M900 Carb issues... Need serious help!

[MonsterDave]

Here's the Readers Digest version.... (also posted on Monster List)

I have a '99 M900 (carbie) that, for the most part, runs good at mostly legal speeds. The problem rears its ugly head  when I reach 90+ and try and hold it for any length of time. Sometimes only seconds!

At that time it totally dogs down and sounds like it's really sucking a lot of air. Almost like it's out of gas. When I roll off the throttle (about 1/3 of the time) it seems to pick up and run OK. The other 2/3 of the time it almost dies completely. I have just picked it up from the dealer where they have checked the jetting for a new exhaust I put on (Gia Ca Moto) and they told me that it did not need new jets, just some tweaking.

Well, I took my first ride on it yesterday (weather finally warmed enough) and sure enough, it did it again.  The only thing I can come up with is the wind/air movement is somehow affecting the mixture and causing the problem. Is this really possible? It seems odd that I don't hear more about it if it is. I would think everyone would have that problem then.

What's killing me is that I love this bike and don't want to get rid of it but I'm coming home pissed off everytime I ride it. I'd sell the thing and get something different if I could but, who'd buy a hopped up Monster that doesn't hop?

I need help! I think I'm pretty mechanically inclined but I do not have "the coolest set of tools" and would be a bit leery about taking on more than I could handle. I've read a bunch of threads here that sound similar but not quite the same. (and, most are EFI bikes)

Anyone have any thoughts on this?

[Duck-Stew]

Hey Dave...

Well, there are a couple of 3/8" vent lines coming from the carbs which are supposed to go into a 'dead-air' box which is located on the side of the bike.  Trouble is, they're ugly and easily removable.  If care is taken and the hoses (which are identifyable by dark-grey filter-looking things in them) are routed to some dead air space then the bike runs fine and the ugly boxes on the sides of the frame are gone.  If they're not routed to some dead-air space...  Then as wind blows on them, they raise up the slide partially which messes with the carburation some.  Could be your problem.

(dead air space:  Not a vacuum, but somewhere that if the wind blows it won't be affected like routing the hoses up under the tank next to the battery)

Other possibility?  Weak fuel pump.  When you're experiencing this problem, you're using a lot of fuel so the demand on the pump is high.  If it's getting weak then it could be the culprit.  DON'T go to a dealer and ask how much the pump is.  You'll have a stroke and die.  Instead, there's a Polaris fuel pump rebuild kit that's available that will work just fine and it's under $20.  The fuel pump that's on your bike is the EXACT same as the Polaris BTW...so there's no cobbling something to make it work.  It just works..

[ducpainter]

Not much more to add...

except maybe check the float level.... 

[needtorque]

And check the fuel filter as well.  Cheap and easy and with the increased load at the higher speeds it may be not letting enough fuel through.

[MonsterDave]

Sounds like something to try

I did have some problems with this before and took it to a local guy that owns a performance shop (mainly cars but he rides Duc's and BMW's) and he added the hoses to the carbs. It did seem to help quite a bit at first but then didn't anymore. This was before the new exhaust. I currently have an open air box. I did try and switch with my wife (she has 01 Dark) and it was hard to tell if it was the lid or something else.

When I took it to the dealer last month to have them re-check the jets for the exhaust, the mechanic removed the hoses.

I'll try putting hoses back on first, then different air box lid, then fuel pump.

Thanks for the comments.

[Stangman]

Probably your "open airbox" would be my guess.  You can get away with enlarging the opening in the stocker, but I was told by several people not to completely get rid of it or you will have rideability issues.

Worth a shot, let us know. 

[MonsterDave]

Probably your "open airbox" would be my guess.  You can get away with enlarging the opening in the stocker, but I was told by several people not to completely get rid of it or you will have rideability issues.

Worth a shot, let us know. 

The air box is not completely cut. The gap between where the snorkels go is cut and the snorkels are gone. I have tried my wifes (she has a 01 M600 Dark) and it seemed to help but have not tried it since the jetting was checked. I'll also check what Duck-Stew mentioned and see exactly what I've got going on with the air tubes that used to be there.

As long as Mother Nature plays nice, I should be able to check this stuff out this weekend.

[MonsterDave]

Here's where I'm at so far...

I did put some hoses on the carbs and routed them to some dead air space. It does help some but the problem is still there. Also, on the front side of the carbs there are a couple of holes (in the float area). On my wife's bike (M600 Dark) there are little rubber plugs in those holes. Should I have those?

Next step is to check the float height. I got a web site link from someone on DML that explains this process quite nicely so I should be OK with this.

I have not replaced the fuel filter yet. I have seen many people comment on NOT buying from the dealer. Do you have a suggestion where to go? I live around (or can get to) all the major auto parts shops but I'm pretty sure they are not going to carry a factory Ducati part number. Does anyone have that part number?

Also, since I have never removed the carbs before, or pulled apart the fuel filter, should I be draining my gas tank or is it going to go every where?

I know I'm coming off kind of inept but honestly, I've never worked on motors before. If you want me to rebuild your stereo or PA system for your band, I'm the guy  So, I really appreciate the help you guys are giving me.

I'm going to start pulling the carbs off tonight. The weather is supposed to warm up mid to end of week so I should be able to get out again and check it out.

I'll keep you posted!

[ducpainter]

I hear autozone has an exact replacement for the carbie filter.

[needtorque]

Just take your filter to autozone or advance auto and match the inlet/outlets to the same size and it will work fine.  They usually have a small wall of filters to choose from.

[64duc]

Put a pair of needlenose vise grips on the fuel line upstream of the filter. That way fuel does not leak.

[Howie]

The Ducati dealer will charge you a few bucks more.  If the dealer is close by and the convenience is worth it to you there is no reason not to go there.

[MonsterDave]

 


Join Date: Mar 2004
Posts: 52   

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OK! Here's the latest...

I have removed and adjusted the floats to be the recommended 14mm. (actually, not as hard as I thought it would be)

Took it for a ride... when I left home, it worked great but the longer I rode it, the worse it got. Right to the point that it actually killed about 4 times in the last 5-7 mile ride home. Within the last mile or so it completely died and I'm sitting on the side of the road on the edge of town waiting for it to cool down, rest, whatever it needed to do to work again. When I started it up again, now, not only does it still suck air but I have a nasty grinding noise that to me, sounds really bad. I can't even tell exactly where it is coming from. The only thing I can think of is that I did crank the revs up quite a bit to keep it running. Man I hope I didn't break anything else!

It gets even better! I lost my job on Monday! Now I have time to work on it but I have no money to spend. What the hell?

My next step is to replace the fuel filter. Didn't look bad from what I saw but what the heck.. can't hurt.

I gotta tell you, I'm about ready to dump this thing and go back to a jap bike. I never had any problems with them. I know, blasphemy

Part of me wants to dump this thing completely and part of me wants to make this work. Maybe I need a new motor... or most of a new motor... I don't know.

Unless I'm being totally stupid, I don't see a fuel pump on my bike. Shouldn't I have one? What's the darn thing look like? (showing my ignorance here but remember, I've never worked on motors before)

I'll keep everyone updated to my saga as it continues.

Thanks for listening to my venting 

[DirtyDuc]

Very sorry to hear about that (bike & job etc.). 

I can totally sympathize.  The wife & I both lost our job within a month of each other (with a new born baby at home).  After a few months I have found work, wife still looking...  Oh, and my bike won't run either!

Just trying to say, I feel for you and wish you nothing but good luck!!! 

[Howie]

Sorry about the job.  Anyway, change the filter before going any further.  Always go for easy and cheap first.  The filter might look clean, but the filter medium can still be clogged.  When your bike came out of the factory it was equipped with a vacuum operated, pentagram shaped fuel pump sitting between the cylinders on the right side.  It may have been replaced with a substitute.  Anyway, if you follow the fuel line from the tank to the carbs you will find it.