Generator Backfire, Goodbye Muffler !

[alumascoupe]

I had a guy stop by yesterday to have me fix his onan generator muffler, it had burst apart from an apparent backfire which he did confirm. The nearest local dealer wanted almost $700 for a new muffler installed, so he asked if I could patch it.
I was able to work the case back together and refold the seam to get him by, then I welded it for better strength in case of a future backfire. When he asked the dealer why so much they said it was a special muffler with spark arrestor, It looked like any regular oval automotive muffler to me. If spark arrest is necessary, are there other cheaper options like a quad/atv muffler if his does give out? Its pretty rusty already.
The owner said they're heading to the Fl keys in a few weeks so I informed him to be careful not to "load" the gen with excess fuel trying to start it, and he may need to get the carb looked at. It took him several tries to get it started, waiting for the fuel to clear out, you could smell fuel in the exhaust. The PO had receipts for carb work just before he bought it. Any input for a cheaper muffler anyone ?

[Protagonist]

There's nothing special about an Onan muffler. A buzzard is just a bird, and an Onan muffler is just a muffler. Any small engine muffler for an engine of similar displacement/horsepower should work, as long as they match the exhaust system diameter. Can't vouch for equal noise reduction, though; that may be worse, or may be better than the Onan equivalent.

Briggs & Stratton mufflers should cost less than $100, and depending on which particular model he chooses for best fit, it may be less than $50. The work should be doable at any lawn mower repair shop, anywhere in rural America.

[Wazbro]

As far as work on the carb with ethanol in the gas if it sat unused for more then 3 months with gas in it, it probably needs it again.

[Steve Bryant]

Since pump gasoline now a blend of petroleum and ethanol, engines that are infrequently or intermittently used have more fuel system problems (compared to the days when gasoline/petrol was purely a petroleum product). Several people have recommended the use of a gas stabilizer in all small displacement two and four cycle engines and I've found that they are exactly right. I've been using a product called STA-BIL for a couple of years now and it really works.



I also agree that a muffler is a muffler is a muffler. It has baffles or fiberglass or something to reduce the noise and some kind of internal screen if it is a spark arrestor.

Often times carberutor/fuel injector problems can be cleared up by running a cleaning solvent in a tank or two of gas.

Steve

[AldeanFan]

I buy only ethanol free gas for my small engines and use a fuel stabilizer too. It's alot more expensive than regular gas but my engine's always start and run great.

I also drain the fuel and run the gas out of the Carb if the engine will be in storrage for any more than a month. The extra work is worth the hassel when you know your equipment will run when its needed.

Our Toyota is extremely sensitive to stale fuel. It's job is to pull the trailer so it is often parked for extended periods of time. If the fuel is more than 2 months old the check engine light will come on until you fill her up with fresh gas.

[ROBERTSUNRUS]

Originally Posted by alumascoupe

The owner said they're heading to the Fl keys in a few weeks so I informed him to be careful not to "load" the gen with excess fuel trying to start it, and he may need to get the carb looked at. It took him several tries to get it started, waiting for the fuel to clear out, you could smell fuel in the exhaust. The PO had receipts for carb work just before he bought it. Any input for a cheaper muffler anyone ?

Hi, I have experience; This happened to me once [with an old car] and never again. Check or change the crank case oil. If it has too much gas in it [went past the rings] you can have a crank case explosion.

[polarlyse]

Backfiring in engines is often related to valve timing being out of whack. I'm not sure how small engines are adjusted to compensate.
Regarding stabilizer in the fuel the Sta-bil product is good stuff but read the label. They have 2 formulations and one is for the ethanol based fuels. Check to see if the Onan company makes their engines or more likely they use a Kohler or Briggs. Replacement parts would be readily available most anywhere. Not so easy if they make their own stuff.

[Denis4x4]

Thanks to those wonderful folks at the EPA, there are more and more products designed to reduce emissions on small engines and must be used by authorized dealers.