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Simpleton7016

Disappearing Carb part (Briggs 16)

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Simpleton7016
Oh oh....I was out prepping the fleet for winter duty when I noticed that i was missing the end cap on the carb. I have two questions: 1. What is this piece called so that I can speak intelligently about it as I seek for a replacement? 2. I am uncertain how long it has been missing. It probably came of when i pressure washed a few weeks ago, but it is possible that it has been missing for several months. Nevertheless, this particular tractor has seen very limited use and only rototilled for about a half hour. But if it was open when I pressure washed, then water most certainly got in there. Plus, it has been starting harder than normal. It turns over several dozen times before she fires. Once fired, she runs pretty good (except for an annoying surge-tendency at low RPM's - but that is for another day))My question is this: is there anything I should do before replacing that cap? Should I douse it real well with carb cleaner? Anyone have any tips for replacing that cap to make sure it stays on tight? Thanks in advance....here is the picture:
[img]/club2/attach/Simpleton7016/carb piece.jpg[/img]

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UCD
It is called a Welch plug. Should be available at any Briggs dealer or auto parts store. The welch plug is domed in the center, set it in the opening with the dome faceing out and give it a sharp blow in the center with the ball end of a ballpeen hammer seating it in place. This expands the diameter of the plug. You can also stake it using a center punch at equally spaced increments around the out side diameter of the welch plug. You can also epoxy it in.

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BrownA
Well said by Maynard, While you have easy access it couldn't hurt to spray a little carb. cleaner in there and clean what is accessible. That plug being out gives you a better view inside there to see whether its clean or not. The Welch plug is either going to be Briggs and Stratton number 221747 ( 1 3/4" diameter ) used on most 14,15,16hp engines or 221997 ( 1 1/2" diameter ) used on most 6,7,8,10,12 hp engines. I hope this helps, Al

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B.Ikard
It takes a few of these to get the hang of seating welch plugs. The secret is hitting dead center and just enough to expand the plug. Many people continue to beat them untill the plug contracts again and gets loose. Dont bother trying to beat it back in, it is a one time good deal. That being said, if this is your first one, get a couple of plugs while at the dealer-they are cheap. Worst case scenario you will have a spare plug. I have had good luck driving/expanding welch plugs this size with a golf ball and hammer. Old Dertoit Diesel piston pin sealing plug trick. Put the golf ball center of the welch plug and smack it good. One blow should expand the plug. I'd probably consider spreading epoxy lightly on the carb surface as these missing plugs are a chronic problem. Brent

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HubbardRA
I have used plugs more than one time. When I put one back in, I will stake it with a punch at about six places around the outer diameter. I have not had one come out that I staked in.

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JohnFornaro
My wife always seems to have leftover nail polish in the refrigerator. I paint the outside of the welch plug with fingernail polish. It's real heavy paint, seems to hold up to the summer heat of running the engine. I had one which was staked, but loose in its groove. This approach made it solidify. Never thought of epoxy though.

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msiebern
Maybe I just can't do it properly, as I kept losing them regardless of how I staked them, so I opted for this fix. Automotive or swimming pool suppliers offer a rubber expansion plug that you insert, tighten the nut and I have not lost it since. You can remove them for inspection or cleaning the carb and reinstall them without issues.


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Simpleton7016
Excellent advice friends. The dealership I went to had one left. I allowed them to gauge me to the tune of $3.50. I came home and used the golf ball trick. One good whack and it sealed right in! Then I coated the seam with fingernail polish. Oh and before doing all of this, I cleaned out the carb real good with some carb cleaner. I have no idea how long that welch plug was missing, but my machine fires up infinitely quicker now. I don't know why that is, but if someone could enlighten me, I would be most interested. Thanks guys!

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HubbardRA
The wide open carb has less flow restrictions and also the length of the tube going into the throat of the carb (the venturi) are different. The way a carb performs is relative to the pulses from the vacuum of the engine and the way they bounce around inside the carb. Shortening the flow distance from the outside to the venturi can have significant changes in the way the pulses reflect and their actions on the overall vacuum at the venturi. The carb had originally been tuned with the plate in place. Without the plate, the actual carb tune is quite different. When the plate was reinstalled the flow was changed back to the way it was when it was originally tuned. It is likely running just a little bit richer with the new plate in place. It probably was running quite lean without the plate.

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JeffNemes
I use two hammers - one ball peen slightly smaller than the welch plug is steadied against the plug and holding it in place. The other hammer taps them both just until the plug is flat. This gives it the most tension and helps avoid missing the plug center. To further secure I stake it in place by "rolling" a flat wide 3/16" punch with rounded edge (similar to a wide blade flat screwdriver) over the thin edge of the carb in at least 3 or 4 spaced places toward the inside. This actually peens an aluminum piece over the edge against the plug to help secure it permanently. It probably isn't worth the effort to get or make the tool for one job but if you do it more often it may be of use to you. I haven't broken a carb yet (there's always a first time though) but if you are not sure about how much pressure to use when staking it is best to use the rubber expansion, epoxy or lacquer nail polish method - just make sure the epoxy is gas resistant, as not all are. I believe JB Weld is ok. I am also not sure how the rubber in the expansion plug will react with the gas fumes over a period of time. Also many silicons are not gas resistant.

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