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Feb 23, 2020, 11:55 PM
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pathfinder's Avatar
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Discussion

low speed adj.


....Was this carb. designed this way or is there something missing. There is no adj. screw for the low speed adjustment.

Blurry pics sorry.
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Feb 24, 2020, 06:24 AM
Still gassin' it.
I am anyway not seeing a throttle lever, but my instinct would say, that that protrusion sticking out of the barrel should have been your LS needle.
Why it does not have a screwdriver-slot, beats me.
Feb 24, 2020, 06:40 AM
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surfer_kris's Avatar
The lever is in the picture, it is the clamp type.

I don't think that the throttle barrel will move in and out on these ones (easy to check though).
Check the spraybar, I think there is a cat's eye style and a counter slot that can be turned/adjusted.
Feb 24, 2020, 09:39 AM
Master re-kitter
SRQFlyer's Avatar
Hmmmm - anybody think that the "outside" end of the low speed needle is broken off? The picture is fuzzy, but it looks to be uneven and rough.
Jim
Feb 24, 2020, 11:38 AM
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surfer_kris's Avatar
It is not broken off. You can see the number 3 stamped/written on it.

I have never had any of these engines myself, but I believe they came with different inserts in order to adjust the low- and mid-range. So possibly they came with three different ones, and it has the size number three in there right now.
Feb 24, 2020, 11:42 AM
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pathfinder's Avatar
Thread OP
might be a better picture.
There is nothing broken. There is a #3 stamped where the screw slot should be for the low speed adj.
When I slide the throttle arm back on you can see the #3 inside the throttle arm.
It has the #74 stamped on the front of the carb.
Feb 24, 2020, 04:00 PM
Master re-kitter
SRQFlyer's Avatar
Aha! That would make setting the low end a bit laborious.
Feb 24, 2020, 04:14 PM
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pathfinder's Avatar
Thread OP
I cranked it up today .It runs really good. It just doesn't have a snappy throttle. It will idle a good long time but will eventually load up a shut off. It will run just above low idle all day long..

RedMax 10% with castor added , Fox long reach idle bar glow plug, APC 11-8 prop.




































5
Feb 24, 2020, 05:55 PM
AMA 46133
SeismicCWave's Avatar
Quote:
Originally Posted by pathfinder
....Was this carb. designed this way or is there something missing. There is no adj. screw for the low speed adjustment.

Blurry pics sorry.
Can that stud with the number 3 stamped on it turn independently to the throttle barrel? If it can then it is some sort of adjustment. If it is an adjustment then you are missing a piece.
Feb 24, 2020, 06:33 PM
Pro Hoarder
turbonut's Avatar
They are interchange able idle mixture units
See here..all the way at the bottom a photo of your parts ..Series 72 carb. Number 3 is the mid or standard unit
http://www.vrhc.co.uk/images/Heli%20...072%20carb.jpg
Last edited by turbonut; Feb 24, 2020 at 06:41 PM.
Feb 24, 2020, 07:24 PM
AMA 46133
SeismicCWave's Avatar
Quote:
Originally Posted by turbonut
They are interchange able idle mixture units
See here..all the way at the bottom a photo of your parts ..Series 72 carb. Number 3 is the mid or standard unit
http://www.vrhc.co.uk/images/Heli%20...072%20carb.jpg
Thank you. Finally the mystery is solved. So the OP not only is missing one piece but two more pieces of the carburetor. According to the article there should have been three idle mixture unit. Thus the stamped number 3 on the end. I am sure the other two pieces would have the stamped numbers 1 and 2.

So this #74 carb OP has is a carry over from the Series 72 carb.
Feb 24, 2020, 07:29 PM
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turbonut's Avatar
I wonder how many people still have all the mixture units ..seems like the first thing to loose in to the forever gone box
Latest blog entry: In flight
Feb 24, 2020, 07:56 PM
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pathfinder's Avatar
Thread OP
Quote:
Originally Posted by turbonut
They are interchange able idle mixture units
See here..all the way at the bottom a photo of your parts ..Series 72 carb. Number 3 is the mid or standard unit
http://www.vrhc.co.uk/images/Heli%20...072%20carb.jpg



It is series a 72 carb. I said in a post it had 74 on the carb. Wrong on my part, , it has 72 on the front. I believe I have those other pieces. I will look and see .It will be interesting to see what effect it has on the way it runs.. Thank you for that article. I keep forgetting about Peter Chinn's article's.
Feb 24, 2020, 11:21 PM
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turbonut's Avatar
With it at idle try the pinch test..Squeeze the full line off and wait for it to quit..Large RPM rise means it is too rich..No rise just quits is too lean..slight rise is a good sign
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Feb 25, 2020, 01:20 AM
AMA 46133
SeismicCWave's Avatar
Oops, I spoke to soon. The numbers per the article is 2, 3 and 4. So the 3 meant it is the middle of the road richness for idle. 4 is rich and 2 is lean.


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