K75 Cutting Out

I apologise if this is going to the same people on different forums, but I'm hoping someone may have experienced a similar problem and found a fix. The full thread can be found here: <!-- m --><a class="postlink" href="http://www.bmbikes.org.uk/Forum/viewtopic.php?f=13&t=15874" onclick="window.open(this.href);return false;">http://www.bmbikes.org.uk/Forum/viewtop ... 13&t=15874</a><!-- m -->

but to summarise: BMW K75RT 1993

The bike is regularly cutting out at exactly the same point on my commute to and from work. There are no warnings or symptoms but she'll run fine for the first mile or so, then cut out. It's a sudden cut out, not a gradual fade.

Once she's stopped, all the warning lights come on, the starter will turn, but she won't fire. The fuel pump is still operating as I turn the starter. At this stage I don't know if she's sparking or not.

After about 5 minutes, she'll start again, and then I can drive the remaining 20 odd mile without problem. Even if I stop at a garage or shop, there will be no further problems. The journey is a mixture of stop/start traffic, and open road. It only breaks down in the initial warming up period. She's been fine on longer 100+ mile journeys.

So far I have replaced battery, fuel pump, fuel filter, fuel sender, water temp sender, thermostat, coolant, FI relay, air filter and plugs.

Zitat von "Webberle"

Is the cutting out in any kind connecetd to the exact location?

Not specifically - explained below.

Zitat von "Webberle"

Or maybe it is dependent on the running time after cold start?
Will it cut out if you take a different route?

Just to geht some thoughts about possible reasons...

It's this one. Dependent on time after cold start. In the morning (6.30am) it's usually about 3 miles from home (about 8 breakdowns on the same 100metre stretch of road). Last night I increased the tickover from 800rpm to 1100rpm and it happened about 1.5 miles from home.

In the way home, it happens about 0.75 miles from work (as the air temp is higher?) and has been different locations as I often change my route home.

In all occasions, once it's happened and corrected itself, I have no further problems.

The uniformity and regularity of the fault tends to suggest to me that its not a broken wire, or a duff earth or such like, as these problems tend to manifest themselves in a more random manner.

Yeah, the Hall Sensor has been mentioned several times - my concerns are that a) I can't replicate the problem - I've had the bike running on the centre stand for about 25/30 minutes, reaching temperatures of 100+ degree and it doesn't cut out. This is far far in excess of the temperature it's running at when it cuts out in the morning/evening and b) I would expect it to cut out also on my commute - I spend 20 minutes of my journey home in stop/start traffic, after a 70mph stretch. The engine gets very hot and it doesn't cut out. On Friday, went for a 45 mile ride out in the afternoon, it was a scorching day, the bike was heavily laden for camping and the heat from the engine was almost bordering on uncomfortable, and again it didn't cut out.

A can of freeze type spray would be easy to carry around though, so it's worth a go!

To provide some more info:

I tried a couple of experiments this morning. Usually, my first few miles to work are quite calm and sedate. This morning i caned the poor girl. My thought was that if it was heat, she might break down quicker, or if she was flooding, then a wide open throttle would perhaps negate the effect.

However, the reality was that I broke down after 5 miles (a good two miles further). When she did cut out, I was accelerating hard, at about 80+ mph. Thankfully it gave me momentum to coast to a safe stopping place. However, it was a cold morning and by the time I'd stopped, and taken my glove off, the exterior of the engine was warm but not so hot that I couldn't keep my hand on it.

When I initially tried to restart, the rev counter needle didn't move, suggesting that it is an ignition based problem.

From comparison with yesterday, the ignition needs to be 'on' for the fault to rectify itself. It was only about 3 minutes today before I was off again.