Monster 695 recently making a strange noise from engine

[Howie]

If your air bleeds are already screwed in either your throttles are opened too much or you have a vacuum leak affecting both cylinders.  Balance will not reduce that idle speed.

[Lieutenant Dan]

Yes, I understand that. But with this (Bing) throttle body, since there are no separate LH and RH throttle stop screws, it's important to know it's balanced before I can mess with any other settings, especially setting the TPS, right?

[Howie]

In your case, difficult to say since I don't know what has been messed with.   This is what I would do:

Set the throttle stop screw, worry about the TPS side.  Seat the air bleeds and turn them out about 1/4 turn.

If the throttle on either throttle touches the bore, then compensate with the synch screw, otherwise leave alone.
Set TPS.

Start bike and warm up.  Use fast idle as needed.

Synch throttle bodies at, oh maybe  2K RPM.

Adjust to 11-1300 RPM turning air bleeds in or out equally.

If you have an exhaust analyzer, set Co trim at 4-6% CO.  There are bongs with hex head plugs in the headers for checking CO.

Using the air bleeds, balance CO between cylinders.  No exhaust analyzer, skip these two steps

Reset idle speed if needed.


Other suggestions?  Paging Brad Black!

[Lieutenant Dan]

Good advice. Thanks.

Just out of curiosity, before I go through all the trouble of this, what makes you think the backfire is caused by the throttle bodies? With my fairly limited knowledge of engines, I would think such a thing is caused by timing.

At the last service I had, the dealer did say he synched the throttle bodies. (the reason I would still make all these adjustments in lieu of that is because obviously he did something wrong if it's idling at 1800 RPM.)

[Howie]

Good advice. Thanks.

Just out of curiosity, before I go through all the trouble of this, what makes you think the backfire is caused by the throttle bodies? With my fairly limited knowledge of engines, I would think such a thing is caused by timing.

At the last service I had, the dealer did say he synched the throttle bodies. (the reason I would still make all these adjustments in lieu of that is because obviously he did something wrong if it's idling at 1800 RPM.)

Timing on your bike will not change unless someone does some serious work or your computer goes bonkers.  Basic fuel mixture input into the computer is RPM and throttle opening.  Mixture is then further corrected  by temperature sensors and, when in closed loop, the O₂ sensor.  If TPS is off the computer does not know where the throttle is, this can affect both mixture and timing. 

[Lieutenant Dan]

I see. Thanks. And out of curiosity, how does one check for a vacuum leak?

[brad black]

not that i've ever looked, but are you sure there's no lh throttle stop screw?

[Lieutenant Dan]

not that i've ever looked, but are you sure there's no lh throttle stop screw?

As far as I could tell, but I couldn't get the airbox all the way off. For the most part, I just took your word for it from your article...

[brad black]

oh.  what did i say?

found it.  so i did say that.

in that case, you'd do a linear tps baselining procedure - http://www.bikeboy.org/ducatitps.html - using the rh stop and noting whatever the reset vaule is.   then you'd set the balance as required, then adjust the rh stop to return the throttle opening to the reset value as read via the diagnostic tool.

if the balance is adjusted again later and the tps via the diagnostics no longer read the reset value, then the rh stop would again need to be adjusted to bring the throttle opening setting back to the reset value.  doing another reset instead would upset the throttle/tps relationship.

[Lieutenant Dan]

I just thought those who were following this issue way back when might
be interested in an update.

As a recap, if I could, I would change the title of this thread to
"Backfire Through Intake - Vertical Cylinder" since that's what the
real problem is here.


Basically since the last post, the bike has been in the shop being
worked on. They tore apart the engine and found that the valve guides
were worn. Since this shouldn't be the case (2007 M695 with 14,000
miles), they got Ducati to give me free valve guides. I ended up
paying for 10 hours of labor for the work they did installing them and
adjusting everything.

When I fired the bike up, I was pleased to find that it ran 100 times
better. It started right up and there was less searching for idle. The
idle was smooth, consistent, and at the right RPM. I took it around
the block a few times and it ran well.

To my dismay, after riding it home, once the engine was warmed up (265
degrees for this bike), pop!, pop!, there was the mysterious backfire
and associated jerk again. It happens at lower RMP, usually while
accelerating and carefully trying to work the throttle and clutch at
the same time. Though it has happened when cruising steady at 4,000
RPM, parking lots are particularly embarrassing. It's such a shame that such a good looking bike sounds so sickly. I've even had people make that very comment to me!

After all that time and money spent, I am not very happy. I most definitely do feel better about Ducati in general because of their good will in providing me new valve guides free of cost, but I'm just about fed up with this bike after all the hell I've gone through tryin to get it to run right.

I have one other hunch, but I wanted to hear the opinions of the forum first on (1) the cause  and (2) on what to do next.  Thanks!

[Lieutenant Dan]

I just checked it for vacuum leak. Found no evidence of any. Still looking for ideas...

[Lieutenant Dan]

Crickets... Crickets...

[BastrdHK]

I dunno about your valve guide issue.  Honestly, I think you may have been taken advantage of.  Of course, I am not there, didn't see your valve guides, etc. but I have a few alarm bells going off.  Sounds horrible to suggest (and don't take offense), but your new dealer may have taken one look at you and saw a walking atm they could pull some unnecessary shop time out of.  Also, sounds like your previous dealers did this to a lesser extent"...throttle bodies?....synched no problem, everything is good."

So you weren't successful synching/balancing your throttle bodies yourself?  Did you ask the current shop to do so while they were replacing those "worn" valve guides?  (By the way, worn valve guides would cause you to use some oil, maybe puff a little blue smoke, but not cause backfire through the intake....hence my first paragraph)

March right back there and demand they synch, balance, set CO trim and TPS.  If you paid for 10hrs of labor, you are probably into them $1000.  If you were eating at a restaurant and they gave you a plate of oysters on the house, but charged you for the diesel the boat used to get out to the oyster beds, the rubber boots they used to walk through the mud with, and the pack of Marlboro's they guy smoked as he dug them, you would be pissed right?  This is essentially the little scenario the shop has placed you in.

I know I don't have any right to call this shop out, but that is my take on your situation.  You shouldn't pay another dime, and they should bend over backwards to get your balancing issue sorted!

[Lieutenant Dan]

Thanks for the reply! So are you saying its almost definitely a simple throttle body / tuning issue?

I must say that it was running like crap (hunting idle, quitting at idle, inconsistent rpm (ranging from 800 to 4,000) with the fast idle lever selected to max and the throttle itself left untouched) when I brought it to them and all of these issues were fixed when I picked it up. They did say that after the valve guides were replaced and the engine was put back together they performed a full tune. Btw, you are correct. It was 10 hours at $100 an hour coming out to exactly $1,000 even. But that's just for the last service done.

[BastrdHK]

Good to hear they included a service/tune/oil change? as well.  YES, this is definitely throttle body synch/balance issue.  Take it back to the shop, explain/show the issue to the service writer/mechanic.  It should've been corrected during the service, so they should "make it right" without you having to pay for this again.  Use your discretion, if they take extra time to accommodate your concerns and do a good job, offer to reimburse them (if they are not charging you for this followup).

Just to throw a little more doubt into the mix.  Ducatis are notorious for coming from the factory fueled very lean to pass emissions standards.  Your bike might be on the lean side of things even with the throttle bodies correctly setup.  Most people correct this by adding a power commander (or other tuning module), reflashing their ecu to add more fuel, particularly in the low-mid throttle range.  This accompanied with an experienced tech on a dyno, will give the "optimal" fuel map for your motorcycle.  My tuner charges $100 for custom map/dyno tune.  The fueling modules mentioned above range from $200-$1000 depending on what you choose and how much control you want of the fuel mapping process.

Note:  A good shop/mechanic should be able to correct this issue using the stock parts without you having to spend money on the aftermarket accessories.

Good luck, and let us know when you sort it out.