Porting A 390XP Top End For A Worksaw

[Mastermind]

More....

The work in the intake was just to remove the casting lines. I didn't widen it at all.

 

[Mastermind]

I'll get this sent off to Bob @Spike60 tomorrow.

 

[Brush Ape]

It's too bad you can't compost all that swarf Randy.

 

[Deets066]

I don’t see deep gouges in the intake.....

Or Mickey Mouse ports that are covered by the piston skirt.

you sure it’s gunna run?

 

[Mastermind]

It's too bad you can't compost all that swarf Randy.

I used to give it all to a hippy chick that made some sort of aroma therapy BS out of it.

you sure it’s gunna run?

Yeah.......I think it will.

 

[jacob j.]

You sure do beautiful work sir...

 

[5155]

Dumb ? here.
With Spike having the BE, and you having the TE.
How do you know how much to raise or lower?

 

[XP_Slinger]

Nice looking work Randy. Thanks for taking the time to do a thread.

 

[Mastermind]

You sure do beautiful work sir...

This is far from my best work.

Dumb ? here.
With Spike having the BE, and you having the TE.
How do you know how much to raise or lower?

I have a PDF file for each saw I do.

390XP​

Stock:

Compression: 150psi
Squish: .014 W/O Base Gasket
Ex: 97°
Tr: 122°
In: 78°

Ported:

Compression: 195psi
Squish: .023
Ex: 99.5°
Tr: 122° 1.200”
In: 81°

Notes:

Taking .030 from squish and .033 from the base with a base gasket netted a 195psi compression.
Ignition timing should be advanced 6-8

 

[Tor R]

Good to see you’re making threads like this Randy. I’ve actually missed stuff like this.

 

[5155]

Very good.

Leads me to think factory parts are "pretty" consistent, while the AMs are who knows. (I found that out).

Thanks, I'll never be a machinist, I just always want to know why.

 

[Mastermind]

Good to see you’re making threads like this Randy. I’ve actually missed stuff like this.

I appreciate that Tor. I wish I had the desire and time to do more......but it seems like there's really nothing new to post.

 

[Mastermind]

Very good.

Leads me to think factory parts are "pretty" consistent, while the AMs are who knows. (I found that out).

Thanks, I'll never be a machinist, I just always want to know why.

They are very consistent......usually. There are cases of things changing though. For instance, Stihl had been using Gilardoni jugs and KS pistons in the 661 since they first came out. Then....a few months ago I started seeing a Stihl branded jug and a KS piston. Squish clearances didn't change, but the intake port is much different.....

 

[p61 western]

I appreciate that Tor. I wish I had the desire and time to do more......but it seems like there's really nothing new to post.

Maybe mess with some of your older saws Randy? Oh and good job btw.

 

[Mastermind]

Maybe mess with some of your older saws Randy? Oh and good job btw.

I wish I had time Mike.....

I've got a nice 084 that has a small fuel issue.....simple stuff. Ain't had a chance to fix it. If I get any "spare" time I either spend it with my family, or my cows. LOL

 

[Agent Smith]

Very nice work and thanks for showing how to properly do some work on s 390!

 

[andyshine77]

I like the numbers, that will make a reliable, strong work saw.

 

[Mastermind]

An example of how consistent these parts are....



I cut .040" outta the squish on these 572XP jugs. Just checked the clearance on them. They vary only .002"

So, I can cut .050" off the bases of them all without worry. The tightest will be .020"...

 

[NCPT]

Great thread here and thanks for taking the time. I like your tricks you use, I appreciate you sharing this stuff.

 

[Wonkydonkey]

I wish I had time Mike.....

I've got a nice 084 that has a small fuel issue.....simple stuff. Ain't had a chance to fix it. If I get any "spare" time I either spend it with my family, or my cows. LOL

I think I know the ones you love the most......

All of them