The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: 79beem on September 11, 2011, 05:34:15 AM
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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 ??? :-
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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
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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.
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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.
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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
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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
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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.
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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.
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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.
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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.
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... 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.
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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?
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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?
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... 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? ::)
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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?
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Apologies if this has already been covered but you will get low readings unless you do the compression test on a hot engine with the carbs off or throttles open and Slides manually lifted ?
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Engine warmed up, carbs on, throttle closed, just kicked over until i got the highest reading. So going back to my last posted questions?
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79beemer - if you did not perform a compression test in the manner that Barry indicated, then your numbers are invalid. Nothing useful can be gleaned from them unless/until the test is performed with (ideally) carbs off completely, or at least throttles held wide open on a fully warmed up engine.
You're asking the equivalent of guessing how fast you can run the 100 meter dash, based on a single timing of how well you ran the 400 meter run with duct tape over your nose and mouth with nothing but a soda straw to breathe through.. make sense?
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You're asking the equivalent of guessing how fast you can run the 100 meter dash, based on a single timing of how well you ran the 400 meter run with duct tape over your nose and mouth with nothing but a soda straw to breathe through..make sense?
Wonderful analogy !
79 beemer, You asked the engine to compress what it could breathe through a straw ... the amount of air available to it at idle.
If you let it breath I'm sure you'll get good compression figures.
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Sorry Barry,read your reply at 4am .
So the the clymer appears to contain errors in it procedures?
I didnt read anywhere to take the off carbs or to open the throttle,slides up.
Cheers for your patience
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...So the the clymer appears to contain errors in it procedures?
Multiple. Frequent. Contradictory.
I have the Clymer and Haynes manuals plus the original BMW R65 owners handbook -available in our FAQs section- plus the best resource for the R65... R65 dot org.
The commercial manuals often assume a certain level of mechanical knowledge. And you know what happens when you assume something.
Not to worry. Nothing damaged and you may end up saving a few shekels. [smiley=thumbsup.gif] Press on!
Monte
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OK forget what Clymers says lets be clear about your compression test.
Your compression results should not be a cause for concern yet and you may not need new rings.
When carrying out a compression test it is always required to have an unobstructed inlet because the engine needs a good supply of air at atmospheric pressure to compress. With the throttle closed at idle there is only a tiny amount of air able to get through so you are trying to compress a partial vacuum and a low result from your compression test is inevitable. To carry out a compression test with conventional slide carbs it's acceptable to just fully open the throttle which lifts the slides clear. With a CV carb that won't work because there is not enough air velocity to lift the piston so you must either lift them manually somehow or remove the carbs to leave an open inlet. Frankly if you leave the cables connected it's probably easier to remove the carbs from the inlet rubbers and hang then to one side a little. A 2 min job. If you do another compression test like this with open inlets you will get much higher figures that can be properly compared with the specs.
As for Clymers I don't have one so I don't know how good or bad it is. Manuals tend to get a bad name but I find The Haynes quite good for the most part and in this case it describes a compression test correctly including making the distinction between slide and CV carbs.
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... 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? ::)
[/quote]
Don't be Tom now, Monte! ;D
Ok, so if it's not the main jet, the large center screw on the base of the carburetor. Oh, and tighten out is "dumb ass" for loosen or unscrew. ;)
Seriously though, between the various adjustments (idle adjust, choke cable adjust, ect.) is there a "baseline" where to start when balancing your carbs?
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Proper procedure = excellant results :D
Did the proper check last Dec, just following up now.
Thanks chaps.
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I also experience high idling revs on my R65 - but only when the engine gets quite hot - i.e after a ride of about 10 - 15 kms.
During start up, or when the engine is still cold, the engine runs at low revs (about 700 Rpm).
Why is the engine running at higher Rpm when the engine gets hot ?
Thanks.
Danie
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There a couple of possibilities .
Valve clearances have closed up, performing a carb synchronization with the engine not up to operating temperature .
Advance mechanism in the 'bean can' hanging up and not returning when the engine speed is reduced .
Intake system leaks between the carb and cylinder head .
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Why is the engine running at higher Rpm when the engine gets hot ?
It's normal for an engine to idle slower until fully warmed up because the engine just doesn't run efficiently until then. Besides less than perfect fuel atomisation producing less power it takes that long for the oil to reach proper operating temperature and for oil drag to reduce.
There are a couple of reasons for run away idle speed but 9 times out of 10 it's carb settings and a failure to set the idle speed with the engine fully warmed up.
Going off on a bit of a tangent the effect of valve clearances on idle speed is interesting. We all know that valve clearances should be set before setting idle speed but why ? There is the possibility of closed up clearances which will make an engine not want to idle properly at all due to loss of compression. The actual gap also has an effect on idle speed because the valve timing or more particularly the valve overlap when both inlet and exhaust valves are open at the same time is being varied slightly and the engine is very sensitive to this at slow speeds. Opening up the valve clearances reduces overlap and makes the engine run slightly more efficiently at idle so the idle speed goes up. This is not just armchair theory opening up the clearances by 2 or 3 thou will actually produce quite a noticeable effect. All of which is to say you must set the valve clearances before adjusting the carbs.
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It's normally just tune-up stuff as already mentioned. I'll bet if you adjusted the carbs after a ride when it's idling high, you'd fix it right there!
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Thanks for all comments. The engine usually runs at about 700 Rpm when cold, and at about 1300 Rpm when warmed up.
I will check the valve clearances, and then have a look at the carb settings.
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The engine usually runs at about 700 Rpm when cold,
We usually say if an engine will idle stone cold with the choke off then that's a good indicator that the idle is set too high and possibly too rich. All depends on ambient temperature I suppose and no doubt it's a touch warmer where you are. Mine won't idle at all just after starting. It manages 800RPM after 3 miles and 1050 RPM when fully warm.
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Agree with Barry. A nice idle on a cold engine ain't right. Makes for a less than satisfactory ride 10-15 minutes later.
Good to hear from you, Danie.
Monte