m38a1 carter carb i.d.

wingnut · Post by **wingnut** » Sat Jan 03, 2015 1:38 pm

hi the carb on my a1 looks to be brand new but runs extremly rich. i am wondering if it could be one of those overseas copies mentioned elsewhere on this forum it has carter YS cast in the bowl and also a plastic white decal on top of the air intake showing a date of march 2003 could this be a m38 carb on a m38a1 throttle base.Best regards Bernard.

Post by **wesk** » Sat Jan 03, 2015 2:52 pm

Without seeing what you have and seeing some dimensions of what you have we can't help you much.

You can start in my photo album with hundreds of detailed technical photos and brush up on the fuel system in our Downloads section where the manuals are free for you to download.

http://www.willysmjeeps.com/v2/modules. ... _album.php

http://www.willysmjeeps.com/v2/modules. ... =Downloads

Generally too rich equates to too much gas or not enough air.

too much gas would be caused by high fuel pressure, bad or stuck float, deteriorated old style rubber diaphragms in the metering or accelerating pump systems (caused by the effect of modern ethanol fuels on the old rubber products.).

Not enough air is the result of over choking (make sure choke plate opens all the way) make sure the entire induction system is clear. Don't overlook nests in the intake manifold and the crossover pipe and excess oil in the bottom of the oil bath air filter.

Trying to use either carb's bowl assembly on either carb's base results in air/fuel metering issues since the air and fuel passages do not align.

This is the YS950S (M38A1) carb.
The diapragms I mention are Y & DD. The gasket Q will help show you any mismatch between E & X.

Here you see the two compared. Note the verticle half round bump on the left half of the M38 carb view.

In this comparison view note the round plug in the center of the M38 carb mid section.

This view offers several things that differ between the two.

Big diff here are the bases.

Here you can see the obvious difference in base port diameters. M38 is 1" and the A1 is 1 1/4".

wingnut · Post by **wingnut** » Sat Jan 03, 2015 3:32 pm

Hi. thank you sir for your fast reply i will check out the detailed differences in the photos with what is on the a1 soon as i am able and also try and post some photos of what is now fitted . many thanks . best regards Bernard

wingnut · Post by **wingnut** » Wed Jan 07, 2015 12:07 pm

Hi. I have looked at the carb and it looks like the correct m38a1 model. But i'm thinking it may be a repop . Based on that do you think it's worth putting a new repair kit in it or should i just rebuild the original carb that came with the jeep just in case there is a problem with the repop casting. Thanks again. Best regards Bernard.

Post by **wesk** » Wed Jan 07, 2015 10:21 pm

If it has Carter YS in raised letters on the bowl it's not a repop.

wingnut · Post by **wingnut** » Fri Jan 09, 2015 3:26 pm

Hi Wes thanks for the advise also thanks again for the comparison photos.As it seems to be a n.o.s. carter ys i will get a good rebuild kit and overhaul it. I will keep you informed of how things go. Best regards Bernard.