Author Topic: 350 Engine - Tickover adjustment problem  (Read 1971 times)

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Online moonpup

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Re: 350 Engine - Tickover adjustment problem
« Reply #20 on: June 08, 2018, 04:56:49 PM »
             
Thanks very much, Mike, for sectioning the idle circuit, good job,very helpful. What is the length of the 2.5mm section hole.   Looks like a shouldered rivet could be used to restore the seat and would make a better job than the brass tube I used. I was worried it might partially blank the the carb drilling that runs back to the pilot jet.  ...snip....


Overall, it's pretty close to the 4mm you thought it'd be. I can't be real accurate though since this was the carb I was experimenting on with the brass tubing you suggested. So the hole has been drilled out a bit and had several attempts at inserting the brass tubing in there which stretched and marred it up a bit.  Sorry....
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Re: 350 Engine - Tickover adjustment problem
« Reply #21 on: June 08, 2018, 05:33:37 PM »
           
....snip....   I still feel the differences you are finding between the early/late carbs are just normal production variations. I can't really see any benefits from an engineering point of view. The needle has to be 'bottomed out' to be able to set the 'turn out'. The main problem is the spring strength which makes it difficult to feel when the screw tip just touches the seat and the carb alloy is quite soft, resulting in the orifice being easily enlarged.
       Another piece in the jigsaw,  Brian
   

To me, the "engineering point of view" would be lessening the chance of over-tightening and damaging the seat.

I measured the distance between the top edge of the casting and the top edge of the screw itself first without the spring and fully seated and then with the spring on and screwed in until I felt resistance from either it being seated or the spring bottoming out. The measurements were virtually identical. So with the spring on there's no possibility of bottoming out and damaging the seat and if it wasn't fully seated, it's close enough that when you "turn out", it's probably like you said... "Fine tuning the airscrew doesn't really make that much difference."

I need to get my hands on a "after21H" carb body to cross-section!  ;D
« Last Edit: June 08, 2018, 05:43:45 PM by moonpup »
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Offline BRT-GTR

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Re: 350 Engine - Tickover adjustment problem
« Reply #22 on: June 08, 2018, 06:11:05 PM »
            OK, I understand what you are saying re the spring acting as a limit stop on the screw. That would require very accurate machining and forming of all the parts and drillings required. Not impossible but unlikely on a high volume production basis, in my opinion.   
  At least one of the airscrew seats on my NOS carbs had  been previously overtightened to the point where the airscrew was ineffective.
       We might have to agree to disagree on this one but again many thanks for the carb section. If I attempt another seat repair, I will post full details.
              Brian.
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Offline coxy

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Re: 350 Engine - Tickover adjustment problem
« Reply #23 on: June 08, 2018, 07:04:08 PM »
nice autopsy DR Moonpup
ive never had a problem with this but thanks for the posts
I'm working on a set of newer carbs at the moment
Mike if you have a set of new and old bowls laying around it might be worth a photo
I cant upload a picture from my phone and have lost the camera for my computer
cheers

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Re: 350 Engine - Tickover adjustment problem
« Reply #24 on: June 08, 2018, 07:31:25 PM »
Andrew, I don't have any nos bowls, just the ones on the carbs and a couple extra that I've cleaned up & lapped. (see photo below)

Is there something in particular you're looking to verify in regards fuel/float bowls? I'm not aware of any differences for those.

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Re: 350 Engine - Tickover adjustment problem
« Reply #25 on: June 09, 2018, 08:58:15 AM »
             Here's a couple of float bowl variations that I found on my spare carbs.

      First pic,  note only single starter circuit boss on right carb - may be from a pre 1000 engine. All my other bowls have two bosses.

      Second pic,  note strengthening webs on front of right carb bowl - I believe this is a late carb and an attempt to reduce flange warping.  There are no webs added to the rear flange.
            Brian
           
« Last Edit: June 09, 2018, 09:06:00 AM by BRT-GTR »
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Re: 350 Engine - Tickover adjustment problem
« Reply #26 on: June 09, 2018, 09:30:16 AM »
Wow, thanks Brian.... I learned something new this morning!  banana

There are at least 3 different bowls.  8)
1- single boss/no webbing
2- double boss/no webbing
3- double boss/webbing
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Re: 350 Engine - Tickover adjustment problem
« Reply #27 on: June 09, 2018, 04:45:03 PM »
the later model carb with the two enriching tubes ,one is blanked off at the base from casting .unless mine is blocked with crud it seems to serve no purpose

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Re: 350 Engine - Tickover adjustment problem
« Reply #28 on: June 09, 2018, 07:40:20 PM »
Great work Mike on the cross section of the carb!

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Re: 350 Engine - Tickover adjustment problem
« Reply #29 on: June 09, 2018, 08:09:09 PM »
Great work Mike on the cross section of the carb!

Thanks..... it was actually kind of fun!
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Re: 350 Engine - Tickover adjustment problem
« Reply #30 on: June 09, 2018, 08:11:52 PM »
the later model carb with the two enriching tubes ,one is blanked off at the base from casting .unless mine is blocked with crud it seems to serve no purpose

Yep, that side is non-functioning and serves no purpose for our bikes.
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