ST4S engine will not start and idle

horst

Hi, after years of no ducati fiddling I bought a 996/ST4s engine for small money. Originally built by a renowned German tuner, which unfortunately can no longer be contacted after an accident.
I don't know, whether the engine did ever run properly, but i have a protocol of a power measurement, so it should have been run before.
The following parts are installed.
T1-cams, ported heads, cam timing is like original SPS-motor,
Pankl-Ti-con rods, Pistal HC-pistons, balanced crankshaft
Some other nice magnesium parts, deep sump like 996RS cases

Now the problems:
(1) The starter motor turns the engine normally without spark plugs (approx. 300rpm), with spark plugs installed you can count the revolutions. Tested w/ different batteries. Always same results.
(2) The idle speed cannot be set below approx. 3000rpm, motor stalls below 3000rpm.

What is going on? Compression too high?
Any thoughts? Comments?
cheers,
horst

stiglarsenDK

What CPU , Eprom, harness, TB do you use ?

brad black

does it have closing springs? without closing springs and with closing clearance it won't idle.

a/a, ecu and specifically ignition advance or lack thereof?

starter motor needs brushes, needs bigger starter cables, drag in the starter system?

horst

stiglarsenDK wroteWhat CPU , Eprom, harness, TB do you use ?

Harness from a Monster S4, with modifications, but not on motor path
ECU Monster S4 Performance for T1 cams and Termignoni (open) exhaust

Seller told me on second ECU is from Dyno tuning runs,
according to diagram 138.5BHP @ 10300upm, 107,6Nm @ 7820upm

Stalling problem have both ECUs, below 3000upm motor stops.

cheers,
horst

horst

Hi Brad,

brad black wrotedoes it have closing springs? without closing springs and with closing clearance it won't idle.

according to invoice tuner has installed "racing" closing springs, don't know the difference.
during checking valve clearance -all in sprec- and cam timing you see the springs.

brad black wrotea/a, ecu and specifically ignition advance or lack thereof?

ECU i'm fiddling right now is Monster S4 performance for T1 cams and open exhaust.
Second ECU from tuning runs have the same stalling problem.

brad black wrotestarter motor needs brushes, needs bigger starter cables, drag in the starter system?

OK, will invest in thicker cables and check brushes. Will take awhile.
rest of starter system runs smooth and noise free, new sprag clutch.

cheers,
horst

stiglarsenDK

horst wroteHarness from a Monster S4, with modifications, but not on motor path ECU Monster S4 Performance for T1 cams and Termignoni (open) exhaust Seller told me on second ECU is from Dyno tuning runs, according to diagram 138.5BHP @ 10300upm, 107,6Nm @ 7820upm Stalling problem have both ECUs, below 3000upm motor stops. cheers, horst

Hi Horst ,
If you have the Dual Pick up and timing gears left side from SPS, incl incl sensors, gears and flywheel ? , I dont Think you Can use the monster CPU as it has a different timing. If you have the original left side w single Pick up, the s4/St4s harness and ecu , TB etc should work fine ..

I have the Dual Pick up left side and used a P8 harness, TBs and P8 CPU from the SP5 (Eprom from sps 2000, 965032AAA) it started 1`st time and have been running ever sice, Best option in my opinion given availability of the special parts .

horst

stiglarsenDK wroteHi Horst , If you have the Dual Pick up and timing gears left side from SPS, incl incl sensors, gears and flywheel ? , I dont Think you Can use the monster CPU as it has a different timing. If you have the original left side w single Pick up, the s4/St4s harness and ecu , TB etc should work fine .. I have the Dual Pick up left side and used a P8 harness, TBs and P8 CPU from the SP5 (Eprom from sps 2000, 965032AAA) it started 1`st time and have been running ever sice, Best option in my opinion given availability of the special parts .

i still habe the single pickup from ST4s, left side is original ST4s. Pickup sensor shows clear and fine
signal without spark plugs

https://drive.google.com/file/d/10ONXXrPECANlLZQwV-IDTWAwDvlzyo3T/view?usp=sharing
nice signal you can each tooth on timing gear

https://drive.google.com/file/d/10NuJQLeC4zsAX4Buee-6JPPYxvGn2aq-/view?usp=sharing
when the spark plugs are installed, the rationspeed decrease, that you only can imagine where the ignition signal is. ECU does not inject.

hope you can see the oscilloscope diagrams

cheers,
horst

griff851

Don't you need 400 rpm before ignition and injectors will fire?

BARONROJO

I have a very similar engine, ECU and wiring harness and my bike starts, idles and runs perfectly. I made a custom map on the S4R ECU but before that it started and idled perfectly too.
I'd say you have TWO different problems.
1) The bike does not start. When turning the engine w/o sparkplugs the pick-up signal is perfect. With the sparkplugs in, 'descending' pick-up signal suggest that the starter draws too much current and what remains is not enough to feed sensors and actuators properly. Probably the decreasing signals are caused by the compression strokes.
2) The engine doesn't run under 3000 rpm. There's some kind of problem with engine management. It may be an improperly set or faulty TPS, an inadequate map (doesn't seem your case but I've seen it before on some badly bodged customers' bitzas) or some other issue.

See if you solve it with a new brushes and/or wiring and try another starter relay (the latter cause starting issues on my 851/996)