backfire

[dwarff]

hi evryone,ive just bought a 1990 906 in blue and white. this bike rides absolutely perfect but is a pig to start.backfiring very loudly before it finaly purs into life,any ideas? regards

[higgy]

Welcome to the wonderful world of the 906 and Ducati
Where are you located Dwarf?
I have many ideas.......

[Mc tool]

The quick answer is to get a volt meter and stick one probe into the power feed to the magic box ( at the box itself ), and the other on to the + batt terminal. This will show any voltage drop between the batt and the magic box, should show 1 - 1 1/2 volts ( ignition on ). switch on headlights and or start the bike whilst watching this meter. If at any stage you see a reading of more than 3 volts , this indicates that you have a bad connection (s ) between the batt + and the magic box , most likely at either the multi pin plug to the right hand switck block or the plug to the ignition switch. I have previously posted on this topic, might be worth a look , good luck

[persempre907]

I had a blue 906 as yours.
She used to have the same problem.
The Ducati mechanics said me it was normal.
Really, she used to have those misfirings even after all the setting of the carburettor I paid (very expensive stuff)....
Ciao

[higgy]

Excellent post Mctool, I love it when you talk dirty. I would offer up that anything over a volt is trouble tho,even on an Italian bike.
A voltage drop test is always the quickest way to the route on any electrical issue.

[dwarff]

hello again,i live in worcestershire,thanks for the advise.regards.

[paso750]

when you`ve gone through the electrics you could also check if the carb is synchronized correctly and maybe change spark plugs. I had tried all kind of different brands at the beginning and Champions seemed to work best.

[jcslocum]

How many miles???

Compression test done yet?

[higgy]

pull the plugs out and take a look. If the are black sooty and wet,replace them. You got work to do after that.
Keep posted and there will always be an idea or two here where to go next

[Tamburinifan]

just bought a 1990 906

Do you know last service/valve check?
Valves out of spec = bad behavoiur.
+1 on new plugs.

[dwarff]

hi evrybody,just got in from doing another 12 hour stint in the seat,thanks for all the advice.this is my first ducati and im absolutely enthralled. ive bought it to restore after it was crashed and stored for 5 years. thanks again. regards dwarff.

[paso750]

did you just fire it up and ride it or did you do all maintainance incl changing the old belts first ?

[duckboy]

these engines can be really hard to start if your valves are not seating correctly. holding down the starter button, and squirting in petrol can lead to fuelling up the exhaust canisters with fuel mixture, this can cause the big bang when the whole lot ignites. I'd suggest a compression test, as well as a leak down test.

[dwarff]

hi all,yeah i did rush the start up a bit,my son came to help me get it unloaded and talked me into trying to start it.after fitting a battery from an r1 and half gallon of petrol,i switched to on the fuel pump ticked and petrol squirted on the floor. the pipe between the regulator and the carb had a whole so i replaced pipe.pressing the starter only turned the motor very slowly so i jumped it off my car it went over for ten seconds and backfired so hard sam thought hed been shot in the leg. it then ran faultlessly,its got 25000 km on the clock wich im sure is right, the plugs are ok,as are the belts for now,im wondering if the starter is weak,or do they have special batteries?

[paso750]

somehow it sounds as if the bike was standing for a longer time or am I wrong ?
If so you should drain the fuel in the tank and put in fresh one. Next to the check of the electrics (ie voltage at the coils) and carb synchronisation when was the last time valve clearance was checked ?
The battery is a 12V-19Ah (I`m using a 12Ah and never had a problem)