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willysmjeeps.com :: View topic - M38a1 Idle Issues
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M38a1 Idle Issues

 
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UncleSam
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Joined: Aug 08, 2017
Posts: 2

PostPosted: Wed Aug 09, 2017 6:31 am    Post subject: M38a1 Idle Issues Reply with quote

I have a 1953 M38a1 with a YS Carburetor.
It has trouble idling, but only after running it as high RPM's for an extended amount of time. When I go out and start it for the first time that day, it will sit there and idle all day(it does have a little rough idle).
I just rebuilt the Carburetor with a kit, and the needle it came with was longer than the one that's in it. When I set the float to 1/4" with the needle that's in it, it floods bad. When I tried to put the new(longer) needle in it, I couldn't even get it to adjust to 1/4" with adjusting the metal tab. How should the needle sit in its seat? Should the bottom of it be flush or should it stick out some? I want to make sure I'm using the correct needle.

I'd like to add that I adjusted the original needle to a larger gap than 1/4" and that's where it is now.


Last edited by UncleSam on Wed Aug 09, 2017 10:18 am; edited 1 time in total
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wesk
Site Administrator
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Joined: Apr 04, 2005
Posts: 12751
Location: Wisconsin

PostPosted: Wed Aug 09, 2017 8:58 am    Post subject: Reply with quote

There is no substitution of parts that will work. Who's kit are you using?

Are you following the TM we have loaded to our web site?

http://www.willysmjeeps.com/v2/modules.php?name=Downloads&d_op=getit&lid=142
This manaul was based on the M38's carb YS637S. Differences with the m38A1 carb YS950S are minimal and are explained well enough in the M38A1 parts manual and the attached YS950S spec sheets. Be care when using the TM 9-1826A page 114 fig 60 shows the metering rod spring item BB on the wrong side of the vacuum diaphragm. I have posted a corrected fig 60.


This is the best kit out there:


Here's a closeup of the needle & seat:


Here's the YS950S spec sheet:


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Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php
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UncleSam
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Joined: Aug 08, 2017
Posts: 2

PostPosted: Wed Aug 09, 2017 10:47 am    Post subject: Reply with quote

I got my kit from here: http://www.ebay.com/itm/Willys-M38A1-M170-Carburetor-Master-Rebuild-Kit-Carter-YS-950-Jeep-Carb/171634790931?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

One difference between needles is that the one in it now has a rubber tip and is shorter, the new one is solid brass(I guess) and is a little longer.

Something I noticed when I looked a the TM was the "Tube for balanced venting" is just plugged on my carburetor. Is it essential to have this tube from the air horn to the air cleaner?

I did follow the directions correctly for setting the float, but it floods terrible when I set it to a 1/4". I don't think the extra 64th would make a huge difference, but I could try it. Maybe the float itself is bent and not the tab?

Also, if I set the idle adjustment screw to 1 turn open, it won't idle. I have it open at least a couple turns right now.

Thanks for the help, this site is pretty amazing. I joined it because I have been pretty stomped with this issue. I'm surprised there are people who help and ask nothing in return.
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RICKG
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Joined: Aug 31, 2010
Posts: 1518
Location: SO IDAHO

PostPosted: Wed Aug 09, 2017 12:30 pm    Post subject: Reply with quote

UncleSam wrote:

Something I noticed when I looked a the TM was the "Tube for balanced venting" is just plugged on my carburetor. Is it essential to have this tube from the air horn to the air cleaner?

.


Sam, the YS carb by nature is closed to atmosphere. The fuel bowl MUST be vented, that's where the tube comes in. That one observation may be cause for much of your carburetion problem.
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RICKG MC 51986 DOD 01-52
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