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Fuel (?) problem?

9K views 9 replies 7 participants last post by  MotoTechDCinLV 
#1 ·
Hi everyone,

Last week I took my 1999 Monster 900 out for the first time after winter. Over the space of a few days, I went on a few short runs, and then went on a longer run of about 160 km (100 m).

Everything seemed to be going fine until I got about 1 km from home, when the engine cut out like I was out of fuel. The fuel light hadn't come on, and I could only fit 10 litres in when I filled it up later. After waiting for about 5-10 minutes or so, the engine would start again, but then also cut out again a few hundred metres further down the road. It also seemed to cut out immediately when I tried to rev it over maybe 4000 RPM.

I had a very quick look at the fuel filter and didn't notice anything obviously unusual.

This weekend I tried it again and went maybe 15 km with no problems, like nothing had happened.

I'm a little afraid to go on any further rides in case it dies again. Does anyone have any ideas what may have happened?

Cheers in advance,

James
 
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#2 ·
Check your fuel lines from the tank into the pump, directly over the engine case. Most have a pretty sharp kink here, either replace the line or fix the kink. The problem will be exacerbated when it is really hot out. If that's not it double check that your fuel pump diaphragm is not cracked. Also, check that your tank is breathing from the fill port area, there is a small hole that should be free of obstruction.
 
#4 ·
I just experienced the exact same problem with my 2001 Monster 750. I've been reading thread after thread and its just been hard to find a solution for this!! Losing my mind since its been so nice to ride....

Just like the first post I was out riding the bike possibly the 4 time after winter (1 Full Gas Tank) and it just died out of nowhere! hasn't started right since.

Been trying to find out what the problem could be and so far did the following;

-Checked all the fuel hoses, everything seems to be flowing fine. From the fuel filter, petcock, fuel pump spews gas continuously.
-Vacuum hoses are sucking good, on both the petcock and the HEX fuel pump. no kinks on them.
-Fuses under the seat are working fine, kickstand and ignition.
-Spark plugs have spark
-Gas tank was clogged on both drain holes. Ended up cleaning them out and removing the Carbon Emission Canister along with all the hoses. Plugged the one going to the carbs. (Seemed to help a bit) Canister seemed clogged with water/fuel on the intake hole.
-Battery is good and charged with a battery tender.

The bike now starts only in choke but stays in low RPM's 1000. Just sits there with some hiccups and eventually dies out. I can't even pull the throttle it dies.
Both exhausts have compression and are working. No way to even ride the thing...

I was under the impression it would be water in the gas, so I removed all the gas and put new gas with injector cleaner. Still no good. I pored carb cleaner directly on the carbs and that got the bike going because before it wouldn't even start.

Now I'm stuck and I hate to tow it to the dealer. I like to know my bike and see what the problems are vs having the dealer take care of it and charging an arm and a leg. Its the principle of owning a motorcycle and knowing your way around it.

Next steps are getting new spark plugs and if that fails I'm ready to take apart the HEX fuel pump and finally the carbs...

I'm desperate to be hitting the blogs now...
 
#5 ·
If you can get the RPM's up by spraying carb cleaner, starter fluid, etc directly into the intakes, then you most likely have clogged idle jets as was stated in a previous reply. Your floats could also be stuck closed. With today's ethanol based fuel the old Vitron tipped float needles have been known to swell up when not used and stick in the inlet preventing fuel from flowing in. Might be dripping by slowly, that allows you to start the bike with a bad idle but then prevents more fuel from getting in and eventually kills the motor.

But the key in the last reply/question for me was that you say you can get it to start and stay running on choke. The choke on these bikes is a bypass loop. When you open it, fuel flows around the carburetor to the outlet side and drops fuel directly to the intake manifold. So if your idle jets are clogged you are bypassing them. If the idle is really low, keep in mind that the idle jets would be providing fuel for about 900rpm and your choke would raise that about 900-1000. If the jets were clogged, then you'd only see the rpm created by the choke.


I realize you've done all the easy stuff, have you physically pulled the carbs from the bike and checked out the float bowls and jets? Idle jets tend to not come clean from adding things like carb cleaner or Sea Foam, if it is a physically clog such as rust, then it can't be dissolved like shellac or lacquer. The obstruction will need to be pushed free with a fine wire.
 
#6 ·
caferacermike thank you for your quick response.

It makes a lot of sense what you explained. I don't see any problems with the fuel reaching the carbs or electric problems.

Today put in new gas, I bypassed everything from tank to carbs and still only started in choke. I tried bleeding the float bowl and just clean gas came out. Filled up quickly after. It barely starts in choke and just hiccups and misfires until it stalls....

Guess I will be taking apart the Carbs and checking the float bowls and jets like you said. Has to be some type of clog on the jets...

Well this will be a fun little project, should I get a repair kit for the carbs while I'm at it or just keep it simple and clean what I need.

Once again thanks for the support Mike!

I was losing my mind....
 
#7 ·
I 2nd Mike's opinion, sounds like the low speed jets are clogged. Did you leave fuel in the carbs while it was stored?

It wouldn't be a bad idea to go ahead and install a gasket kit while you have it apart. Go to your local Home Depot or Lowe's and get a MIG welder tip cleaner, they work well for cleaning carb jets as well. Check your emulsion tubes while you have it apart, if they're egg shaped they need to be replaced also. It's an issue, but usually on pretty high mileage bikes.
 
#8 ·
So I took the Carbs apart and cleaned them thoroughly. They were pretty dirty. I soaked them in white vinegar then in carb fluid.
Put them back together, left the floats stock and everything else looked good.
The fuel/ air mix screw was 4 turns out, seemed excessive but left it the same. Taking those factory plugs off was a B@#$!

Mounted everything back on the bike, tested it out a few times and nothing... not even with the choke on... engine turns no firing..
The float bowls were full of gas, the spark plugs were somewhat wet but dry on the tips.

To note the beautiful Carbon Canister that sits on the back was removed, seemed to be clogged while troubleshooting the fuel and air feeds. Now the hose that connected to the canister is covered with the plug. Will this be an issue?

Charging the battery and giving it a shot tomorrow... but extremely depressed, summer almost over...

Some thought;
Buy new saprk plugs
Take apart the fuel pump
Bypass the petcock

Final option take it to the dealer! :/
 

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#9 ·
New Updates,

This thread is for newbies like myself when encountering a situation like mine on Ducati monsters with carbs. Hope it might help you.

Long story short, after cleaning the carbs I should have just got new spark plugs.

This was my process, I took out the old spark plugs sprayed some WD40 in the piston chamber to build suction. Ran it with out the plugs for a few revolutions then installed the new spark plugs NGK DR8ES. Cracked it a few times, it still didn't want to start... Sprayed some carb cleaner down the intakes and finally it came to LIFE!!! Finally!

Let it run for a while while it sputtered and farted all over the place... the RPMs were waving up and down.
I took it for a short spin around the block even got stopped by the cops but luckily they were cool and understood I was testing it out.

It felt like a new bike. More torque for sure, like a ducati should feel. The carb cleaning absolutely payed off.

Eventually got flooded and bogged down. Started again and was able to bring it home.

Now a few problems:

The bike is way too rich, it dies if I accelerate too much. And gets flooded easily.
I went and adjust the Air/Fuel screw about 2 turns out. And will test it better tomorrow during the day.

I hear the Fuel tank bubbling and farting. Even with the bike off it whistles.

Also I have a screw in the Carbon Emissions Canister intake hose since I took it out. Unsure if this will affect the Carb performance.

I will adjust the carbs tomorrow or so my bro has the tuning gauges lets see how it rolls.

Thanks for any input or support.
 
#10 ·
I don’t know if anyone knows this but in the fuel line that connects from the fuel pump to the carbs there is a filter in the gas line. It’s very possible that it’s clogged and preventing gas Feom going in try taking the hose off and checking the filter in the hose closest to the carb fuel inlet
 
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