Stalls when warm on a run - won't idle

[John Lang]

I just checked my Haynes manual. The OEM thermostat does NOT fail open. It stays closed and lets you know by shooting boiling water over your right leg.

[bluebossa]

It would reach halfway in a perfect world, perhaps. Gauge condition, sensor condition, coolant quality, and wiring all could have an influence on where the needle registers. I'd expect it to register somewhere in the middle third of the scale. Test your existing thermostat in water brought to a boil to determine when it opens.

If you test your moto after each component installation, we might all gain from the result, instead of using the shotgun approach and replacing everything at once.

Thanks Laitch, I'd agree except Gauge zooms to 100% on earthing, sensor is perfect, connections clean and coolant is new. So I'd expect it to read higher and faster, takes ages to get to that level... mostly only gets to around 20% of full scale, that was after a few minutes stationary running.

Re component installation, will do - I've got the following, be good to get your prediction on which first and which, if any, cures the running!

• Injectors - refurbed
  HT Leads
  HT Coils
  Thermostat

I will report back as and when they arrive... and I fit - what do you think?

[bluebossa]

I just checked my Haynes manual. The OEM thermostat does NOT fail open. It stays closed and lets you know by shooting boiling water over your right leg.

Hmm - thanks John - I think it's overcooling somehow.

[Laitch]

I've got the following, be good to get your prediction on which first and which, if any, cures the running!

• Injectors - refurbed
  HT Leads
  HT Coils
  Thermostat

What do you think?

There's no need to predict. There are simple tests and/or inspections on the site for each. I'd do the tests with the least effort first—the coils and the leads, then the thermostat. The injectors would be last.

[bluebossa]

There's no need to predict. There are simple tests and/or inspections on the site for each. I'd do the tests with the least effort first—the coils and the leads, then the thermostat. The injectors would be last.

OKy doke - Wilco and will do..

I love the K75 just want it to run 100% and don't mind improving components as I go by replacing... seeking that reliability factor, I know when I get there...

Pic from yesterdays warm up run... still Blue Skies here, though getting colder..

[The Mighty Gryphon]

Your gauge reads the same as the gauges on Ilsa and Moby Brick Too.  If you look at the owner's manual you will see that is where it should be.  Mid scale is at the high end of the normal operating range.  The upper half of the scale is where the fan is working when you're stuck in traffic on a hot day.  Red is where your troubles begin.

[Laitch]

Where are you based by the way, and have you posted a picture of your Bike?
You've guided me quite a lot over the last year or so here, first with that troublesome Café Racer K, now my own RT... how long have you been a K owner and what other Ks have you owned?

Where I'm based is attached to each of my posts. There is a picture of my Brick in the Show Us Your Motobricks section. I've explained my history with the Brick a couple times on the site. Now that you know how to search the site, the information is yours to peruse.

[johnny]

greetings...

that exposed horn is known to cause that kinda whack... you can disconnect the wiors at the relay to eliminate that component...

j o

[bluebossa]

Just got back home after a week in Prague on Business.... reconditioned Injectors were on my desk so I just fitted and replaced the originals and took it for a 20 mile test ride.

TRANSFORMED

No stalling, no hesitating, Revved well and got to 90mph with 9k showing - super smooth and turbine like, however...
The injectors were £70 from a guy in Spain I think - reconditioned to a lovely standard and also have 4 spray holes rather than one - which seems to make a difference.

Link to eBay for sale...
https://www.ebay.co.uk/itm/BMW-K75-Motorcycle-upgrade-Bosch-fuel-injectors/132780390330?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

Runs great though and feels like 70 bucks well spent, but maybe still a tweak or two left, I guess the oirginals can be cleaned and painted, seems they needed a break from duty!
Hope that helps others with similar running issues - seems like plugs, leads and coils are all fine...

Only one slight puzzle remaining...
I took the plugs out after the Run to check how things were going in there and 2 of them are perfect, nice and dry and a good colour with number 3 a little wet - picture attached, plug on left is the one that's fuelly..

Any ideas - does that indicate over fuelling in that cylinder?

[Laitch]

I took the plugs out after the Run to check how things were going in there and 2 of them are perfect, nice and dry and a good colour with number 3 a little wet - picture attached, plug on left is the one that's fuelly..

Any ideas - does that indicate over fuelling in that cylinder?

According to your descriptions, that cylinder has always had a wet plug to one extent or another. Swap the plug with another cylinder and see if the condition travels with the plug.

[bluebossa]

According to your descriptions, that cylinder has always had a wet plug to one extent or another. Swap the plug with another cylinder and see if the condition travels with the plug.

Will do - back soon...

[bluebossa]

According to your descriptions, that cylinder has always had a wet plug to one extent or another. Swap the plug with another cylinder and see if the condition travels with the plug.

Hey Laitch - no difference on switching Spark Plug, always number 3 that get's wet. Plug fires in other Cylinders.

Weirder than that - I pulled the HT lead on 3 while it was running and it made no discernible difference to running revs??
I pulled leads on 1 and 2 while running and Bike would slow or stall... see video

I am hesitant to believe that all this time, it's only running on 2 Cylinders - could it really pull 90mph on 2 firing Cylinders - if so, then a mighty hats off to it - can't wait to ride it on 3 cylinders!
But that's what it's pointing too... would you agree?

I'm still waiting on the set of HT leads and 2nd User Coils I've ordered, but be interested on your take on this new diagnosis.
Quick Video with Sound - though I'm thoughtfully standing in front of the Camera! You can hear me shout 1,2,3 though as I pull out plugs from front of Bike(1) to back(3) - 3 no difference!

[bluebossa]

V Strange

[Laitch]

I am hesitant to believe that all this time, it's only running on 2 Cylinders - could it really pull 90mph on 2 firing Cylinders . . . Weirder than that . . .

Maybe the speedometer is failing, too.  Test outputs of all three coils then compare.  O, the tests that can be run! The engine sounds puny to me. Nothing is really weird or strange here. 

[bluebossa]

Maybe the speedometer is failing, too.  Test outputs of all three coils then compare.  O, the tests that can be run! The engine sounds puny to me. Nothing is really weird or strange here.

Puny? What do you mean - sounds strong to me...

Pulls well, very smooth and nice ride - Motorway speeds, definetely over 70/80 mph - which would amaze me on 2 Cylinders.

[Laitch]

Puny? What do you mean ...

Weak.

If it's running strong, why be preoccupied with it or solicit others' opinions about it? Run it more and often. The highway beckons. O, Bluebossa, Bluebossa Wherefore art thou, Bluebossa?

[bluebossa]

Weak.

If it's running strong, why be preoccupied with it or solicit others' opinions about it? Run it more and often. The highway beckons. O, Bluebossa, Bluebossa Wherefore art thou, Bluebossa?

Ha - well I have some news oh wise Laitch one... "Because it is there"

I decided to have another poke around and test the Coils as you were prompting me to do to see what was happening after earlier Video confirmed No 3 was suspect.

I found a broken coil plug wire... unreal, I fixed the Earth on that coil on rebuild, but the Black and Green on No 3 Coil had snapped and was hiding away, behind HT lead - pics attached..

Got the soldering iron out, cleaned and stripped back and refitted carefully into the connector - plugged it back in, fired it back up and Cylinder3 clearly fired up for the FIRST time as the Oil and Paint started to burn off the back of the Engine and the exhaust steamed and burned off excess fuel... Conclusion - it has never fired since the Engine swop.

The plug was the Magic clue - wet = not Firing
It's been spitting fuel into that Cylinder and out of the exhaust for around 100 miles... All 3 plugs post ride now light brown... Idle had to be turned down again.

Back to the local Motorway and OMG as they say - pulled my arms off... won't talk about top speed now, but Bike is again transformed - can't believe it ran so well on 2 Cylinders and new Injectors - could have done a long trip like that... in short it is now AMAZING - revs like a Banchi - what a Bike..

Delighted... and THANKS>. P-)

[Laitch]

. . . can't believe it ran so well on 2 Cylinders and new Injectors - could have done a long trip like that...

Not as long a trip as you might have imagined.  :falldown:

[bluebossa]

Not as long a trip as you might have imagined.  :falldown:

Why, what do you reckon would have happened?

Video now...

[Laitch]

Why, what do you reckon would have happened?

Overheating, coolant gushing...

Nice story - Glad I didn't see it through to the Uber part,..
I was sleeping on the mystery of where the heck does 100 miles of injections/fuel for one Cylinder end up?
 - and I'm guessing at the bottom of the manifold from the Exhaust Valves - no wonder it smoked and steamed a bit when the third cylinder kicked in..

Coils and newish leads arrived this afternoon
- switched out leads as one of mine was a bit melted, I could see some arching last night when pulling them... but leaving the Coils as spares...

Couple of runs down the local highways and bighways here this afternoon, on what has turned out to be the very last of the summer in the UK - I can confirm 3 cylinders are much better than just 2 on a 75.
- 24 degrees predicted tomorrow which is unheard of in October, but the Bike really is lovely now... last Summer rides await before the Rain and the Cold kick in here..

I can now finally see why this has been called BMWs best ever Bike - great to ride, stable, smooth and great little Engine whirring away - is it a Car is it a Bike.. I now know what it should sound like.
Great machine - long live the K75... just done a small shopping errand on it... tragkorbs come in a treat.

All is well in the World... thanks for sticking with me, your challenges helped me challenge the logic and the Bike...