Tuning help needed

[GWGAllisfan 159]

I've been working on the 23D in my landlord restoration. I've had quite a time with it. At first I had a no spark condition. That has been cured with a new coil. Spark is very strong, and consistent. Now the motour has a strange condition. If it has been setting for a while, I can start it if it's choked and the throttle held closed. It will start with little problem. At that point it will run, as far as I can tell, as long as it has gas, at most any steady speed. I was even able to drive it around the house. But, if it stops, either by the key, or choked down (once by my hand over carb throat, a few times when throttled down) It won't restart no matter what I do. I've checked the plug and it is not wet at this point. Looking down in the carb, I can see some fuel in the bottom of the carb. Once after I got it restarted, tried adjusting to a lean main mixture. It ran fine but still wouldn't restart properly.Here's a picture of the carb area
[img]/club2/attach/GWGAllisfan/100_1084_smaller.jpg[/img]
The carb on it is a 4 bolt type, just recently professionally rebuilt. I do not know which engine size it was originally for. Is it possible this carb is just too big for the 23D to give enough air flow at cranking to atomize properly? On this theory I have a medium flo-jet soaking for potential rebuild and use. Question / Call for opinions: Anybody have an idea what this problem could be? Does my theory sound reasonable?

[PeppyDan 3]

I'm not sure what the cfm difference is but the 4 bolt carb was original on the 24000 10hp and larger engines. Yours should have a 3 bolt carb. Dan

[gregc 3]

Have you checked valve clearance? Could be leaking or sticking valve.

[toomanytractors 0]

Make sure the throttle shaft and bushings are good and snug in the carb body. the shaft and bushing seems to wear worst on the back side toward the block. I've had this problem and that was the cure. This will cause a lean condition on startup. ( Sucking air around the shaft) I've had the best luck removing the bushings with a short spiral easy out. I start with the idle air screw turned out one and a half turns and the high speed screw at two and a half turns and fine tune from there after warmup. Good Luck, Dave

[GWGAllisfan 159]

I forgot to mention that when it does start it puffs thick black smoke from the exhaust and has to be babied for a few seconds then settles down and runs perfectly until shut down. The plug will have a black sooty deposit that wipes off easily. I Haven't checked valve clearance, haven't been that deep into the engine.

[B.Ikard 2]

Randy, I have a couple of 3 bolt carbs over here, and a kit if interested. Back in town since Wednesday:D Brent

[UCD 14]

That black smoke and sooty plug tells me you have a vacuum leak, bad carb base gasket, manifold gasket or worn throttle shaft. Could even be a bad head/gasket. [url]http://www.simpletractors.com/club2/topic.asp?TOPIC_ID=35948[/url]