another one M38A1 carb problem please!!!

ktm25089 · Post by **ktm25089** » Thu Jun 01, 2017 11:13 am

Hello,
I have rebuild my carb.Soda-blasted,chemical and ultrasonic cleaned.repaired some threads with helicoil and installed a NAPCO 11-0578C japanese kit.The carb start and works very good.with the only problem on idling.Its very rich and smoking black from the exhaust.When you touch a little the throttle its clean and working good.Its so rich that with the mixture screw close it continue to smoke black and working rough.
Some told that the hole on the metering rod when the pin goes to attach in on the diaphragm is in the wrong place on the japan kits.any suggestions?

Thanks

Post by **wesk** » Fri Jun 02, 2017 12:26 am

1 - Use your original jet & metering rod and spring. (CAUTION the springs are not the same in the accelerator pump & the metering rod diaphragm wells.)

2 - Make sure both diaphragms are still fresh, flexible and not leaking.

3 - Make sure you got the correct spring on each side and both springs are in the correct position, both springs between the diaphragm & the diaphragm cover.

This is my corrected illustration from the Carb manual.

This will help check dimensions on metering rods.

Make sure these are still in the accelerator pump well!

The ball & weight are items "T" & "U" in this illustration.

ktm25089 · Post by **ktm25089** » Fri Jun 02, 2017 3:07 am

Wes,
All checked and it is OK.Do you have some dimension on the diapragm.I suspect that the see-through hole where the pin goes to attach the rod is on wrong height.
I have found more people have the same problem with the japan kit.They replaced the diaphragm with US made and the problem corrected.

George

Post by **wesk** » Fri Jun 02, 2017 9:06 am

In that case measure your old one and compare. If it's definately in the wrong location then just drill a new hole in the correct location.

ktm25089 · Post by **ktm25089** » Fri Jun 02, 2017 12:48 pm

the problem is that i dont have the old ones!!!!Thats the reason that im asking some measurements
And another one question.as the diaphragm goes back and pull the rod to the cap the mixture goes rich or lean??

Post by **wesk** » Fri Jun 02, 2017 11:52 pm

ktm25089 · Post by **ktm25089** » Sat Jun 03, 2017 4:07 am

Thank you!!!!!!

cabinfever · Post by **cabinfever** » Sat Jun 03, 2017 6:19 pm

Thia thread is very timely for me. Today, I rebuilt my YS950 using a kit from Midwest Military.

When I took the car apart, there was no check ball and check ball weight in the carb. (And. "no", they did not fall out when I took the carb apart) The jeep seemed to run fine without them. The rebuild includes a new ball and weight.

Also, there was no metering rod pin that is used to secure the metering rod to the diaphragm assembly. The rebuild includes the pin. A problem seems to be that the pin, even though it seems to be flush with the diaphragm sleeve, moves. This movement causes the pin to contact the sides of the carb body which seems to hinder the movement of the diaphragm sleeve/metering rod assembly. Perhaps when there is gas in the carb, it will act as a lubricant so this binding caused by the sliding pin will not be a problem.

Post by **wesk** » Sat Jun 03, 2017 9:21 pm

The pin should stay put. If it is very loose (no fit friction at all then I suggest a wee bit of lock-Tite between the pin tips and the sleeve. Of course you will need to insure both are clean, dry and oil/gas free.