M38 YS Carb problems?

[Keith]

First little background information working on a 51 M38 with a later style YS carb. 4 months ago I rebuilt the carb myself, the kit was from debella. I paid very close attention to making sure the float was set exactly .250, and I also have all the proper vacum lines connected. I spent 4 months getting everything under the hood back to original.

Its been running great for the last 4 months, the throttle was very respnsive. only a little white smoke when it first starts. Starts first try with a little choke then able to push the choke in right away with good idle. All new fuel lines, fuel tank refurbished and coated on the inside & out, clean fuel filter.

Here is the new problem I took it for a short (4 mile) drive and when I slowed down getting to the house i noticed it running kind of rough, then when i wanted it to idle it wanted to stall out unless i kept it throttled up, I park it and hoped it was just a fluke. The next day I started it up and it ran great until it warmed up then again it would not idle and it started blowing black smoke. With it running i tried adjusting the idle screw, no change, I tried adjusting the timming, no change, what could change so quikly? I checked everything from the out side and everything looked normal. Any clues would be great. I went over the trouble shooting area in the carb download and it could be many different things I understand. I was wondering if anyone else might know what is the most common cause of this sudden problem????

Thanks
Keith

[oilleaker1]

Keith, we are both having YS problems. Yours sounds like it got some dirt or foreign material in and it's letting too much fuel through with the throttle at idle. You probably need to clean it all out again. Check the float chamber etc. John, I did the same, etc. Debella kit, and it runs great except for idle . It surges cause it has gas, and then it doesn't. I got 3 springs in the kit, and am wondering where each type should go. 2-long and one short, all the same width. Can you remember which 2 go where???? John

[oilleaker1]

Another note: My CJ3A was giving me fits until I discovered the carb had worked loose on the base gasket (thick one under the carb) If I tightened it, all was well. I ended up putting star washers under the nuts that mount the carb. That has really helped! White smoke = water, black smoke = gas, blue smoke = oil! John

[wesk]

Black smoke means "Too Rich". Too rich means too much gas or not enough air.

The "too much gas" thing can be a sticking float valve or dirty inlet needle allowing too much gas in the bowl. It could be you forgot to put the spring on the idle mixture screw and the screw vibrated out some and made the idle mixture too rich.

The not enough air thing can be a loose connection of the choke cable letting the choke plate stay partially closed.

Keith,
What exactly is a "Late Model YS Carb". I only know of one model YS637S that fits the M38.

[Keith]

I was refering to the 2 YS carbs pictured in Ryan's book pg 62.

I checked the idle mixture screw it does have the spring on it and is very tight. I even closed it all the way and no change. By the way what is the # of turns out of this screw from it being srewed all the way in?

Checked the choke and is in the correct position, everything tight.

So it must be one of these two options, a sticking float valve or dirty inlet needle allowing too much gas in the bowl???

Checking the parts list & exploded veiw of the YS I cant find the float valve could it be called something else??

Thanks
Keith
9/51 M38

[oilleaker1]

keith, 1 turn out from all the way in, check my thread for Wes's carb diagram. my bet is dirty float or bad float is causing too much gas. At least you don't have to take the whole thing off to look John

[wesk]

That is a cosmetic change in the middle casting and has no effect on function. I am not sure how the early vs late conclusions were reached on that either.

The float valve is what we old timers often refer to and is AKA inlet valve or inlet needle. Items MM NN PP QQ RR below.

[Keith]

Thanks everyone for the help. I will let you know the results.
Keith

[gianjeep]

have you cheks the weight JJ and the ball HH in the exploded view?
Also i've removed from my jeep in carburettor the step jet( CC) and i've fix a new jet AA taken from my MB... very good sound obviosly carter ys 950s