Ducati Monster Forum

alright guys got a puzzle for ya.  1994 monster 900... mikuni carbs, ran fine until i pulled the carbs out and cleaned them up a bit.  now it spits gas out of the breather.... i'm about to pull them again and i'm a total noob so any help would be great.  what do i look for etc.  i think the float settings must be off..... let it sit overnight and it filled both carbs full and fouled my plugs.  i guess that would indicate the fuel diaphragm being messed up as well.  i'll post more detailed info after i get them loose again.

Replace the vacuum petcock for sure. Those things can fill the cases with gas if the diaphragm fails.

It could be that there is just some dirt on the float needles causing them not to seat.

I think the recommended float level is 14mm on those carbs, but do a search before you believe me.

+1

Factory Pro site has a good guide for tuning these carbs and setting the float level.

You could give the float bowls a tap with the back of a screw driver to help reseat the float needles and dislodge any dirt (lazy old timers trick). It's helped me out on the side of the road.

There have been a few guys on this forum who have fitted the alternate type OEM fuel tap or some nice on/off aftermarket types. Great when you want to work on the bike, drain the tank, etc.

     thanks guys,  can anyone recommend a good carb kit and setup for a pretty much stock bike.  i'm running stock airbox(hopefully going to pods when money isn't so tight.) with a cored stock exhaust.  before this whole fueling fiasco it was running really rough from 2000 to 3500 rpm.  been tinkering with the carbs and cleaned them out twice now (going to be thrice after tonight).  i really just want this thing to run, distance style.  in fact planning a trip to arizona in 1.5 months.  and love the factory pro sight thanks koko [thumbsup]

How many miles?

You should look at the needle jets if it runs kinda doggy at low throttle openings.

Personally I used a dyno jet kit because that's what my dealer used and had a good supply of jets. Many people rave about the factory pro kit.

+1

Bugger! Twice now my replies evaporated.

Buy factory Pro needle jets when you replace them because they are stainless and will last longer (cheaper too).

Tell FP and DJ your plans and they will recommend a jet kit for your needs.

Is your bike due for a valve adjustment? Say every 6000 miles.

Dont fit pods or modify the air box untill you are fitting the correct jet kit. ( you reckon it runs rough now!)

Edit. If the bike has done 12000 miles on it's cam belts or if the cam belts are two years old, replace them before your long trip.

The bike will be a real pleasure when it's tuned and serviced.

Cheers

10,987miles on the odometer. so i guess it's gettin close.  tomorrow i'm gonna get a manual shut off and bypass the vacuum shutoff.  i'm very new to this sort of thing and really appreciate you guys and all the good info so far.  due to an extreme lack of funds at the moment i'm forced to do all my own work, i believe i read something in here about monsters turning riders into mechanics lol.  i don't really have a complete mechanical history on this beast but i do know it had a complete service about 1.5 years ago at a dealership in AZ.

Do you know what was done at the service? Are you confident the bike was cared for by the previous owner? Any paperwork?
You got any pictures of your bike? Someone eagle eyed may spot something that needs attention.

Have you got a workshop manual yet? Haynes make an ok one. Maybe other books are out there that would help. This forum is great. There are threads about the servicing needs of your bike on this forum too.

For parts required check the sponsors on this forum. They seem like enthusiasts.

Good move on the manual tap. Manual fuel taps are better IMO.

On a real tight budget I would make sure the belts and valve adjustment are good and replace the needle jets. Belt failure is a Ducati owners worst nightmare. If you have any dough left over fit a jet kit that has enough jets to allow future mods. Dynojet and Factory Pro will advise you.

Besides that just the normal new owner servicing to be sure before the long trip, you know checking oil, chain and sprockets, etc.

Good luck and keep us updated on how you are going with it.

These bikes aren't mega horsepower but they are mega fun! Bikes that get you in.
Cheers.

it's alive mwahahaa!!!  bout to take her for a test drive.

the carb for rear cyl was absolutely full of powdered rubber.... apparently i scraped the airbox gasket when re-attaching it last time.  the needles look brand new, no signs of wear.  i'll report after a short ride as to how she's running.

  [bang]
(insert explitive's here)

ran great for a short 5 mile run....  brought it back and shut it down for about 20 min.  then tried to start it again and it's flooded.  never had any trouble before i fixed the stinkin' vacuum leak on the front cylinder....  guess i'lll tear her down again tomorrow.  i have a sneaky suspicion this is going to go well past just the carbs....  gotta dig up the service record. [coffee]  maybe the vacuum pump is pushing fuel past the needle and seat....???  aargh

http://www.ducatisuite.com/jetkit.html (http://www.ducatisuite.com/jetkit.html)

Might be helpful, jet change, float height etc.

alright.... clean service record from tom hull ducati in az...   150 mains 40 pilot... set on 1st clip with a 2mm plastic washer..... floats are at 11mm(i think it's too high)..... anyone know how to figure float setting for my configuration with partially cored exhaust...

Float height is 14mm, regardless jetting.

very helpful sight thank you.

i was under the impression that larger jets required more fuel which means raise the floats( which is backwards on these things), am i incorrect in my assumption?  every day this exquisite piece of machinery sits in pieces breaks my heart. 

Yes.

Float height is f correct function of carbs generally.
Other jet sizes handles more/less fuel.
Just fix correct float height as f now.

You changed the needle jets yet?

Is that clip position #1 the notch on the top of the needle or the bottom? (Generally count from the top). Do the needles have hardly any taper or do they taper off at the end quite a bit? Stock needles barely have any taper.
The 2mm plastic washer (white) is stock and an essential part of the kit whether you run stock or aftermarket jet kits.
40 pilot is standard or close to. Stock main jets are usually 140s. The needles stock clip position is usually closer to the middle.

You either have a DJ or FP jet kit in there or the main jets were enlarged, possibly to accommodate the exhaust changes. If the needles are set on the bottom clip position (raised to the max) and especially if they are aftermarket then your midrange will be way too rich, exacerbating any richness caused by worn needle jets.

If the needle jets are a brass color then they are probably worn. Check em for ovalness as per the FP site tips.If they are are stainless color (FP ones) they will most likely be fine. Any pictures of the carb parts?
Sometimes people adjust the float levels to compensate for another problem. I would rather fix that problem and run the recommended 14mm float level. An 11mm float level is way too rich also, making low speed carburation very lumpy. Set em at 14mm and leave it (Factory Pro site has some how to/guidelines as does Ducati Suite site). Trying to fine tune the float to fix other issues can drive you crazy.

Sorry about the great rant in my PM advice. Trying to save you alot of hassle.
 

It's great the bike has a clean service record.

Keep posting to let us know your progress.

Cheers

EUREKA!!!!
 [bow_down]>greenmonster!
 [bow_down]>koko!

finally got it fingered out,  the floats were so high because the retard mechanic who worked on it before didn't see the massive vacuum leak.  he was compensating by dumping extra fuel into the bowls.
set the floats to 14mm and she runs like a champ now.....  still have to re-adjust a bit so it'll idle correctly but i did get to ride it today... pulled plugs after my run and they're like new.  gonna put the fuel pump back on tomorrow......   you guys are the best.  guess i'll be seeing you guys in the mods area soon. [moto]

oh yes and btw
the needles are set on the first clip (nearest the blunt end) and all associated pieces look shiny and new with no signs of wear.

 [thumbsup]

That's great. Plenty of reason for your bear to dance!