Porting A 390XP Top End For A Worksaw

[Pincher]

Would you use same recipe on a 2186 jonsered?

 

[Mastermind]

Would you use same recipe on a 2186 jonsered?

Yes sir.

I advance the ignition.....and use a 372XT coil too.

 

[Stump Shot]

Now.....let's see if we can keep this thread about the how and why of porting a 390XP and not about hack saw builders.

Any questions about the saw?

Timing advance?

Muffler mods?

Etc....

Besides what's already been gathered, are there any other "don'ts" that you learned in your experimentation with the 390xp?

 

[Mastermind]

Besides what's already been gathered, are there any other "don'ts" that you learned in your experimentation with the 390xp?

Yep. RPM......

Too much of it and the 390 will rattle itself apart. They installed that 13,000 coil for good reason.

 

[andyshine77]

I forget what rpm are those 372xt coils set to? 13,200

 

[Mastermind]

I forget what rpm are those 372xt coils set to? 13,200

13,500

 

[andyshine77]

13,500

I thought 13,500 was the last OE 372's and it was lowered a bit for the XT. I only had one XT on the bench though and that was like 6 years ago so we know how that goes lol. Now my 04 372 has the black coil of course.

I like the blue 346 coil or a non limited coil, for ease of tuning, but I try not to rev it out without at least some load, and 32:1 does seems to help. But yeah keeping the rpm down is probably a really good idea for a real work saw.

 

[Mastermind]

I thought 13,500 was the last OE 372's and it was lowered a bit for the XT. I only had one XT on the bench though and that was like 6 years ago so we know how that goes lol. Now my 04 372 has the black coil of course.

I like the blue 346 coil or a non limited coil, for ease of tuning, but I try not to rev it out without at least some load, and 32:1 does seems to help. But yeah keeping the rpm down is probably a really good idea for a real work saw.

I tune the 390s I send out to 13,200

I haven't double checked the coils in some time.....I could be mistaken.

I'll be sure to check next time I do one.

 

[mdavlee]

There’s 13.3k blue coils out there too. I like the 14.1k coils for 385/390 if you want to race some.

 

[Mastermind]

There’s 13.3k blue coils out there too.

Those are from the 576XP.

 

[mdavlee]

Those are from the 576XP.

I couldn’t remember where I got them from but I ended up with a pile of them and the 13k ones

 

[TreeLife]

How far is too far to advance the ignition timing on the 390? Do they like a bunch or do they get upset quickly?

 

[Agent Smith]

So this 372 I've been messing with has this black coil. Tag on the saw says its from 1999 if that matters. Do i have an unlimited coil or no?

 

[Mastermind]

How far is too far to advance the ignition timing on the 390? Do they like a bunch or do they get upset quickly?

I take about 1/3 of the key. I'm looking to move the outside edge of the flywheel about 1/4" CCW.

So this 372 I've been messing with has this black coil. Tag on the saw says its from 1999 if that matters. Do i have an unlimited coil or no?

You have an unlimited coil. All the black non-autotune coils that I'm aware of are unlimited.

 

[Agent Smith]

Cool thank you sir

 

[lehman live edge slab]

I have a 372xp in the shop right now with a 13,200 blue coil, not sure but I thought the 357xp I just rebuilt had one too. The 372 is an xt

 

[Robert Krogh]

How far is too far to advance the ignition timing on the 390? Do they like a bunch or do they get upset quickly?

I set one up and marked the flywheel for stock timing as well as +2.5 +5. +7.5. and +10. I never tried a +2.5 advance. At +5 there was a noticeable improvement. At +7.5 it really came alive in every aspect. At +10 I couldn't tell a difference from +7.5 with no signs of any issues. I installed the flywheel at +7.5 and left it. This was all with an OEM unlimited black coil.

 

[Terrence Jefferson]

Robert are you talking degrees on your measurements for flywheel advancements?

 

[Robert Krogh]

Robert are you talking degrees on your measurements for flywheel advancements?

Yes, degrees of crank rotation.

 

[huskyboy]

The black coils seem to like advance more than the blue ones from my experiences.