Carb problem case 310B

[rob vds]

Hi, I am trying to start an old case backhoe. I took the carb apart and cleaned it up a bit. There is no seat for the high speed needle and it can't bottom out so how do I find the initial setting? It is a Marvel carb but the book shows a tsx635 for gas or a tsx680 for "low cost fuel". I have the drain cock under the bowl like the lcf model but somebody could have swapped out the original plug during the last 50 years. How can I identify my carb?

 

[Joe (Wa)]

1. Tag is on engine block side as mounted on 300-300B. The 2 5 is actually 2 56, date of mfr.

2. General instructions for MS carbs, will work for 300-300B.

 

[rob vds]

That is a great start thank-you!I suspect the tag is gone from mine but I will check tommorrow.The brass plug shown bottom left of your pic is called a nozzle hole plug in my book, it is a small steel slotted head set screw that I didn't remove because it will break. Blowing air from the high speed needle hole in the bowl showed no obstruction to the nozzle seat so I decided it wasn't worth the trouble. Was that a proper decision? ( I havn't looked at a carb in many years)
My tractor won't run at all so I still need a bench setting for the two needles. I don't understand the instructions given for air and fuel adjustments for the low speed screw?

 

[Joe (Wa)]

The small plug is just below the main jet orifice. In my day it was called a sand plug since the loose crap tends to collect there and impede the fuel coming from the power needle orifice. If you can't get it out, don't destroy it. Blowing air down the power needle hole isn't very effective. To clear that passage you just about have to soak the carb and blow back through the other way from the top of the nozzle.

The pic is what your nozzle should look like.

I wrote a long post on how these things work years ago but I am too old & dumb to do it again. It might be in the archives.

So go to the link. M&S carb starts page G2-S5. You can read the whole section or just pages G2-S7 & G2-S8 (this is generic but you need to understand the basics). Now do the "next 12" jump and apply what you read to Fig S-18 on page G2-S11 then you'll know as much as most of us.

Click on the page(s) to enlarge for reading.

Continue on for teardown & assembly pics. Not very clear pics but some help comparing with parts in your carb as you proceed.

Initial setting for TSX-635. Mixture screw 1 turn CCW off the jet seat. All the way in CW is full rich if you need it to get started. Generally ends up about 1/2 turn CCW. Power needle doesn't effect starting much just needs to be open some. Turn in and back off about 2 turns and go from there. CCW is rich. Take the air cleaner pipe off and make sure your choke fly is wide open for running adjustments.

Joe

mjs manual

 

[rob vds]

Thanks Joe, that should provide me with all I need for the carb. I am going to post a new question about the distributer so the search function is effective in years to come.