High idle speed and timing chain question

[Zerode]

Hello, I've done about 300 miles on my R65LS and loving it, perfect BMW for the French Alps.
Holding back on the cafe racer project because its so original and fun to ride right now.
I did have to matt black the wheels though...
I have a couple of questions that I hope someone could shed some light on.
First one is the idle speed once warm, the revs stay around 2-3000 rpm when you back the throttle off, for example when you pull over and stop it keeps revving at around 3000 rpm for half a minute or so before dropping back to normal idle speed. It got a bit scary when coming into a corner yesterday and the engine braking not working!
Also I only got 200km out of a tank of gas, is that normal or maybe the bike has an over fueling problem. Any suggestions?
Also  the bike has 29000km on it, around 18000 miles, and the timing chain is quite noisy. It has a full BMW service history and the last oil change was around 500km ago and 6 months ago. I'm wondering if it has had the wrong oil put in it that maybe too thin to operate the tensioner correctly. It shows a synthetic 10w50 BMW oil.
So suggestions on how long the chain should last and the correct oil to use for the old airhead engine. I was trying to find 10w40 SG mineral oil but the only stuff available is the cheap non branded supermarket oil. Not sure if I should run oil like this in the BMW engine.
Thanks again, Jason

[Bob_Roller]

The high idle when the engine is up to operating temperature, usually is the result of a carb synchronization being done on a 'cold' engine .

Valve clearance being too 'tight' is also a possibility .

At 18,000 miles, the timing chain should not be worn to the point that you can hear it, if the bike had 70-80,000 miles I'd say probably need to be replced .

These bikes make some unusual noises and if you are new to airhead bikes, they can be of a concern .

[Barry]

The 10W 50 BMW oil should be fine and in fact 10W 40 would be a touch thinner at operating temperatures. I doubt your oil is having any influence on the timing chain. As Bob said it shouldn't be worn at that mileage. Trouble is there is no easy way to check for certain short of dismantling the front end. One thing that does give away a worn timing chain is ignition timing flutter. If you check the timing with a strobe and the image is not jumping around to much (no significant difference between the two sides) then that's one indicator that the timing chain is probably OK. Don't expect a rock steady image though strobe lamps are no that perfect or at least mine isn't.  To try and put some figures to this I would say if the image jumps around much more than 1/2 a tooth or approx. 3mm it's possible there is some wear.

[Bengt_Phorqs]

Ditto on Bob & Barry's comments.  There are quite a few threads on this site about synching the carbs.  Run a search for carb synch for a 12 month period.  You'll probably find several.   Multi grade oil is fine, most folks stay away from synthetics though as it's reported that it can cause seal leakage.  Recommend you stay with dino oil but make sure it has an SG grade or use a zinc additive.

[montmil]

The odd noise from the timing chain case, if heard primarily during deceleration, may be the timing chain tensioner "shoe" being worn out.

Earlier tensioners had a metal substrate that would contact the edges of the timing chain links during deceleration; when that side of the chain has most slack. Newer style tensioners have a different and better construction method.

Unfortunately, the timing case must be removed for inspections of all the above mentioned components.

I have a timing chain DIY photo essay in the R65 Photo Gallery which you may find helpful.

Your high idle issue is probably improperly set idle mixture screws. Betcha...

[Zerode]

ah yes the photo gallery, cant seem to get it to work as when i click the link it asks me to login but wont accept my login or password and they say my login email address doesnt exist...

Cheers for your comments will have a look at balancing the carbs, I am a gasfitter so have had a bit of experience with a monometer.
Might just do an oil change for good measure and then check out the timing chain.

Jason

[nhmaf]

Oops - to access the photo gallery I believe that one of the moderators has to add your email to the photo gallery list - I cannot recall how, but Rob Valdez knows.
I guess that I should learn about that part and take notes..