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Discussion Starter #1
OK folks, I've noticed a miss in the engine at idle and when first moving out. At high RPM's I can't hear the miss.

This shade tree mechanic has done the following with no good results:

1. adjusted the valves to make sure I didn't have a tight/leaking valve. It was time to do it anyway.
2. replaced all 4 sparkplugs
3. placed a used injector at #3 cylinder as I thought that was the culprit due to the color of the plug in that cylinder when I replaced the plugs.

I took a ride yesterday and it performs the same way so I made no improvement.

The next thing for me to do in my opinion is to load it up and take it to Engles in Kansas City and have them do a engine diagnosis. I haven't called them to make an appointment as yet.

Sooooooooooooo, if someone here on this site is excited about using their GS-911 on my bike PM me.

Also, if I've missed performing something simple that I should do before hauling the bike to Engles, then chime in. I don't have anything to do a compression test as that has crossed my mind.

Please note that I now have 149,777 miles on this bike/engine. If this turns out to be a major engine repair, then I'll be looking for a used '03 or '04 LT to buy with fewer miles.

So fire away and thanks for this outstanding site to vent on and to obtain super info.
Vern :bmw:
 

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Vern,
You didn't mention it in your post, but what have you checked for spark? You could have a wire that is leaking spark. It is hard to see the small holes that will leak spark,try looking in low light. Another check is to gently mist the wires all the way to the plugs with a fine water mist. It won't hurt anything, just don't drown it.
 

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Discussion Starter #3
John,
Hadn't done that. Guess I could see that at night. I have pulled the plug wires one at a time and it bits like hell. LOL
But I guess it still could be jumping off someplace it's not supposed to.

I didn't think about the plug wires. Maybe I sould take them off one at a time and give them a good going over.
Thanks for the tip.
 

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A vac. leak will cause a miss at idle that goes away with RPM.
At idle spray WD40 around the intake gaskets. If there is a leak RPMs will go up.
 

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Good suggestion from John. :thumb: IIRC, It has something to do with amount of voltage needed to jump the spark plug gap, and I can't remember if more voltage is needed at idle or less, but seems like that's why it's more noticeable. If this doesn't pan out, then here's some info I found online:

Lean Misfire
The lean misfire is another common reason for an engine "miss"—this is due to an imbalanced air/fuel ratio (too much air/too little fuel). Since an engine needs a richer (more fuel) mixture for a smooth idle, this problem may be more noticeable when the vehicle is idling. The lean misfire may decrease or disappear as the engine speed increases because the efficiency of the volumetric flow into the combustion chambers increases dramatically. This is one reason why a vehicle gets better mileage on the freeway than in the city. An EGR valve that is stuck open, a leaking Intake Manifold Gasket, a defective Mass Air Flow Sensor, a weak or failing fuel pump, or a plugged fuel filter are some of the many causes for a lean misfire.

The information was regarding automotive engines, but the info is applicable to m/c as well.
 

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Check carefully where your wires pass through the end of the plate on the valve cover. They are prone to leakage at that point. You can try running it with the cover removed and applying some electrical tape to the wires at that point. Not a permanent fix, but a good diagnostic method. Also look for continuity in each wire. Note that the resistance is linear and corelates with the length of each wire, but each one should be measurable.
 

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Discussion Starter #7
jwacree said:
A vac. leak will cause a miss at idle that goes away with RPM.
At idle spray WD40 around the intake gaskets. If there is a leak RPMs will go up.
Actually, I don't think the miss goes away at higher rpm's I just can't hear the miss like I can at idle. It dies at a stop sometimes but will still run 90 mph in 3rd..

Jeff, you brought up a lot of good questions/ likelyhoods for my search in your post. Thanks. I wonder if any of those symptoms show up on a GS-911?

I just now sprayed water over the wires and ran it in the dark. No visible sparks nor did it affect the engine speed.

I don't use wd40 (just ether), but I don't want to use ether for a vacuum leak test. (BOOM) Next time I'm in town I'll get a can of wd40.

Thanks fellows :bmw:
 

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Another good diagnostic tool is a propane torch. Just open the valve and put it close to the intake system (unlit of course). The propane does the same thing as the WD 40 and leaves no mess. WD 40 doesn't work quite as well as it used to either as I think they changed their propellant to something non-flammable.
 

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deanwoolsey said:
Another good diagnostic tool is a propane torch. Just open the valve and put it close to the intake system (unlit of course). The propane does the same thing as the WD 40 and leaves no mess. WD 40 doesn't work quite as well as it used to either as I think they changed their propellant to something non-flammable.

Dean, the propellent used to be butane/propane but they changed it since we were using WD40 for unintended purposes (like seating flat tires on the bead). Either that or some other silly safety related reason.
Robert
 

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Actually, I don't think the miss goes away at higher rpm's I just can't hear the miss like I can at idle. It dies at a stop sometimes but will still run 90 mph in 3rd..

you have done a compression test haven't you, and not just check valve clearance?
 

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Can't remember but does the LT still have the little rubber caps on some vacuum connections at the base of the throttle bodies? I know my 85 K100 RT did and these were prone to cracking and leaking. With 150K on the clock the seals between the throttle bodies and the head could also be getting hard from the heat / cooling cycles. These were bad on My 85 but it was also 20 years old at the time.
 

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each wire should be very close to 5 ohms - had a pretty good miss in my k100 was plug wire - my k1100 plug wires were cracked and had holes but engine ran perfect even wet
 

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Scouter-50 said:
Dean, the propellent used to be butane/propane but they changed it since we were using WD40 for unintended purposes (like seating flat tires on the bead). Either that or some other silly safety related reason.
Robert
Yea, that and potato guns. Well, and backyard flame-throwers. :D
 

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Discussion Starter #14
Axle said:
Actually, I don't think the miss goes away at higher rpm's I just can't hear the miss like I can at idle. It dies at a stop sometimes but will still run 90 mph in 3rd..

you have done a compression test haven't you, and not just check valve clearance?

Nope, haven't done a compression test as mentioned above.

I looked at the #3 plug again and it's oily so I'm thinking something serious. IE broken ring/cracked piston/Ugh! Might try another spark plug and some "restorer in a can" before I get another LT. If I get an '03 I'll have a whole bike of parts to use/sell. There is an '03 LT in the classifieds that's the same color as mine. I may have to go to Alabama to see it. The owner hasn't given me any details about the bike yet.

Oh well......................spring is getting closer!!!!!!!!!!!!!!!!!!! :bmw:
 

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Mine has an "oil wet" #4 cylinder. Smoke clears up shortly after cold-startup and I have to watch the oil fill level to always be lower than halfway up the sight glass hot oil engine off for at least 10mins.

I wanted to do compression test but so far can't find reasonably-priced tester with that tiny of a plug thread. Anyone have a recommendation?

Look around like beemerboneyard.com and ebay you can find good used motors complete for under $600. If your bike is otherwise in good shape that's probably the way to go.

Afterwards take your time, open up your old motor and see what's wrong. They use the nicasil (spel?) chromed cylinders so a really bad scratch may not be fixable in the cylinder bore. Correct me if I'm wrong.
 

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2005 K1200LT
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You are correct. At least for a reasonable cost that is. I understand it can be done but it is expensive. Far easier to swap in a used engine. Steve Rowe had low compression and high oil consumption on his bike. Otherwise it drove fine. This post shows what we found. Also upon further disassembly I found all pistons had fractured ring lands, but just the one broken ring.
 

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Discussion Starter #17
Update.....................I decided to call the Stealer in Kansas City to get a diagnosis. They scheduled me for next tuesday afternoon.3/12/2013. Hope they can decifer the problem then I'll decide what to do. For sure, I won't have them fix it at $84 bucks an hour.

After reading the last post about a chunk out of a piston, I'm thinking I have something similar to that.

I've had the intake off my bike to replace the vent hose assembly on top of the engine once and that was 45,000 miles ago. Even though I used rags to prevent something from falling in the holes, it is possible something hard could have dropped before I got it back together. I didn't hear any "crunch" when I started it up though. LOL

I'm really slow at mechanicing so I sure wish spring wasn't so close. Ugh! I don't think I want to attempt the "a used engine route".

Thanks for all the ideas/help. :bmw:
 

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helmutdryer said:
A miss at high RPM is common to all engines bike or automotive and is indicative of
bad spark plug wires.73 Jerry
Go back and read the first sentence of the OP.
 

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Darn Vern ;least you got the original shifter and clutch;not most people can say for sure.
No really I hope it all works out for you Vern;with out being to costly

Gary
2003 K1200LT
 
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