Plugged 4 Cycle Muffler

[Nubs]

I built a 295 for a fella last week and today he calls me and says he installed the engine and it has no power and runs hot, i told him to bring the cart over and i'd check it out. Drove the cart and it didn't even want to shift the clutches all the way up. So i checked the compression, etc and all was good so i went and installed the muffler from my test stand and drove it again. problem solved. I cut a hole in the top of his old muffler and its plugged tight, 99% of the Perforated Holes in the inner chamber are shut. those holes are suppose to be the same size as the ones in the exit pipe. if ya ever have an engine check out good but don't pull right try pullin' the muffler loose at the manifold and see if the power comes back. its free to try and i'm runnin' into it more and more.
So yes even a 4 cycle Muffler can become plugged

 

[Radicalgolfcarts]

Good deal!! I've never seen a muffler plugged up on a 4 cycle. I've seen it on 2 strokes though.

 

[dirtysouth]

Good info.

 

[Gale Hawkins]

Any thoughts on what could have lead to that happening?

Thanks for the photos.

 

[Nubs]

Its a combination of carbon and unburnt oil, when the motor starts to loose compression from overheated rings and or bad intake valves it starts to push oil out the exhaust. most don't run long enough at a time to burn it out of the muffler, that muffler in the picture weighted over 3 pounds more than the new one i had installed. i have been workin' with a local engine shop that lets me buy time on there engine dyno that they use for there snowmobile engines, a new 295 will make between 8.5 and 9 hp with and new factory muffler. we installed five different used mufflers on the same engine and found the hp dropped as much as 3.5 hp. thats a ton when ya only got 8 to start with.
with a base hp of 8.25 i installed this 250.00 zemco muffler on that same engine with no other changes and got 8.75. I removed the factory air box and it dropped back down to the 8.25. When i installed a 92 jet with no air box and pulled 9.3, then added a foam style air cleaner and got 9.75.
So its my opinion that when guys say that these aftermarket exhaust make power with no other mods its more about replacing a plugged muffler than a power upgrade.

Now when you do the head porting and carb replacement the zemco header will add 1.5 over the stock muffler and thats pretty good all i'm sayin' is any ez go 4 cycle with alot of hrs on it needs a new muffler, at a 150.00 its a cheap tuneup and can save ya the cost of repairs from overheating if your a trail or road driver

 

[Gale Hawkins]

Nubs thanks for your detailed answer.

Not knowing carts but a little about RV generators I went with the EZGO PDS electric in part for the lower purchase price but also I use it around the place and may only go 100-300 foot at a time then will be stopped for a long time.

The RV owners that boondock a lot and use the generator to only run the microwave at meal times develop performance issues. Onan even puts in their manuals if used in that manner to run the generator for two hours non stop with at least 50% load once a month. That is hard to do with carts.

I would like to get a gas cart at some point and if I do I will remember if a well tuned engine seems weak to try a new muffler.

Sea Foam is something I put in all of my stored gas and vehicles that are parked a lot. I find it will decarbon engines well. Not sure it regular use would help with muffler carbon build up.