Muff mod advice

I'm not too mechanically inclined but attempted a muffler mod on my 290 farm boss last winter.

At first there was a noticeable difference in power and throttle response. It ran really well last winter.

Now I started cutting again a month or two ago but it seems to bog down when it's under minimal loads. The chain is always sharp. Any ideas on what to check besides the plug?

 

Have you tried tuning the saw?

 

Did you tune carb? You could try retuning it.
You could just be used to the new or now same old power it is making. I know on my 290 it made a good difference then I got used to it until I used another stock 290 it was night and day.

 

I've attempted adjusting the carb. I've got it where it starts four stroking when held wide open, that's what I read to do. But when I attempt to sink the bar into wood it is unimpressive. Actually it worked better before the mod as of late

 

Did you retune in the winter after the muff mod?

 

Yes. It ran really great this past winter. Guess that's why I'm puzzled

 

Do you have good compression?

 

Good question. I don't have a gauge but will give it a guess

 

Did you rinse the muffler real good after the mod to make sure you got all the metal shavings out. If not it could of suck shavings in to the cylinder.

 

Sounds like it needs tuned, to do this you really need a tach.... establish your rpm, then tune the 4 stroking.....

 

I bought a tach and rarely ever use it. I do on occasion check with the tach to see how high a saw is tuned after porting.

 

If I had to guess, and without the saw in front of me thats all it is, I would say it's a tuning issue. There is a really good tutorial here on how to tune a saw carb:

Saw Carb Tuning

 

Pull the muffler and if the piston looks anything like this:

Your piston is shot.

 

Another vote for needs a slight tune up. You mentioned it's unimpressive with the tune. Is it possible that you're on the "fat" side of rich? I know from tinkering with my saw for fun, that if it 4 strokes with no load, and is still 4 stroking constantly under load (cutting), it's too rich, and loses power.

I usually have my saw set about as rich as possible, and it just bounces in and out of 4 stroking.

I think bobdog has a video of a little chinese saw where the tune is a touch rich, and bounces in and out under load. If you can find that tune, and lean it out a hair, you would be right on the money in my opinion.

 

Thanks for all the suggestions. I will give them a try

 

I looked back on bobdogs posts, and found the video I mentioned.



You can hear kind of a bounce between 4 stroking and cleaning up. Often my saw is tuned like this on a full tank, and it cleans right up after 5 minutes of cutting.

 

Thanks . Mine might be too rich

 

If you tuned in the winter cold then in the summer heat you will be running rich. It's normal to re-tune each winter and summer seasons.

 

I too think it's tune. And I second those that say if you tuned in winter it's possibly too rich in the summer.

I had a cheap Chinese saw I tuned in the winter. Ran and idled fine then when it was 90F it would idle and slow and slow till ot cut off. Turns out it was loading up with fuel and flooding at idle. A slight adjustment of the L screw in this case and it's was back to running perfect. Was just the 30f difference in temp and humidity difference causeD a bad tune

 

I cant believe how much lucky i am , i never have touch theese screws , and for a mysterioys reasons that i can not explain never have problem with my saws

who knows maybe here in Greece the weather and temperatures are more good for the saws