YS 637 Rich Idle

[Stiknruddr]

I’m going to try a pressure regulator but also check the pvc, ect. I’m pretty sure I had a base leak replaced with multiple gaskets and actually had it running with air screw open 1+ turns. Before almost closed. Ya know I worked at motorcycle shops for years race car ect but this thing is baffling me. Yea I made some rookie boo boos but it’s put together best I know how. All clean jets in spec but gonna pull it apart one more time as well as check timing, pvc and do a pressure regulator it could be upsetting the internal balance

[Stiknruddr]

Update. I found 2 things wrong with the carb after looking again. There was some obstruction in the economizer area of the low speed circuit. And although the metering rod is marked 74-535s it’s dimensions are identical to the 950 rod.(thanks Wes for your image and dimensions) Have the proper rod ordered. Also found distributor advance spring off the stud. With the wrong metering rod in it (till I get the proper one) it has great power and pretty good idle till it sits idling for a min then starts loading up. A blip of the throttle cleans it out will idle ok for another min then start loading up again. Otherwise runs well. Will be interesting to see how it does with the proper metering rod. Thanks for all the help!

[Stiknruddr]

Hmmm, when I installed the cross over tube and air cleaner....very rich idle and spotty power. With no tube or air cleaner just loads up if idled a while. Otherwise spunky power even with the wrong metering rod. Any ideas?

[wesk]

Richer with crossover pipe connected usually means plugged up air cleaner, top right fording valve closed (Needs to be open for normal driving) or plugged carb bowl vent tubing (more likely to cause the spotty power).

You would be surprised at how much plugging can occur to a fifty + year old filter that has been very mistreated, rarely cleaned or inspected and often left a few years at a time to the elements and rodents.

Running the oil level above the mark in the air filter will also restrict flow.

That crossover pipe has two little tiny 1/8" bent tubes inside that plug up occasionally as well.

[4x4M38]

Ok,
So we finally got to this part:
“Is everything factory on the jeep?

Remove the hose from the carb to the crossover tube and see if there is a difference.”
_____



With the crossover tube and air cleaner connected
properly, remove the hose between the crossover
and the air cleaner.

It it improves the air cleaner is dirty or plugged.
If it does not improve there is a problem with the
crossover tube or hose between the crossover and
air cleaner.

This assumes, and goes back to my original post,
that everything including all the ventilating lines
are installed per factory.

My two cents.

[Stiknruddr]

It’s probably too high oil level in filter. I serviced it just before installation. I’ll drop the level let all know results

[Stiknruddr]

Through all of this carb issue I didn’t have the vent tube to the crossover hooked up didn’t have the fittings. After installing it the idle improved. I suspect there is a balance built into the design. Also, none of the rebuilt kits being sold have a metering rod with the proper dimensions they are marked correctly but are YS950 metering rod dimensions. Still haven’t located a proper metering rod the dimensions Wesk shows it to be.