Carter YS 950 S Questions

seyit · Post by **seyit** » Wed Mar 02, 2016 5:21 am

YS 950 S Questions
Hi everybody.I am posting from Turkey.I have a 1962 Kaiser CJ 5 with F-4 134 engine and civillian YF 938 Carter carburetor.
On the other hand I have a second carburetor ( YS 950 S).This second carburetor has been sitting on a shelf for over 15 years.Back in those 15 years ,I put this YS 950 on,but after using it for 3-4 days I took it out and put back the civillian one.What I remember is as follows;
1. Cold Start= was fine
2. Cruising= was fine
3.Idling= don't remember now
4. Hot Start= was the problem which got me take it out again.
Nowadays I am planning to put this YS 950S on again,but before that I want to solve that hot start problem.Thinking that it might be float adjustment I dissassembled the carburetor.To my surprise the inside of the carburetor is unexpectedly clean.It all looks to be new , but aged on the shelves.Seeing this I didn't want to dig any deeper.Only I suspected the float height adjustment which looked to me kinda odd compared to the civillian carb float height.So I tried to measure it.I am not familiar with 9/64",, 3/32", , 1/4" etc but with metric drill bits I checked it and and found that 2mm ( which I think around .78 " ) hardly could be slided under the float.but still pushing it slightly upward.From some articles posted here previously I read that it should be 1/4" or some other gurus insist that it should be 9/64". This 9/64 still looked critical to me when I first adjusted it to this height.Then I readjusted the height with 6 mm ( 0.236 220 ...") drill bit which looked to be more reasonable.
I don't know if I can upload some pictures here,but at first the lip to adjust the float was almost flat at the bottom.
Another point is;
When I put this carb on some 15 years back, the air cleaner was the civillian type and there was no cross over tube.So I could not not hook the opening ( Looks to be vent on top of the air horn , just behind the " L " shaped air intake) to the air cleaner or to the cross over tube, and just plugged it with a screw.Now this bites me that plugging it might caused some preassure inside the carburetor and kept pumping gas into the manifold after stopping the engine and fload the manifold.
Currently the air cleaner is from an M 38A1 with a cross over tube which enable me to make the connection.
As a summary,What do you think caused my hot start problem in the past with the clues above?

BTW, in the exploded view of the carburetor seen in pages here Willys M , the spring is between the diaphram of the metering rod , looks to be sliding over the metering rod assembly and the carb body.When I disassambled the one here , the spring was between the diaphram and the outer cover.Which is correct?The exploded view puzzles me.

Xamon · Post by **Xamon** » Wed Mar 02, 2016 7:39 am

one of the manuals was printed with an incorrect picture and many carbs where rebuilt the wrong way because of it. There should be a cup on the diaphragm that the spring seats in though.

seyit · Post by **seyit** » Wed Mar 02, 2016 8:03 am

Xamon wrote:one of the manuals was printed with an incorrect picture and many carbs where rebuilt the wrong way because of it. There should be a cup on the diaphragm that the spring seats in though.

Thank you,Xamon.The spring in my carb came out of it the right way then.That cup and spring in cross sides got me suspect about the drawing.
I think correcting the float adjustment and taking the screw out from the vent hole on top of the air horn,then connecting it to the air cleaner will solve the hot start problem.
Because all the inside and outside yellow zinc plating still looks rather new and the brass parts are all very shinny.Even the gaskets came off without any sticking.I don't want to use the tune up kit since all the parts are so new.
Only perhaps,I want to recheck the two strainers which are in the tune up kit,but I suppose I have not seen them in the carb.
Thank you again.

Post by **wesk** » Wed Mar 02, 2016 11:05 am

9/64 = .18. The argument between 1/4 and 9/64 has been on going for years. A difference of 1/64th is not going to cause any malfunctions. The argument has arisen because the TM 9-1826A Carb overhaul only covers the YS637S. The boneheads argue that is the only correct setting. However Carter disagrees. The individual spec sheets show 1/4" for the YS637S and 9/64" for the YS950S.

This is the corrected illustration. Make sure HH the discharge check ball isn't missing.

Make sure the choke plate is adjusted correctly for full travel and correct travel direction!

Usually hot starting issues are either timing incorrect (too advanced) or heat soaking of the carb which percolates the gas out of the bowl. The Army added the hand prime pump to the fuel pump to address this issue.

Military fuel pump.

The vent must be left opened on top of the bowl. You can add a hood to keep dirt out or connect it to your air cleaner.

Deteriorated diaphragms on either the vacuum operated accelerator pump or the metering rod will cause flooding.

Make sure you download the correct TM 9-1826A manual excerpts.

http://www.willysmjeeps.com/v2/modules. ... it&lid=142

This is stored in my drop box. You download a copy by clicking on the the small square box with three ... 's in it at the top right of the web page.

seyit · Post by **seyit** » Wed Mar 02, 2016 1:07 pm

wesk wrote:9/64 = .18. The argument between 1/4 and 9/64 has been on going for years. A difference of 1/64th is not going to cause any malfunctions. The argument has arisen because the TM 9-1826A Carb overhaul only covers the YS637S. The boneheads argue that is the only correct setting. However Carter disagrees. The individual spec sheets show 1/4" for the YS637S and 9/64" for the YS950S.

This is the corrected illustration. Make sure HH the discharge check ball isn't missing.

Make sure the choke plate is adjusted correctly for full travel and correct travel direction!

Usually hot starting issues are either timing incorrect (too advanced) or heat soaking of the carb which percolates the gas out of the bowl. The Army added the hand prime pump to the fuel pump to address this issue.

Military fuel pump.

The vent must be left opened on top of the bowl. You can add a hood to keep dirt out or connect it to your air cleaner.

Deteriorated diaphragms on either the vacuum operated accelerator pump or the metering rod will cause flooding.

Make sure you download the correct TM 9-1826A manual excerpts.

http://www.willysmjeeps.com/v2/modules. ... it&lid=142

This is stored in my drop box. You download a copy by clicking on the the small square box with three ... 's in it at the top right of the web page.

Thank you wesk.
If we go one by one;
1. The carburetor in question here is YS 950 S. The float needle is bored to the float side and there is a tiny spring and a small pin that go in the bore.When the air horn is turned down side up and the float rests on the needle by its weight the height is higher than 6 mm ( 0.236 ... " ) but there is not much pressure on the tip of the needle.I assume it will allow gas to get in.When I begin to depress the float without applying much pressure the tiny spring is gradually compressed first and than the needle gradually sits at the bottom stopping the fuel to get in the bowl.At this point the float height is 6 mm ( 0.236 " ). This is what I have currently adjusted the float height( but have not yet test it on the engine). Anything right , or wrong so far?
2. When I dismantelled the carb the discharge check ball weight was there .No idea if the discharge check ball itself was also there or missing.Since the inside of the carb looked so new I didn't take the weight out and did not see what was/not underside.Sure I will check it this time..
3. No problem with the choke plate.
4. I don't think I had/have the timing problem.I own an ignition timing light and set the timing at 5 degrees BTC . Also have an engine analyser this time . ( I lacked years back when I put the YS 950 S on) However ; With the same advance setting , I didn't experience the hot start problem when I put back the civillian carb. So all that problem obviously caused by the carb.
Currently the fuel pump is of civillian type with vacuum chamber and glass bowl.No hand prime pump.Do you think I will need a military fuel pump with hand prime?
5. Now I realize that I made a serious mistake pegging the vent outlet by screwing a bolt in there.I have the possibility to connect it to the air cleaner this time,because I replaced the civillian cleaner . Now I have an M 38A1 air cleaner and my strict intention is to make aconnect there.
6.The pump and the metering rod diaphrams still look to be very new and fresh.I think the only gas entered in this carburetor when I used it 3-4 days some 15 years ago.Now both of the diaphrams are quite soft ,too.
In any case, I have a tune up kit and I can replace them both.But I want to give a chance to the current ones first.
Finally, I will check and download the Technical Manuals you indicate.
Thanks for answering.

seyit · Post by **seyit** » Wed Mar 02, 2016 1:19 pm

Not he carburetor perhaps,but some pictures of this early CJ 5 of mine can be seen in the link below.

http://blog.kaiserwillys.com/my-longtim ... nd-delight

Post by **wesk** » Wed Mar 02, 2016 7:48 pm

The spring type needle/seat were developed to deal with off road bumpy driving. They help keep the needle on its seat while the jeep is bouncing or is tilted excessively. The float is adjusted to 9/64" with the air horn inverted and ONLY the weight of the float itself on the needle. Do not press the float hard down onto the needle when setting float height.

Your CJ5 is very nicely done. The doors are an outstanding piece of work.

Looks like you are up in the mountains of Turkey. I visited Ankara on aircraft business back in 1996. Had a great time. I enjoyed the pleasantries of your country a great deal.

seyit · Post by **seyit** » Thu Mar 03, 2016 1:41 am

wesk wrote:The spring type needle/seat were developed to deal with off road bumpy driving. They help keep the needle on its seat while the jeep is bouncing or is tilted excessively. The float is adjusted to 9/64" with the air horn inverted and ONLY the weight of the float itself on the needle. Do not press the float hard down onto the needle when setting float height.

Your CJ5 is very nicely done. The doors are an outstanding piece of work.

Looks like you are up in the mountains of Turkey. I visited Ankara on aircraft business back in 1996. Had a great time. I enjoyed the pleasantries of your country a great deal.

Thanks,wesk for both the info on carb,and the nice comments on the jeep and the country.