2006 Monster 620: poor cold starting

[Mark_W]

I've recently picked up a 2006 Monster 620 for my niece. From the beginning it has had a cold starting issue. Cold being a relative term. We are in the Phoenix AZ area so right now, 6 AM "cold" means 85 F or more.

Sliding the fast idle lever to max, press the starter button, wait. Maybe it will start. Try again. Usually on the second or third try it will start. The fast idle is not very fast. Maybe 1500 rpm at best. Starting without the fast idle on at all yeilds the same result. Once started, the idle is slow and a bit lumpy for a bit. Initially it will take no throttle at all, after a few minutes the fast idle is off and throttle may be added, but not too quickly. Once running and warming up, everything is great. Hot starts are not stellar, but are OK and usually successful on the first try.

Over the past few weeks: new spart plugs, checked coil specs, checked plug wire/cap resistance, new air filter. Did some reading about the throttle body balancing and TPS adjustment. Sounds very, very, similar to BMW's I used to work on. Tackled that process. This bike has Bing throttle bodies, so no left side idle stop screw. Checked the TPS voltage before making any changes, was at .330v Set the idle bypass screws to the same setting and balanced the TBs using a Twinmax meter (from my BMW days). Set best balance at 4k rpm, still decent at idle. Backed out the throttle stop and fast idle screws. Set the TPS to 150 with the butterflies fully closed. Set the idle screw to .434v on the TPS. Started the bike with less difficulty and fully warmed it before setting the fast idle to 3k rpm with the temp gauge reading 190 ish. I tried fine tuning the idle with the idle air bypass screws but they had little affect on idle speed. Mostly idle quality. it sounded more like mixture adjustment than idle speed.

Now, I can set the fast idle fully on and start the bike on the first press. The idle speed is below 1k rpm and unsteady. If I very gradually add throttle and the Duc does not quit. All will be well and it's rideable. Within 1/2 mile the fast idle can be completely off. Still, it's that first minute or so that I'd like to clean up. If it would fast idle when "cold" that could solve the issue.

I tried raising the fast idle speed but that did not seem to help. Hot, the idle was up at 3k, at the initial start the idle was not "fast".

[stopintime]

You have clearly done a lot, but maybe not the complete job....  Valves? Fuel filter?

Last year I went through all your symptoms - and more. What it needed most was a really good, deep service + pistons. I'm not saying that that's what you need, because I'm not an expert - just trying to get the ball rolling.

Also, let's not forget; this is an old Ducati from the days when half of Ducati's ideas were poorly executed. Let's (not!) talk stock mapping....

[Howie]

Service records?  If the timing belts are 2 years old or have 12,000 miles on them they need to be replaced.  Do check valve clearance and change the fuel filter.  Check CO with an exhaust analizer and make sure the temperature sensors are working.

[Mark_W]

The fuel filter is good. While I was in the tank repairing the fuel pump connections I took care of the other in-tank stuff.
I'm wondering about a temperature sensor? The temp gauge is working but from the numers I see I'm guessing that the gauge is reading oil temperature. Is there a separate temperature sensor that feeds the ecu cylinder head temperature? I'm guessing that there is, somewhere.

I don't yet have any software, nor an ecu cable, for the Duc so I can't yet read ecu values. From what I've read the idle mixture is adjusted solely electronically, so that's waiting.

Valves and belts are on 'the list'. I've seen desmo valves adjusted but I've not done the work on my own. At least I won't have to shim bevel gears.

[stopintime]

From the sump to the instruments.
From the horisontal head to the ECU.
From air to ECU (also air pressure) behind the headlight.

[Mark_W]

Thanks for the info. It was easy to find both sensors that feed the ECU. I checked the workshop manual and did not find values for either sensor. I guess that maybe this is software and cable time. I have been using ECM Spy with Buells for about 15 years but it does not look like they supported Ducatis. Is there a recommended package for accessing Ducati ECM information?

[Howie]

I have never seen official published specs for the sensors.  Technoresearch VDST stopped making a tool for Ducati. 

https://www.bmdiag.co.uk/ducati-bike-diagnostic-tools
https://matthewnavis.com/product/ducati-diagnostic-tool-with-software
https://www.bmdiag.co.uk/obdstar-iscan-ducati-motorcycle-diagnostic-tool

I have no first hand experience with these tools.

[koko64]

I was also wondering about the temp sensor.

[koko64]

That being said, the comments about baseline tuning (TPS, throttle synch and valve adjustment) are correct. Tight opening shims or sloppy closing shims impact idle quality.

[Orange16]

For diagnostic you can download the IAWDiag from the GuzziDiag site and buy the required cable from Lonelec.  That will give you all the diagnostics you need.  You can see what information the sensors are giving the ECU.  This is much more relevant than checking sensor resistance.  If the values the ecu shows for engine and ambient air temperature, or air pressure are not correct, it's obvious.  Then you know you have a problem, but I doubt very much that you have a problem apart from poor baseline setup and tuning.  Don't assume any prior techs who have touched the bike have done it right.

Adjust the valve clearances.  It might not be the problem, but unless you do, you won't know.  Closing clearance zero with no drag on the camshaft when rotated.

I don't understand your comments about the fast idle and cold idle.  I would not expect it to idle cold without the fast idle activated.  The maximum rpm the fast idle lever gives will increase as the engine warms up.  You just use the fast idle as required.

The air bleed / bypass screws change both the idle speed and mixture, but their function is to set the idle speed.  They will have quite a big influence on the mixture on a 620 if you are not following the procedure as intended.  You set the idle speed, then adjust the mixture using the idle trimmer as required.  Not setting the mixture is a common problem, as most owners don't have access to CO analysers.  Use the diagnostic tool to change the idle trimmer.  Try steps of 3 or 5 increments and ride to assess if it needs to be richer or leaner.  If you make it worse, you simply go the other way.

"Also, let's not forget; this is an old Ducati from the days when half of Ducati's ideas were poorly executed." is just a silly thing to say.  Properly set up, it will perform just fine.  Properly is the problem.