Ducati Monster Forum

1999 Monster 900

My friends bike has been riding well until now. Its having a major fueling issue. I can get the bike to start up, no problems, but after some riding (say 20 mins), it will cut out and behave like its out of gas. After this, any subsequent attempt to start her will get her to fire up for a few cycles of the piston and immediately cut out even if i try to give it some gas after i get the engine to fire upI suspected a clogged fuel filter and replaced it (it was all sorts of rust nasty) and it ran great for a while, then went back to having that problem, but its not as severe.

Any tips? the tank is venting properly.

I am thinking that there could be something logdged inside the vaccum pump or carbs and just needs to be completely cleaned out.

When the bike stalls open the float bowl drains and see how much comes out.  Three likely possibilities; vacuum fuel shut off, fuel pump or the fuel hose that runs by the bottom of the cylinder collapses when warm.  I assume you checked for good spark and flooding.

+1. My bike had similar symptoms.
Be ready to clean the tank, carbs, tap and pump (or replace it). I went through a few filters when my tank shed a layer of scale. The bike had been sitting when I purchased it. I ended up with a Mikuni rectangular pump from Cal Cycleworks. I also changed to a clear plastic filter to keep an eye on things. I can look at how the fuel is flowing and what crud is accumulating.

okay here goes the whole check list

1) Riding the bike cold it runs great. After about 20 minutes the left side of the bike has gotten EXTREMELY hot. About as hot as a 4v radiator fan blowing hot air right into it, possibly worst.

2) Bike ceases to run after above mentioned.

3) Bike will turn over great, you can hear and feel the bike starting up, it just wont keep the idling. but it will start up. It will only hold over for about 3 cycles of the piston before going dead.

4) Check for spark? yes, nice big fat red spark on both pistons.

5) Fuel filter? was originally orange, but replaced it with a Napa equivalent. I blew through both filters, old filter was very clogged.

6) After replacing the fuel filter, bike was much more resonsive, but after 20 minutes the same issue, when ridding at 6am, bike is great, on the way home in traffic, it dies again. Refuses to start. The bike actually starts on first try every time. Its a very good motor.

7) emptied the fuel tank, inspected interior, no signs of rust.

8) removed the line between carbs and vaccum pump and cycled the bike, there was more than enough gas coming through it with just the starter motor running the engine. But it seemed kind of weak, not a strong pulse or anything just kinda dribbling out.

9) opened up the vaccum pump, looks fine, but i wouldnt know what a damaged one looks like.

thats all i have. Cleaned the carbs too. bike gave 1000 no problem miles until now

Spark should be crisp and blue

it was crisp, but red. what does that mean?

Not positive, but you may have an electrical issue...not fuel.

Check the spark when things cool off.

will check again in the morning, but the color was read when the bike was sitting for over an 3 hours already.

Would it run with that spark?

yes, it will idle just fine i hauled the bike about 3 blocks from my house and rode it the remaining 3 blocks into my garage and it rev'ed up without issue and developed full power on the butt dyno.

then I guess that isn't the problem.

I've never seen a red spark from an internal combustion engine coil.

I've seen blue ones...they're good...and yellow ones...not good.

Sometimes ignition faults are revealed when a coil or module reaches a higher temp and they may work fine until they reach that temp. A cracked coil winding is an example.

Is the weather hot where you are?  The heat on the left side, would you call it excessive?

to answer howies question before, there was adequete fuel in the bowls. not as much as i expected.

the heat on the left side is BEYOND excessive. Ive ridden 4vs in traffic and it sucked hardcore. this one was worst. it was actually scorchingly painful. the weathe risnt hot, this all happend in the lower 70F

That level of heat and on one side is a worry. No more riding until the area is inspected. Do you think the heat is coming from the alternator cover or cylinder/head area?

A thought would be to check how many volts are getting to the battery. If spark is only off the battery then that would explain weak color. I hope nothing is binding or grinding under that cover. The support beating can go, taking out the alternatoe and if you leave it, possibly the bottom end.

Just being over cautious.

Another thing for the checklist, is the oil level in the sight window dropping when the motor is started?. Just checking.

The color of the spark indicates temperature.  It should be blue and jump at least 1/4''.  Red is not good.  Extremely lean, as in low float bowl level will cause a notable increase in engine temperature, but, as koko states, so can an internal engine problem.  Easy shade tree check?  Pull the spark plugs and turn the engine over mechanically when cold.  Run the engine until it stalls.  Pull the plugs and rotate the engine again. 

Oh, have you looked at the spark plugs?

the spark plugs look normal. the battery had been trying to start the bike all day, so it might actually be low battery since the spark was running directly off that. i will throw the batt on the charger and try again.

the heat is defintely coming from the upper head since its my inner theigh that burns. it was never like that before.

howie, what is it that im trying to look for if i pull the plugs and mechanically turn it over then run it till it dies? I have no idea how long it will idle for, but if it is a float bowl level problem, it would die after the float is emptied no? I took apart the bowls and they are clean as a whistle.

used known good plugs and battery, the spark is still this pink/piurplish color.

i was reading into the collapsing of the fuel line under excessive heat...the excessive heat caused by lean condition.... caused by not enough fuel coming from the carbs. the carbs are operating fine, so i am going backwards...

im also thinking it might be the vaccum petcock. Any way to test the device? going to remove it today. and see if autozone has a manual petock.

okay, tested the petcock, it works fine. Its vaccum operated. (step aside gay jokes abound!)
 
I sucked on one end and had a friend suck on the other end. it was blocked until i sucked on it. which makes sense.

the only thing i that was left to test was the fuel pump. I read somewhere that the fuel pump should have strong pulses of fuel squirting out. this thing was uhhh. very weak pulses, but it seemed like it was defintely enough gas.

The flow rate of the Ca-cycleworks fuel pump is 14Litres an hour which it looked like ( i was pumping the fuel into 1 quart glass jars and 1litre = 1 quart for all intents and purposes at this point.

so im stuck here. i ripped off each and every single line and tested them for blockage. its all clear. i did find a spring between the fuel filter to the petcock which i autoatically assumed its suppose to be there given how long it was...

any help from here on is much apperciated. the spark is strong enough to fire the bike up on the first go. Bike fire up better than my S2R1000.

I'm not familiar with the carbed models. Do they have any sensors which measure heat and prevent ignition?

It can also be a vacume issue. On my 240 I had a cracked vacume bung. A hose was clamped on but air still found it's way in the manifold. Metal expands when hot so the crack may be amplified.

If fuels ok it's gotta be air or spark. From everything you've done doesn't look like fuels an issue. what controls ignition? Can the heat affect those parts?

Inlet air leaks on the rear head, or a timing issue for that cylinder (more unlikely).
Synch plugs/screws falling out and leaky manifold rubbers could make things dangerously lean. Dont want to hole a piston.

 Ive never heard of an ignition pick up working loose and advancing. I spose its possible. A faulty kgnition box?

Any pinging?

no pinging.

but i will check all the parts you are talking about.

actually which ones are the synch screws on a carbed bike?

the bike is over 12 years old with stock rubbers so the hoses could be a possibility

I mean the vacuum plugs you screw the manometer into. They are flat head type brass (usually) screws on the manifolds. They should never fall out, but who knows. I have heard of people forgetting to put them back on after a carb synch.
The fuel pump hose off the rear cylinder manifold could have perished, letting extra  air into the rear cylinder and also failing to pull hard enough on the pump causing low flow.

Pull the plugs on the engine when cold.  Turn the engine over with a crankshaft turning tool or the rear wheel in high gear.   It should turn easy.  You know the feel since you have done your own valve adjustments and belts.  Put the plugs in.  Run the bike until it stalls.  Pull the plugs and turn the engine over again.  If the effort is notably higher you have an engine problem.  This is only to eliminate the engine as a source of your problem.  As far as the vacuum shut off goes, as a test you can just bypass it.  You do stand the risk of spilled fuel  in a tip over, but since they usually fail in the open position I don't think the risk is great.  You can even bypass the fuel pump for test purposes, just make sure the fuel level in the tank is higher than the carb inlets.  

The float bowls will still have some fuel in them, but nowhere as much as normal.  

I think you have more than one problem since you feel excessive heat from the vertical cylinder and do know what normal is.  You do have weak spark and the heat is likely a symptom of lean running or an engine problem.  Off hand I can only think of three reasons for your weak spark; bad coils (unlikely), bad resistors (spark plug caps) on the ignition wires or excessive clearance at the ignition pick ups.  Checking pick up clearance requires removing the alternator cover, so that is a last resort.  Coils should read 3.4K ohms+% from + to - and17K ohms+10% from the spark plug towers to ground.  The resistors should be 5K+10%.

Hope this helps.

 [thumbsup]

Any progress he man?

nope, i have midterms this week so im stressing out over studying instead. :(


I went searching for a rebuild kit. the Diaphragm on the fuel pump is looking thin in some areas and flat. While im in there i was thinking about rebuilding it or replacing it.


suggestions? Pick up a rectangular one from CA-cycleworks or rebuild the pentagon one?

i found this rebuild kit, which is kind of misleading cause its a pic of a rectangular one...
http://www.bikebandit.com/mikuni-fuel-pump-rebuild-kit-for-pentagon-pumps (http://www.bikebandit.com/mikuni-fuel-pump-rebuild-kit-for-pentagon-pumps)

I went the Cycleworks pump and got two for a spare at the great price.  They are smaller. Painted mine black to blend in a little better.

are there advantages to the square pump? because the genuine rebuild kit ($15 bucks) is cheaper.

that is assuming hte rebuild kit was as they stated it. (it says brand : Mikuni)

Just size from what I can tell. Also lighter! :D

The rectangle pump produces less fuel volume.  This should not be a problem on a stock bike, particularly since it runs koko's modified machine.

How much less howie?  Athough mine isnt leaning out at 9000rpm, Im interested.

http://www.mikuni.com/c-fuel_pumps.html (http://www.mikuni.com/c-fuel_pumps.html)

The pentagon pump shown is two outlets, I assume ours is similar.  Seems to me 65 liters/hour should run a large V8.

Thanks for the info, Howie.

He Man, how's it goin'?

Just getting to the garage today. I  am going to redo do the vacuum lines (1.19cents a foot on mcmaster, im pretty sure NAPA will have some silicone hoses i can use as well) this is to ensure a good vacuum so i can relocate some things away from heat.

What size should the vacuum tubing be? what about the fuel lines? Im not sure how much those run, but i think those are pricey.

Now what color? :P
http://www.mcmaster.com/#tubing/=ekpn5g (http://www.mcmaster.com/#tubing/=ekpn5g)

I am looking for a  100% guaranteed genuine Mikuni Pentagon rebuild kit if anyone knows where i can find one.

This is the diaphragm for the fuel pump. looks sad. im pretty sure its NOT suppose to look like this and should be taught.

(http://kuixihe.com/gallery3/var/resizes/Tutorials/Vaccum-Pump-Rebuild/20102011422.jpg?m=1319131845)

(http://kuixihe.com/gallery3/var/resizes/Tutorials/Vaccum-Pump-Rebuild/20102011424.jpg?m=1319131825)

http://www.sudco.com/CatalogJPG/507.jpg (http://www.sudco.com/CatalogJPG/507.jpg)  for the rebuild kit.

5/16 or 8mm fuel hose, I'm going to take a guess at 3/16 for the vacuum hose.

i was o nthat page but im pretty sure that the double outlet pentagon is bigger than the one on our bikes at 65L/hr it almost has to be bigger!

I got my Mikuni rebuild kit from bikebandit, pretty sure it's this one http://www.bikebandit.com/mikuni-fuel-pump-rebuild-kit-for-pentagon-pumps (http://www.bikebandit.com/mikuni-fuel-pump-rebuild-kit-for-pentagon-pumps)

The pic is obviously not correct, but the parts were.  And my old Mikuni diaphrams looked like yours.  I replaced the little valves too, mostly because they came with the kit.  The old ones looked fine.

what brand was it?

Mikuni.  I made double-sure of that before I got it.

I believe the only difference is the amount of outlets, since I haven't bought one I can't say for sure.  Why not give them a call?

thats always the answer isnt it? lol


i actuallyed called bike bandit yesterday and they couldnt identify the brand because they dont actually have it in stock through customer care only  but at the warehouse.. but the brand says mikuni and if mongo also verified it, i will go with that.

okay, why is this so cheap?

http://www.bikebandit.com/motion-pro-clear-vinyl-fuel-line (http://www.bikebandit.com/motion-pro-clear-vinyl-fuel-line)

the tygon ones are much more expensive....

I forgot the package came with a weird '70's looking sticker huh.  Yes I keep empty packages for Ducati parts.  At least I don't horde cats or actual ducks (yet).

(http://i56.tinypic.com/2d0astt.jpg)

And be careful putting the pump back together, I figured it would only go one way but was off by a side or two of the pentagon, then wondered why it wouldn't fit back in the bike.

so as long as  it works!

i just had this thought... bike only has 16,000 miles, but the pump is over 12 years old so im not sure what to say about it failing or if it is even the culprit.


hopefully this clears the issue, as i see it, all the lines are clear, all the vacuum lines are in good standing condition, the vacuum petcock works great, the carbs are clean. brand new fuel filter and the bike had always fired up on the first go.

failure happens when the bike has been on for a while. if you let the bike sit down and lift the tank for it to cool down, the bike works again. so perhaps the heat is causing the already frail pump diaphragm to stop working (though its relatively far from heat sources). so im kinda at a lost if it isnt the pump because i cant question anything else except for electrical issues as DP pointed out, the color of the spark aint quite blue. but that wouldnt explain why the bowls were so low.

Back of mikuni package says it's for df62-702, df62-705, df62-706.  So also guessing same internal parts, different # of outlets.

I actually thought I was the last to rebuilt the OEM pump, but you win.  I think ethanol has something to do with the deteriorating, but I'll soon be on my THIRD 1098 tank due to expansion.  I'm sure you've checked to make sure no kink in the fuel line loop?  That happened to me years ago, I just put the tank down easy then peak under to make sure no kinks.  And to make sure the fuel line isn't contacting the rear cyl.  That just never seemed very safe.

Come to think of it, its seemed my top cyl has been running rather hot lately too.  Ugh.

Thats why im thinking about redoing the fuel line.

Good idea He Man. It's good to replace fuel lines every five years or sooner if they have deteriorated due to heat, fuel additives, etc.

Some hoses harden in no time at all . I changed to that fancy transparent hose recently because some new hose went very hard and brittle within a month. It looked ready to fracture with vibration!

how much hose you got left? i doubt i could ever use 25 feet. and how is it holding up to heat?

Just a tiny off cut.
Seems to be ok. Local Yamaha dealer had it and said it was the best hose they have had.

rebuild kit came in today from bike bandit, its a genuine mikuni!

now to install it and put everything back together...


im guessing its a good idea to just put everything together and fire it up from a bottle of gasoline and let it idle for a while before its good to go? i dont want to patch it all up and figure out its no good

I didn't.  Just make sure you put the pump back together right - I only realized when it didn't fit back in it's space.

well i put the fuel pump together and hooked everything up and ran the bike from a bottle of gasoline placed above the carbs. (well above the carbs).
i pinched the vaccum line for the petcock and bypassed the fuel filter.

while cranking for about 1 straight minute, i killed the battery. the bike kinda wanted to start.

I cranked open the bowls of the carbs and gas came out the right carb, but not so much the left carb.

The left carb ironically is the one that connects to the rear cylinder (which was getting stupid hot before)

The carb checks out to be mechanically fine.

Question: Does one carb fill up before the other, there was no way the carb was full after cranking for 1 minute. do i need to prime the pump first?

Either the mesh filter in the carb intake is clogged or the needle an seat are sticking closed.  The screen does affect both carbs though.  Ah, look fir a restriction in the tee

Most have a T piece between them, but if the bike is on its side stand then maybe.

Thats a lot of cranking without a start. I suppose its primed now with all that cranking. Mine didnt take too much to start. A full tank may help prime it better, but if there was fuel in the bowls it should have started.

Try a full tank next time and watch the lines for fuel flow. Mine courses thru quite impressively.

You seeing the fuel run thru the clear hose when you crank it? When I turn on the tap the hoses fill.

which needle?

I havent taken a look at the mesh filter. i never opened it up that far.

there is no restriction at the tee that i know off. ( i removed the tube and blew air into it, seems like i am getting carb vapor (or just the rampant smell of carb cleaner that can melt brains) from both carbs equally.

I'd give the bat a good charge & try again.  For some reason, my bat will crank hard & fast but not have enough juice to power the plugs.  Throw it on a charger, BANG starts right up.

The thing connected to the float that allows fuel into the bowl.

He Man, hows it going?
Find a fuel blockage? Pump and tap ok?

okay put everything back together. and tightened the belts (they were make the beast with two backsing LOOSE!) of course, id venture to say that the 12k service was NOT done as the owner said because how the belts got that loose? easy, it wasnt serviced. :p

anyway, with a new fuel pump diaphgram the bike is running good and idles great. had it sitting and idling for 10 mins with no issue and held the bike at a high RPM for about 1 whole minute (headers getting red) with no issue. Im trying to recreate the heat that the bike seemed to have failed in the last few times and im having my buddy ride the bike around in city traffic for an hour to make sure there are no issues.

AFAIK, the pump seemed like it was the issue the whole time as i found nothing else wrong. Took the carbs apart and they looked good. the emulsion tubes are kinda worn and could use a rebuild soon.

I had the same exact problem you describe a few years ago with my '95 M-900. It started after I replaced the fuel filter with a NAPA filter. After a lot of time on the side of the road, and going  through everything I could think of, I took a closer look at the filter. The outlet on the NAPA filter was on the opposite side of the stock filter. When I put the tank down, it pressed the gas hose on top of the valve cover. After a few miles, the heat from the valve cover would soften the line and, because it was pinched, it would restrict and eventually block the gas from flowing. On cooler days, it took longer for it to leave me on the side of the road. Apparently, the cooler ambient temps helped keep the gas line hard.
I believe there's a pic in the Haynes manual of the stock gas filter. If you have one, compare it to the filter you have installed. That may be your problem.

problem occurred before the filter, but after putting 5 miles in heavy traffic (which by the way is not easy thats like an hour in traffic!) the bike is showing no signs of cutting out.

so hopefully problem is solved, but there really is no way to tell unless u ride it.

Glad you got it sorted.  Please don't so the above again - it's really bad to have high revs with no load, even for the nearly indestructible M750.  It's rather easy to peak under the tank when it's down & make sure the fuel line isn't kinked or sitting on the cylinder - I always make sure my breather tube is between the fuel line & the cyl.

i really had no other way to recreate the heat generated by the heavy traffic. It has droped nearly 20 degrees in ambient temp since the bike started to fail. so that was the only way i could even remotely do that.

the fuel line was defintely not the problem. it was defintely the fuelpump, considering how messed up the diaphragm was.

the bike ran great, however, i now have a dead 1098 on my hands to work on. :\

Dead 1098?  What's wrong with it?  Switch over to the ducati-superbikes.com, we can help  ;D

haha im on ducati.ms :p

i dont knwo whats wrong with it. i turned it on for baout 10 mins idling to get the STABIL into the system. then shut of it off. washed it. and fired it back up. then my frined stalled it cause water got into the clutch but it just so happened that it also ran out of fuel.

now when i hit the starter, the bikes lights shuts off and goes through the startup procedure, except no power gets to the starter. Strange because that bikes been through hurricane rain and a rag defeats it? im pretty sure a fuse is blown somwhere.

Yeah the banner ads & format of that site drives me nuts...

Unusual 1098 problem - if not a fuse (I actually doubt it's a fuse) check out the solenoid, it's (relatively) easy to get to, it's in front of the battery box.  Can't believe there's no locktite on the terminal nuts, mine were a bit loose.

well i didnt look at anything. it just started fine today. guess water got into the perfect spot to stop it from starting. odd considering this bike rode through a hurricane.

Yeah washing them with more than a spray bottle is a bad idea.  I remember people used to get water in the swingarm & screw up the hub, but riding in the rain is fine.  I always figured the heat from riding evaps the water, so its always fine when it's hot.  Washing cold, not so much.

ive shot a hose at my bike with no issues. though i avoid the gauges and theres not much in terms of electronics on the bike aside from the gauge/ecu battery. the later being underneath the tank and almost impossible to get wet...