Won't idle

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BevHevSteve
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Re: Won't idle

Post by BevHevSteve » Thu Aug 07, 2014 9:35 am

please do the following in regards to the 1 pump ...

* pull out that pump jet and stick a carb spray cleaner straw inside and squirt out to make sure the tiny hole isn;t blocked then reinstall.
* remove the non return that is on top of the pump housing.
* drop a teaspoon of gas inside
* use finger to block non return hole (just put your finger over the top to seal)
* pull (only) that throttle cable up and hole 3 seconds then gently bring back down (do NOT let slide snap down)
* you may have to repeat a few times to get fuel to squirt out of the pump jet.
* if you repeat 6 times with no gas squirting just add more gas and keep repeating until it does.

That will solve 1 problem. Now keep looking for the other(s)..
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427man
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Re: Won't idle

Post by 427man » Thu Aug 07, 2014 10:08 am

Ok. I tried most of these steps except the hold and slow release. Will let you know. Thanks, I appreciate the help. This bike is so close...
1981 Ducati 900SD Darmah
2007 Ducati 1100S Multistrada
1973 Honda CL350
1979 Honda CBX
2001 Kawsaki ZRX1200R
1968 Norton Atlas
1973 Norton Commando 750
1974 Norton Commando 850

Ray O'Donohue
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Re: Won't idle

Post by Ray O'Donohue » Fri Aug 08, 2014 6:22 am

Silly question:Is it possible to put the slides in backwards? You mentioned the crescent-shaped gap...worth a look anyway.I did it on a Honda once,arrgh.Wouldn't idle.

machten
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Re: Won't idle

Post by machten » Fri Aug 08, 2014 6:40 am

The symptoms you're describing are still consistent with an air leak on the intake side....you have checked idle screws have a washer fitted behind the o-rings, right?

The other possible source of a leak is the manifold vacuum tuning screws...they need to be sealed properly.

Kev

Ray O'Donohue
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Re: Won't idle

Post by Ray O'Donohue » Fri Aug 08, 2014 6:54 am

Unless you have plenty of compression-a thumb in the plug hole will answer that question-do a quick check of valve timing.Maybe you're a tooth or two off or have sheared key somewhere..Quick-check the valve timing at TDC on overlap.Both valves/rockers should be open,and in about an equal amount.
Last edited by Ray O'Donohue on Fri Aug 08, 2014 7:29 am, edited 1 time in total.

machten
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Re: Won't idle

Post by machten » Fri Aug 08, 2014 7:14 am

Here's a startup of a Darmah engine last week with a new top end after a four year holiday. First start up. The relevant part is that you should hear the intake sucking like this before start if things are healthy. You can also hear the effect of choke on and choke off.

https://vimeo.com/102397663

Kev

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BevHevSteve
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Re: Won't idle

Post by BevHevSteve » Fri Aug 08, 2014 8:58 am

Ray O'Donohue wrote:Silly question:Is it possible to put the slides in backwards?.
No it is not possible to do this as there is a pin inside the carb bore and a groove in the slide to assure the slide goes in the right way and can't rotate around.
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Re: Won't idle

Post by Ray O'Donohue » Fri Aug 08, 2014 9:05 am

Yes,but if there is right and a left slide (is there? been many years for me.) you can do it.Probably not.

machten
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Re: Won't idle

Post by machten » Fri Aug 08, 2014 9:06 am

Not to mention where the pumper arms might fit. It's possible on some "non pumper" Dellorto's, though Ray.

Kev

427man
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Re: Won't idle

Post by 427man » Fri Aug 08, 2014 9:32 am

machten wrote:The symptoms you're describing are still consistent with an air leak on the intake side....you have checked idle screws have a washer fitted behind the o-rings, right?

The other possible source of a leak is the manifold vacuum tuning screws...they need to be sealed properly.

Kev
Yes, there is a washer, but now I can't remember if I put it on the spring side or carb side of the O-ring. I will check. I will also check to see if the O-ring O.D. is too small. The vacuum plugs on the manifolds were in tight with a small washer/seal.
1981 Ducati 900SD Darmah
2007 Ducati 1100S Multistrada
1973 Honda CL350
1979 Honda CBX
2001 Kawsaki ZRX1200R
1968 Norton Atlas
1973 Norton Commando 750
1974 Norton Commando 850

427man
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Location: Ashton, Maryland

Re: Won't idle

Post by 427man » Fri Aug 08, 2014 9:36 am

Ray O'Donohue wrote:Unless you have plenty of compression-a thumb in the plug hole will answer that question-do a quick check of valve timing.Maybe you're a tooth or two off or have sheared key somewhere..Quick-check the valve timing at TDC on overlap.Both valves/rockers should be open,and in about an equal amount.
Nope. The heads were pulled, valves adjusted and heads reinstalled by a local Ducati racer/tech with decades of experience. As I said, the bike fires right up, will run on the choke, will run and rev above 2,500 rpm. It just won't idle.
1981 Ducati 900SD Darmah
2007 Ducati 1100S Multistrada
1973 Honda CL350
1979 Honda CBX
2001 Kawsaki ZRX1200R
1968 Norton Atlas
1973 Norton Commando 750
1974 Norton Commando 850

427man
Mariana
Posts: 27
Joined: Thu Mar 13, 2014 3:29 pm
Location: Ashton, Maryland

Re: Won't idle

Post by 427man » Fri Aug 08, 2014 9:40 am

I will keep trying. Tonight I am supposed to be packing up to go on vacation, but maybe I can get a hour in the shop. I will lose 2 weekends of being able to work on the problem. I'd like to stay home 1 extra day or come home a day early but NOOOOOO. My wife doesn't understand me. :roll:
1981 Ducati 900SD Darmah
2007 Ducati 1100S Multistrada
1973 Honda CL350
1979 Honda CBX
2001 Kawsaki ZRX1200R
1968 Norton Atlas
1973 Norton Commando 750
1974 Norton Commando 850

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BevHevSteve
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Re: Won't idle

Post by BevHevSteve » Fri Aug 08, 2014 7:01 pm

Responding to a couple of previous posts:

On both the mixture screw and idle screw, take the spring and slide it over the screw then slide on the washer then the appropriate o ring. The purpose of the washer is to keep the spring from gouging the o ring.

Regarding left and right sides: yes there are left and right side CARB BODIES but there is no difference on the slides - they go in only 1 way only - there is no way to rotate around and install 180 off.

Yes if you have let the throttle slap closed and have worn out the idle adjuster ramp on the slide then you can take the slide out and put back into the opposite side carb - now that worn ramp does nothing as the adjuster screw rubs against the opposite ramp now.
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427man
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Re: Won't idle

Post by 427man » Sat Aug 09, 2014 8:45 pm

BevHevSteve wrote:Responding to a couple of previous posts:

On both the mixture screw and idle screw, take the spring and slide it over the screw then slide on the washer then the appropriate o ring. The purpose of the washer is to keep the spring from gouging the o ring.
I had a few minutes before leaving to work on the bike. I pulled out the mixture screws and found they we assembled correctly. O-ring first, then the washer and spring. I changed out the O-ring for one in the rebuild kit that had a slightly larger outside diameter. The inside diameter was the same. They were a tighter fit in the carb body. It appeared this would provide a better seal. I reset the screws to 1.5 turns out. No change. I went to 2.5 turns. Still no change. If there is a leak, this I not the source. I will move to the carb to manifold and manifold to head seal next. I will try running the engine and spraying WD40 at those areas. An increase in RPM will indicate a leak.

I have not checked the float height yet, but I think it is unlikely the float could be that low that the jet is not reaching the fuel in the bowl.
1981 Ducati 900SD Darmah
2007 Ducati 1100S Multistrada
1973 Honda CL350
1979 Honda CBX
2001 Kawsaki ZRX1200R
1968 Norton Atlas
1973 Norton Commando 750
1974 Norton Commando 850

427man
Mariana
Posts: 27
Joined: Thu Mar 13, 2014 3:29 pm
Location: Ashton, Maryland

Re: Won't idle

Post by 427man » Fri Nov 07, 2014 10:20 am

Well Gentlemen -

After nearly 3 months I have finally figured out the problem (actually it was figured out for me). After returning from vacation I let the bike sit neglected while I tended to other issues on other bikes. Since I tried everything everyone said without success, I just ignored it for a while. Anyway, I finally threw it in the trailer and took it to the local Bevel Head expert. He has decades of experience working on and racing these bikes. The bike fired right up on choke as usual. Choke off, it sputtered and died. His response was "Oh, these bikes are really cold blooded. You have to get them really warmed up." Once it was warm it idled fine. :oops: I thought at some point in my life I would stop being reminded that I'm an idiot. Guess not.

I plan to ride it Sunday for the first time. Thanks for everyone's input and help.
1981 Ducati 900SD Darmah
2007 Ducati 1100S Multistrada
1973 Honda CL350
1979 Honda CBX
2001 Kawsaki ZRX1200R
1968 Norton Atlas
1973 Norton Commando 750
1974 Norton Commando 850

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