Finishing 290 to 390 conversion

[shortys7777]

I am about halfway putting everything back together but had a few questions. Some people on YouTube add oil before they seal the upper and bottom together. It looked messy and I did not do that. Do I need to add anything before firing it up? I want to mod the muffler a little too, but nothing crazy. I've seen videos on this too but none on this saw. Is there anything else I should do before firing it up? I have a compression tester and a tachometer. Thanks.

 

[anlrolfe]

I use little dabs of oil here and there. Smear some on the seals, a drop or two in the bearings, film coat in cylinder and on piston.
Pouring it in.... I don't think so.

 

[a. palmer jr.]

I usually put a few drops down the intake and exhaust onto the side of piston before start up.

 

[67L36Driver]

I’ve never put an engine together ‘dry’.

[emoji19]

So, from the intake neck with the piston at TDC; squirt some oil on the rod so it runs down to the big end bearing. Then roll it on its right side an give it a squirt so it runs onto the PTO main bearing. Give it some time and then do the left side.

Go to the exhaust port and give the piston skirt a few drops. Run it up /down to get it to spread. Same dance on intake side of the skirt.

 

[67L36Driver]

I use little dabs of oil here and there. Smear some on the seals, a drop or two in the bearings, film coat in cylinder and on piston.
Pouring it in.... I don't think so.

I wouldn’t be above pouring it 1-2 oz (liquid measure) in and ‘sloshing’ it around.

Only conceivable downside is smoke at first run. The excess will just blow out the exhaust (and make a mess).

[emoji16]

 

[4CornersPuddle]

My first round of muffler mod on my 390 only went about halfway to where it needed to be. I achieved a noticeable gain in power and a lesser gain in torque.
While cutting with a friend (his saw a 310, if I remember correctly), running our saws side by side, we got the idea to switch mufflers. His was stock. His saw woke up a bit; mine lost power with his stock muffler.
Figuring I was on to something very interesting, I took my saw home and opened the muffler outlet to 85% of the surface area of the exhaust port on the cylinder, as is recommended here on AS. There was an immediate and large increase in power and torque compared to what I'd achieved earlier after my first mod.
I would encourage you to not mess around with a little mod to your muffler. Measure the exhaust port area. Do the math to determine 85% of that, and open the muffler outlet that much. No need to go more, as you'll achieve more noise than anything beyond the 85% level.
This 390 of mine now out cuts my 036 which has a muffler mod not determined by math, but by "that looks pretty good." So, time to do the measuring thing on that 036 muffler.
Good luck. I'm impressed by my 390, now that it can breathe.

 

[cgeb]

Ok here is the scoop, squirt on the bearings, wipe on the piston and cylinder. Thats it everything else (mating surfaces) need to be brake clean-clean and shiny so the sealant can bond to it. You don't want oil all over the surfaces you need to seal up.

 

[a. palmer jr.]

I wouldn't put an engine together dry either but they don't need to be to greasy, just a few drops on the bearings and a little on the piston and rings but I make my mixture a little rich for the first tank or two..