Bogging at low RPMs

5824 Views 15 Replies 8 Participants Last post by Bhambren, Feb 22, 2019

Frosti108

Discussion Starter · Sep 11, 2014

1998 ducati st2.
Just got it. 32k miles. I just put new timing belts on and checked valve Clearance. Also new NGK spark plugs.

Took it out for first ride and it seemed good. Cluster lights are dimming when turn signal goes on so I know there's some type of electrical deficiency going but I'm not sure if it has to do with my problem.

After about 5 minutes of running the problem started to occur (right when warmed up I guess)

Main problem is that when I try to accelerate under 4k RPMs or so, the bike has no power and wants to die. Also bucks on and off. Higher RPMs seem to run fine. The bike is pretty much un rideable like this. Have to basically burn the clutch to go anywhere.

Please help. thanks

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Frosti108

Discussion Starter · #2 · Sep 11, 2014

Oh and it starts fine and idles fine (kind of lopey like it could use a sync) but doesn't try to die at idle

jet057

· #3 · Feb 5, 2015

There may be more than 1 problem here it sounds.Electric wise the neg grounds should all be checked and cleaned.On the motor it may be something as simple as the body throttles out of sink.This is where i would take it in to a ducati tech to put it on the computer.Once fixed then it shouldn't come back.imo

chadboothe

· #4 · Feb 12, 2015

I also have a 98 ST2. 35,000. Same issue with gauge cluster. Throttle seems a little unsure under 3k. Kind of stumbles a bit sometimes but still running fine. It needs a little TLC but loving every second I spend on her. I'll try to post any of the stuff I do to help keep these bikes alive. I think the perfect blend of sport and tour. Sorry I'm a little bias

jet057

· #5 · Feb 14, 2015

Chad that little stumble under 3k should be looked at,open the cap then turn the key and see if you get bubble's or fuel surging around,possible fuel line crack or leak.Check all ground wires to,good luck sir..

chadboothe

· #6 · Feb 15, 2015

I popped the cap and the only fuel movement was from the initial power up from the pump. No bubbles. That doesn't seem abnormal to me.

RedSquare

· #7 · Feb 16, 2015 (Edited)

I have 1997 ST2, chasing around the same problem for a while now. Got to the point where it runs perfect until it warms up, then splutters for a few minutes then runs ok again.
My mechanic has spent some time on it and so have I. I have DP carbon fibre exhaust, opened up airbox and have tried DP, Triton and FIM EPROMS. Triton seems best.
My mechanic swapped an ECU from another bike, it ran perfect. So I have an ECU from eBay on order.
According to the Ducati.ms forum, there are many possible causes:
Throttle position sensor
ECU itself
Potentiometer lean/rich adjuster in ECU
Engine temperature sensor
Crank position sensor
Poor earth connection to ECU
Spilt fuel tube in fuel tank
Fuel pump
Fuel pressure limiter not working
Sticking throttle vanes
General crappy Italian wiring, particularly the main connector between front and rear looms, fills up with water and shorts the power connector (as it had on mine)

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Ascalon

· #8 · Feb 26, 2015 (Edited)

It would be worth giving the primary earth a clean as it is a steel fitting going into aluminium and so the dissimilar metal issue means the alu can corrode quickly and limit the earthing abilities.

Also, check under the main fuse box for corrosion/bad connections too.

I'm chasing the same issue on an ST4s.

When my fan comes on, the temp readr out can jump by 10c!

Also, when crusing at 75mph with the dipped beam on, if I flash the pass (full beam with dipped beam) it can drop onto one cylinder!

This necessitates turning off the headlight altogether to restore both cylinders and then continuing.

This can be very disconcerting on a rainy motorway at night.

A

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Reactions: 1

RedSquare

· #9 · Feb 26, 2015

Well, after fitting a replacement ECU from eBay I can confirm....
The problem was not the ECU.
Dammit.
Have new temp sensor, will try that next.

Reactions: 1

2ducs

· #10 · Mar 2, 2015

Add me to the growing list. I've replaced the fuel filter, hoses, water temp sensors, spark plugs, ECU chip and ECU. Issue started several months back when the air temps were much warmer. Got it out this morning and rode for an hour or so and never missed a beat.
Only difference was that the air temp was 49 degrees and the water temp never rose above 153 degrees F. Seems to me to be temputure related.

Reactions: 1

PhilCurrie

· #11 · Mar 6, 2015

Hi RedSquare and 2ducs:
I have the same issue. When it is cold out, the bike runs fine. Get's a little warm and it can no longer pull past 4K. I have taken it to the shop and replaced the following:

Wiring from the fuel tank/fuel pump
fuel pump relay
air temperature sensor

If anyone finds an answer that would be a great post.

I don't think I am going to replace the ECU from what I have read above.

jet057

· #12 · Mar 6, 2015

This Sucks Man

Time to take this to the Ducati Discussion,chime in on top and see if someone can help.....

2ducs

· #13 · Mar 7, 2015

Outside temp here about to hit 60 so I'll be out riding soon. I only replaced the ECU because I have had a new unit as a spare I had purchased about a dozen years ago.

If it acts up today, I'll have a Norge in the garage by the end of the month!

RedSquare

· #14 · Apr 11, 2015

Ok, so it's all fixed on mine. I should have followed the advice I found on a couple of forums, before I bought an ECU.
So the symptoms were: ran perfect when cold and when hot. Between 64 and 69 centigrade ran like crap, spluttering and surging, like it was on one cylinder.
It was the water temperature sensor that the ECU uses. I replaced that, runs great at all temps.
It costs very little and is an easy replacement, don't need to drain the coolant if you do it quickly (when cold).

2ducs

· #15 · May 7, 2015

2ducs said:
Outside temp here about to hit 60 so I'll be out riding soon. I only replaced the ECU because I have had a new unit as a spare I had purchased about a dozen years ago.

If it acts up today, I'll have a Norge in the garage by the end of the month!

Wanted to post a follow up.

Passed on the Noge and added a FJR1300.

Bhambren

· #16 · Feb 22, 2019

Greetings from Birmingham, AL. I have “new-to-me” ‘98 ST2 and had a similar issue with bogging and stalling at lower RPMs, especially with neutral throttle or accelerating after engine braking. 5k seemed the sour-spot for it to start acting up. The engine would keep running but bucked in and out of smoothness. Heavy throttle usually snapped it out of the funk but the condition would return without warning. The former owner suggested it may be the old, original ignition coils, so I found and installed two NOS ones. No joy. Then I installed a NOS pulser/pickup coil. Again no joy. Thanks to this thread, I tried two new water temp sensors (I used the NAPA TS5520) which seems to have worked! I wanted to share the good need that this worked for my bike and thank everyone who posted here so long ago... the advice is still helping others. Thanks! Matt

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