m38a1/ys950 hard start

1952 - 1968, M38A1, M170, questions, discussions, regarding anything related to the M38a1 series.
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Heehaw
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m38a1/ys950 hard start

Post by Heehaw » Tue Sep 13, 2022 3:44 am

Have m38a1 with ys 950 . Been fight hard start/running rich issues. New points & condenser on iay 12v distributor . Rebuilt carburetor with good kit. Would start but not idle below 800-1200.with surges. Disconnected pcv and clean it. Hooked up vacuum guage to manifold I noticed if I try and start it with choke out & pedal down there is no vacuum at manifold till I let off the pedal
Is this normal or is one the circuit in the carb plugged.


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Scoutpilot
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Re: m38a1/ys950 hard start

Post by Scoutpilot » Tue Sep 13, 2022 3:58 am

Did the kit come with two metering rods? Which one did you install?
Did the kit come with three diaphragm springs? Which one did you install with the accelerator pump diaphragm?
Barring those two items you may just need to readjust and balance the idle stop screw and mixture screw settings.
'70-'71 'A' Batt., 377th FA, 101AB
(Slicks and LOH's)(Col's LOH Pilot)
'71-72 CHARLIE TROOP,
16TH AIR CAV, 1ST AVN BDE (AEROSCOUTS)
LOW LEVEL HELL.
'46 CJ2A
'47 CJ2A
'48 CJ2A
'48 B1PW126
'69 CJ5

Heehaw
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Re: m38a1/ys950 hard start

Post by Heehaw » Tue Sep 13, 2022 5:04 am

Scoutpilot, thanks kit came with 2 meter rods . Remember Measuring them and the springs. But it seems like metering rod .078+ change and the one that came out was .0802. Don't remember if the old one back in or use the closest one in the kit.

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Scoutpilot
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Re: m38a1/ys950 hard start

Post by Scoutpilot » Tue Sep 13, 2022 8:48 am

Find the one you didn't use and note the number on the square part of it.
'70-'71 'A' Batt., 377th FA, 101AB
(Slicks and LOH's)(Col's LOH Pilot)
'71-72 CHARLIE TROOP,
16TH AIR CAV, 1ST AVN BDE (AEROSCOUTS)
LOW LEVEL HELL.
'46 CJ2A
'47 CJ2A
'48 CJ2A
'48 B1PW126
'69 CJ5

Heehaw
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Posts: 13
Joined: Wed Aug 18, 2021 2:43 pm
Location: Cypress tx

Re: m38a1/ys950 hard start

Post by Heehaw » Wed Sep 14, 2022 2:51 am

I'll look, but seem to be fixed .was ignition and vacuum related. Never look at the pcv valve, had 5/16 hose barb mated to a 3/8. Caused the hard start and surging.


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