1986 K75 Sputtering to a stop then Re-starts fine...

[Beemahdad]

Hi, everyone

I am having a problem on initial startup that hopefully some of you can help me isolate.

Upon initial startup in the morning, the bike runs fine for a few blocks (3 or 4) then sputters to a stop. It happens either when I start to pull away from a full stop or as I?m coasting to a stop. Then, I usually push the bike to the side of the road and go through a sequence of ignition off/ignition on/starter engage, repeat for about 1 or 2 minutes. Usually by half a dozen or dozen attempts and some patience, the engine will fire back to life and I?m back on the road without further incident.

I plan to replace my hoses in a few weeks and re-treat my K&N air filter. I always run premium fuel and I think I did my plugs last summer. I believe my fuel filter was replaced summer 2012. Maybe I need the throttle bodies adjusted by BMW guys at Shails?

Any other suggestions?

What I have been doing in the meantime is just keeping the throttle slightly engaged in hopes I don?t stall

It's not a major problem but an irritating one.

Thanks

 

[PGlaves]

Hi, everyone

I am having a problem on initial startup that hopefully some of you can help me isolate.

Upon initial startup in the morning, the bike runs fine for a few blocks (3 or 4) then sputters to a stop. It happens either when I start to pull away from a full stop or as I?m coasting to a stop. Then, I usually push the bike to the side of the road and go through a sequence of ignition off/ignition on/starter engage, repeat for about 1 or 2 minutes. Usually by half a dozen or dozen attempts and some patience, the engine will fire back to life and I?m back on the road without further incident.

I plan to replace my hoses in a few weeks and re-treat my K&N air filter. I always run premium fuel and I think I did my plugs last summer. I believe my fuel filter was replaced summer 2012. Maybe I need the throttle bodies adjusted by BMW guys at Shails?

Any other suggestions?

What I have been doing in the meantime is just keeping the throttle slightly engaged in hopes I don?t stall

It's not a major problem but an irritating one.

Thanks

I'm not sure what the root problem here is, but step one with that bike is to junk the K&N air filter. Compared to OEM filters they do a horrible job of filtration, and an exceedingly uneven one at that. In normal street use the OEM paper filter is likely to be good for at least 50,000 miles, and even then may need only to be whacked against the work bench to use again.

There may actually be a brand/model motorcycle that benefits from a K&N oiled filter, but it isn't a BMW K75.

 

[98lee]

What is the outside temperature?

Which click do you have your choke (fast idle) lever on?

Is the fast idle lever properly adjusted? (Does the first click move the idle screw 1.5mm off the stop and the second click move it 3mm off the stop?)

Do you have cracks in your crankcase vent hose?

Are there any cracks in your throttlebody rubber tubes?

Do you have cracks in you throttlebody vacuum caps?

Just because you changed you fuel filter last year does not mean that it is clear today. You can take it out and test it.

 

[tinytrains]

It may or not be related, but my K75 developed a bad Hall Effect sensor for the ignition. It would start and run fine for 8 minutes and then stop dead. All I had to do was pull in the clutch and hit the starter to keep going. And it only happened in the mornings, but every morning.

 

[72r60/7]

'86 sputtering to a stop

Just for the fun of it, clean and scarify both ends of the Negative ground, battery end and transmission connection. Positive battery connection while you are at it, can't hurt either.
Charlie

 

[cele0001]

At this point you have to narrow it sown to see is it fuel or spark. If you are saying that holding throttle slightly open will make the bike not stall it should be fuel issue (or general mixture problem) and not spark.

 

[Beemahdad]

I'm not sure what the root problem here is, but step one with that bike is to junk the K&N air filter. Compared to OEM filters they do a horrible job of filtration, and an exceedingly uneven one at that. In normal street use the OEM paper filter is likely to be good for at least 50,000 miles, and even then may need only to be whacked against the work bench to use again.

There may actually be a brand/model motorcycle that benefits from a K&N oiled filter, but it isn't a BMW K75.

I guess trying the oem paper filter would not hurt. Thanks, Paul

 

[Beemahdad]

What is the outside temperature?

Which click do you have your choke (fast idle) lever on?

Is the fast idle lever properly adjusted? (Does the first click move the idle screw 1.5mm off the stop and the second click move it 3mm off the stop?)

Do you have cracks in your crankcase vent hose?

Are there any cracks in your throttlebody rubber tubes?

Do you have cracks in you throttlebody vacuum caps?

Just because you changed you fuel filter last year does not mean that it is clear today. You can take it out and test it.

I am fortunate to be on the westcoast while the rest of Canada is under constant chill this winter. Air temp is slightly above freezing.

I don't usually run with the choke/fast idle.

I will check for cracks as you suggest.

Thank you for your thoughts.

 

[98lee]

Air temp is slightly above freezing.

I don't usually run with the choke/fast idle.

Under those circumstances, you should be starting the bike on the second (fastest) click of the fast idle lever.

After the idle is steady at over 1800rpm, you can click it down to the first click. (This can be done while you are riding or while you're putting your gloves and helmet on.)

Start riding! After a couple of miles, if the bike will smoothly idle above 1600rpm with no throttle and come to stops without stumbling, then click the fast idle back to 0.

But, under very cold conditions, you should be starting your ride with some fast idle until everything is stabilized (exactly what you are doing by holding the throttle partially open for awhile.)

The fast idle is not just for starting, it is for the first several minutes/miles while everything gets warmed up and settled in. Use it.



Still check for cracks (air leaks), as it will cause a lean mixture that will aggravate the situation.

 

[timtyler]

Upon initial startup in the morning, the bike runs fine for a few blocks (3 or 4) then sputters to a stop. It happens either when I start to pull away from a full stop or as I?m coasting to a stop.

I had that problem, although maybe not quite so drastic, for months when my bike was new to me.

After replacing filters and plugs, and TB syncing, I finally solved it by adjusting the exhaust valves which were crazy tight.

 

[rzwartus]

Sounds like your bike was adjusted whilst cold. Make sure you warm the bike thru (driving it, not idling!) and then set the idle. Next time you start you'll need to use the 'choke' lever when the temp is below 15-20 C, but that's OK. But if the bike's new to you (or you haven't checked yet) any way you can get false air will offset the running of the bike, so making sure that the rubber hoses/plugs are good is important. False air will change your idle.

 

[98lee]

I had that problem, although maybe not quite so drastic, for months when my bike was new to me.

After replacing filters and plugs, and TB syncing, I finally solved it by adjusting the exhaust valves which were crazy tight.

Tight exhaust valves (exhaust valves tend to tighten over time) will cause numerous problems (including stalling at stops). Therefor it is important to stay on top of your valve adjustment ( I would suggest at least every 10-15,000 mi. And would suggest setting the exhausts to the loose side of spec.)

Trying to troubleshoot a poor running engine without being SURE your valve adjustment is CURRENTLY correct can lead to a lot of frustration. Been there, done that.

 

[72r60/7]

K75 Sputtering

98lee said check the valves.

Best advice yet.
If you do check them, please follow up w/ existing clearances and corrections and any effect toward solving your problem. It will help a lot of people, most of which you will never hear about.
Charlie

 

[barryg]

Check your fuel tank for water/gunk at the bottom of tank generally around the fuel filter. Pull the fuel filter and see if it's stopped up with water or gunk. Check your fuel level sending unit. They are known to go bad and work intermittently . I've moved the connecter around and killed the engine. All three of these problems can cause the engine to run intermittently. Check the fuel injection control unit at the connector plug. Disconnect, then connect it. Do it several times. Sometimes this will solve the problem.

 

[Beemahdad]

Glorious... It turned out to be my exhaust valve clearance(s)

Hi and thanks for everybody's valuable input. First, the stalling issue is fixed! Hallelujah!

Fuel hoses replaced, vent hose, airbox cleaned, and valve clearances checked. Oh, I must point out that for those who are religious about checking valve clearances, I now see why. I bought my K in 2009 at 162k km and it's now at 220k... The clearances have never been checked since I owned her. I brought her to the shop and learned that these should be checked every 7500 km so it was long overdue.

The acceptable range being 0.010 to 0.012 inch... My shop measured 0.003 at #2 exhaust, the worst he recalls seeing. Not sure about the other clearances (I will find out if the mechanic remembers next time I go in.) The old shim was 2.55mm and the replacement shim went to 2.35mm.

It feels like a new bike with the absence of stalling at startup while providing smooth, predictable power. The engine sounds great also.