Need porting advice for ms390 top end on ms310 bottom end(same saws just different bore)

[Ethan Hamby]

I just got an ms310 and did a muffler mod on it. And just today my ms390 top end came in to put on it. Any advice on how to go about porting this cylinder would be greatly appreciated.

 

[Mastermind]

I moved this over the the main saw page Ethan.

It will get more traffic.

Personally, I'd just widen the intake and exhaust, advance the timing, and do a good muffler mod.

These guys will help you out. Welcome to OPE.

 

[Ethan Hamby]

Advance the timing in what way? And OK so widen them to within what tolerance from the edges of the piston skirt?

 

[Ethan Hamby]

And I'm glad to be here!

 

[Mastermind]

Dig around some........you'll find a lot of info here.

 

[Ethan Hamby]

Won't widening the ports without looking at the actual dynamics cause issues?

 

[Mastermind]

Do you have a degree wheel?

 

[Frank bierce]

There are lots of threads on here about porting. Use the search function...lots of pictures, and fantastic
Info.
Yes..if you widen too much, it will definitely cause problems.
Welcome to OPE!!

 

[Ethan Hamby]

No I do not

 

[Ethan Hamby]

I'm missing a few critical tools as is haha

 

[Mastermind]

That's what I figured Ethan. The first jug I ever modified was done with a piece of a rat tail file in a drill. Stick around and learn.

 

[Ethan Hamby]

I bought a set of needle files just for this project but by the looks of it they're going to be useless. I need an air die grinder and bits to

 

[fearofpavement]

If the 310 is running well now, I wouldn't do an engine mod on if it was mine. I'd wait to find a blown up 1127 saw. There's lots of them around as it includes 6 different versions (029, 029S, 039, MS290, MS310, MS390)
If I grind on one, I usually just widen the intake and exhaust ports a bit (not much) but by far, the largest improvement is by opening up the muffler.

 

[fearofpavement]

I bought a set of needle files just for this project but by the looks of it they're going to be useless. I need an air die grinder and bits to

A die grinder is going to be too aggressive, you would do better with a dremel and a few carbide burrs. Stones don't work well on aluminum as they clog up easily.

 

[Ethan Hamby]

You know I was very surprised when I first opened the muffler up on it. It went from barely lagging a 25 inch bar to hauling ass with the bar buried deep in oak.

 

[Ethan Hamby]

I opened it up to around 80℅ of the exhaust port area(yes I actually measured it) then put the deflector plate back on and cut a decent notch out of it. With no tuning it ran 13,600 and hot. But I had removed the limiters on the carb and after I tuned it it runs amazing and much cooler than stock also. I completely bypassed the baffles by the way. I just went straight through the baffle retaining indention.

 

[Mastermind]

Those saws have a really stopped up muffler. Now advance the timing about 1/4 at the outside edge of the flywheel.

You want to move it CCW.

 

[Ethan Hamby]

How should I go about that?

 

[Ethan Hamby]

I can't find any info on that

 

[Mastermind]

Lots of good info here.

The 310 has a key that is cast into the flywheel rather than a removable key.....but the method is the same.

http://opeforum.com/threads/mastermind-meets-the-ms461.506/