stihl ms290 carb tuning questions

[slowcar281]

just picked up a nice used ms290 saw. after a full tune up i cut slots above and below the baffle and drilled 5 holes in the baffle to open the muffler way up. also drilled like 6 holes in the deflector to make sure it flowed real good. i dont trust myself tuning the carb so i took to a stihl dealer to tune the carb and i explained that i opened the exhaust way up and told him to richen it up and tune it the best he can.

i get the saw back yesterday and he tells me that idle is 2800 and the saw maxes out at 12900 rpms. saw runs and cuts great.

with no load on the saw at WOT it 4 strokes real good. it also 4 strokes at WOT when cutting wood unless your real deep into a thick log. cuts really well....... just sounds funny when cutting.

this is my first stihl saw and i love it. is this how it supposed to run after doing the muffler mod? is the mixture too rich?

btw im using 93 octane fuel mixed 32:1`with the stihl hp ultra oil.

 

[Stihlofadeal64]

Could you post some pics of the muffler mod. If it has been modded like you said it is definitely going to sound different. I would be more comfortable (preference) with the top at 12,500. If it is 4 stroking you may be ok, but I would want to hear it in the cut myself, and coming out. The problem with having someone else tune your saw is --you really gotta trust them. Since I tune my own I don't trust the tune to someone else. The muffler mod should give you more grunt in the cut, did it do that for you?

 

[slowcar281]

I wouldn't be able to get pics till next weekend, but it's like some of the other pics where people have gutted below the baffle, I went ahead and cut above it too plus I drilled straight into the recessed area on the muffler so a lot of exhaust gasses bypass the baffle altogether.

The deflector is just basically full of holes now. So I know it flows pretty well.

The guy that tuned the carb has been working on stihls at the same shop since 1982. He even had the oem tools to remove the limiter caps.

It 4 strokes 99% of the time while cutting unless I'm real deep in a thick log really working the saw. As soon a I back off of it it will 4 stroke again. Anytime cutting through small logs or branches it 4 strokes and cuts really well. You have to really try to get it NOT to 4 stroke.

I was just wondering if it's normal for it to 4 stroke like that......: I'm guessing its a good thing?

Btw I only cut with it stock 1 time and that was the night I received it in the mail. I instantly went online to to do research about it and that's when I found the muffler mod.

All I do know is this thing cuts like an animal.... I've never had anything this nice before. I'll never buy another chainsaw that isn't a stihl, that's for sure

 

[RedFir Down]

How sharp is your chain?
If your chain isnt sharp it would take alot of force on the saw to make it clean up in the cut.
Try sharpening the chain... give that saw something to do!!

 

[AKDoug]

Ah yes, the beginnings of CAD. Try a 036,360 or 361 and you'll probably sell that 290 Get a ported 261 and you will really smile. :msp_w00t:

It really sounds like your dealer did a good job on your saw. They fact that he was willing to remove the limiter and tune it is something many dealers won't bother with.

 

[slowcar281]

Chain is 2 days old, I bought a carbide tipped stihl chain the day I had the carb tuned.

I think I'll just leave it alone. I was a bit worried about the 4 stroking but I guess a bit rich is better than too lean.

In time I would love to own a bigger saw. We have a couple of 660's at work. I never payed them no mind but next time I see one I may have to find something that needs cut lol

Btw does anyone run their equipment 50:1? Reason I ask is I talked to the guy who tuned the carb and he does not recommend it. Says he has people come in with scored piston and cylinders all the time that run the motomix premixed fuel. He says there just isn't enough oil in it for heavy use.