cover without getting in the shit?

I am going to Europe on it next week and don't want a big headache before I go, would rather put up with the high idle.

Thanks,

Damien