Ducati Monster Forum

Hey everyone so I have a 2001 monster 750 I recently just bought and I have been having trouble with it, replaced starting relay and battery and thought that was the end of my problems but now my bike is not getting enough air.  When just sitting, it would turn on if I give it some gas but if I ride it around the bike will die out and I took out the air filter and the bike ran perfectly fine, rode it around without a air filter and had no problems if the bike is on and I try to put a air filter on it (brand new) it will die out not sure what the problem is if any one has any ideas on what it could be I am open to all suggestions.

It may mean too much fuel. Do you know if the carbs have been rejetted or overhauled?  How many miles in the bike?

The bike only has about 6500 miles on it and as for the carbs I do not know I just got the bike about two months ago.

OEM Paper or oiled K&N filter?

What came in the bike was k&n filter then I bought a new oem paper filter and neither worked. Get the same result with both. I currently have mesh paper wrapped in the medal band and that is my riged air filter and it works fine I can ride around without any problems of course I don’t want this to be permanent.

Assuming the bike was running fine before something had to change.  Was it?  As koko said, sign of rich.  When you remove the air filter are you putting the lid back on?  Does the bike idle when warm?  How well?  At what point of throttle opening does it stall?

Yes the bike was running fine about a month ago I changed oil and starter relay went bad and replaced that and got a new battery only things I have changed. And bike didn’t come with lid just medal band that’s goes around oil filter to hold it down. So no to lid. And yes bike idles when warm perfectly fine and doesn’t stall with throttle but at any point if I try putting air filter in place the bike bogs down and dies.

The bike dies at idle with the filter in place?  First thing I would check is the air jets.  They are visible in the air horn.

Could it be that the bike had individual air filters?

I have ordered the carb rebuild kit and will be taking it out and cleaning everything hopefully that would work and as for the air jets they seem fine but again I’m just taking the carb out and cleaning everything out. And I bought a stock ducati air filter and that was just one for both so I’m assuming it is mean to be that way.

Paper panel filter or K&N DU0900.

You may have worn needle jets so ordering sone Factory Pro needle jets is a worthwhile upgrade if you have the stock brass ones in there.

I am a fan of Dynojet needles (stage II for open air box) and Factory Pro needle jets.  The brass needle jets oval over time.  When you rebuild make sure all the internal passages are clean.  I like Piper Cross filters.

What difference do you see using the Dynojet needles? And same question for the filter? I am fairly new to motorcycles so I am curious and of course I want my bike running well at all times. I haven’t don’t anything to the bike and it is mostly all stock 

IMO, Dynojet needle has a better profile for transition from idle to mid range.  My experience is K&N filters pass a lot of dirt compared to the Pipercross filter (foam).  Stock paper filter (when clean actually flows quite good), just not a good idea with an open air box.  Paper and rain don't go to well together.  I can't find it on the inerwebs any more, but a reputable source found the OEM paper filter flowed as well as a K&N  on the ST2 with factory air box.

Do wait for koko64's opinion, then make a decision.

Hmmm. So the bike was fine and just started running rough? When it runs badly, any fuel dribbling out of the overflow hoses which connect to the base of the carburettors? Have you changed from regular to premium fuel lately?

I run K&N filters because I run open airboxes. If under oiled they let dirt through and if over oiled they cause rough low rpm running. They may let significant pieces of dirt/sand/silt through if you dont grease the rubber sealing gasket on the filter perimeter. That's the main cause of many issues imo.
If I ran closed airboxes I would run oem paper filters and change them regularly, say every third oil change and just wear the cost. An Aussie company called Ryco made oem equivalent paper filters, not sure if thats still the case.

So are the dynojets worth having I found them for around $80 and as for filter I think im going to try the k&n filter and see how that does

And yes at first the overflow tube was leaking fuel but after getting it started and running it a bit it doesn’t seem to leak anymore and since I’ve had the bike I have put premium fuel nothing else.

Ok. Your carbs have been flooding and that can give those dymptoms. Run regular gas as premium can foul plugs and cause rough running. You would only run premium if you had hi comp pistons and I'm guessing the bike is pretty stock.
If the bike is stock and you are running an open airbox lid then get a Dynojet or Factory Pro jet kit fitted. With a closed stock sirbox you can run stock jetting. If the bike has vacuum fuel tap (under the tank at the back with two hoses) then get a manual tap and plug the vacuum hose with a small bolt and clamp. They can cause issues and there are threads you can search here on how to do it.

Shoulda thought about flooding.  That would explain the sudden change.  And float height.  750's are pretty low compression, 9:1.  Regular gas! 

If you live in the US, Dynojet stage one with OEM springs.  US bikes had different jetting than the rest of the world, notably leaner.

So me being new and all I tried sticking to the Manuel and doing what it says and it calls for premium gas so your saying to run regular why again? I didn’t want to harm the bike just trying to make it run at its finest. So for sure getting dynojets now and I will try to use the k&n filter if it seems to run weird or sluggish. And as for gas I just filled up my tank with premium two days ago but after that tank is done I will try running reg gas and seeing how that does for the bike.

The only reason for high octane, or premium fuel, is to prevent detonation. It is accomplished by using chemicals to inhibit the fuel burning too quickly.

Your 750 is too low compression to detonate on regular fuel, and the chemicals that are used in high octane fuel will only cause carbon in your bike. Trust them...they're telling you right.