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Gidday folks
I have an ST4s 2003 996, awesum bike love it!!!
Mods are Airbox back cutoff, K+N filter, Leo Vince carbon Cans and 14 tooth front sprocket.

Goes really well, when I can get it started.

Ive done a search on starting and there seems to be a few having this problem.
However I dont think its the ecu.

This is what happens:
(Good battery) Ign on, fuel pump runs then stops, I hit the starter button and the engine cranks and fires instantly then dies, because the starter is still on it catches and fires it up again and then the engine fires and dies again.... repeat repeat repeat.
Its like the starter is keeping it going.

Its just on the verge of running but if I even think of twisting the throttle or the fast idle lever 1 billionth of a milimeter it wont go at all, it back fires thru the airfilter, the starter surges or lunges, it makes over timed ign pulses and basically gives the engine a$$holes.

Its like the str mtr doesnt have enough to get it going properly. Or the engine doesnt take off from the starter and keep running once it does fire.
Once i do get it up and running I can put the fast idle on to warm the engine up, and from then on absolutely no problems.

Ive taken it in to the local Duc dealer, he put on the mathesis tester and told me is was set to 2, so he has richened it up to 20.
He has adjusted the air bleeds on the throttle bodies to give about 3% co.
Ive checked the plugs, coil leads, side stand switch, all 4 relays (2 under seat 2 lhs by fuse box) checked all fuses, removed battery terminals and refitted ensuring good tight connections.
removed and refitted all fuses inc the 40amp start fuse.... still i cant get it to nicely start.
When its hot I will sometimes have to sit for about 5 minutes trying to get it to catch and increase the idle past the str mtr's rpm so it will idle.

any ideas??????
 

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Ducati Designs
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Boy, that sounds annoying! I think my first exploration would be the crank position sensor. These have caused similar problems when the gap is off a bit.

Also note that when the battery gets weak, the load of starting can put the voltage below that needed for the ECU to function.

Good luck with it!

pg
DD
 

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I had similar symptoms recently and it turned out the the boots between the airbox and throttle bodies were loose. A guy I know locally who has a TLR1000 and he suggested the fix to me. In his words (more or less) "sometimes big twins burp and knock the airbox loose". I haven't heard of anyone here other than me having the problem, but apparently it does happen.

-Mats
 

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When I first got my 02 ST4S I had similar difficulties.

I recommend double checking the battery condition.....mine checked out fine with 2 battery outlets but not with the 3rd...and they were right.

It does seem that these bikes are very sensitive to voltage variations.Mine has now been a trouble free starter (if I keep the battery charged) for a couple of years.

In tracing the source of the problem I did what others have done and put bigger cables on the starter circuit and went thru the electricals with a fine tooth comb....but it was just the battery.

Colin.
 

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Rereading your post it occurs to me to ask if you are using the throttle lever by the clutch when you're cold starting?
Don't mean to be insulting if you are doing the obvious, but my bike would definitely display the symptoms you talk of if I don't have the lever about 1/3 open.
When it's hot there's no need for me to use it.
Is it worth checking the cable to the throttle bodies is actuating the throttle when you turn the lever by the clutch?
 
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