Ducati Monster Forum

Moto Board => Tech => Topic started by: desmodoktor on April 03, 2011, 06:48:28 PM

Title: bad Gas? throttle head tuning needed? I dont know..
Post by: desmodoktor on April 03, 2011, 06:48:28 PM
02 M750 7500miles .. dual arrow exhaust , new battery, new ducati air filter, new champion spark plugs.

early today in the morning started going for a ride.. after 30miles ride stopped for gas at some shell gas station upstate NY...  (93 vpower)
filled her up.. and drove 2 miles to my friends house.. after we had breakfast started going up the mountain...
We were doing 80mph on the 5th gear.. suddenly the rpms dropped and backfired 5-6 times in a row .. downshifted to 4th , the rpms started jumping from 4 to 6 and down .. the bike was throwing me up and down ..  :o    pulled over , the engine was running .. dropped it to neutral and started again ... after 2 miles it started doing the same thing again .. except the continuous backfiring ..  pulled over , let the bike cool off ... started again and rode all day.. the problem didnt come back .. So i dont know what to think.. was it the gas? do i have to adjust the air to fuel ratio? no idea..  if you had this problem before or u know what it is write me back so i fix it .. (its kinda scary when your bike is jumping up and down in the middle of the parkway)  :-[

thx , SVP
Title: Re: bad Gas? throttle head tuning needed? I dont know..
Post by: EEL on April 03, 2011, 07:23:10 PM
My bet is on clogged vent line. If it happens again, open your gas cap, close it and see if it goes away.
Title: Re: bad Gas? throttle head tuning needed? I dont know..
Post by: ducpainter on April 03, 2011, 07:25:11 PM
If the bike was fine...

and you put gas in it and it wasn't fine...

it's probably the gas.

Stay away from premium. It gets used less and there is more water in the tanks...besides it doesn't make as much power as regular in your bike.

Try a small amount of dry-gas and some 87 octane.
Title: Re: bad Gas? throttle head tuning needed? I dont know..
Post by: desmodoktor on April 03, 2011, 07:41:05 PM
Quote from: ducpainter on April 03, 2011, 07:25:11 PM
If the bike was fine...

and you put gas in it and it wasn't fine...

it's probably the gas.

Stay away from premium. It gets used less and there is more water in the tanks...besides it doesn't make as much power as regular in your bike.

Try a small amount of dry-gas and some 87 octane.


thank you dp! u never let me down! i ll try to do that..
i need a small favor from you if u dont mind...
it looks like i have to adjust the throttle bodies.. but idk where to start from .. and where the nipples are, where the manometer connects..  or the ``screw``
i will try to build a manometer same way this guy did .. Manometer, Throttle, Bodies, Carbs, Balancer, balancing carburettors, throttle, synchronization (http://www.youtube.com/watch?v=0nKaGEMLZjs#normal)    and adjust them . . .
please advice me so i get this job done  [thumbsup]
Title: Re: bad Gas? throttle head tuning needed? I dont know..
Post by: MongoReturns on April 03, 2011, 08:39:58 PM
Wow that's the coolest thing I've seen in awhile.  I always use a vacuum gauge, pinch the tube to prevent pulses, and switch from downtube - downtube.  Pain in the ass.
Title: Re: bad Gas? throttle head tuning needed? I dont know..
Post by: desmodoktor on April 04, 2011, 03:07:48 PM
Quote from: MongoReturns on April 03, 2011, 08:39:58 PM
Wow that's the coolest thing I've seen in awhile.  I always use a vacuum gauge, pinch the tube to prevent pulses, and switch from downtube - downtube.  Pain in the ass.


yeah , its pretty cool .. i ll try to make smth similar..
but i have no idea where to connect it at????  do i have to disconnect some hose before i connect the manometer? of yes which one?
(i haven't looked for it yet) any advice?
Title: Re: bad Gas? throttle head tuning needed? I dont know..
Post by: ducpainter on April 04, 2011, 03:21:05 PM
Quote from: svp88 on April 04, 2011, 03:07:48 PM

yeah , its pretty cool .. i ll try to make smth similar..
but i have no idea where to connect it at????  do i have to disconnect some hose before i connect the manometer? of yes which one?
(i haven't looked for it yet) any advice?
Look on the intake manifolds.

There should be a hose attached to each one. That's where you attach

Turn the airbleeds all the way in to synch and get it as close as possible. The synch screw should be in between the throttle bodies.

Then when you get it close back the airbleeds out about 1/4 turn. Check the synch again and make any small corrections by turning one or the other airbleed in or out slightly to get the manometer to match on both cylinders. You can also use the airbleeds to make idle adjustments if necessary.
Title: Re: bad Gas? throttle head tuning needed? I dont know..
Post by: Slide Panda on April 04, 2011, 03:22:07 PM
+1 to DP. I only put 89 in on the hottest days around here, just to help with *possible* pre-ignition troubles. But I'm talking ambient temps in the 90s. Otherwise it's 87 all the way.

The air cooled ducs don't run at high enough compression to make good use of high octane gas. Octane actually slows the burn process, all things being equal. In a high compression engine, the compression mitigates that retardation as the compressed air/fuel mix is closer to a detonation point. So n the high comp, the octane prevents pre-ignition and evens out the combustion.

But in a lower compression engine too much octane will result in incomplete ignition. That means less power and wasted fuel out your tail pipe (why you got explosive combustion out your tail pipe). And if you had to worry about emissions, you'd probably toss up huge hydrocarbon numbers from that, unburned fuel.
Title: Re: bad Gas? throttle head tuning needed? I dont know..
Post by: Bianca on November 07, 2012, 06:46:50 PM
Quote from: ducpainter on April 03, 2011, 07:25:11 PM
If the bike was fine...

and you put gas in it and it wasn't fine...

it's probably the gas.

Stay away from premium. It gets used less and there is more water in the tanks...besides it doesn't make as much power as regular in your bike.

Try a small amount of dry-gas and some 87 octane.

So I've been running my 07 695 Monster on 89 octane gas, but yesterday I filled her up with premium 91, on the recommendation of a friend. About a mile from the gas station, making a right turn from a stop, it just puttered out on me and shut off. I don't believe I stalled it (although it's possible), it was more like I opened the throttle and it just drained out and stopped. Wouldn't restart on the first try, but after I waived two cars around me and walked it to the side of the road, it restarted and was fine for the 25 mile ride home.

Since I just filled it up with new gas, I figured it might be the gas. Searched the posts, and here is a confirmation of that belief. Although my manual specifies that I should use 95 - 98 RON (89 - 91). Thoughts?
Title: Re: bad Gas? throttle head tuning needed? I dont know..
Post by: cyberswine on November 07, 2012, 11:29:07 PM
I only use 91 Shell because it's ethanol free locally.  The bike loves it and I have had no problems in over 13K klicks so far.  If you get problems after a fill up I'd think it's more likely an issue with the gas itself rather than the specific octane rating.
Title: Re: bad Gas? throttle head tuning needed? I dont know..
Post by: Slide Panda on November 08, 2012, 05:35:57 AM
Bianca you're in the US right? If so, use the lower numbers - basically regular or mid grade.
Title: Re: bad Gas? throttle head tuning needed? I dont know..
Post by: Bianca on November 08, 2012, 08:51:49 AM
Thanks Cyber n Panda. This was a Chevron station -- closest to work. I'd hate to avoid that station altogether as the only other station nearby is Arco, and I suspect their gas is poor quality. I will avoid the 91 in the future and stick with 89. Cheaper anyway!