Thinking about muffler modding my ms290

[tec498]

It's 1.5 years old, my warranty is already up right? If I take it in to have something done will a shop work on it if I'm paying for the service? Is there anything illegal about doing it? It pulls an 18" b/c good now so I assume it will pull a 20" bar great after the mod? Does anyone know roughly how much I have to back out the L and H screws from stock to make sure it's getting enough fuel? I'm a little nervous about doing it because it will be the first time I've nodded a muffler but I feel like I will be very happy with the saw if I do it. I've been reading about it here on the forums for a few days, talk me into it!

 

[Saw Dr.]

Cut the opening on the deflector bigger, and open the area between the two holes on the muffler under the deflector and enlarge the slot. You can always add more holes, but it is hard to put material back. First item should be to remove the limiters and trim them. Muffler modded 1127 saws run surprisingly well for what they are. If you drill holes under the deflector in the indented area (inside the baffle) it will end up being ALOT louder. Some folks don't mind this. I have had good success without having to drill in the baffle, though I do remove quite a bit of the material outside the baffle. You can use or delete the screen as you see fit. I generally keep it, as it does not seem to make much difference in performance, and it will keep the bees out of your newly enlarged muffler openings.

Good luck. Make sure to pull the limiters and re-tune. Otherwise, you may be in the market for a Baileys 390 kit sooner than you think.

 

[old-cat]

I did the MM trick with my MS 290 after reading a lot of the info here. I liked the sound after I did it but that's about all I got out of it! When I bought the saw , I also got a 20" bar and a 28" bar both with 3/8' pitch chain and I thought they were just fine.
Then I used an MS 441 and I realized it wasn't so great. The best mod you can do to that saw is a 390 piston/cylinder, 64cc. Just put a plug in the compression release hole, you don't need it.

 

[ncfarmboy]

Absolutely! It will make a big difference. You will need to retune carb. after the MM. Doubtful a Dealer will do it. It's against the EPA law for the to modify any OPE. Carrys a BIG fine if caught. MS 290 is pretty easy. There are threads on how to. I would still stay with the 18" bar tho it will pull it with more authority. Longer bar does not necessarily cut faster.
Shep

 

[phillipmc]

I did it on mine. Steps I took:

1.) remove muffler from saw
2.) In the big dimple behind where the deflector is I drilled 2 3/8 holes beside each other close and removed the remaining material, then took a file and smoothed it the edges and making the holes into a big oval.
3.) took the deflect to the bench grinder and grind about 1/2 inch or a little more back at an angle then removed the burrs.
4.) with compressed air I blew all the little shavings out making sure none where left to get sucked back into the cylinder. (VERY IMPORTANT STEP!)
5.) reinstalled muffler with deflector and screen to keep the trash out of it.
6.) removed the limiter caps with a dry wall screw and trimmed the limiter tabs and reinstalled them. retuned carb (VERY IMPORTANT STEP) before even starting the saw I turned the H screw OUT 1/8th turn and left the L screw alone
7.) cranked saw (making sure it was full of fuel let it warm up and nailed it to WOT for about 5 sec and it seemed a little on the fast side so I left off the throttle and turned the H screw a little more OUT about another 1/16th turn (this depends on saw and fuel and oil mixture) It should 4 stroke out of wood then clean up in the wood.
And there you have it. Took about 20 to 30 min And the saw now runs cooler, cleaner and is a little more torquey. Also I wouldn't go any more then 18" bar . If you need a bigger bar then get a bigger saw.

 

[kodiakyardboy]

phillipmc did the same as I did. Remove defector and cut out the whole square indented portion, open the deflector a little wider and retune. It was the first muffler mod I did and probably made the biggest difference on any saw I have done. Go for it, you will be suprised how much more power it will make! Post pictures when you are done. Mine pulled a 25" chain with no problem afterwards other than it had problems oiling it properly. Your results may vary, I only have spruce to cut. Should pull a 20" in hardwood no problem...