Thread: tuning cat mufflers vs non cat

Originally Posted by Chris J.

Arse about = backasswards?

Yep.

Sorry Chris, another Aussie idiom sneaks through

You have to be very careful richening the cat because the excess can plug the muffler and raise the temp too high. Husqvarna has extra precautions on saws with cat mufflers regarding regular maintenance and tuning. They advise that the cooling system must be checked daily on saws with catalytic mufflers. Also, on the 359 the max rpm is 13500 on non cat saws and 13000 on cat equipped saws. They also have a separate section(357xp,359) on carburetor adjustment of cataytic converter equipped saws. These two issues alone illustrate Husqvarna's concern of the issue of the extra heat generated by the cat muffler. The problem is, the saws are fairly lean to begin with so who wouldn't want to richen the mixture?

thanks for the great input yo. muchley appreciated. i mainly get alot of stihls to work on in my shop and only have worked on a few E-techs husqys. i have a 359 etech that was given to me as a trade to work on a few saws and noticed it runs way different then my non EPA e-tech husqy.

when i bought my 359 it had the cat muffler on it and i bought a new 357 muffler and sent it to get modded and then adjusted my saw according and it runs much better, seems snappier and had a little more grunt to it, and sounds much better to. been running like that for 4 years now,

I have a Dolmar 5105 and I removed the cat from the muffler. About 1/2 hour with a screwdriver busting up the honeycomb. Muffler runs much cooler now. I cut the trim tabs on the carb and now can run a richer mixture without issues.

A cat will run very hot if the saw is running rich. Those people who cut the trim tabs off on cat saws better be careful not to burn something up.