I bought 2 used M/S 241B carburetors off of eBay. I cleaned them both and put in a new complete overhaul kit in both. One of them has the old economizer jet stuck down in the hole, so I left it. That carb runs great. The other one was the booger. I cleaned, re-cleaned, tested, cleaned some more but I just could not get the dang thing to run under a load without needing a little choke. Idled fine, down to about 550 rpm and would throttle up nicely while sitting still. Put it in 3rd and throttle up, starts hunting for fuel. Pull the choke out a little and it runs fine. Same thing with the harrows. Fuel flow through the carb drain plug was a good, steady stream for at least 2 minutes. I checked multiple times for an external air leak, since it was acting like it was getting too much air. The idle circuit seems fine, since it purrs fine at idle and picks up great when you gun the throttle. I ruled out the economizer since it only had a problem when full-open. Had to be an air leak somewhere.
I made several phone calls to GB in MT to get some help. He helped me to get the first carb running fine (even with the stuck economizer jet), but I could not get the other to run properly. I have a carb that I bought from Gary a few years ago and it runs great. I did a fuel flow test using mine and Gary's carb. Using the same tractor, one at a time, I opened the drain plug on each, let them go for 2 minutes and measured 18 oz with Gary's and 22 oz with mine. So I assumed that the float and needle/seat were working fine. I finally bit the bullet and opened up Gary's carb to do some more testing. I put my bowl on his carb upper body and it ran fine. Put his bowl on my carb upper body and it still needed choke at full throttle. Finally, after about 40 times pulling the carb off of the tractor over the past 2 months (really, I can do it blindfolded now!), I got my wife to walk out to the shed to look at the carb and act as a sound-board. She will not let me work on the carbs on the kitchen table anymore. Go figure. Anyway, I was explaining about how the carb works and she asked me if I tried Gary's venturi on my carb. Aha! Something new to try.
The venturi that came with the eBay carb had a brass venturi, Gary's was plastic. I have another set of carb parts including a plastic venturi so I tried it and now the carb works perfectly! I measured the total height of both venturis and the brass one was .007 in. shorter than the plastic one. (I wonder why my wife went right to size of the venturi? Hmmm.) I just assumed that the brass venturi was an original part so I never thought it would have been the problem.
My conclusion is that the brass venturi was just a hair too short allowing air to pass around the outside of it, thereby reducing the vacuum produced at the tip of the fuel nozzle causing a lean condition. Adding a little choke induced more suction at the tip of the nozzle which enrichened the mixture. I do not believe that this is a case of brass versus plastic. Rather it is a case of an incorrectly sized part. (Why would she go there...?)
I hope this helps someone else. I spent a lot of time reading about carbs online and many YT posts on carb woes. Gary's knowledge and assistance was what got me over the initial cleaning and testing hump. He told me not to rule anything out, but apparently I did! It was the venturi. Thanks Gary!
Jimps in GA.
I made several phone calls to GB in MT to get some help. He helped me to get the first carb running fine (even with the stuck economizer jet), but I could not get the other to run properly. I have a carb that I bought from Gary a few years ago and it runs great. I did a fuel flow test using mine and Gary's carb. Using the same tractor, one at a time, I opened the drain plug on each, let them go for 2 minutes and measured 18 oz with Gary's and 22 oz with mine. So I assumed that the float and needle/seat were working fine. I finally bit the bullet and opened up Gary's carb to do some more testing. I put my bowl on his carb upper body and it ran fine. Put his bowl on my carb upper body and it still needed choke at full throttle. Finally, after about 40 times pulling the carb off of the tractor over the past 2 months (really, I can do it blindfolded now!), I got my wife to walk out to the shed to look at the carb and act as a sound-board. She will not let me work on the carbs on the kitchen table anymore. Go figure. Anyway, I was explaining about how the carb works and she asked me if I tried Gary's venturi on my carb. Aha! Something new to try.
The venturi that came with the eBay carb had a brass venturi, Gary's was plastic. I have another set of carb parts including a plastic venturi so I tried it and now the carb works perfectly! I measured the total height of both venturis and the brass one was .007 in. shorter than the plastic one. (I wonder why my wife went right to size of the venturi? Hmmm.) I just assumed that the brass venturi was an original part so I never thought it would have been the problem.
My conclusion is that the brass venturi was just a hair too short allowing air to pass around the outside of it, thereby reducing the vacuum produced at the tip of the fuel nozzle causing a lean condition. Adding a little choke induced more suction at the tip of the nozzle which enrichened the mixture. I do not believe that this is a case of brass versus plastic. Rather it is a case of an incorrectly sized part. (Why would she go there...?)
I hope this helps someone else. I spent a lot of time reading about carbs online and many YT posts on carb woes. Gary's knowledge and assistance was what got me over the initial cleaning and testing hump. He told me not to rule anything out, but apparently I did! It was the venturi. Thanks Gary!
Jimps in GA.
[/i:bafd667230][/b:bafd667230]