The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: georgesgiralt on February 25, 2016, 05:12:24 AM
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Hello Lads,
As you may know I own an R65 made April 1982 which I bought new in 1984. Since then I've done around 190 000 km. She stand unused roughly from 2000 up to 2012 when I decided to ride her again after a thorough update. I started front, then progressed to the rear. Including frame powder coating...
Last winter, she stumbled between 4000 and 5000 RPM. i tried about everything and exchanged the carbs diaphragms in January. This seemed to solve the problem. This winter, again she was playing dumb with me.
I triple checked everything I could think of, finding nothing wrong. A local Guru told me that the tank is vented through the cap with a diaphragm keeping the vapors in. He says that this membrane becomes stiff in winter and the tank is not properly vented. So I rode the bike with the tank partially open. This vastly reduced the problem but did not solve it totally.
As when I was young I was told that "when you think it is carburetor related, it is not. It is an ignition problem. And when you think it is ignition it is a carburetor problem..." I'm ready to put back the "Crack-O-Matic" coil to see if it changes something...
So here I am seeking for a ray of light in this situation...
Help, please :( :-?
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By loosening the fuel cap, the tank no longer created a vacuum that prevented full flow of fuel. I believe that's a strong clue as to where your search should continue. With only one petcock on the R65 tanks, I'd be suspicious of a clogged or partially collapsed fuel line, a blocked mesh filter over the petcock straws, clogged petcock or even the carb's stub at the fuel line connection.
At the noted 4-5K sustained revs, reduced fuel flow would cause the engine to stumble.
;D You may be the first person to actually want to go back to that nasty Bosch "CrackO". For a short test maybe not so bad, but how will you know if the stumble continues? You do know the Crack-O-Matic is first cousin to Lord Lucas, The Prince of Darkness.
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Montmil,
My gray Crack-O-Matic albeit heavily creaked did not cause ignition trouble. :P
I played chicken and put a new coil in place because it looked so weird.... But I bet the old coil is still good..
Once my tank empties a bit, I'll remove the petcock and see what the problem is.
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Can't fault Monte's logic - if increasing the fuel flow improved things then it needs increasing some more.
The restricted fuel flow must have resulted in a low fuel level in the carbs which will have been the direct cause of the weak mixture stumble. So another way of looking at it is to say the fuel level needs to be increased. Whether you need to increase the level by improving fuel flow or whether it's just too low regardless of fuel flow is less certain.
By way of experiment you could shut off the fuel tap when the stumble occurs and quickly remove the bowls to observe what the actual fuel level is. If it's lower than normal then there is still something restricting fuel flow. If it's no different than normal the either the normal level is too low or the fault lies else where.
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Yes Barry, the logic is good. But how come the bike only shows in winter ?
Last but not least, when I open the throttle fully, the bike seems to have too much fuel to swallow. If I back up the throttle a little, she seems to will accelerate ...
I hope that tomorrow I can empty the tank and have a look at the petcock.
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Yes Barry, the logic is good. But how come the bike only shows in winter ?
One possibility is that because the air is colder and denser in winter a carb will run slightly leaner.
Last but not least, when I open the throttle fully, the bike seems to have too much fuel to swallow. If I back up the throttle a little, she seems to will accelerate ...
This sounds like the old main jet test where you get the engine pulling hard on full throttle and then suddenly back off to 7/8 throttle. The theory is that this creates a momentary richer mixture so that if the engine suddenly picks up when you roll the throttle off then then it was running too lean.
Seems to me that both the winter only aspect of the stumble and the roll off main jet test point towards you having a marginally weak mixture.
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Where do you have the needles set at .
Long before the main jets meter fuel, the needles are in control .
I operate my R65's from 19 F, -7 C, to 122 F, 50 C and never see issues like this on stock factory setting jets, needles, etc .... .
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Bob,
Full stock.
And all new "copper" in the carbs from top to bottom.
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Bob,
Full stock.
And all new "copper" in the carbs from top to bottom.
Likely brass. You mention winter operations. Do you have a different gasoline blend sold in winter months? Not uncommon here.
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I do not think so but it could be. Last winter was cold, this one wasn't. So the densiry difference is not as large as it was last year.
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Almost certainly a winter blend. It's a matter of legislation in the UK that the fuel companies have to deliver a winter blend between certain dates and it has approx 3% lower calorific value due to the more volatile fractions - which means 3 % weaker.
There is no question that winter air temperatures and winter fuel will produce a slightly weaker mixture in an uncompensated carburettor. That wouldn't matter unless the the mixture was already marginally weak even in the summer. This is my whole point that the symptoms point to a weak mixture probably due to low float level, the only thing to determine is the cause.
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So,
Yesterday, the tank was quite empty. Spend some time removing the petcock and cleaning it. Had a look at the little mesh filter at the base and found a very small chip of paint. Removed it.
Put a lot of air pressure in the fuel tubing after having removed the floats and the little pin. No obstruction at all and nothing comes out of the tube. Did it in reverse also just to be absolutely sure.
Today, I took the bike for a ride after having topped up the tank with Super 98/88 fuel which may contain up to 5% ethanol and added a dose of lead substitute.
Alas, on the highway, the bike still stumble between 4K~ 5K RPM. And this whatever gear in use.
If I open the tank to cope with a possible venting problem, nothing changes except I smell gas :(
I'm completely at loss here.
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Hello !
Through this week end, I've verified all item related to carbs. From the tank and petcock to diaphragms and brass in the carbs. Still no joy.
As I had to fill the tank, I discovered that the gas consumption is huge. It is at 7.0 l/100km. A lot above what I measure normally (around 5.5 to 6 l/100km)
As requested, I've measured the compression, with an hot engine and carbs removed. the figures are : Left 11,0 bar and Right : 10.2 bars. So in the "good" range.
Next point is to do the same to the ignition system and see what it gives.
I'm unnerved a bit .... >:(
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I discovered that the gas consumption is huge. It is at 7.0 l/100km. A lot above what I measure normally (around 5.5 to 6 l/100km)
Could be running a bit rich, eh? Time to dig into the carbs as something has come adrift.
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Montmil,
Spent two days dismantling, cleaning, adjusting verifying the two carbs. Nothing wrong. Everything perfect as I did renew them less than two years ago and did not driver the bike that much since.
I'm beginning to suspect an ignition problem.
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Montmil,
Spent two days dismantling, cleaning, adjusting verifying the two carbs. Nothing wrong. Everything perfect as I did renew them less than two years ago and did not driver the bike that much since.
I'm beginning to suspect an ignition problem.
How might an ignition problem cause such a huge increase in fuel usage. Just doesn't compute. Your bike is passing way too much gas.
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Like you, I'm puzzled.
But the jetting hasn't changed and the diaphragms are in perfect shape. As the air filter (OEM) is brand new, it can't be the culprit. (the previous one was far from dead but I changed it anyway as a possible cause).
I think there is something cutting the ignition at certain RPM which cause the engine to stumble and the gas to go un-burned causing the low mileage.
Finding this intermittent is the puzzle I face.
Honestly, I've checked and adjusted EVERYTHING I can think of. And still have the problem. So ignition, having not being thoroughly checked is/can be the culprit.
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Is the ignition advance working properly.
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Will tell after I check it ;-)
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Just doesn't compute. Your bike is passing way too much gas.
I have been accused of the same thing from time to time. ;D
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Just doesn't compute. Your bike is passing way too much gas.
I have been accused of the same thing from time to time. ;D
Was waiting to see whom, among the usual forum suspects, would rise to this bait. [smiley=1drink.gif]
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Hello !
This afternoon, the timing lamp was out of it's drawer and served to see that the advance was set a little less than specified *. And I saw that the bob-weights are perfectly working and the advance develops between 1500 RPM and reach the Z maximal value around 3500 RPM.
I'll go ride her in a couple of hours and see what gives.
* : the S mark is underlined. This underline is aligned with the lower part of a starter teeth. My advance was set at the other side of the top of the teeth. So not a huge difference !
The bike runs better. When hot, she runs quite without any stumble. So definitely an improvement.
I think I'll try to substitute the new Bosch coil by either the old Crak-O-Matic or a Fiat Punto double coil I stock in case ... (0,8 Ohm primary and 7K secondary so in between the new Bosch design and the old one ).
My problem seems to have a lot of little causes (venting the tank, small obstruction on the petcock filter, bad initial advance, maybe bad air filter, poorly gaped spark plugs ....).
Friday I do not work. If the weather is fine, I'll take the bike in a trip around 200 km to see how she goes. I'm delighted in town by the setting I get using Advrider Grok Harmonizer. She is very very sweet. So it is a pity that she refuses to go fast...
Once I've cleared this problem, I'll document it into my log book in order to speed up the process next time !
Edit : added information after test.
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Update,
This morning I took the R65 to go to the local Airhead Guru shop.
100 km total including deserted small roads and a return by the toll highway. She is a sweet bike ! On the small roads, i was able to open the throttle fully and see the cars disappear in the mirrors. Then o the highway, going back home I was able to have her go towards the red line in fifth gear so definitely and improvement ! I think I passed a traffic enforcement radar with the bike at full speed... Hope I'm mistaken.
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This morning I had an appointment at the doctor.
I went there driving slowly because the roads where busy. But on my way back, I did a extra and rode on back roads, making 3 times more km on the return journey than on the initial....
Boy, the Harmonizer is such a fine piece of gear ! The bike is as smooth as silk and run like she was new ! I'm more than happy !
How fun it was ! I'm waiting for the mileage figure to show to see if I also get the mileage I expect .... If yes, anuthing will be PeRfEcT ! ;D ;D
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Conclusions? :)
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The stumbling was caused by :
(by order of discovery)
1) grunge around the emulsion tube
2) small chip at the petcock filter
3) corrosion at the coil tower (inside)
4) incorrect static advance (a little bit to few)
and maybe a slightly clogged air filter. Add to this a possible venting problem of the tank. *
As I synchronized the carbs at every search and modification, I was sure about it every time I ran the bike after a session. Every step showed an improvement, and total remission was when I corrected the static advance.
Hope this helps.
* : The tank is vented trough the cap by a diaphragm which become hard with age. The local guru says it sticks when weather is cold (this could explain why I experienced this problem in winter). The bike ran better with the tank partially open but still had problems so i pursued investigation.
Then I found that the stumbling was existent even with the tank open. So I closed it completely and that did not change a bit the bike behavior...
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Thanks georgesgiralt for your comprehensive conclusions. I read your comment about the Harmonizer and wondered what it was. After checking some more, I ordered one last night!
It will be good as a back up to my 2ft length of garden hose. ;)
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Frankly, it has nothing to do with the garden hose.
I own a lot of sync devices. One is a 2m lo,g mercury double column I got from jet engine set up and tune-up. I also own a set of dial gauges I used for 25 years. Then I got the harmonizer. And it made a huge difference.
The main difference is that you can set the difference to be really null as the device displays the true numerical value. And it is fast enough to display the difference when you open the throttle. So you can see that there are differences at various RPM !!! (this is due to difference in compression, valve lash etc... and this induce variations in efficiency so a different vacuum produced that the one on the other cylinder). So you can adjust for the best overall discrepancy or for the perfect balance at the RPM you use the most (or use art cruise speed).
This is the first time that I see a device apt to do such things. And it make a difference.
I've used it on an oilhead, which had been set-up using abig professional tool (made by Souriau) and I showed the mechanic that there was still a difference between the two cylinders. I set the balance perfectly for idle. The engine was purring like a cat afterwards... I was happy ;-)
I have no connection with Grok except a very satisfied customer. If he made a 4 cylinder version, it would be fantastic !