ducatipaso.org

Hi folks!

Great news: I rode my 907 3000+ miles to Laguna Seca from Canada without problem (almost)! Great bike and got more attention and had more fun than anyone with me including a new Ducati. handled superb, was comfortable, fast, power band was usable in all situations, scraped pegs and centre stand in the twisties and had a terrific time.

Bad news: The bike developed some sort of fueling issue: Sometimes the idle would go from a really nice steady 1200 rpm (never had the typical 907 idle issues with this one) to 3500 or so. Then it would suddenly be okay again. It happened completely randomly- not connected to engine temperature, hard or gentle running, or altitude. The throttle cable runs free at both ends and does not seem to be the issue. Have any ideas?

Thanks,

Sheldon

a good place to start would be test the TPS (throttle position sensor). it governs the fuel delivery.
this is done with a multimeter and might pick up a fault...but could be difficult if it is only occasional.
the closed throttle "zero" position [150mV +/- 5mV] should always come back on throttle return.

this page might help to understand TPS functions:
http://www.bikeboy.org/ducati2vthrottleb.html

to test the TPS thoroughly it needs to return to 0mV when fully closed - but you need to take it off the shaft to test this...if it doesn't come back to 0mV it could indicate a faulty TPS

the RPM's sound too high to be something mechanical like a stuck choke.

the other "wildcard" would be the spark advance pick up on the timing shaft might be failing...although I'm unsure how this would affect the revs depending on mode of failure..

Thanks Laddie:

do people replace their throttle position sensor? Any idea what they cost or where one gets one?
(thinking ahead).

SMS

pretty much what I wrote happened to me...

My TPS was "suspect"...I was having misfire problems..
the old unit would come down to 150mV but no lower...so it was decided to replace it.

No; it didn't solve the problem...Grrrrr...

they aren't cheap!!! it cost about $AUD700 (say $US500) but I expect that if you hunt around the Weber-Marelli PF-9 TPS used in cars like the Alfa-Romeo will be cheaper; Ducati charge an arm and a leg to put it in an OEM parts bag...
there are some eastern bloc countries that sell them "cheap" but I don't know the quality.

anyway...test it BEFORE you buy one..it just seems to be a likely component related to the RPM anomaly

you could also check the throttle balance screws; could be / maybe one has come loose and one butterfly sticks open a bit occasionally; the screws can be adjusted for both opening AND closing alignment / balance.
the throttle shaft can be "sticky" because it has to go through both intakes and then line up with the TPS
mine has a tight spot that seems to grab the shaft on gentle acceleration - I can't get rid of it...