Won't idle

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427man
Mariana
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Location: Ashton, Maryland

Won't idle

Post by 427man » Mon Aug 04, 2014 11:51 am

Hello Guys - I just finished the resurrection of my first bevelhead (1981 900 SD Darmah). It had a pair of Delloroto PHFs. It will start on the choke, but I can't get it to idle at all. It seems to rev pretty well and will run if you hold it around 3,000 rpm. No amount of adjusting the mixture or idle (slide) screws makes any difference. So, I figure the idle circuits must be clogged. I pulled the carbs back off and went through them again. Carb cleaner will blast through all the holes I can find as does compressed air. Still no change. I started with the idle mixture 1.5 turns out and went up the 2.5 with no improvement. What am I missing? :(~ Any help/suggestions are greatly appreciated. Thanks
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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abmartin
SSD900 Darmah
Posts: 358
Joined: Tue Apr 10, 2007 5:08 pm
Location: New Brunswick, Canada

Re: Won't idle

Post by abmartin » Mon Aug 04, 2014 3:03 pm

My SS with 40s wouldn't idle either until I replaced the valve seals and the two exhaust valves, put in new piston rings, replaced the rear cylinder camshaft which had been scored because a closing rocker was too tight, readjusted the valve gaps and synchronized the carbs. Now it idles nicely. Sometimes the problem isn't in the carburetors.

Bruce
1979 900SS
Fredericton, NB
Canada

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BevHevSteve
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Re: Won't idle

Post by BevHevSteve » Mon Aug 04, 2014 4:51 pm

have you read this? viewtopic.php?f=26&t=10
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427man
Mariana
Posts: 27
Joined: Thu Mar 13, 2014 3:29 pm
Location: Ashton, Maryland

Re: Won't idle

Post by 427man » Mon Aug 04, 2014 9:26 pm

Oh yes I have. That's where I started. As I said it makes no difference where any of the settings are. the heads were removed and the valves adjusted by a highly qualified bevelhead tech.
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

machten
MHR / S2
Posts: 481
Joined: Sun Oct 29, 2006 8:37 am
Location: Perth, Western Australia

Re: Won't idle

Post by machten » Tue Aug 05, 2014 4:37 pm

Do both carbs fail to be affected by both idle and mixture adjustment? That seems "unlucky".
Did the bike idle OK last time it ran?

A couple of things to look for...

The adjustments wont work if you have air leaks on the intake side. Check your manifold rubbers for leaks - it's worth replacing the rubbers if you haven't already. The other contributor might be the o-ring seal on your mixture screws. Check that it and the small washer are in place and that no old O-rings have been left in the idle screw cavity in the carb.

Idle adjustment can fail to take effect if your slides are worn at the ramps on the slide. You should be able to see the slides lifting when you screw in the idle screw. If they don't then either the idle screws are too short or the adjustment ramps are worn. If the ramps are worn, you can swap the slides between carbs and that will use the ramp on the other side of the slide.

Kev

427man
Mariana
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Location: Ashton, Maryland

Re: Won't idle

Post by 427man » Wed Aug 06, 2014 8:10 am

Thanks. I will double check. All of the o-rings and seals are new. The slides are new too and the adjusters work. You can see them moving the slide. I have them backed out to the point where they just barely start to move as a starting point. You can screw them in as far as they go and nothing happens. The bike will run on the choke (roughly) then is just dies slowly once you flip that off. So I know it's getting gas through the choke circuit. It's not pulling gas through the idle circuit.
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 » Wed Aug 06, 2014 8:17 am

What ever I did, it is both carbs. It has got to be something simple I did or I missed in the rebuild on both carbs.
The bike sat for 8 years in a guy's kitchen. (I traded a 70 Triumph Bonneville for it). The Darmah was not running when I got it.
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 » Wed Aug 06, 2014 8:51 am

is the slide closed all the way or is there a gap (1 side should close all the way the other side there will be a gap due to the angle of the bottom of the slide) when you say you have the slide screw just touching?

When you screw in the slide screw are you completely compressing the spring on it keeping it from screwing in further?

* what I am getting to is that maybe you have an old style carb with new style slides and they by design will not fall all the way down into the bore and need to be machined for clearance to do so. ?
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427man
Mariana
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Re: Won't idle

Post by 427man » Wed Aug 06, 2014 10:26 am

The engine side of the slide is fully closed. The air filter side has a 1/4 moon gap because of the angled cut out on that side of the slide. The slides I got from you are identical to the ones that came out. You can screw in the slide adjusters all the way to full spring compression and visibly see the slide travel up several mm. That looks like it is working as it should. Still no change in rpm. It's like no gas is making it through the idle circuit. All my Amal and Mikuni experience is failing me.

BTW your hydraulic clutch kit is fabulous. :-D It went in easy, and cut the pull effort drastically. Now the clutch feels better than any of my Nortons or my Multistrada. It went from my worst clutch by far to one of my best. Can't wait to figure out this carb issue and ride this thing.
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 » Wed Aug 06, 2014 3:22 pm

HEY - Maybe I have the float levels too low and the idle jets are not picking up gas? Trying to think of anything.
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

Vince
750 Sport [BEVEL]
Posts: 205
Joined: Tue Nov 09, 2004 12:28 am

Re: Won't idle

Post by Vince » Wed Aug 06, 2014 10:02 pm

This is con traversal,and I bet will get some comments.One of the Laverda blokes here uses a couple of number drills and a hand chuck to clean out the idle passages through the body of the carbs.You need to go dead slow,don't remove any metal or brake a bit but it works well.
These passages are straight and link,how else would they be made in the first place.Having the carbs sit around results in bloody hard deposits choking them up,he started doing it even when his ultrasonic cleaner didn't help.BTW I don't know the bit sizes so you need to work that out and its at your own risk.

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

Re: Won't idle

Post by 427man » Thu Aug 07, 2014 8:21 am

I could see doing that on a very crusty carb, but mine were extremely clean. I can get solvent/cleaner to blast through all the passages/jets as well as compressed air. One friend told me he had to go 4 turns out on the idle mixture to get his to run. (That would indicate the idle jet is too small, I suppose.) I went out and tried 4 turns out and got no change. I haven't dropped the bowls yet, but I swear the float must be set too low, not allowing gas to reach the idle jet. If that's not it, maybe I do need to consider the Roto-Rooter technique. :shock:
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 » Thu Aug 07, 2014 8:56 am

427man wrote:BTW your hydraulic clutch kit is fabulous. :-D It went in easy, and cut the pull effort drastically. Now the clutch feels better than any of my Nortons or my Multistrada. It went from my worst clutch by far to one of my best. Can't wait to figure out this carb issue and ride this thing.
Image

For anyone wondering what 427man is talking about, click the link here and read up on it.... The thing does indeed work very well at reducing clutch pull effort tremendously as well as making it easier to find neutral at stop lights etc. And yes we can set you up with whatever type of Brembo master cylinder you want from the choices shown on the order page.
https://store.bevelheaven.com/Engine-Re ... vel-Twins/
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Steve Allen (925)798-BEVL[2385] Ride'm, Don't Hide'm
Ducati/Euro Spares -> https://Store.BevelHeaven.com
Facebook > http://facebook.com/Bevel.Heaven
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BevHevSteve
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Re: Won't idle

Post by BevHevSteve » Thu Aug 07, 2014 8:59 am

Now back to your problem - I think you have a massive air leak somewhere. You have either left out a critical oring on idle and/or mixture screw, or maybe on the pump jet? Did you replace the tiny oring on the pump adjuster screws? You do need to get in there and check the float level too.....
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Steve Allen (925)798-BEVL[2385] Ride'm, Don't Hide'm
Ducati/Euro Spares -> https://Store.BevelHeaven.com
Facebook > http://facebook.com/Bevel.Heaven
Twitter > http://www.Twitter.com/BevelHeaven

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

Re: Won't idle

Post by 427man » Thu Aug 07, 2014 9:19 am

Yep. All new O-rings purchased in kits I got from you. One accelerator pump is working fine, the other not at all.
Not saying you are wrong, and I will check it all again. Whatever I did wrong, I did on both carbs. I know it is something simple. I'll carefully reference the Dellorto exploded diagrams when I'm doing it too.
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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