As motor temperature rises, the idle speed rises??? *FIXED*

[st2sam]

I have a 1993 907ie I bought this past summer and so far have been very pleased with the bike.
The bike runs great, except? When the motor temperature rises past 175* and the radiator fan turns on, the idle speed rises to about 2,200rpm.
The only time it happens is when I'm stuck in traffic and at idle, it never (the motor temperature) goes above 175* when in motion. Once I start moving and the temperature starts falling back under 175* and the fan shuts off, normal rpm idle speed returns. (1,000rpm)

Is this normal? Is it suppose to increase idle rpm to make extra volts too run the fan motor? The battery is new and in excellent shape as it's on a battery tender when bike is parked.
I'm thinking it might be an electrical problem?

Any input or ideas will be helpfull.
thanks, Sam...

[oceanhunter]

Hi Sam,you answered your own question,i would assume (assumption is the mother
of all #$%@ ups!) you are right on the money as it makes sense to up the
output of current and increase coolant circulation.

[persempre907]

No, on both my 907s the idle is still, about 1000/1200 RPM, at any temperature of the engine.
Really, I don't know because on yours there is that rise of idle.
I hope someone on the forum can say something about.
Ciao

[Mc tool]

With out having a 907 to play with .... logically there are only 2 reasons why the idle will increase , either the engine is getting more air , from either an opening throttle valve or an air leak that starts when its hot ( check intake manifold sealing ) or a change in ignition timing. Ya need to find out if the idle speed goes up because the fan switches on or because if the actual temp goes up ( not the same thing!) 1st start bike and while still cold bridge out the fan T/stat and see if the idle speed goes up , if it does check to see if timing changes as you bridge /unbridge T/stat , if it does you can pretty much rule out an air leak and start getting a bit suss about the earth/ electrical connections .( voltage drop test ) If the engine has to be hot ( actual temp .... not what the fan t/stat or the temp gauge may be telling you ) for the fault to occur then Id be lookin for extra air getting in there somehow ( I have seen engines suck enough air down knackered valve guides to cause men to go bald scratchin thier heads trying to sort idle speed/ mixture issues ........ not lookin at that @#$%in capri in the driveway ) .... have fun

[st2sam]

With out having a 907 to play with .... logically there are only 2 reasons why the idle will increase , either the engine is getting more air , from either an opening throttle valve or an air leak that starts when its hot ( check intake manifold sealing ) or a change in ignition timing. Ya need to find out if the idle speed goes up because the fan switches on or because if the actual temp goes up ( not the same thing!) 1st start bike and while still cold bridge out the fan T/stat and see if the idle speed goes up , if it does check to see if timing changes as you bridge /unbridge T/stat , if it does you can pretty much rule out an air leak and start getting a bit suss about the earth/ electrical connections .( voltage drop test ) If the engine has to be hot ( actual temp .... not what the fan t/stat or the temp gauge may be telling you ) for the fault to occur then Id be lookin for extra air getting in there somehow ( I have seen engines suck enough air down knackered valve guides to cause men to go bald scratchin thier heads trying to sort idle speed/ mixture issues ........ not lookin at that @#$%in capri in the driveway ) .... have fun

Thanks too all that have replied.

Mc tool, when you say bridge/unbridge I'm not excatly sure what you want me to do. Connect-disconnect?
I was leaning toward an electrical issue, I didn't think an air leak would be the cause, "however" when I "blip" the throttle at idle, when the motor is hot, I get a slight backfire through the airbox.
I'm not sure "exactly" when the idle starts increasing but I think it's at an indicated 175* on temp gauge, a "little bit before" the fan kicks on. The bike temperature never goes higher than 175* when moving, most of the time it runs at about 150*...
I'm going to disconnect the fan motor and see what happens, I'll keep you posted with my results.

[persempre907]

I didn't think an air leak would be the cause

Instead, I do think the cause could be just an air leakage.
Ciao

[Crumpati]

Check the coolant hose isn't expanding and pushing on the throttle cable, there is a post on here about it.

[st2sam]

Check the coolant hose isn't expanding and pushing on the throttle cable, there is a post on here about it.

Thanks Crumpati, that is an excellent suggestion. I just recently had my expansion tank replaced with a tank from a Honda, It's worth a try.
Tomorrow (Monday) I'll pull all the body work and try all that was suggested, we'll see what happens.
Allways start with the simple stuff...

Thanks, Sam.

[st2sam]

I didn't think an air leak would be the cause

Instead, I do think the cause could be just an air leakage.
Ciao

We'll see, and you might be correct, but that would be my last guess because it only happens after a higher engine temperature is reached.

thanks, Sam.

[Mc tool]

What I meant by " bridge / unbridge " is to remove wires from t/stat and join em together to trick the fan into switching on while motor is still cold , that way if the engine revs increase while engine is cold them you would know its not temp related but electrical. That tip about the coolant hose pushing on the throttle cable is exactly the sort of thing it could well be ..... bloody obvious but not the sort of thing you'd think of unless you'd already been bitten. Never assume the worst .... it usually aint If you suspect an air leak try squirting a bit of water at the suss area and if the motor takes a dump then you know you've hit the spot . Kinda obvoius but have you checked throttle cable adjustment ?
Hamish

[907pasonut]

hi Sam, just remove L/H side fairing and cable tie the radiator hose to the frame, away from accellerator shaft, as motor gets hot the rad hose expands and rubs agaist butterfly shaft (or whatever you call it)...simple fix, as I said on a previous post, I had the same thing happen to my bike (15yrs ago) but reving higher (3-4K) common problem with the 907

[Derek]

Although I can understand the effect of the cooling hose pushing on the throttle cable I doubt if it would coincide with the fan switching on every time. I'm more inclined to think that it is an electrical issue, perhaps a poor earth for the fan is affecting the output of the engine temperature sensor.

[907pasonut]

I think the fan coming on is coincidental (due to heat) and may not be related to this problem...heat...hang on a minute, isn't it freezing cold in the states at the moment

[st2sam]

I think the fan coming on is coincidental (due to heat) and may not be related to this problem...heat...hang on a minute, isn't it freezing cold in the states at the moment

Yes it's been cold but at present we're having a warm spell, 40's* (F)............
Now is the time for fix/repair. I rode with this issue all summer and while not that bad (I tried to stay out of traffic) it's not right and should be fixed.

Thanks everyone for your suggestions, I can't wait to get started later this afternoon.
When I sort out the problem (If I do) I'll post the winning soloution!

Thanks, Sam...

[st2sam]

OK guys here's the scoop.
The good news.
I did get to work on the bike today, it was so nice weatherwise I even got to go for a ride.

The bad news. OK really not "that bad" because, other than the idle speed issue this bike runs like a bear.

I did all that was suggested, but no change.
I took my time and let the bike warm up at idle speed, 1200rpm..
As the temp started to rise the idle speed increased little by little, no increase at about 150-170*, where the bike runs most of the time.
When the temp reached about 175-180* idle speed started to rise slowly to about 1700-1800rpm, at about 180-190* when the fan started idle speed was 1900-2000rpm..

OK,I got on the bike and went about a mile, the temp went back to about 150-170*(where it normally runs), I stopped at a stop sign and idle was back to normal, about 1000-1200rpm...
This is how it's been since I bought the bike last summer.
Break. Ha-Ha...

It'll be going in the shop, needs belts (over two years old) but not much else. When it's there I'll ask the Ducati tech and see what he thinks? He is an excellent mechanic who has benn wrenching on Ducati's for over thirty years and is familier with this 907ie..
However, getting the bike there is a pain in the butt as it's 150mi., so it has to be loaded in the van. It's an all day affair and it'll be very costly!
Thanks again to all who tried to help.

Sam...