YS 637 Rich Idle

Stiknruddr · Post by **Stiknruddr** » Sat May 12, 2018 2:41 pm

Rebuilt the carb with a good kit, runs great except a very rich idle. Timing no help checked float hirleght on rebuild was a tad high so adjusted. Idle air screw doesn’t seem to have any effect. The ball and weight are in the proper position. Any ideas? Thanks.

Stiknruddr · Post by **Stiknruddr** » Sat May 12, 2018 3:55 pm

Help?

4x4M38 · Post by **4x4M38** » Sat May 12, 2018 4:45 pm

Is everything factory on the jeep?

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

Post by **wesk** » Sat May 12, 2018 5:03 pm

Which illustration did you use to assemble the carb?

This illustration from the Carb TM is incorrect on placement of the spring, item BB.

Stiknruddr · Post by **Stiknruddr** » Sat May 12, 2018 6:29 pm

I got B.B. in the right position. Figured that out on the rebuild. Runs great except idle. Blowing black smoke and 2 stroking. Help?

Post by **wesk** » Sat May 12, 2018 9:35 pm

Too rich = float to high, bowel inlet needle not seated, carb body cracked, idle mixture screw damaged, fuel inlet pressure too high.

Your two stroking comment is odd. Do you mean she is dieseling?

Stiknruddr · Post by **Stiknruddr** » Sun May 13, 2018 11:49 am

I meant running so rich only hitting on 2 cyl hot. The spring position may be the culprit I’ll check it when I get a few mins it runs great other than the rich idle. I mic’d the rod and jet out of the 4 I have every one was different specs I used the largest diameter rod and seems fine under acceleration and Cruise. Just overly rich at idle especially when hot. Black sooty exhaust and no ability to tune.

Stiknruddr · Post by **Stiknruddr** » Sun May 13, 2018 12:18 pm

Wes you’re a genius and gentleman. The spring was the issue. Runs and idles perfectly. Now to determine the exact timing. I rebuilt the (12v) distributor and did my best on the curve but there are no timing marks on the pulley and someone installed the flywheel 180 out. I guess oil in the cyl at tdc?

Post by **wesk** » Sun May 13, 2018 9:39 pm

The L head can be set up for a timing tab on the crank pulley. The easiest to work with is the later M38A1 F134 timing tab that uses two bolts on the timing cover to mount.

On L heads with the piston not under the spark plug holes I have always had good success with a fabricated wigler. It is a short piece of stiff wire bent several times so it can rest on the top of the piston when inserted in the spark plug hole. Then you can determine when tdc is reached by the short period it does not move. You mark the crank pulley with chalk the instant it stops moving and then make the second chalk mark the instant it begins to move again. TDC will be halfway between those two chalk marks. Then use a degree wheel on the crank pulley to locate 5 deg's BTDC and make a notch in the crank pulley that is in line with the 5 deg mark on the tab.

Stiknruddr · Post by **Stiknruddr** » Mon May 14, 2018 9:13 am

Well I spoke too soon. The spring was in the wrong position but now has poor power and is not hitting on all cylinders. With the spring in the wrong position it ran great except at idle. Now has multiple issues. Stumped. I carefully rebuilt this carb I guess take it apart again and double check everything.

Post by **wesk** » Mon May 14, 2018 4:02 pm

Do you have the fording vent system installed? If so make sure both valves are open. Make sure your PCV valve is not plugged or stuck shut. Make sure your tank vent system is working and the cap is not in the fording (closed) position.

Stiknruddr · Post by **Stiknruddr** » Mon May 14, 2018 6:39 pm

All not a issue. Something is really not right. It’s a carburetor and not my first rodeo. Very frustrated but there’s a answer. I’ve got something screwed up. Not sure what but I’m falling back to brick one. It’s a dang carb it wil not defeat me!

LTDan · Post by **LTDan** » Mon May 14, 2018 10:16 pm

Check your gaskets carefully, I have had "good kits" have a passage blocked off.
Also pull out your fuel cut off needle and give it a good wipe off. It only takes one little bit of trash and it will not shut off the flow.

Test the fuel shut off by blowing in the inlet with the float upside down and then moving it with your finger, it should have the air completely shut off from blowing through it, Don't use a lot of compressed air, I just blow through it with my mouth.

I have built and fought with many a carb and 9/10 time it is the fuel shut off valve. I have even had to go back through a carb 3 or 4 times if the trash was really bad.

Then if it is not your carb.
Check Timing, Ignition, and Valve adjustment.

Oh and also check for any vacuum leaks. A little bit of starting fluid sprayed around the base of the carb with it running will tell you if you have a vacuum leak at either the base or in the throttle body. My YS950 i just rebuilt has a crack in the throttle body half way around it, I just plugged it with JB weld for the time being until i get another.

Stiknruddr · Post by **Stiknruddr** » Tue May 15, 2018 3:28 pm

Thanks for all the help. I pulled it again today I had a pump spring on the step up (metering rod) side. Went through it again all ports are open the gasket ok not blocking anything. I did find the metering rod pin dragging fixed. Checked the float valve and height all ok. Actually idles reasonably but no acceration. I’m looking at the metering rod again. Also I’m using a CJ2 fuel pump and it may be putting out too much pressure for the YS. Upsetting the balance internally. Funny with the metering rod spring in the wrong position it ran great except at idle so it’s got to be something with the high speed circuit.

LTDan · Post by **LTDan** » Tue May 15, 2018 3:39 pm

Stiknruddr wrote: Also I’m using a CJ2 fuel pump and it may be putting out too much pressure for the YS. Upsetting the balance internally.

It very well could be putting out too much fuel pressure for the carb, I run an electric fuel pump that puts out 8-12 psi which is much too high for the 950.

I ended up installing a pressure regulator and have an oil filled pressure gauge on the line, I have mine set for about 3 psi and she likes it quite well.