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pitts muffler

Old 08-15-2006, 04:44 PM
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Default pitts muffler

I have an o.s. 61 with a pitts muffler mounted ina great planes ultimate 40 bipe sideways. I cannot get the muffler to put out any pressure to the tank and as soon as the tank gets half empty the engine quits. The lines and nipple are all clea. I even pinched off one pipe still nothing. It blows great with the standard muffler. Is there something missing in the muffler? looks like just a box with 2 tubes coming out so how can it build up pressure to the nipple?
Old 08-15-2006, 07:23 PM
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Default RE: pitts muffler

Have you recently tried the other muffler to make sure it is just with the pitts and the problem isnt originating from something else? I wouldnt think the problem would wait until half a tank to act up. A lot of times once the engine is up and running you can disconnect the pressure line altogether and the engine will still run bc the carb is drawing the fuel.

Is the engine in a cowl? It could be possibly overheating and thats why it dies at half a tank after it leans out a tad.

Just ideas.

Sometimes pitts do take a little tweaking (such as crimping one of the outlets like you did) but if its a pitts made for that engine it should work.
Old 08-15-2006, 11:18 PM
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Default RE: pitts muffler

i,m sure you checked this but i had this prob it ended up being the clunk/line in the tank and it only happend when the tank was 1/2 full or less (below the intake line). i say, just to be safe, check it. i have a pitts muffler on my 50sx no trouble. if it is not that , got no clue. hope this helps.
Old 08-16-2006, 12:56 PM
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Default RE: pitts muffler

Does it have a pressure nipple? your description seems unclear. If there is no nipple, go the LHS and buy one and drill and tap the muffler and install the nipple.
Old 08-16-2006, 01:59 PM
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Default RE: pitts muffler

The vast majority of Pitts style mufflers generate little or no back pressure. That's why they may seem to boost performance on your engine.

The negative factor to this power increase is the lack of muffler pressure for the fuel tank.

Try this: Plug up one of the outlet pipes with a dowel, or something that will not blow out.

Tune the engine and see how long it runs.

I'd bet MinnFlyers house that it'll go through a full tank just fine.

"Ultimate" (get it? Ultimate?) solution is to permanently plug up the pipe, or maybe pinch both down to a smaller size.

That's the only way you'll develop muffler pressure from most of those kind of mufflers.

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