290 to 390 issues

[jasonw0586]

Have a 290 converted to 390. Oem top.
Ported, muff mod, timing advance, and popup piston.(yeah lipstick on a pig I get it) anyways....have maybe 15 tanks through it. Cutting ash and maple. I can go through 2 tanks of gas easily before I'm out of oil.currently has a 20in sugihara bar. my bar isn't getting hot or messed up. And there is oil when you lift up the chain but I feel its under oiling compared to about any other saw ive ran. saw seems to run and idle fine cuts great mid to the end of the bar.if you try to rotate around the spikes or even just cut back by the powerhead it bogs down. Also bogs down if you try to cut anything bigger then maybe 12 to 14 inches. Sharp chain properly tightened clean Air filter
After coming out of a larger cut most of the time i have to blip the trigger or it will die..if it dies one pull and it fires right back up with a decent puff of smoke. Lots here know more then me but im thinking the high screw is just too fat? I dont have a tach so I want to be careful.but im thinking Maybe also thats affecting the amount of oil or am i missing something else?use premium gas and stihl brand 2 Stoke oil. Thanks for any advice

 

[Fatherwheels]

First off, don’t use that saw until you sort it.
You say it bogs down in anything over 14” wood, that shouldn’t be.
There is a problem with fuelling, you could be running lean and the engine
spinning way too fast, this alone could outpace the oiler,
but a poor oiler and a fast engine will certainly destroy a bar in short time.
But if your burning all that fuel then you could be loosing power and bogging down too.

No idea whether the oiler in the 290 is up to it, never mind on a ported saw.
But once you heat the bar enough it will never be much good, the rails
will grab the chain because the clearance when hot is not enough, and it
will only get worse.

I only ever heard one of those saws running, don’t think it was modified in any way,
but to me it was already screaming too much, a muffler mod would be all I would
have done to that model.

When your sure your carb is set right,
make sure your rakers are right, give the saw a good bite, sharp chain
is a must, otherwise you will run fast and cut little.

Put a tach on the saw and set it to factory spec for now.

I bought two identical saws, one could oil a little better than the other, but they
both oil very well.

 

[Fatherwheels]

15 tanks is a lot of fuel to burn, you should have noticed the bog before that.
Try setting the saw to factory spec for the top end you have.
Would be great if you took a video of the saw starting cold,
and then warm it a minute and do some cutting, that way it would
give those who know these saws an idea in what direction to comment.

 

[jasonw0586]

Also should have stated oiler is all the way up.saw never seems to get hot..like at any point i can put my finger directly on the block
And its warm but nowhere near uncomfortable..im guessing that means its not too hot??...and the carb is from a 044. Running 40:1

 

[Fatherwheels]

Here is a link to setting carb on a 039/390, from 6 min on.

 

[Fatherwheels]

Also should have stated oiler is all the way up.saw never seems to get hot..like at any point i can put my finger directly on the block
And its warm but nowhere near uncomfortable..im guessing that means its not too hot??...and the carb is from a 044. Running 40:1

If the saw never gets hot then you are running a lot of fuel through it,
that will bog you down,
Take a look at the video I linked, the last part is about carb setting, he says clearly
what will happen in the cut if fuelling is not right.

Your current settings are safe, but will rob you of power, and wont be good in the long run,
too much fuel at 40:1 might carbon up your rings sooner than you would want.

Use a Tach, this guy set his at 13,250, a bit less will be better considering
your saw has just about broke in.

 

[Fatherwheels]

Check the oil filter, when was it changed, was it ever changed, check the pipe is
not perished and closing in.

 

[jasonw0586]

Thanks man ive tuned a few saws before without any problems and ive leaned it out some but still being careful

 

[anlrolfe]

Doesn't the 039/390 carb take a bigger main jet. I recall reading that somewhere.

 

[Fatherwheels]

Thanks man ive tuned a few saws before without any problems and ive leaned it out some but still being careful

That’s the way to go, you should still here the saw four stroking out of the cut at WOT,
and clear up when cutting. A tach is useful, as a lot of saws have a limited coil
that make it difficult to tell four stroking from coil cutting back.

 

[Fatherwheels]

Doesn't the 039/390 carb take a bigger main jet. I recall reading that somewhere.

Think he said there’s an 044 carb on it, will be good to hear he gets it to work.

 

[farmer steve]

The 290 will use 1/2 tank of oil to 1 tank of fuel. That's how it is. Maybe a bit more with the top end change.

 

[motorhead99999]

My 290 and my 390 both oil one tank of oil to two tanks of fuel. I just run winter oil in them all year

 

[Junkwrencher]

I have experience with the unmodified port flat-top piston 039 and MS390 saws. Not to assume anything or question what someone has or has not done I will offer what others have taught me. Replace all oil, fuel, and impulse lines and hoses with new o.e.m. Stihl has a new straight fuel line for this series that eliminates some of the kinks in the old "S" shaped fuel line. Part # 1127 647 9400. Replace the oil and fuel filters in the tanks. On a rebuild on this series saw always replace the crankshaft seals with new ones. Use Dirko sealant on the engine pan. Pressure test the assembly. Tune the saw to "four-stroke" with no load and clean up in the cut. I do not think these coils are limited. When the ports are modified and ignition advanced strange things can happen....

 

[Junkwrencher]

Also should have stated oiler is all the way up.saw never seems to get hot..like at any point i can put my finger directly on the block
And its warm but nowhere near uncomfortable..im guessing that means its not too hot??...and the carb is from a 044. Running 40:1

Something else I just thought of on this series. Early models did not have a compression release on the cylinder and the last models did. This could be a source of leaks as well. You did not mention if the replacement cylinder was o.e.m. or otherwise. Port timing can vary between brands.

 

[Junkwrencher]

Something else I just thought of on this series. Early models did not have a compression release on the cylinder and the last models did. This could be a source of leaks as well. You did not mention if the replacement cylinder was o.e.m. or otherwise. Port timing can vary between brands.

Correction you did state o.e.m. in your text.

 

[Junkwrencher]

Without compression release...

 

[jasonw0586]

Without compression release...View attachment 812998

There is no decomp

 

[grizz55chev]

There is no decomp

What’s the compression # s?

 

[jasonw0586]

What’s the compression # s?

Dont have a tester atm...just by pulling on it seems good but I know thats not exact