I seem to have a problem blowing mufflers on my 23 touring. Just blew the 3rd one this summer. The first one I forgot to switch to mag and did so while driving along,BANG. The second and third ones I was driving along at 5mph or so in low on mag and it just went BANG and keep running. What am I doing wrong. These mufflers are getting expensive. Thanks, Tom
Try running with a leaner mixture. Unburned gases are making their way into your exhaust until the air/fuel mix gets right and then: POW.
That's what happened when you switched to mag. The split second without ignition allowed unburned fuel to enter your exhaust pipe.
If you have a bad misfire it can do the same thing, by not allowing the gas to burn where it should; the combustion chamber.
Check your switch I blew one because of a bad connection in the ignition switch
Oh, do I feel you pain Tom.
Do as Jerry & GR suggest, AND check the wire from the Mag post to assure the insulation has not been worn away, causing an intermittent short to ground.
Also, you might want to consider having your favorite weld apply a spot weld or three along the seam of the muffler before you install the next one. The weld won't cure the problem, but you might be able to get a couple of extra backfires out of the next muffler before it needs a rebuild.
Incidentally, if you have time some rainy day, and a whole lot of patience, AND the muffler seams came apart rather "neatly", you may be able to put the outer shell back together...and some baling wire & a trip to the aforementioned welder, and you may be back in business having spent only your time.
Tom, You could just change your muffler metal sheet with a Shell kit only, cheaper than changing the entire muffler. https://www.modeltford.com/item/4025S.aspx
But You have to fix the problem first for sure. Check the wire from Mag as previous fellow said but also check your timing too...
Had the same problem. The shell would blow out. Usually happened about once a year one reason or another. I solved it by going to a muffler shop who does diesel work. They have 5" exhaust tubing. You need a piece about 12" long. You have to measure what is left to be sure. Mine was 11 and 7/8 to make the inner baffle tight. Hardest part is to get a square cut on the end.
The tubing is seemless and will not blow out. Don't know why the vendors dont build them this way
Excellent idea Greg. I could not find a source for tube of the correct diameter when I went looking.
The purists among us do need to see a seam. I may have accidentally found a solution to blow-outs. I removed some stainless steel splashbacks from a kitchen some time back. A local sheetmetal shop rolled me up three sets of shells from the material. These have the proper double crimped seam, and being stainless, they are much tougher to roll and fold together. That same toughness has meant I have yet to blow one apart.
Allan from down under.
The original muffler that came off my 21 which is the correct type with the exhaust pipe going thru it, has a better crimp then the replacements sold also it is spot welded in several places along the seam.
Also, if the car will run on magneto, try starting it with the key in the magneto position instead of battery.
My unproven theory is that, if a spark plug does not fire, the raw gas is dumped into the hot exhaust manifold and ignited by the next cylinder that fires, so the bang does not occur in the cylinder, but in the exhaust pipe.
Slowly turning the switch from Bat to Mag could allow for several gas loads to be dumped in the exhaust manifold and then lit of with a good bang.
Yes, had that happen once. Hit the key on the coil box with my foot by accident. I turned it off ... and when I turned it back on again it went kaboom! Stopped the car and fixed it with the hammer I kept in my tool box.