rough running

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dcdrive
Cucciolo - the Lil Pup
Posts: 11
Joined: Wed May 26, 2010 6:36 pm
Location: Holly MI.

rough running

Post by dcdrive »

I could use some input as i have been reading these post to help solve my problem with my 1981 Darmah.I have put carb kit in have new wires and good readings on Bosch ignition pick-ups. Got a sync pro and started to get it running and have good readings at idle and at 2500 rpm's. Top cylinder runs alot hotter, have new exhaust and intake gaskets have checked for leaks in manner explained here ...alll good. this cylinder has strong exhaust note ,sounds good... Lot's of sputtering back fire at higher rpm's will idle at 1000 rpm's till a hick-ups comes along.I manualy lifeted the slides on both carbs and the top or hot cylinder rpm's will change with just a small movement, the other the cooler runner nothing changes when i lift the slide no matter how much i move it. Yet it will idle along. Have switched the bosch boxes and still same. Thanks Dave

rwhc80
750 GT
Posts: 174
Joined: Sat May 16, 2009 7:19 am
Location: Melbourne Australia

Post by rwhc80 »

Hi dcdrive,

Was the bike running the same way prior to the carb kit, or has this occurred since ? also were the new pickup wires done at the same time as the carb kit ?
Sometimes just a process of elimination, but it will help to know what's been changed since the problem arose,

Cheers
Rick
I have desmo disease, I just hope they never find a cure !!!

dcdrive
Cucciolo - the Lil Pup
Posts: 11
Joined: Wed May 26, 2010 6:36 pm
Location: Holly MI.

rough running

Post by dcdrive »

Hey Rick
Did all at the same time, but i do think that i was acting a bit strange when i last drove . But can not remember as this bike has been in my garage sitting for 28 years, just kinda got busy with other things and havent had time to look at bike. Thanks ...Dave

Crashfangio
Mariana
Posts: 35
Joined: Fri Aug 15, 2008 6:48 pm
Location: Melbourne Australia

Post by Crashfangio »

Regarding the hot/cool cylinder, you will probably find that the cool (horizontal?) cylinder is not sparking/firing correctly. When you lift the individual carb slide, that particular cylinder should increase in revs. I had exactly the same dramas with my 750GT caused by a fouled plug.

To confirm, have a sniff around the horizontal cylinder pipe tip (don't burn your nose!!) while it's running or just after shut-down to determine whether it's getting fuel. You should be able to smell the fuel clearly.

If you can smell fuel, throw the sync pro away just for now. Concentrate on getting both cylinders running correctly independant to one another. I have found that removing the good cylinder spark plug helps to isolate the lame cylinder of any resistance, allowing you to at least get it running.

Once you have it running, replace both plugs but remove one lead at a time to set the idle speed and mixture to a reasonable standard. Now grab the sync pro and go through the carb balance procedure as detailed in this forum.

Finally, when you start this process, make sure you have a new pair of plugs and a fresh tank of fuel. Fault finding is a process of elimination, bare in mind it may be a combination of two or more problems.

Good luck, let us know how you get on...[/i]
73 750GT

Lumpy
SD900 Darmah
Posts: 327
Joined: Sun Mar 25, 2007 5:49 am

hot pot

Post by Lumpy »

Dunno but the hot pot sounds timing issues to me. I had to change the pick up wires on my 82 SS due to one pot running really hot and loss of power. Sure way of telling is to hook up a degree wheel and use a timing light if you have or can get access to both.

dcdrive
Cucciolo - the Lil Pup
Posts: 11
Joined: Wed May 26, 2010 6:36 pm
Location: Holly MI.

rough running

Post by dcdrive »

Thanks for the in put on my Darmah,
Isolated both cylinders like rick suggested. Horizonal cyclinder will only run when i shoot fuel down carb or when choke is on. Dismantled carb cleaned and inspected ..all looked fine to me, but then only second time apart. The first when i put a rebuld kit in. It looks a little worn and dingy all looks to be there., accellarotor pump works fine. Would changing some of the jets be a direction to go next?.. will apreciate some input as this forum is getting me closer to solving this issue...Thanks for the time ..Dave...

User avatar
abmartin
SSD900 Darmah
Posts: 358
Joined: Tue Apr 10, 2007 5:08 pm
Location: New Brunswick, Canada

Post by abmartin »

Here's a quote from Stephen Eke's book:

"The commonest fault of all on Ducati V-twins is a refusal to run on the front cylinder, this is a positive indication that the carbs are not properly set."

My own experience confirms this - if you have properly synched the carbs is the float in the front one sticking or set too low?

Bruce
1979 900SS
Fredericton, NB
Canada

Crashfangio
Mariana
Posts: 35
Joined: Fri Aug 15, 2008 6:48 pm
Location: Melbourne Australia

Post by Crashfangio »

Dont muck with the jet sizes (providing they are in the ballpark), just ensure that there are no blockages.

You mentioned a backfire. Was this comming from the front cyl?? If so it could be an indication that it is too lean (ie not getting fuel) and this assertion is supported by the fact that it will only run with the choke on or with a squirt from the pump.

Start by looking at the pilot or idle circuit, is the idle mixture screw turned out far enough?? I got caught out with the same drama, my front 32mm Dellorto mixture screw needs to be roughly 2 turns out, not the 1.5 as suggested as a benchmark. Start at 2 - 2.5 turns out and see if it runs as a benchmark. Check your float heights while your at it.

Now you have isolated the problem it won't take long to get the front cylinder ticking over on its own. Once you achieve this start worrying about syncing etc. Also, download the Dellorto PDF manual, it helps explain how the different circuits influence one another throughout throttle progression. Its an interesting read.

Cheers, Dave.
73 750GT

rwhc80
750 GT
Posts: 174
Joined: Sat May 16, 2009 7:19 am
Location: Melbourne Australia

Post by rwhc80 »

Dave,

sounds like you're getting close to solving !! ....good info from Crash, dont mess with the jets at this stage.
You didn't mention whether the front carb bowl was full of fuel when you pulled it apart the second time ???

Cheers
RIck
I have desmo disease, I just hope they never find a cure !!!

dcdrive
Cucciolo - the Lil Pup
Posts: 11
Joined: Wed May 26, 2010 6:36 pm
Location: Holly MI.

rough running

Post by dcdrive »

Thanks for all the input-rick-crash-lumpy-abmartin/ i am chasing down the issue with all the good input from all of you. The bowl was full of fuel when i removed and that is what prompted me to think that jets to be the problem. I cleaned the jets carefully with cleaner then dryed finished with blast of air through out. Am getting fuel to carb just not to cylinder, when i ran with choke on it sounded strong so i think a good spark is there and it ran alone without the other cylinder helping as i removed plug. The horizonal cyclinder was the one backfireing . Thanks again for getting involved and sharing that Ducati knowhow with me Dave..

dcdrive
Cucciolo - the Lil Pup
Posts: 11
Joined: Wed May 26, 2010 6:36 pm
Location: Holly MI.

rough running

Post by dcdrive »

Evening all,
I looked at what crash had to say and applied it to carbs and came up with a plan backed out idle speed screw alot to just get horizonal running . Ended up with the solution to it . Might sound wrong but idle screws are set at 5 turns out and the thing idled fine got the horizontal cyclinder to heat up for the first time since started working on bike . The dell-orto' information on this site helped alot didn't know it was here, thanks for the heads up again crash./, There it listed either a mixture-adjusting screw or with an air adjusting screw. Now i will run onward to the carb sync and what ever else that crops up. ,/Dave

rwhc80
750 GT
Posts: 174
Joined: Sat May 16, 2009 7:19 am
Location: Melbourne Australia

Post by rwhc80 »

Great news Dave,

Glad to hear your on your way.

With the bike sitting for so long it was almost guaranteed the carbs would need some attention, the idle circuits are particulary prone to gumming up if they sit for a long time, and I think 28 years constitutes a reasonable lay off.

keep us informed, especially on your first ride ???

Cheers
Rick.
I have desmo disease, I just hope they never find a cure !!!

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