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

[Al Smith]

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.

Back in the day Big Dave used a 1/4" drill motor and the broken end of a chain file .The first one I ever did,a Poulan was done with a couple of files .I used an old clock face for a degree wheel .

 

[Ethan Hamby]

Back in the day Big Dave used a 1/4" drill motor and the broken end of a chain file .The first one I ever did,a Poulan was done with a couple of files .I used an old clock face for a degree wheel .

that would work good you could get decently close to the degree measurement anyways

 

[Ethan Hamby]

It would just be 6° for every second measurement haha

 

[MustangMike]

I had a burned out 029 and put the Hutzl 390 P&C on it, with muff mod & timing adv. Runs good, but I think compression is low (and you cant change it), and does not compare to my 044/440s, or even my 362.

A guy that was running an 041 really likes it though, so that is likely where it will go.

 

[drf256]

Welcome Ethan.

I'd add the 390 jug, advance the timing and leave your muff modded. I wouldn't touch the ports on it without the proper tools. It's very easy to ruin a jug and chances are that you'd do more harm than good.

The issue with clamshell motors is the amount of work needed to modify them. It's very difficult to check port heights because you need to put the entire engine back together and take it apart everytime you make a change. Also, adjusting the squish is nearly impossible to do unless you have some special tools and series skills. There are software programs around that can help you measure ports and not need to use a degree wheel.

If you choose to play with the ports, make sure you've got some diamond coated balls to chamfer/debur the port edges.

Good luck bud, and remember, one of the bar studs needs to be removed (and generally sacrificed) to pull the engine out.