The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: qwerty123 on June 22, 2017, 01:44:25 PM
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Hello all,
I'm experiencing an infrequent stumble or loss of power at or above 60mph/ 4000rpm. Engine sound changes, I lose power, and opening the throttle further does nothing. Closing the throttle, even for a short time, fixes it.
My first thought was fuel starvation, so I disassembled and cleaned the petcock and screen, as well as replacing the aftermarket paper fuel filter. I also confirmed the fuel overfill vent isn't clogged and tested with the gas cap loose--still occasionally get the stumble.
It happens in the wet and dry, but doesn't appear to happen with a full or nearly full tank. I mostly notice it about 150-200 miles into a tank. I've been measuring low 50s miles power gallon.
Spark plugs looked fine.
Any ideas? Thanks much!
Matt
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It's a tricky one as I think you have already done a good diagnostic.
While it does sound like a lack of fuel, the intermittent nature is odd and starts me thinking about ignition but then it doesn't do it on a full tank which pushes the thought process back to fuel again as the mixture will be very marginally rich with a full tank and a potentially higher fuel flow rate.
Some ideas. Assuming it's safe, when it does it again shut the engine off quickly, close the fuel taps and coast to a halt. Whip the float bowls off to see if the levels are low. If they are then you know it's fuel but not yet why. Given the extra head pressure of a full tank solves the problem, instinctively my first action would be to ditch the fuel filter if only as a temporary test.
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Two things I can think of, low fuel level in the float bowls, and holes in the carb diaphragms .
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Thanks for the thoughts. My mind is now running to ignition as well. A couple more pieces of data:
1) I rode the bike through a deluge a couple days ago, and the last few hours has been the only truly dry air it's seen in a while
2) There is a sucking / maybe slight popping upon closing the throttle at higher revs (as the revs come down) that I don't remember from earlier in the bike's life
3) I can see fuel in the clear plastic fuel filter when it happens
4) It occurs to me that the lack of a problem after a fill-up could be down to the bike getting a few minutes to cool as it's filled and I stretch, rather than the pressure from a full tank
5) I might describe it as a stutter rather than a stumble, in terms of noise. It does happen only a little / a blip that could've been a bump in the road, but when it's fully happening it's a clear change in engine note as well as no power.
The notable binary nature of the problem (rather than smooth in and out of it, it's happening or it's not) makes me think ignition (any way to test that?), but the fact that it really only happens at highway speeds in the middle of an extended run (i.e., when fuel usage is highest) makes me think fuel / air / mixture...
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Do you have a black and gray ignition coil ??
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Mine looks like this
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Yes, that's black and gray coil, a very well known problematic part .
I would suggest taking a good look at it, most likely you will find mutliple cracks in the coil case .
Just a suggestion, replace it when you can .
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When I have mine jetted to get over 50mpg
It does not run very well until the temps are over 60
I keep mine jetted to get mid 40's mpg since we ride all year round
If you do get a new coil keep the old one for a spare on long trips
It can at least get you home
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Here is one option for a replacement coil
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Thanks guys!
I'm going to have to see if I can get a coil somewhere around Austin, TX (Presuming it's the coil, which seems likely. I'll have a look tomorrow morning).
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An inspection of the black coil doesn't show any cracks, but there is a raised area that looks like a crack--however, I don't think it's a crack, I think it's a casting / moulding artifact. A close inspection reveals it's raised, smooth with no crack I can see. And the way it goes around the edge of the cylinder--I'd expect a crack to continue, this does not. The coil has been replaced, I think? This is the later BMW 12 13 1 244 426 / Bosch 0 221 500 203.
However! Close inspection of the coil led me to look at the (brand new) silicone plug leads, and...there's an area where the insulation has worn away! I'm thinking maybe under certain circumstances this could be shorting directly to the engine top cover where the plug leads lie, and so could be the culprit? I'll cover it with some silicone self-fusing tape (great stuff by the way, highly recommended) and see if the problem recurs. If it does I'll try to source a new coil.
The "crack" you can see in the photo looks for all the world like a casting / moulding artifact to me, but do let me know if I'm way off base here--I've left my magnifying glass at home.
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No, that doesn't look like a crack to me either .
The OEM coil ending in 426, is red and black .
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That is why I have Vinyl tubing covering my wires
They will rub thru laying on top of the vibrating motor
It is not going to be easy to find a coil that will bolt up with out making a bracket
I would not get one with less than 1.5 ohms resistance unless you have a ignition module that can handle it
It looks to me you already have the latest coil that should have a primary resistance of about .7 ohms
Get a Volt ohm meter and check it .
If this is the case you may be over stressing your ignition module and causing the problems you describe
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Thanks for the suggestions guys. Unfortunately repairing the spark cable did not fix the stumble :-(
Next stop new coil I guess. I will test the resistance of the one I've got this evening.
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Where are you now ??
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At this very moment a cafe called "Fuel" in Llano, Tx (quite a nice little town). The plan is Abilene tonight.
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Do you plan on being in the Denver area ??
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Yup, I do plan on passing through Denver.
A couple thoughts/data points I had today whilst riding:
--The engine oil is probably overfilled by a bit. I used the dipstick while cold, it looked too low, so I added some. Measuring warm, it's on the high side. I can see oil coming out near the airbox on both sides, dirtying my block and dripping on my boot.
--It doesn't happen at 55mph, but 60+ it does
--I tried hitting the kill switch briefly while on the road. The slowdown from just turning off the ignition is much smoother than the problem I'm trying to diagnose. This makes me think it's something that's causing an imbalance (i.e., it's only happening on one cylinder). The sound is very different, too.
--I adjusted the valve clearances today, to 0.010 exhaust, 0.006 intake. Left cylinder was already at those settings, right was at .008 exhaust, .006 intake.
I'm going to measure coil resistance and perhaps remove a little oil tomorrow.
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There is an online site Euromoto Electric , located in the Denver area .
John Rayski is the owner great person to do business with .
He also has a BMW motorcycle shop .
May want to contact him when you get into the Denver area .
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Thanks for the tip Bob! I've done business with them before and have been nothing but satisfied. Perhaps time to pay a visit in person!
The plot thickens a bit:
I pulled off the bowls and there's a bunch of fine sediment in the left bowl...but I pulled them and the main jets and cleaned as well as I could before the trip (granted, a couple thousand miles ago at this point). But where did it come from?!? Fuel is going through the tank screen and a paper filter. Maybe I got a bunch of crap in there? Maybe it's from the lines themselves? But why then only the left bowl?
Anyway, suggestions for a side-of-the-road carb cleaning more than welcome!
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Run by Ft. Worth, TX, and I'll see if I can help. Am PMing you my phone number...
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Thank you very much Justin! I'm much obliged, and will keep it in mind---after a thorough-as-possible carb clean, Penelope appears to be running sweetly. But it's also 20F cooler than yesterday!
I'm feeling pretty good about making Colorado, and so am headed to Grulla Reserve in NM. I did determine that I have an old style ECU but a newer low resistance coil, so I'm planning to upgrade some bits with the Euromotoelectrics folks anyway.
Thanks to all here for the support, and thanks to Matt in Austin for showing me some mighty fine roads!
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Good to hear you got it sorted out, nothing worse than having issues on the road far from home .
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--I tried hitting the kill switch briefly while on the road. The slowdown from just turning off the ignition is much smoother than the problem
I would not do this it could back fire and blow the exhaust apart :o
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If you get a new Ignition module
Get the heavy duty one and remember to get the adapter bracket
Keep the old one for a spare
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The mounting bracket states that it is needed if your ignition module is mounted on top of the frame .
Was the ignition module moved on later model year bikes ??
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John also sells a nice adjustable voltage regulator, as long as you're there...
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Yeah, I may just pony up for the enhanced ignition kit (now the question is do I get the charging system at the same time, since the timing sensor is specific to each alternator...but the combo is 1/3 the cost of the bike!)
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.but the combo is 1/3 the cost of the bike!
Certainly makes you stare at the menu for awhile when ordering , huh? :-/
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The mounting bracket states that it is needed if your ignition module is mounted on top of the frame .
Was the ignition module moved on later model year bikes ??
The new heavy duty IGN MOD is larger than the earlier ones and the mounting bolts are wider apart
So it has to be mounted at a angle to the top tube instead of perpendicular
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After upgrading to LED's I think the up rated charging systems are Obsolete and completely unneeded
It will just make parts more difficult to get
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--I tried hitting the kill switch briefly while on the road. The slowdown from just turning off the ignition is much smoother than the problem
I would not do this it could back fire and blow the exhaust apart :o
It's when you turn the ignition back on that the exhaust goes bang. It blew the baffle out of my very first bike, a 1970 Ducati single, the baffle was then promptly run over by a truck. I made a new one out of a baked bean can stuffed with wire wool. Happy days.
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Hmmmm...yes, well, no more highway kill switch use for me! I seem to have escaped unscathed.
Mrclubike makes a very good point about obtaining parts. It's an especially good point because it saves me the time and expense involved with a new charging system! I feel pretty good about my ability to identify and limp along with failed charging given I've got a volt meter on the dash now and a lithium back-up battery. Unless somewhere REALLY remote an ATV or similar battery that fits can be had at most any auto parts store--I used one for years. Could just alternate batteries, charge both overnight.
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Well, I thought I'd close the loop on this. After noticing it intermittently for several years, I finally figured out that it's loose-fitting fuel hoses on a jaunt from Boston to St. Louis! The hose going from the tank tap on the LHS to the aftemarket filter, and from there to the tee that splits it so it goes to both carbs, was 5/16 not 1/4 (or the more correct 6mm). I bet it felt pretty tight when new, but age has made it loose. I think that under high-flow situations (e.g. open throttle up a long hill on a highway) it was sucking air through the gaps. I'm not sure exactly what problem that *should* cause, but replacing with new 1/4" ID hose seems to have solved it. And it only took three years!
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Glad you found it.
Not quite sure how air gets in since fuel is under gravity feed and wants to get out! Possible rubberised junk in the pipes or swollen inside?
I had to uprate the fuel lines on my old 250 RD. 220 main jets, Micron MKI expansion chambers and various reed, port, head and case mods plus 30:1 petroil meant fuel consumption was a bit heavy with the rev counter clockwise past the high beam lamp. Lack of fuel on those meant either instant skirt or ring seize near the exhaust port or melting of the plug earth bar and subsequent arcing to the piston crown. The bottom ends were pretty tough and the piston usually destroyed itself in a way that didn't score the barrel or disperse aluminium into the main bearings. i never had the exhaust side of the piston go soft, usually something much more spectacular.
Lifting the front wheel at 40 with the cheery wave of an L plate as you took MGs, Jags, CX500s and CB750s off the island was always fun. Well not so much fun with a CX500.
Memory kicks in that I had to split the fuel pipe to the two carbs just under the tank or something, with bigger pipes and bored out fittings. Suzuki reed blocks and RD400 carbs also now remembering. They had a series in Motorcycle Mechanics or Superbike about how to tune your RD. I was well in front of the curve with that. Been there, blown it up twice already. Still using Yamaha reed blocks? How quaint.