High idle revs

[79beem]

Just replaced points,set gap to .45mm. Took her for a warm up before setting timing. i park her in the stable and she's revving madly. 3000rpm + rising. several restarts + checks on return springs + cables uncovers nothing + she's still revving away. carbs were squeaky clean
 with new kit 5000km ago. revs have taken their time to settle @ idle in the past and have moved up and down. plugs clean. whats going on chaps   :-

[montmil]

I would say there are two possibilities causing the high idle rpm;

1)  And this #1 -with a bullet- is usually the culprit... the engine was not at the proper operating temperature when the carb synchronization was done. The idle jet screws and idle stop screw adjustments may be incorrectly set. 90% probability it's carb adjustment and tune;

2)  Sticky advance weights in the ITU. I used to believe in the sticky theory but experience with my two R65s and the input from other knowledgeable Airheads cured me.

Rig up the manometer, go for a minimum fifteen mile ride, then begin the carb synchro chore from the beginning. You'll calm 'er down.

Monte  

[79beem]

Thanks Monte, i will dust off the manometer, but what i dont understand is why the 2200rpm increase now? Why not when i balanced the carbs mo
nths
 ago? And i can assure you i rode her for a good 1/2hr up and down twisty mt roads. The ITU, under the fuel tank? Is it servicable? If so what do i do? My manual doesnt give any details. Thanks again.

[Barry]

revs have taken their time to settle @ idle in the past and have moved up and down......but what i don't understand is why the 2200rpm increase now? Why not when i balanced the carbs

Maybe if the revs have taken their time to settle @ idle in the past you were just on the verge of the runaway idle. Changing the points may have advanced your ignition which tipped you over into the high idle revs.
I'm agreeing with Monte that it's also carb related but your ignition timing  may have contributed.

As you have points I would do a static timing check which with care can be done very accurately say within 1 or 2 deg.

It will be interesting to know what you timing is set at.

[montmil]

ITU = Ignition Trigger Unit. The BMW term for our "bean can".

ICU = Ignition Control Unit.
    That's the bit under the tank that loves the heat sink paste renewal. Same electronic component as found in my VW Cabriolet and several other VW products. Possibly other Euro autos. If you ever need one, buy it from an auto parts outlet as BMW Motrrad gets double $$.

Monte

[79beem]

Thanks Barry, that makes sense. Why do you suggest a static test over dynamic? High revs? Going 2 check valves before i balance carbs, so won't know where she's @ till the wkend. Thanks for your help.
 Monte, stupid question time. My clymer shows ITU as a black box under tank, so what are they talking about ? I have points so i wouldnt have an ICU. cheers again

[Barry]

Why do you suggest a static test over dynamic?

I always need to do a static check before running the engine after fitting new points because I remove the bean can to fit them which disturbs the timing. Even if the points are fitted with the can in place the timing still gets disturbed a little. I'll usually follow up with a strobe lamp to check the full advance but I don't do that on a cold engine.

[79beem]

Cheers barry,
i replaced the points with bean can still installed. ( just a tinsy bit  of swearing )
So with revs so high would you agree after valve adjustment,winding out throttle stops until revs settle, then do both timing checks,then manometer balance?
Manual suggests not to use manometer until timing etc correct but i cant check timing until idle revs settle.

Kinda thinking out aloud here.
 
Monte, oops haha. Read manual wrong.

[Barry]

So with revs so high would you agree after valve adjustment,winding out throttle stops until revs settle, then do both timing checks,then manometer balance?
Manual suggests not to use manometer until timing etc correct but i cant check timing until idle revs settle.  

Yes except you can do the static timing check now. It takes 5 minutes.

Turn the engine over slowly plugs out with an Allen key in the rotor bolt and watch for the S mark in the timing hole. As the S mark approaches the notch in the side of the timing hole turn really slowly. You'll need to back off and try it several times. Ignition off I pull the cable off the points can and use an ohm meter between the points can spade terminal and earth to detect when the points are opening.  With care timing can be done very accurately this way. When I check later with the strobe I almost never have to make an adjustment.

Strobes are attractive and they are needed to check full advance. They be wonderful if they gave a bright crystal clear and accurate static image of  the timing marks. My strobe and it is a Xenon type is just not that good which is why I'm happy doing static checks.

[79beem]

OK Barry,

 so i did a static test with a 12v circuit tester ( No i don't have a multimeter), showed timing advanced,adjusted timing.

Reset idle mix screws to 3/4 turn out, throttle stops one turn out.
Adjusted throttle cable / choke free play. 2.8mm was max i could get out of left side,so did 2.8 on right.

Checked valves, hadn't moved in over 12k km  

Took her for a spin,WHOA! 4000rpm at idle.
1/4 turn in on throttle stops was the temp remedy for timing purposes.

Timing light showed system advanced, circuit tester close but not enough.

Did compression test  right 90psi :-/ left 95 psi. Wet test - 120psi both sides.

Took her for another spin as oil burn-off from the wet test kinda made shed a bit unfriendly for a while and i wanted to see how the idle behaved after the first adjust.

(Also became glaringly obvious that the exhaust pipe nut seals and balance pipe connections were rubbish.)


Tried the manual, plugs out carb balance approach.
Manometer showed carbs way out of balance as a result, reset screw/stops balanced carbs/idle and then cables @ 3500rpm.

Oh boy! is she running sweeeeeeeet, heaps more grunty, powerful, smooth and loud!   4500rpm vibration???
She's a different bike. Much better than my first manometer balance.

So Barry and Monte you were right. Cheers.

My plan is to talk to the local beemer mech re piston rings next week, but for now whats your opinion regarding them? I rode behind her recently on my mates GB500 and she didn't blow any blue smoke even when given plenty of whelly.

And what about the leaky pipes?

I believe the nut can be a bit troublesome to get off, i have a tube of "maniseal" expanding silicone based exhaust system sealer, is that OK for the balance pipe connections? I couldn't see seals in the exploded diagram in the manual?

Cant help but drooool at the thought of an extra  60psi and sealed pipes.

Thanks again for your help.     

[montmil]

... Reset idle mix screws to 3/4 turn out, throttle stops one turn out... Took her for a spin,WHOA! 4000rpm at idle...

Also became glaringly obvious that the exhaust pipe nut seals and balance pipe connections were rubbish.

And what about the leaky pipes?

I believe the nut can be a bit troublesome to get off, i have a tube of "maniseal" expanding silicone based exhaust system sealer, is that OK for the balance pipe connections? I couldn't see seals in the exploded diagram in the manual?

Has the idle speed been reduced to approx 1000 rpm?

On both my R65s, 3/4 turn out on the idle mixture was too much. With slack throttle cables and no contact between idle speed adjust screw and the butterfly lever, I pinched down the idle mixture screws just a touch and the idle dropped to spec.

I would offer counsel to not use any exhaust sealant materials on the x-overs or the head's butterfly nuts. The sealants I'm familiar with will make it near impossible to ever remove and separate the exhaust components without damage.

[79beem]

Yes she's purring at 1000rpm, do you think i shouldn't have followed the instructions in the cylmer re carb balance with a manometer?

She seems very happy.

So are there seal for the x over pipes?

Whats your thoughts on exhaust nut removal and low psi/new piston rings?

[Milo_357]

Hey, can i jump in?

This may seem like a stupid question (Hey, I seem to be full of those), but when people talk about tuning carbs, there is a list of items to be looked at FIRST; valves clearance, Ignition timing, etc.  

Now, Ignition timing is for pre-1981 bikes, correct?  This involves adjustments to the timing chain?  Bikes with electronic timing do not require adjustment, do they?

The reason I ask is, my bike is a 1982 R65.  I've had the valves adjusted, replaced the bean can, regulator, spark plugs, and spark plug wires, and cleaned & rebuilt the carbs.  On the way back from a trip the bike started running rough and vibrating very slightly. Not so much that I could not ride though. I HAD also made minor adjustments to both carburetors (tightening the main jet to 1.25 turns out) & the idle adjust just before leaving in an attempt to reduce the idle which was running around 3000 rpm when warm.  My gas milage also dropped about 10 mpg.

I read Snowbums tech paper on adjusting carbs.  I believe I have checked all the items on Rober's list of items that should be checked Before adjusting the carbs.  Is it manometer time?

[montmil]

... Now, Ignition timing is for pre-1981 bikes, correct?  This involves adjustments to the timing chain? Bikes with electronic timing do not require adjustment, do they?

Incorrect. Ignition timing is required for all airheads, no matter year of manufacture or points v electronic. Ignition timing has absolutely nothing to do with the timing chain -unless you have a worn out chain and automatic tensioners that you are replacing. And that timing concerns the cam timing, not ignition -although if done incorrectly, you'll definitely will have ignition problems.

... I HAD also made minor adjustments to both carburetors (tightening the main jet to 1.25 turns out) & the idle adjust just before leaving in an attempt to reduce the idle which was running around 3000 rpm when warm.  My gas mirage also dropped about 10 mpg.

Tightening it out? The main jet is not adjustable by loosening or tightening. Variances in the main jet are solely the responsibility of the jet's orifice. If you have loosened the main jets in the Bings, go tighten them back up immediately.

... I read Snowbums tech paper on adjusting carbs.

Really?

[79beem]

Re capping and canvassing for answers,

Read above for full story, but compression test showed 90 and 95 psi 120/120 with wet test.

She doesn't blow any smoke yet, only on start up due to resting on side stand.

Do i replace the rings asap?

How much more can they drop before it becomes a problem?

Any tips for the replacement procedure?