A Tale of Three Saws

[husq2100]

since no one anwsered my question regarding pop ups doing more than just raising compression I'll put it another way. Some race saws only have 150 or so psi compression, but have had the heads removed and changed to something with a smaller CC compaired to stock....

im guessing the smaller CC is offering something and that a pop up may be a way of achieving a similar thing.......not just compression..

any thoughts???

 

[Andyshine77]

since no one anwsered my question regarding pop ups doing more than just raising compression I'll put it another way. Some race saws only have 150 or so psi compression, but have had the heads removed and changed to something with a smaller CC compaired to stock....

im guessing the smaller CC is offering something and that a pop up may be a way of achieving a similar thing.......not just compression..

any thoughts???

Saws with two piece heads often run alcohol or other fuels, it's a whole different ballgame.

 

[blsnelling]

since no one anwsered my question regarding pop ups doing more than just raising compression I'll put it another way. Some race saws only have 150 or so psi compression, but have had the heads removed and changed to something with a smaller CC compaired to stock....

im guessing the smaller CC is offering something and that a pop up may be a way of achieving a similar thing.......not just compression..

any thoughts???

I believe that's so that they can recover compression they loose when raising the exhaust much higher.

 

[blsnelling]

The MS660 is back together and running. Throttle response is extremely snappy. Max RPMs are 14,300. I have it tuned to about 13,900-14,000.


The 390XP is measured and apart. Here are the specs on it.

Compression 149
Squish .026"
Exhaust 95° ATDC / 170° Duration
Transfers 118° ATDC / 124° Duration
Intake 75° BTDC / 150° Duration
Blowdown 23#°

 

[MCW]

The MS660 is back together and running. Throttle response is extremely snappy. Max RPMs are 14,300. I have it tuned to about 13,900-14,000.


The 390XP is measured and apart. Here are the specs on it.

Compression 149
Squish .026"
Exhaust 95° ATDC / 170° Duration
Transfers 118° ATDC / 124° Duration
Intake 75° BTDC / 150° Duration
Blowdown 23#°

 

[blsnelling]

Yes, it's a Mahle, as are all P&Cs on pro Husky saws.

 

[blsnelling]

Intake

Exhaust

 

[blsnelling]

Transfers

Combustion chamber

Looks like the NiSi goes all the way to the top.

Case

 

[the westspartan]

Is that nick just under the exhaust port an issue? Does it go through the NiSi coating?

 

[MCW]

I see a distinct quality difference between the Stihl and Husky castings Now I know what the earlier guys were talking about in regard to the MS660 pictures

 

[blsnelling]

Is that nick just under the exhaust port an issue? Does it go through the NiSi coating?

I was waiting for that question Fortunately, it was just a spec of lint or dirt.

 

[little possum]

Dont mind me, accidentaly unsubscribed.

 

[Outlaw5.0]

The 390xp looks to be higher quality, like the older Stihls. Probably means nothing though.

 

[blsnelling]

The 390xp looks to be higher quality, like the older Stihls. Probably means nothing though.

It's still a disappointment, and a turn in the wrong direction.

 

[blsnelling]

I thought I'd show a few pics of my porting layout. As you can see, there's tons of room for port widening, unlike the MS660. The 660 is hugely limited by skirt width and ring end locations. The Husky has almost a full circle skirt and the rings end towards the middle of the intake.


Here I've marked the tops and bottoms of the intake and transfers, original port width, desired port width, and ring end pins.

Here you see the skirt edges, original port width, desired port width, and port top and bottom.

 

[FATGUY]

Holy-Flow Batman!!

 

[TommySaw]

I thought I'd show a few pics of my porting layout. As you can see, there's tons of room for port widening, unlike the MS660. The 660 is hugely limited by skirt width and ring end locations. The Husky has almost a full circle skirt and the rings end towards the middle of the intake.


Here I've marked the tops and bottoms of the intake and transfers, original port width, desired port width, and ring end pins.

Here you see the skirt edges, original port width, desired port width, and port top and bottom.

so does the 390 take aswell to porting as the 346 and 372?

 

[little possum]

Brad, may I request a picture of straight through the ports, before and after the porting.
A side by side so to speak.

 

[MCW]

I thought I'd show a few pics of my porting layout. As you can see, there's tons of room for port widening, unlike the MS660. The 660 is hugely limited by skirt width and ring end locations. The Husky has almost a full circle skirt and the rings end towards the middle of the intake.


Here I've marked the tops and bottoms of the intake and transfers, original port width, desired port width, and ring end pins.



Here you see the skirt edges, original port width, desired port width, and port top and bottom.

So what you're trying to say Brad is that this 390 will be 2lb lighter than stock?

 

[AUSSIE1]

Well the 390 is different than the 385 with 170 ͦ Ex. for starters.