Spuds Porting and Tuning Thread

[RobRainford]

Been porting a MS660 this weekend, the figures

 

Exhaust duration - 170*

 

Inlet Duration 158*

 

Transfer Duration 112* ......yup - had to check this a couple of times

 

Blowdown - 29*

 

 

 

There are many restrictions in the MS660 - the exhaust port can't be widened by much so settled for reshaping the profile, the inlet again can't be widened by much so again reshaped it. The uppers can't be taken back by much due to the ring ends so settled to reducing the blowdown figure to 24.5* which gives a longer time the transfers are open so more fuel charge:thumbup:

 

 

 

The lower part of the lowers had the ridge removed and blended in to the cylinder wall.

 

 

 

The piston windows were opened and flowed plus a few changes to the muffler to get it breathing.

 

 

 

Be interesting to hear how it performs - there are some mighty big differences in the MS660 figures to the older 066 - the exhaust port ceiling is lower giving a lower power band, the blowdown is significantly shorter on the 066 and inlet duratiion longer - all very interesting but the changes I have made should give significant gains.

 

 

 

I also extended the exhaust outlet to stop the bendy handle issue that some have reported on this site:thumbup:

 

 

 

The squish came out at 0.65mm so nothing much to do here so left alone.

 

 

I'm very interested in how you get on with this and percentage values if possible. If you get good results mine will be on the way.

 

 

Sent from my iPod touch using Tapatalk

[spudulike]

I'm very interested in how you get on with this and percentage values if possible. If you get good results mine will be on the way.

 

 

Sent from my iPod touch using Tapatalk

 

The saw is owned by one of the Stihl Timbersport team but is his own saw and not a competition saw - the ones used in competition are either standard MS660 or "Hot" saws of non standard build!

 

I am hoping to get some figures back once he gets it back:thumbup:

[wyk]

 

Been porting a MS660 this weekend, the figures

Exhaust duration - 170*

Inlet Duration 158*

Transfer Duration 112* ......yup - had to check this a couple of times

Blowdown - 29*

 

There are many restrictions in the MS660 - the exhaust port can't be widened by much so settled for reshaping the profile, the inlet again can't be widened by much so again reshaped it. The uppers can't be taken back by much due to the ring ends so settled to reducing the blowdown figure to 24.5* which gives a longer time the transfers are open so more fuel charge:thumbup:

 

The lower part of the lowers had the ridge removed and blended in to the cylinder wall.

 

The piston windows were opened and flowed plus a few changes to the muffler to get it breathing.

 

Be interesting to hear how it performs - there are some mighty big differences in the MS660 figures to the older 066 - the exhaust port ceiling is lower giving a lower power band, the blowdown is significantly shorter on the 066 and inlet duratiion longer - all very interesting but the changes I have made should give significant gains.

 

I also extended the exhaust outlet to stop the bendy handle issue that some have reported on this site:thumbup:

 

The squish came out at 0.65mm so nothing much to do here so left alone.

[Daniël Bos]

I did an exhaust mod on my 550xp the other day as it's out of warranty now.

It has really woken the saw up, it wasn't really that snoozy to begin with but boy does it make a difference.

In bar length oak (15") it's quicker than my 880 (with a 46" bar...)

It sounds a bit different but not really much louder which is good and took all of 40 seconds. I'll try and remember to take some pics later in the week.

[wyk]

The saw is owned by one of the Stihl Timbersport team but is his own saw and not a competition saw - the ones used in competition are either standard MS660 or "Hot" saws of non standard build!

 

I am hoping to get some figures back once he gets it back:thumbup:

 

The intake port on my 361 is almost perfectly square. Most Stihl's end up that way.

[spudulike]

The intake port on my 361 is almost perfectly square. Most Stihl's end up that way.

 

There wasn't much other option, I widened it a tad but squared the lower edge to get better flow at the bottom of the stroke and the top to increase flow again.

 

I also opened up the windows on the piston, another tweak worth doing.

 

I should get some vids back from the owner, be good to see it in some wood and how it runs against a standard MS660.

[mendiplogs]

There wasn't much other option, I widened it a tad but squared the lower edge to get better flow at the bottom of the stroke and the top to increase flow again.

 

I also opened up the windows on the piston, another tweak worth doing.

 

I should get some vids back from the owner, be good to see it in some wood and how it runs against a standard MS660.

 

HI STEVE did the STIHL timber boys run a 661 when they 1st come out as there was big show germany was the you telling me about what bar size on it thanks jon

[wyk]

There wasn't much other option, I widened it a tad but squared the lower edge to get better flow at the bottom of the stroke and the top to increase flow again.

 

I also opened up the windows on the piston, another tweak worth doing.

 

I should get some vids back from the owner, be good to see it in some wood and how it runs against a standard MS660.

 

Ah yeah. I like the sound of a ported 660. OK, I like the sound of most things ported, especially bikes.

[burrell_]

I'm intrested in the vids mate as iv got a 660 ;-)

:lol:

[broonie]

https://www.youtube.com/watch?v=Dma2iCqgQpU

 

HOT saw !! Spud new project?