M900 losing power

Started by gbelew, February 01, 2010, 12:26:41 PM

Previous topic - Next topic

gbelew

I have a 1998 M900.  When I get into traffic and sit through multiple lights the bike will start to miss.  When I apply throttle there is little to no power response only backfiring.  If I pull over, kill the motor and wait 10 minutes it fires up.  Once I get out of traffic it runs great.  The plugs are light brown.  My mechanic  cleaned the cards out and enrich the fuel mix.  Still having the problem.  Would appreciate any input.

Howley

I might be wrong, but it could be something with your coils or ignition units overheating.

ducpainter

"Once you accept that a child on the autistic spectrum experiences the world in
 a completely different way than you, you will be open to understand how that
 perspective
    is even more amazing than yours."
    To realize the value of nine  months:
    Ask a mother who gave birth to a stillborn.
"Don't piss off old people The older we get, the less 'Life in Prison' is a deterrent."



Frank C

On my 97, the fuel line would kink by the tank hinge if careless while lowering the tank. 
Also, had a pick up coil take its time going bad.  Similar behavior until it fully died.  Your bike is about the right age for a pick up to go bad.
Check the fuel filter or vacuum fuel pump?

fc

Drunken Monkey

Sounds like the pick-up issue I had a few years back. Worse when it got warm, and it would get better at high RPM.

Didn't need a new pick-up, just needed the gap adjusted.

Something to check if isn't something in the fuel system.
I own several motorcycles. I have owned lots of motorcycles. And have bolted and/or modified lots of crap to said motorcycles...

Howie

From your post I cannot tell if your bike is misfiring or starving for fuel.  If your bike is misfiring there are three likely causes for your misfire when hot.  Pick up coil, ignition module or coil itself.  What makes diagnosis difficult is everything will test good when the bike is running well and you are having the problem while riding and need to find the problem before the bike cools down. 

First step is find out which cylinder is misfiring.  An indication will be the misfiring cylinder and pipe will be cooler.  If needed you can confirm which if firing by disconnecting the spark plug wire on the cylinder you think is running.  If the bike stalls you are correct. 

Now to find the part at fault.  Switch ignition modules.  If the miss changes from one cylinder to the other the module is the problem.  Now do the same with the coils, and if they separate, coil wires.  No change?  Then the problem is an ignition pick up.

Fuel starvation?  First look for kinked lines or clogged vent (hint: If the bike runs better after opening the fuel cap you have a venting problem).  Clogged fuel filter is possible too.  You may also have a fuel pump that is weak when hot.

gbelew

Thanks for all the feedback.  I replaced the fuel filter and installed new fuel lines prior to posting. So I think I can rule that out.  I will check for kinks.  I will run through these suggestions and let you know the results.  This forum is great!

gbelew

I disconnected the coils from the mounting bracket, disconnected the wires from the coils and disconnected the spark plug caps from each spark plug.
On both coils I got 5 ohms between the two wire terminals on each coil.  The reference manual I have says it should be 12 ohms +/- 10 %.
If I connected the wires back to the coils and tested resistance from each spark plug cap to frame ground I get 20K ohms on both spark plug caps.

Do these sound like correct readings for the coils?  Did I do the test correctly?

I started to check the pickup for gap and grime but not sure how to disconnect the pickup.  There is a black plastic threaded cap that the wire runs through into the engine.  I unscrewed this.  The wire runs into the engine but not sure how to access the pickup. What am I missing here?  Thanks

/Users/gregbelew/Desktop/Pickup.jpg

Howie

If you look at your ignition modules you will see a connector on each module with two wires and one connector with three wires.  The two wire connectors are from the pick ups.  You should be reading 19.5 ohms+ 20% from terminal to terminal on the coil, so you are good there.  From the coil tower to ground you should read 4.5 ohms + 15 % and 5 ohms + 10% for the resistors (the caps that attach to the spark plug wires), so your readings are high there, but I doubt that is your problem.  Disconnect the caps from the wires (they screw off) and look for corrosion.   On some Monsters, spark plug wires are permanently attached to the coils, on others they screw off.  If yours screw off look for corrosion.  What "referenca" manual are you using?

gbelew

Ok, I'll check for corrosion.  My spark plug wires are permanently attached to the coil.  The reference manual I have I downloaded.  The manual cover says "lucamonster" DUCATI MONSTER M 900 desmodue Workshop Manual.  It is in 5 languages which makes it interesting!  I have ordered the Haynes shop manual.

Did my question about the pickup connection at the motor cover make any sense?  Thanks for your input.

Howie

#10
Quote from: gbelew on March 02, 2010, 12:30:20 PM
Ok, I'll check for corrosion.  My spark plug wires are permanently attached to the coil.  The reference manual I have I downloaded.  The manual cover says "lucamonster" DUCATI MONSTER M 900 desmodue Workshop Manual.  It is in 5 languages which makes it interesting!  I have ordered the Haynes shop manual.

Did my question about the pickup connection at the motor cover make any sense?  Thanks for your input.

Yeah I guess my answer didn't, due to my leaving out some details, the wires do run through that piece in the side cover, but the wires run from the pick ups to the modules, and that is where you will find the connectors.


junior varsity

Check carb sync. This sounds like a problem I experienced when my bike got "really really really" hot in Vegas. Irish Mike at Pat Clark Motorsports had me fixed up and on the road in minutes.

gbelew

Howie- One of the previous suggestions was to check the pick-up gap and be sure it is clean of grime.  I assumed that was at the engine cover end of the pick-up wiring.  The suggestion described unbolting the pickup bracket from the engine cover.  I don't see any fasteners.  It does look like there is a large hex head threaded fitting that the pick-up wires and the threaded plastic insert go through.  Just nervous about messing with that if not the right procedure.

Ato- Thanks. I will read up on carb syncing.  I have a good manual by JT Snyder that discusses this.  That may be a pro mechanic endeavor!

junior varsity

I know its a fairly simple job if you've got the appropriate manometer (muh-nom-a-ter, engineering professors would hit you in the head with an eraser if you said "man-oh-meter"). Problem is, I don't and haven't yet decided to get one and learn to do it.

Howie

You would need to remove the side cover to check the pick up gap, the gap is between the flywheel and the pick ups.  Go here to view what it looks like  http://www.ducati.com/en/bikes/service/parts/2000.jhtml;jsessionid=ONMTXTWHCJCZMCRNCB2SFFAKFUIHUIV4?family=parts  and select the 750.  This is as close as you will get on Ducati's web site since 900s were fuel injected in 2000.

If you do what I said about switching parts and find you have a pick up malfunction it definitely pays to check the gap before buying parts.  Once the pick ups have been removed you can also check them by placing them in a pot of water with them connected to an ohmeter and bring the water up to a boil.  If a pick up is failing under temperature you will see resistance either rise or fall dramatically when the pick up gets hot enough.