My YS Carburetor problem

Cacti_Ken · Post by **Cacti_Ken** » Wed Jan 30, 2013 11:45 am

Getting back to my carb problem I had in late November.
It was hard to start and keep running.

It finally got warm enough here in the last couple weeks to get in the shop and tinker with it. It was eating my lunch, as I thought that I had cleaned all the ports and crannies in it.

On initial cleaning I didn't remove any plugs, as I was afraid I might ruin or damage something on the body. So I just soaked the pieces real good in carb cleaner and roded the passages with small strand of wire and flushed with carb cleaner spray and compressed air.

After all that it still wouldn't perform correctly. Made sure there weren't any air leaks. Check the pump for proper pressure out.

I had a boss tell me once in my younger years, Ken, "don't ever give up".

I scratched my head and thought about it for awhile and decided I better go ahead and remove some plugs in the body.

I decided to start with the cast iron body because I figured it was prone to rust up inside. I removed all the hardware on it and pulled the copper plug out of it.

Lo and behold there was some blockage in the idle mixture port slot. I used a tiny screw driver to loosen up any particles in the cavity. But it wasn't as clean as it should be.

I decided heck I can't hurt anything so I placed it in the sand blasting cabinet and gave it a few shots with the compressed air and sand. I was using very fine sand. That took care of rest of the rust particles in the cavities.
I''m not afraid to remove plugs now.

I finished washing it out with carb spray and made sure there wasn't any sand in those cavities. Anyway got all the dust out of it. I did have to widen one of the holes in the gasket as it was covering too much of the hole passage.

I don't know what their problem is in making a good gasket
to fit the carburetor holes.

Installed the hardware back on it and mounted it to the rest of the carburetor. And finally back on to the manifold.Adjusted idle mixture screw 1 1/2 turns out. Poured gas in the thru the horn prior to cranking. It took a few times of cranking and running to get the carb bowl full.

Set the idle speed for comfortable idle speed. It was purring good. Let it warm up and readjusted the idle mixture screw for best mixture.

Wow, I thought it ran good before I started having this recent problem.
I'm not exagerating. It is better now with quick acceleration, has better pep, and easy to start. It stays running at low idle with out having to goose it occasionally. Kinda like that CW song..."Boot Scoot Buggy"
Varooom!! Varooom!! LOL!

Now I have another spare I'm working on. The one I broke the screw off in the throttle shaft. I ordered a set of taps and am waiting for it to come in to continuing with the repair.

And the taps just arrived as I'm typing.
I'm outa here.

Ken

RICKG · Post by **RICKG** » Wed Jan 30, 2013 12:12 pm

Good work Ken-these carbs can be tricky little devils!!

Bretto · Post by **Bretto** » Wed Jan 30, 2013 12:17 pm

GREAT! Good job. I can tell you are a very happy with the results.

Post by **wesk** » Wed Jan 30, 2013 12:17 pm

I don't know what their problem is in making a good gasket
to fit the carburetor holes.

Often the gaskets have several different applications and where hole sizes vary they use the size that has no impact on performance in all applications. It's a very common practice.

Cacti_Ken · Post by **Cacti_Ken** » Wed Jan 30, 2013 5:21 pm

Look at the difference in two YS carburetors. The one on the right is the one I got running on the M38 in the last post.

The one on the left is a spare I bought from a individual, hoping to have a good running spare. I put a new kit in it. But it would only run with choke valve closed quite a bit. I took it a part and noticed some difference between it and the one I previously wrote about.
I wonder what kind of mix up I have here with the one on the left.

Post by **wesk** » Wed Jan 30, 2013 7:36 pm

Hello Ken,

The YS637S is a much harder to find and more expensive carb compared to the M38A1's YS950S. It is common to see folks place a M38A1 YS950S main body on a M38 YS637S throttle body.

DJ · Post by DJ » Wed Jan 30, 2013 9:23 pm

" It is common to see folks place a M38A1 YS950S main body on a M38 YS637S throttle body. "

Yup, I bought a "M38 carb" that had the A1 bottom on it. Took the civvy carb off and put the "M38" carb on and the jeep wouldn't run for crap. After much pain and suffering I found the switched bottom. Bought another m38 carb and problem was solved. So 2 carbs made into one wasted 2 carbs!

Cacti_Ken · Post by **Cacti_Ken** » Wed Jan 30, 2013 9:59 pm

Substituting a YS950S main body onto a YS637S throttle body is not suppose to work is it? It hasn't worked for me. And I don't see how it can work when the throat in the 950 is larger than the 637 throttle body flange hole. It would not start from stand still. I had to get pulled to get running. then I had to have the choke 75% closed to get it to stay running. I believe it was getting air into a port in the throttle valve because the main body being larger wasn't sealing the gasket over the X port. The bolts holes will line up perfect, But that's it.

Post by **wesk** » Wed Jan 30, 2013 11:34 pm

I did not say it works. I have actually seen folks piece them together and try to make them work.

The mismatch of bore size is not a big issue. It is the mismatch of vacuum ports and flow rates that give the problems.

Cacti_Ken · Post by **Cacti_Ken** » Thu Jan 31, 2013 12:22 am

Thanks Wes for clearing that up. I did take it that you were meaning it worked. I'll see if the individual has a remedy for this delema.

Cacti_Ken · Post by **Cacti_Ken** » Sun Feb 03, 2013 8:09 pm

One last question.

My thinking is it won't work, but I would like to know for sure so I don't have to remove the YS637s from the engine and visually compare.

The question: Will the the Horn section of the YS950S work with Lower main body section of the YS637S?
thanks
Ken

Post by **wesk** » Sun Feb 03, 2013 8:33 pm

I am not sure. The part numbers for the horns are not even close. Nor are the part numbers for the horn to bowl gaskets. You don't have to remove the 637S from your engine to find out. Just remove the 637S's air horn and stick your 950S bowl under it right over the engine. Personally I think its a waste of time and money to jury rig a 950S to work on a M38. There will always be a ported vacuum issue with the throttle body vs the bowl and a flow rate issue withe the 950S metering system too high for the M38's fuel needs.

Cacti_Ken · Post by **Cacti_Ken** » Sun Feb 03, 2013 9:15 pm

Thanks for the reply Wes, I really don't to jury rig it either.
I think I'll just end up sending the mix match carburetor back.

Ken

DJ · Post by DJ » Sun Feb 03, 2013 9:40 pm

Will they work?? Short answer, no! Mine would run ,barely and idle speed had to be 1500 rpms to half arse run, Iwould send it back if possible.