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Buickgsman

243431 exhaust port thread size

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Buickgsman
I am having difficulty threading in the muffler on my 10HP briggs motor. I dont want to booger up the threads on the muffler so I need to run a tap through it to clean it out. It appears to be a 1"NPT and I tried to clean it out with the correct size tap but the NPT tap is tapered and the threads on the muffler appear to be pretty straight. Should I try and find a different tap? Also, i think the tap is bottoming out on the inside of the exhaust cavity so I cant bottom the tap out all the way. Whats the best way to fix this? Thanks! Bob

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HubbardRA
Did the tap straighten out or re-cut any threads? Does it look like you have enough thread to screw a pipe nipple into? Have you tried screwing a pipe nipple into the threads after running in the tap? Yes, the engine does have tapered 1" pipe threads. If it did not go in far enough to cut sufficient threads, then you may need to grind off the end of the tap to let it go in farther and cut a larger diameter thread. On a tapered pipe thread, it only needs to go in far enough to cut a full depth thread. It does not need to be bottomed out. This is because the thread on both pieces is tapered.

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Willy
Take a 1 in pipe nipple and using a hack saw score it in about 4 or more places lengthways across the threads. Spray some carb cleaner in the hole to soften the carbon and then work the nipple back and forth until you get the threads cleaned out. It takes a little time but I have always had good luck doing it this way. Good luck

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GrincheyOne
Bob, 1. Alternative to a pipe nipple is a 1" NPT plug. 2. You can clean the threads in the engine by using a standard pipe cleaning brush, or a barrel cleaning brush from your gun cleaning kit. These are fairly soft and do not damage the threads. 3. remove the breather cover (behind the carburetor, and clean out any residue around the valve stems, springs and retainers. Be careful not to damage the reed valve in the cover. Any residue can cause future wear, and work it's way down into the oil sump. Wayne

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steve-wis
When a pipe tap is used, the correct depth should be about 2/3 of the tap, or about 4-5 threads left outside of the hole. If you can't get the tap that deep, it won't recut the threads. The only alternative then is like Rod said, grind off the small end of the tap. If the threads are too far gone, I have made a steel plate, about 1/2 inch or so thick, with a 1 inch NPT tapped hole in it, and then bolted it to the engine using the two tapped holes on the sides of the exhaust hole. Steve

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dhardin
A 1" pipe tap is good but most usually not going to accomplish what you need. The block only has 5 to 6 threads that do all the holding. so the taper on a thread cuter will not go deep enough to cut it clean where you need it. Best use a small wire brush and carb cleaner or solvent to brush out the burnt carbine. For my most success, is what your using to put back in the exhaust port. A standard 1" short pipe nipple or elbow you need to cut off the first 2 or 3 threads of the end threads. These are tapered down so much that the insert will bottom before anything gets tight. Plus they make a locking threaded collar. some are made of aluminum/pot-metal. I have seen these melt over time. You need to look for a all steel pluming 1" threaded lock retainer. Once you have the muffler or pipe fitting in and as tight as possible tap the lock right against the block. It must be tight or you will need to weld a flat plate to the muffle/pipe and drill 2 matching holes to do a bolt on muffler as mentioned above.

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