Thread: Chainsaw muffler mods

Originally Posted by OzEo

Hi All,
I was looking on some overseas forums about chainsaws andthey were all pretty keen on muffler mods- opening up the muffler to let themotor breathe better- more power, (more noise) cooler running. Then I read thatthey aren’t as effective in Australia - we don’t have the muffler restricted asmuch in the first place because we don’t have such strict environmentalprotection.
Can anybody confirm/deny/comment on this please?
Thanks, Eo

That's correct about the Aussie mufflers not being as restrictive as the US mufflers. However they are are still restrictive and PROVIDED YOU KNOW WHAT YOU ARE DOING saws can benefit from opening up the muffler.

Bear in mind that if things go pear shaped in public woods you are entirely responsible - the information I will provide assumes you will be using it in an area where the usual regs do not apply.

The degree to which the muffler can be opened up is a "how long is a piece of string question.
The simplest and easiest opening is removing the spark arrester. Especially when these get dirty they can really hit engine performance hard.
The ideal thing is to keep the arrester clean but just removing that can make a difference.
Please note if you start a bushfire because of this I did warn you this might happen.

Next comes things like removing baffles and opening up the exhaust opening.
This needs to be done with some care as this can increase air flow and this will tend to runs a saw lean i.e. too much air for the amount of fuel) so the saw may overheat and you can cook your machine.
When the muffler is opened up the carby needs to be adjusted to suit the new increase air flow by adjusting the H jet.
Not all chainsaws have an adjustable H jet and then this requires that this jet be changed for a larger one.

Making the motor breathe more easily will reduce the engine temperature but power increase will be marginal - i.e. not really noticeable unless if you time some cuts and then you will see a small difference.

In this thread you will see how I muffler modded my 880 that I use on my CSM
https://www.woodworkforums.com/f132/880-muffler-mod-92679

My mod incorporate the ability to adjust the size of the opening.
I eventually opened the outlet from 14 to 19 mm in diameter which is an 84% increase in area.
This generates a LOT of noise but not quite as bad as I though it would.
Power increase was very hard to determine as there are so many variables involved and this could only be noticed by using timed cuts, it was certainly less than 10%
Fuel consumption increased by about 20%
Engine temp did go down - I have a temp gauge on my saw so I could monitor this - I can't say how much exactly because it varies so much during a cut anyway.

To really benefit from a muffler mod the engine (exhaust ports) needs to be opened up. only then will you really notice an perceptible increase in power.

Thanks Bob, nice job on your 880. I don't really have any need to actually
mod my muffler -just curious. I suppose more power is always nice, but I'd probably just get a bigger saw. They're too expensive for me to muck around with and ruin, unless I get hold of a beater to play with. Thanks for the information. Cheers, Eo

Originally Posted by OzEo

Thanks Bob, nice job on your 880. I don't really have any need to actually
mod my muffler -just curious. I suppose more power is always nice, but I'd probably just get a bigger saw. They're too expensive for me to muck around with and ruin, unless I get hold of a beater to play with. Thanks for the information. Cheers, Eo

Thanks OzEo.
Yes I agree - a bigger saw is also more fun