Is my straight pipe the problem?

Just recently my mower has been misfiring and losing power when it warms up. My exhaust is only a inch and a half piece of stainless threaded pipe. I am changing this soon, very soon, so I don't burn up my valves. I removed my head and cleaned off the built up carbon while I had it off but saw no problems with the valves or movement of the valves. I was wondering if maybe the exhaust, or lack thereof, is making my mower run lean, or if it is another problem. As I said I am putting exhaust on soon but was just wondering if that is the problem.

An open exhaust will make your engine run lean, s will an aftermarket air filter.

murraymnan96 wrote:

Just recently my mower has been misfiring and losing power when it warms up. My exhaust is only a inch and a half piece of stainless threaded pipe. I am changing this soon, very soon, so I don't burn up my valves. I removed my head and cleaned off the built up carbon while I had it off but saw no problems with the valves or movement of the valves. I was wondering if maybe the exhaust, or lack thereof, is making my mower run lean, or if it is another problem. As I said I am putting exhaust on soon but was just wondering if that is the problem.

Yes. Your pipe should be at least 12" if you straight pipe, although a muffler would be best. Small engines like back pressure to run right so it will pop a lot and run like crap if you only have a 2" exhaust.

thats what I thought. I am planing on chopping the muffler/baffle part off of an old suzuki 50cc enduro I have and welding it onto a pipe that will lead into my motor. I will post pics when I get it done. Should be cool. Who knows, I might knock the baffles out if it isn't loud enough.

murraymnan96 wrote:

thats what I thought. I am planing on chopping the muffler/baffle part off of an old suzuki 50cc enduro I have and welding it onto a pipe that will lead into my motor. I will post pics when I get it done. Should be cool. Who knows, I might knock the baffles out if it isn't loud enough.

I believe a wider pipe will also help tone it, just fyi.

I added a 1"x8" pipe off the motor into a 90, into a 4" pipe into a 1-1/4 to 1" reducer, in to an eight inch 1-1/4" pipe. Inside the last pipe I have a baffle from the motorcycle exhaust. I thought this length and baffle would give me the back pressure I need, however, my mower still runs the same way!!!! Once it warms up it runs like crap and tries to stall at idle, along with acting like it's not getting enough fuel when on full throttle. I have checked my carb, it is clean, the fuel line and filter are unobstructed and yes, there is gas in the tank, it's full. The only thing is, the baffle doesn't take up all of the pipe. I will chop the part that it hooks to on the motorcycle exhaust off and place that between the baffle and new pipe. Do you guys think this would give me more back pressure and more or less solve my problem or is the problem something else?

kinda sounds like the carb needs adj

gearheadmike wrote:

kinda sounds like the carb needs adj

Look for tiny little holes in the emuslifier tube, make sure they are clear. they very tiny. and can only be seen by a completle disassembly of the main jet.

take your float bowl off and make sure the float isn't sticking closed. (Up) It might be filling with fuel, sticking shut, and then when you start it up and run it, it would run the float bowl dry and die. it might not be your problem, but it happened on my grass cutter.

Something else I've heard is a problem with a warm up, is the coil. Something about heat soak and it will short out but I've never had that happen to me.

just throwing out those ideas in case you tried everything else.

FearlessFront wrote:

take your float bowl off and make sure the float isn't sticking closed. (Up) It might be filling with fuel, sticking shut, and then when you start it up and run it, it would run the float bowl dry and die. it might not be your problem, but it happened on my grass cutter.

Something else I've heard is a problem with a warm up, is the coil. Something about heat soak and it will short out but I've never had that happen to me.

just throwing out those ideas in case you tried everything else.

Over time coils and magnetos are known to break down internally. Spark plugs and plug wires break down over time as well.

Chopperhed wrote:

FearlessFront wrote:

take your float bowl off and make sure the float isn't sticking closed. (Up) It might be filling with fuel, sticking shut, and then when you start it up and run it, it would run the float bowl dry and die. it might not be your problem, but it happened on my grass cutter.

Something else I've heard is a problem with a warm up, is the coil. Something about heat soak and it will short out but I've never had that happen to me.

just throwing out those ideas in case you tried everything else.

Over time coils and magnetos are known to break down internally. Spark plugs and plug wires break down over time as well.

Yeah i would check the wires.