Won't idle

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BevHevSteve
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Re: Won't idle

Post by BevHevSteve » Sun Jun 25, 2017 8:56 pm

Ok your pump diaphragms are probably hard and not working properly. Also just push the pump jets out and make sure they are completely clean and hole not blocked.

I assumed you had rebuilt the carbs but it sounds like you have not and are just spending a bunch of time looking for an easy fix.

You need to take them completely apart, clean out the bodies and use an ultrasonic cleaner on everything, Get a couple complete kits from me, the ones that have everything soft inside the carb included - they cost around $130 for the 2 carbs - reassemble and sync.

I have written up manuals for both the rebuild and the sync you can get on my site. I recommend you get the parts and manuals, do the job right, then you can go enjoy your bike. Use an ethanol treatment and always shut off the taps and run the motor till it dies at the end of each ride.
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Craig in France
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Re: Won't idle

Post by Craig in France » Sun Jun 25, 2017 10:37 pm

herbg wrote:
Sun Jun 25, 2017 3:07 pm
Anyway, it appears that my starting issues are completely connected to not getting squirts of fuel into the carb bodies. Something is stopping from the accelerator pumps from working reliably.

Suggestions on next steps?
Hi Herb,

The accelerator pumps are not involved in either idling or starting. They are there to compensate for a loss of vaccum that occurs in the venturi when the throttle is opened quickly. Or as Dell'Orto puts it:
Pumper text.jpg
Best advice: do as Steve says. Or even better, send them to Steve for him to do. It's not that cleaning & re-building carbs is difficult - but IME it's a job where a little experience goes a long way ;) .

HTH

Craig

herbg
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Re: Won't idle

Post by herbg » Mon Jun 26, 2017 3:29 am

Craig:

Agreed but it seems that the bike starts only when I can give the carbs a few squirts via the accelerator pumps. That doesn't seem to be happening.

I'm hoping I can try to get this going before pulling the carbs and taking them apart.

Cheers,
Herb...
_________________________________
2013 Ducati 1200S Multistrada
1985 Ducati Mille S2
1978 Ducati 900 SS (Blue/Silver Borrani)
1972 Ducati 350 Desmo (Silver Shotgun)
1969 BMW R69S (Earles Fork)

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Re: Won't idle

Post by herbg » Mon Jun 26, 2017 8:23 am

Steve ... I tried pressing out the pump jets with my thumb but they seem a bit tight.

How much force is acceptable to push them out?

Thanks,
Herb...
_________________________________
2013 Ducati 1200S Multistrada
1985 Ducati Mille S2
1978 Ducati 900 SS (Blue/Silver Borrani)
1972 Ducati 350 Desmo (Silver Shotgun)
1969 BMW R69S (Earles Fork)

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BevHevSteve
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Re: Won't idle

Post by BevHevSteve » Mon Jun 26, 2017 8:44 am

whatever it takes. I use a large screwdriver and push a flat up against the end of the jet and lever it in (pushing it out) when they are really stuck. Its the rubber o-ring on it which has stuck itself in there along with gas that has hardened.

This again tells me the carbs need to be completely disassembled, cleaned and put back together with all new soft parts.
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Craig in France
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Re: Won't idle

Post by Craig in France » Mon Jun 26, 2017 11:57 pm

herbg wrote:
Mon Jun 26, 2017 3:29 am
Agreed, but it seems that the bike starts only when I can give the carbs a few squirts via the accelerator pumps.
That's because they're compensating for a problem elsewhere in the carbs*, Herb. So, even if you do get the pumps working and the bike started, you're still going to have to strip and re-build the carbs.

So why delay?

Remember: you can run these bikes without the pumps, should the fancy take you. So, IMO, it doesn't make much sense to waste time on them when there are more significant problems to be fixed.

* E.g. Worn/blocked idle jet, blocked air passage, wrong float heights etc.

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abmartin
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Re: Won't idle

Post by abmartin » Fri Jun 30, 2017 4:00 am

Craig in France wrote:
Mon Jun 26, 2017 11:57 pm
herbg wrote:
Mon Jun 26, 2017 3:29 am
Agreed, but it seems that the bike starts only when I can give the carbs a few squirts via the accelerator pumps.
That's because they're compensating for a problem elsewhere in the carbs*, Herb. So, even if you do get the pumps working and the bike started, you're still going to have to strip and re-build the carbs.

So why delay?

Remember: you can run these bikes without the pumps, should the fancy take you. So, IMO, it doesn't make much sense to waste time on them when there are more significant problems to be fixed.

* E.g. Worn/blocked idle jet, blocked air passage, wrong float heights etc.
I usually give the throttle a couple of good twists before starting my SS with 40mm carbs. Normally starts first kick. I would give the carbs a good cleaning and tuning including making sure the jets and passages are clear. Then just ride the bike for some serious distances to get some fuel through it. Hot starting is usually more difficult and I've never been able to get mine to idle reliably. If the float heights are incorrect my bike refuses to start. I try not to let my bike go on reserve as it seems to cause problems getting fuel to the carbs.

Bruce
1979 900SS
Fredericton, NB
Canada

herbg
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Re: Won't idle

Post by herbg » Sat Jul 15, 2017 5:22 am

You're right ... too many red flags on the operation of these carbs. Embarking on a full rebuild of both to make sure all is correct. Already finding lots of problems.

Thanks!
_________________________________
2013 Ducati 1200S Multistrada
1985 Ducati Mille S2
1978 Ducati 900 SS (Blue/Silver Borrani)
1972 Ducati 350 Desmo (Silver Shotgun)
1969 BMW R69S (Earles Fork)

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abmartin
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Re: Won't idle

Post by abmartin » Sat Jul 15, 2017 7:14 am

Retuned and balanced my bikes 40mm carbs using a Morgan Carbtune. At least for the time being I now have a reliable idle albeit at about 2000 revs. Not sure how the guys on Youtube get their big carbed dukes to idle like a harley.

Bruce
1979 900SS
Fredericton, NB
Canada

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BevHevSteve
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Re: Won't idle

Post by BevHevSteve » Sat Jul 15, 2017 9:03 am

... no air leaks, patience doing the sync procedure and you will get it. Mine idles nicely with big carbs...
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900tlc
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Re: Won't idle

Post by 900tlc » Thu Aug 03, 2017 2:23 pm

Just been reading the woes of engine idling,I had a problem with my GTS not idling correctly.The RPM would go up and down, so we would assume a problem with carburettors/seals etc.
Quite by chance I was reading" Guzziology",which mentioned the same problem. My GTS has the Bosch ignition ,the same as fitted to some Guzzi's.
and Ducati's of course.
The problem was found to be the setting of the pulser ignition coils,they need to be set very accurately,so if you have Bosch ignition,and you have taken the primary case off and accidently knocked the coils,then they need to be reset.
In my case I got the correct tool,and the engine settled to a steady idle. Hope this is of some help,just thought I would share my experience.

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Re: Won't idle

Post by BevHevSteve » Thu Aug 03, 2017 3:10 pm

+ 1 on proper pickup placement being super important....
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