How Heavy Should an ST350 Muffler Be?

[Futility Vehicle]

I fired up my ST350 the other day, and things went fine until it quit suddenly. It sat for a couple of days. I thought maybe it was too low on gas to pick up fuel, so I added some, and it took off. I thought things were okay.

Days later, it quit again. While I was trying to get it going, fuel spilled out on the ground.

Thinking I had a bad fuel hose, I went and got materials to fix it Then I realized fuel was overflowing from the carb.

While I was taking the carb out for cleaning, I came across a video that said Robin engines that smoke usually have bad valve seals, not bad rings. My cart smokes. I decided to get me some seals. The video guy said leaky seals would cause a muffler to fill with oil, and the burning oil would cause smoke. I also found out a plugged muffler would cause fuel to overflow. I thought maybe I had found my main problem. Fix the seals, and the smoking and overflow would stop.

Once I got the muffler off, I ran the cart without it, but the fuel still overflowed, so there has to be a carb problem. I blew into the carb to see if the needle was seating, and it seemed okay, but I'm putting it in the sonic cleaner anyway.

I'm going to clean the carb, install new valve seals, replace the overflow tubes because they are rotten, put in new fuel hoses because I have the materials on hand, and maybe burn out the muffler.

Question: how heavy are these mufflers supposed to be? I have no way of comparing the weight of a plugged muffler to the weight of a clean one. It feels heavy for a muffler, but some mufflers are like that when they're clean.

[Timberwolflt]

Just pulled mine off a couple days ago and was myself surprised by how heavy it was but it was perfectly clear … blow some air through it just to confirm. The fuel issue will most likely be at the carb… either the needle and seat or it’s ill adjusted

[Futility Vehicle]

Thanks for the info.

The carb was loaded up with varnish. Now I need a new O-ring to go between the bowl and the body, but I can't find one online.

[Futility Vehicle]

It appears the O-ring is 53mm x 57mm. Easy to get from China, but US sellers are rare and high on shipping.

[kgsc]

53x57? Is one of those missing a decimal? If you have a small engine shop near you they might be able to cross it to say a briggs gasket.

[Futility Vehicle]

The measurement comes from a digital caliper, so it may not be absolutely correct.

Thanks for the tip.

[kgsc]

I meant that ring should be round so what measurements are those? Is that a range?

[Futility Vehicle]

The ring is 57 mm outside and 53 mm inside. I don't know the vertical thickness.