TPS setting and piston saga

StooL

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Just a note to say what a difference fiddling with the TPS has made. After reading loads of threads in an effort to find a potential cause for my holed piston a few weeks ago, I decided to have a bash at setting my TPS thingymajig today. I had read that it should be set at between 0.37 and 0.4 volts. When I checked its current setting it read 0.34. After a slight (I do mean slight) adjustment I got the voltmeter to read 0.377. What a transformation! The bike now idles much much smoother. I didn't really think it was bad before but this has made a real difference. So anybody with an 1150GS that hasn't done this should do a quick search for the procedure on this site and get it done.

For all you folks that saw the hole in my piston, I still haven't found a definitive cause. The bike has been Dyno'd and aint running weak. I've changed the injector for a bit of peace of mind, checked the timing (ok), balanced the throttle bodies (weren't far out as it happened) and now done the TPS. I've also used one of those spark plug things that you can see through to see the colour to check if the cylinder that holed the piston was showing anything different from the other and they were both the same. The guy at the Dyno place reckoned the bike hadn't been detonating (pinking) as he had raced boxers before, had seen pistons that had done this and mine was different. I guess I may never know (lets hope so).

Although I now have a bike that runs pretty smooth when idling I am wondering if it is normal for these beasts to miss a beat every few seconds? "miss a beat" is the best way I can describe it. I guess its a slight misfire really. Whatever it is, my timing test confirmed that both cylinders did it.

Apologies for the ramble, I've had a few too many!

:beer:
 
I'm going on a vague memory here, but I seem to think that somewhere sometime I read an article in a magazine, not the www and it explained that the leanness of the fuel mixture of the BMW twin set-up was reliant on having correct parameters being electronically sent to the computer.

Of these parameters, three were considered most important for the bike to run correctly and with the correct ratio of fuel to air. In other words running lean or rich. This was a technical article telling the world about the new 1100 twins in 1994.

One, was Top Dead Centre (TDC) from the Hall sensor.

Two, was engine speed, this information is sent to the computer by the Hall sensor.

Three, was the Throttle Position Sensor (TPS)

Now the signal for the spark plugs to go off also comes from the Hall sensor, this could indicate why it's missing a beat, (I know what you mean by that expression) that there is a faulty Hall sensor down there.

I believe that there are actually two Hall effect sensors in the unit and that whilst it's BMW policy to replace the unit if faulty, I believe that it can be repaired for very little outlay for the electronic parts and DIY repairing.

Just some food for thought.

Mick.
 


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