Ducati 900 SS '82 | Front cylinder exhaust running hot

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Kilmer
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Ducati 900 SS '82 | Front cylinder exhaust running hot

Post by Kilmer » Mon Jul 23, 2018 12:19 am

Hi all,

I hope that someone in this forum has some insights that I can use.

My Ducati 900 SS is running very hot on the front cylinder exhaust pipe. So hot that the exhaust pipe is glowing red on an ordinary ride without any specific stress on the engine.

The combustion of both front and rear cylinder is nearly identical.
The compression of both front and read cylinder is nearly identical.
I've had a bevel specialist meassure both cams, beveldrive, valves and timing - all was within specs according to him.
Purchased two new dellortos (40mm), just to make sure that the fault was'nt related to fuelmixture.
The only thing i have not done, is changing pickups..

When measuring heat on the exhaust pipes, there is almost a 100 degree celcius in difference between front and rear cylinder.
When measuring heat on the top near the sparkplug, there is no difference in temps.

Driving the thing is a bid odd too.. At low rpm's the front cylinder backfires alot through the carb and the bike hesitates on throttle. When hitting 4.000 rpm it changes completely.. no misfire, no hesitation.. it pulls like a train and sound awsome..

It is not much to go on, but hope someone has either experiences something like it or has a clue to what is wrong.

Best regards,
Martin
Ducati 916
Ducati 900 SL
Ducati 750 Sport '88
Ducati 900 SS replica
Ducati 900 SS Darmah
Ducati 900 GTS
Laverda SF2
Nordon Dominator 99
Yamaha WR 200

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Gardner
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Re: Ducati 900 SS '82 | Front cylinder exhaust running hot

Post by Gardner » Mon Jul 23, 2018 8:03 pm

Hi Martin, it sounds like an ignition problem, the front cylinder is firing late and the combustion flame is going out the exhaust valve which turns
the pipe red. If the pick up wires have not been replaced yet, I would start there.
1978 SD Darmah
1979 SSD Darmah
1981 900SS
2017 Desert Sled
1982 Bimota HB2

Kilmer
Cucciolo - the Lil Pup
Posts: 15
Joined: Wed Aug 17, 2005 11:53 am
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Re: Ducati 900 SS '82 | Front cylinder exhaust running hot

Post by Kilmer » Mon Jul 23, 2018 9:20 pm

Hi Gardner,

Thank you for the input - I'll check with the specialist who had the engine checked and hear if wiring is old or new.
Will post again when I have an update :)

Best regards,
Martin
Ducati 916
Ducati 900 SL
Ducati 750 Sport '88
Ducati 900 SS replica
Ducati 900 SS Darmah
Ducati 900 GTS
Laverda SF2
Nordon Dominator 99
Yamaha WR 200

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Gardner
Cucciolo - the Lil Pup
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Location: Davenport, Ia

Re: Ducati 900 SS '82 | Front cylinder exhaust running hot

Post by Gardner » Tue Jul 24, 2018 8:14 am

If you look at the wires up top under the tank at the Bosch boxes and inside the clutch cover they most likely will look okay.
It's when you go into the black insulation where it exits the clutch cover that you find the individual wire insulation has decayed and now the pick up wires are cross communicating causing all sorts of strange running problems.

Mark
1978 SD Darmah
1979 SSD Darmah
1981 900SS
2017 Desert Sled
1982 Bimota HB2

Lumpy
SD900 Darmah
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Re: Ducati 900 SS '82 | Front cylinder exhaust running hot

Post by Lumpy » Tue Jul 24, 2018 5:37 pm

I`m with Gardner on that one. My SS did the same thing and it was the insulation on the ignition pick up wires that had broken down with age. Either way they are worth replacement if they haven't been done already. They will give issues eventually.........

Kilmer
Cucciolo - the Lil Pup
Posts: 15
Joined: Wed Aug 17, 2005 11:53 am
Location: Denmark

Re: Ducati 900 SS '82 | Front cylinder exhaust running hot

Post by Kilmer » Tue Jul 24, 2018 9:20 pm

Called the Ducati specialist yesterday and asked him if any work was done to the pickup wiring.
He confirmed that both wires endeed had been in a sorry state, and that the wires had been replaced.

He purposed that I altered the idle jet setting on front cylinder wit the purpose of settling the front cylinder with a more rich mixture.

I guess pickups and pickup wiring could still be the problem, it the job was bodged in some way..
Can timing be off on just one cylinder, even if all marks are set correctly?

/Martin
Ducati 916
Ducati 900 SL
Ducati 750 Sport '88
Ducati 900 SS replica
Ducati 900 SS Darmah
Ducati 900 GTS
Laverda SF2
Nordon Dominator 99
Yamaha WR 200

robax
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Re: Ducati 900 SS '82 | Front cylinder exhaust running hot

Post by robax » Tue Jul 24, 2018 10:54 pm

Check and see if you're getting any advance. Mine was running like this with both rewired and brand new pickups.

Mine's off being worked on elsewhere now after my own efforts failed to resolve the same sort of issue. I couldn't see any advance after several attempts to rectify it. It'll be the ignition, but could be the polarity, or maybe the electronics boxes. Not too sure but I'll know when I get it back.
Rob
Rob - NZ
-------------------------------------------------
1982 Ducati 900ss

Kilmer
Cucciolo - the Lil Pup
Posts: 15
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Location: Denmark

Re: Ducati 900 SS '82 | Front cylinder exhaust running hot

Post by Kilmer » Thu Jul 26, 2018 9:48 pm

Hi Rob,

Thank you for your post. I'm both glad and sad to find another Ducati owner with same type of issue.
I will try and check timing and advance on mine in a couple of days.

If you manage to get the issue resolved, please do tell about it, when the bike returns to you *-*

Martin
Ducati 916
Ducati 900 SL
Ducati 750 Sport '88
Ducati 900 SS replica
Ducati 900 SS Darmah
Ducati 900 GTS
Laverda SF2
Nordon Dominator 99
Yamaha WR 200

ducadini
750 Sport [BEVEL]
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Location: Antwerpen

Re: Ducati 900 SS '82 | Front cylinder exhaust running hot

Post by ducadini » Fri Jul 27, 2018 4:39 am

Last winter after a cold damp night outside near the Waterfront, my Alazzurra didn't start like it used to.
When I got it running I drove slowly the 4 km to the highway.
While waiting at a trafficlight, I saw that my vertical exhaust was yellow (about the same as those smileys here on the right).
Got it home and check the wiring of the pickups : insulation cracked, spray (salt) had "greened" the wires and probably shortcircuited some.
Cleaned the wires, aplied some tape and all was back normal, no further damage (still ran as a +30 year +75k old bike).
That's how easy it is to mess up the ignition.

ciao
ducadini
Nego i ricordi peggiori
Richiamo i migliori pensieri

wdietz186
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Re: Ducati 900 SS '82 | Front cylinder exhaust running hot

Post by wdietz186 » Sun Jul 29, 2018 4:55 am

If the wiring proves to be OK. try switching the Bosch amplifiers cyl. to cyl. As reliable as Bosch equipment seems to be, they are over 30 yrs. old and as we used to say in the old days "never trust anyone over 30". I've replaced about 4 of them in the past couple of years for various running issues and it sounds like the advance circuit doesn't.

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