Ducati Monster Forum

My first post so be kind  :).

My ‘98 m750 will not start cold without starting fluid. Choke doesn’t help and twisting the  throttle doesn’t seem to make any difference either. Once the bike is warmed up, the engine starts right up. I was told that weak ground wires could be the issue besides possible carburetor problems. Bike runs pretty good once it’s started and had a chance to warm up. Any suggestions? Thanks! 

Welcome again.  [beer]

Does the starter motor crank quickly or struggle compared to when it's warmed up? If it cranks strongly and the same then I suspect the carbs.
Check the choke cable running to the back of the carbs. Your choke should make the bike start after a few cranks. Check that the choke actually engages when you use it. Does the choke actuator arm move? The choke jets are the most obvious ones in the carb bowl, they might be blocked.

An old bike that has been sitting a long time with stale gas often needs a carb overhaul. Jets get waxed up, passeges block, etc.

The ground wires may need a clean at their ground points and some add heavier gauge cables. Kits are available or you can make your own.

I honestly don’t know if the choke is operating or not.  I’m gonna start with rebuilding the carbs since they haven’t had any attention other than cleaning the outsides. From what I remember, there are no rebuild kits for these carbs, correct? Thanks for the reply and I’ll keep ya posted on the progress.

Bill

An easy way to see if the choke works is while the bike is idling move the choke lever towards rich and note how the idle changes.  How old is the fuel?

https://www.dellortoshop.com/contents/en-us/d155_Ducati_Carburetor_Service_Kits.html  and your dealer.

Vertical carb needle/seat wears out which causes the fuel to drain into the cylinder when on the side stand.  Lack of fuel in carbs can cause the situation you describe. 

Always a good idea to go through the carbs, just change out the needles & seats when you do.

Inspect all the vacuum hoses to carbs.  If any holes repair or replace.  It made a huge difference for me especially during cold weather.

Last night I checked the choke mechanism and it seems fine. The battery doesn’t seem to hold much of a charge for very long. Could be low voltage not firing the plugs or the coils. But starting  fluid does them job every time. I noticed the idle is lumpy and the part throttle produces some popping in the exhaust and the engine seems to want to die if I let it idle without the choke/some throttle applied.  Thanks for the advice so far!

Next step:
      Recharge the battery and have it load tested.  Replace if needed.  Further diagnostics with a weak battery is like pissing up a rope.

After that:

If the float bowls do get empty, given the small fuel passages, they prime slowly so expect pops and lean spots coupled with unusual running until the fuel gets everywhere it’s supposed to be

Update....

I removed the carbs and the necessary bits involved and cleaned everything. The carb bowls were somewhat better than expected, although they did have some junk in the bottoms. I removed and cleaned out the small jets and checked the floats for proper movement. I also cleaned up the ground wire connections.

Results.....the bike fired up within 5 revolutions WITHOUT starting fluid! A few pops through the carbs at first, but it soon settled and idled without choke or throttle being touched. I also noticed that the bike turned over quicker.

The bummer..... now I have dripping fuel from the overflow tubes and it’s quite a bit, both while  running and when engine is off.

So....I’m getting closer to my goal of making it dependable and easier to deal with. Thanks for the advice!

Bill

Overflowing fuel is another sign of the needles & seats being worn.

Any idea of where they can be sourced from? No luck from Factory Pro.

No idea.  Internet search?

Same link as above   https://www.dellortoshop.com/contents/en-us/d169_Ducati_750_SS_and_Monster_Carburetor_Service_Kits.html   or your dealer. 

Powerbarn.

Update:  I got carb kits from power barn and rebuilt the carburetors. Still had a cylinder down. So....I took all the ignition parts off and checked them for faulty issues. New plugs. Put it all back together and it started like a new bike and idled perfectly. Took it for a short ride and it started cutting out on acceleration.... [bang]

So I got to thinking....pulled the new plugs and both were wet. The idea hit me....the oil was saturated with gasoline from bad carbs! So I changed the oil and the filter and now....finally...it seems to be close to 100%. I did notice that one carb still wants to piss gas sometimes.  I’m thinking that one of the float assemblies might actually be faulty.  Bike will idle and rev fine. Doesn’t shut off or stumble. I’m stumped. Anyway, I’m moving on to the next project....rebuilding the forks and replacing the wobbly front rim. Any write ups on the forks?

Thanks in advance!