The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: Yikes on March 06, 2008, 03:25:07 PM
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I’ve had this continuing problem with my ole ‘82 since I got it last fall. When the engine gets nice and warmed up, after say 10-15 minutes of riding, it wants to idle up in the 3000 RPM range instead of down below 1000. It idles fine when I start it up and when the engine’s cold. That high revving, coupled with my clackety-sounding heads is a real attention getter when stopped at traffic lights, but not in a good way. When stopped, I can slow the revs by easing out on the clutch a bit while in gear with the brakes locked, but when I disengage the clutch or drop into neutral, the revs climb back on up. (I do not do this as rule, for obvious reasons.)
I hoped the high revving would subside when I torqued the heads and adjusted the valves, but that didn’t do it. The throttle cables not hanging up and the external linkages on the carbs are also opening and closing OK as the throttle is moved. I have not worked the carbs other than to clean out some junk from old deteriorating fuel lines that was clogging the opening of the float valves. I also have not adjusting the timing, but I am hoping that will help the problem. The bike has about 52000 miles on it and I wouldn’t be surprised if this is its way of telling me it needs a top end job, but that’s still a ways off in the great scheme of things. Anybody familiar with this syndrome and the cause or causes? Timing, carb synch, bad diaphragms and sticky valves are the theories that contemplating right now. Maybe a combination of all the above.
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One of the more common causes for a high idle when the engine gets up to operating temperature, is doing the carb adjustments, like synchronizing when the engine is still 'cold'.
Check for leaks in the intake system, loose clamps, cracked rubber hoses tubes at the carb, etc.
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I vote for timing advance weights sticking and/or weak advance weight springs.
for the sticking, you need to lubricate the pivot points.
For springs, go to Motobins (http://www.motobins.com/displayfinal.php?function=show&subs=192&title=ADVANCE+RETARD+SPRINGS%2FUNITS). They have replacements. (Only place that I know of that has them)
Here is a very good post with pictures and stuff. The advance mechanism is not real easy to get to. There is an access port on the side of the bean can, but it is tough to work through.
http://suraklyn.com/yabb/YaBB.pl?num=1189274245/0#0
But in reality, you need to do an entire tune-up before you will really know what is going on.
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high revs at idle after warmup is another classic with these bikes [see flat spot at 4k post ] someone somewhere along the line preformed a carb adjustment without the motor being fully warmed up like Bob said. I don't just mean warm I mean fully hot through and through like after an extended ride. A quick beer run just won't do! Rummage around and you'll find a couple of different methods for making a successful mixture / balance adjustment but any of these absolutely requires a nice hot motor for success. Locate those window fans ya use in summer and have them at the ready in the garage so you can keep the motor from overheating while you make your careful adjustments. It does sound contradictory but get it hot first then use the fans to keep the cylinders from getting too hot while you run and adjust. Nice and hot! You'll be surprised at what a great difference it makes. I was skeptical but it werks! Did I mention to do it hot?
rich
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Thanks for reminding me, Steve. I forgot to mention the hot engine for tuning!