Porting My MS660

[BloodOnTheIce]

I've finally got the time, tools, ambition and space to work on some of my own saws, so I'm looking to port my first saw.
I've had my MS660 dismantled for 6 months, and I figured it's time to reassemble it, but not before some engine work.
I've looked through about every single thread about porting and I'm looking for some advice.


-How much larger can I make the intake, exhaust and transfers? I'm not going to mess with timing so I'll leave top and bottoms alone and focus on the sides.

-The exhaust, I know keep the top and bottom a little rounded so the rings don't catch, but do I keep the sides flat or rounded?

-Exhaust smooth and polish, and keep the intake a little rough, just checking if that's correct?

-How wide in relation to the piston skirt can I make the intake and exhaust?

-Should I start with my Dremel using a grinding stone, move to files, then go to sand paper?

Any other applicable information would greatly appreciated.

Here's all the pictures and measurements I could come up with.

Intake

Exhaust

Transfers

Piston

 

[Brownpot Deaton]

way to go, be glad to help..looks like you've got a natural gift for this...you already took port pics on paper, which if transfered to engineering graph paper allows you to find the port timing area which is really what's important, but i wouldn't recommend it just yet simply becuase its a bit advanced for a first port job and you really need the graphs to go with it...

-How much larger can I make the intake, exhaust and transfers? I'm not going to mess with timing so I'll leave top and bottoms alone and focus on the sides.

the exhuast is the single most important thing to focus on, followed by the intake... there are 2 rules with these that have to be followed: 1) do not modify the port width to exceed 70% of your piston bore/width becuase less reliable( some people prefer 65%, i say aim int between). 2) do not allow the port width to come within about .020-.030 of the EDGE of your piston's skirt edge becuase there is some minute vibration and oil sealing at the edges that can cause mixture to escape from the crank case.

(so since your bore is 54mm, the max is either 37.8mm (@ 70%) or the piston skirt edge)
id take the intake and exhuast to the max width personally

for the LOWER transfer i wouldn't really widen it just becuase it's decent from what i see...i THINK you can lower it, but i dont work stihls yet....

DONT touch the upper transfers....!!!!!!!!!!!

-The exhaust, I know keep the top and bottom a little rounded so the rings don't catch, but do I keep the sides flat or rounded?

personal preference, but technically you can get a little bit more port area with a flat side...i personally just focus on keping a nice roud transition. and be carful while doing the sides, you may run into the roof of te exhuast port being raised on the outsides if you dont watch your progress.

-Exhaust smooth and polish, and keep the intake a little rough, just checking if that's correct?

correctomundo!..however, on the intake, it will be much more minute of a gain if you smooth it out so dont worry too much about the intake since it's your first one.

-How wide in relation to the piston skirt can I make the intake and exhaust?

about .020-.040 ranging form very extreme to very cautious...

-Should I start with my Dremel using a grinding stone, move to files, then go to sand paper?

good idea, but i never use files, i just rough it in then go straight to a fairly rough sandpaper....

Any other applicable information would greatly appreciated.

grind out the piston windows..(called lightening the piston)... these restrict the air the most durring the transfer process and can make a considerable addition to your port job..it's not hard at all and worth every bit of it...BUT when you do do it, i would suggest taking pictures of it often and makeing sure you dont get to grinder happy becuase it's the smallest piece you'll grind on....if you look up threads on it, you'll find good pictures of it...it really is a must....

port the muffler is a must too, unless you have the dual factory exhuast ported muffler thing already....gets really loud though....

when you're done, bring it down here and i'll let you know how you did:hmm3grin2orange:...jk..you wont believe the difference ....


oh yeah, forgot, if you want some porting reading material in pdf, email me your email and ill try and send it....one of them is severly advanced and the file is way big, but ill try to send it too if anyone wants to save about $350 or more on this one book..wink wink...for those of you who know which it is.

 

[blsnelling]

Not much to be added to that I do like to use a file after the initial grinding. This helps me make sure the exhaust port walls are very flat. I then follow up with 220 and 400 grit in a slotted 1/4 spindle in a die grinder. I also like to taper the transfers back towards the intake. I think I have pictures of most of this in the Porting the 361BB thread.

 

[Brownpot Deaton]

ahhhh...

so that's how you do the sides that way....god i feel dumb..why didn't i evetr think of that. it's simple too.

hey brad, i recently heard that you're an engineer. what kind and do you have any suggestions for someone who's about to graduate in december with a mechanical engineering degree?

cheers,

jordan

 

[blsnelling]

I'm a software engineer. I think I'd love the work of a mechanical engineer though.

Are you talking about using a cutoff wheel for the transfers? I've had other builders tell me they use the same thing. It works great and can leave a very nice finish if you have a steady hand and careful eye.

 

[smokinj]

way to go, be glad to help..looks like you've got a natural gift for this...you already took port pics on paper, which if transfered to engineering graph paper allows you to find the port timing area which is really what's important, but i wouldn't recommend it just yet simply becuase its a bit advanced for a first port job and you really need the graphs to go with it...

-How much larger can I make the intake, exhaust and transfers? I'm not going to mess with timing so I'll leave top and bottoms alone and focus on the sides.

the exhuast is the single most important thing to focus on, followed by the intake... there are 2 rules with these that have to be followed: 1) do not modify the port width to exceed 70% of your piston bore/width becuase less reliable( some people prefer 65%, i say aim int between). 2) do not allow the port width to come within about .020-.030 of the EDGE of your piston's skirt edge becuase there is some minute vibration and oil sealing at the edges that can cause mixture to escape from the crank case.

(so since your bore is 54mm, the max is either 37.8mm (@ 70%) or the piston skirt edge)
id take the intake and exhuast to the max width personally

for the LOWER transfer i wouldn't really widen it just becuase it's decent from what i see...i THINK you can lower it, but i dont work stihls yet....

DONT touch the upper transfers....!!!!!!!!!!!

-The exhaust, I know keep the top and bottom a little rounded so the rings don't catch, but do I keep the sides flat or rounded?

personal preference, but technically you can get a little bit more port area with a flat side...i personally just focus on keping a nice roud transition. and be carful while doing the sides, you may run into the roof of te exhuast port being raised on the outsides if you dont watch your progress.

-Exhaust smooth and polish, and keep the intake a little rough, just checking if that's correct?

correctomundo!..however, on the intake, it will be much more minute of a gain if you smooth it out so dont worry too much about the intake since it's your first one.

-How wide in relation to the piston skirt can I make the intake and exhaust?

about .020-.040 ranging form very extreme to very cautious...

-Should I start with my Dremel using a grinding stone, move to files, then go to sand paper?

good idea, but i never use files, i just rough it in then go straight to a fairly rough sandpaper....

Any other applicable information would greatly appreciated.

grind out the piston windows..(called lightening the piston)... these restrict the air the most durring the transfer process and can make a considerable addition to your port job..it's not hard at all and worth every bit of it...BUT when you do do it, i would suggest taking pictures of it often and makeing sure you dont get to grinder happy becuase it's the smallest piece you'll grind on....if you look up threads on it, you'll find good pictures of it...it really is a must....

port the muffler is a must too, unless you have the dual factory exhuast ported muffler thing already....gets really loud though....

when you're done, bring it down here and i'll let you know how you did:hmm3grin2orange:...jk..you wont believe the difference ....


oh yeah, forgot, if you want some porting reading material in pdf, email me your email and ill try and send it....one of them is severly advanced and the file is way big, but ill try to send it too if anyone wants to save about $350 or more on this one book..wink wink...for those of you who know which it is.

You done this a few times! I like to just polish the exhaust side only(no porting) and port the muffler and the intake side ruff up as mentioned.Just seems to make a better work saw. squash the head with brown paper sack as gasket

 

[Wild Knight]

Where's the Wolf?

 

[Brownpot Deaton]

wolf is master....

WildKnight
yeah, timberwolf is my favorite 'sensai'....lol... he's just a wealth of knowledge....

smokinj,
lol...i haven't really done so many, just pay alot of attention to what i read and see, then do it myself...and it's really kinda fun.


also, i forgot about taking the gasket out....doh!..easiest mode there is!
personally i use a gasket maker sealant, but i've heard good things too about the brown bag special version....


brad,
i meant using a small file to get a much flatter edge at the side of the ports...did it sound like something else or are the radio waves getting on the wrong frequency???

jordan

 

[smokinj]

WildKnight
yeah, timberwolf is my favorite 'sensai'....lol... he's just a wealth of knowledge....

smokinj,
lol...i haven't really done so many, just pay alot of attention to what i read and see, then do it myself...and it's really kinda fun.


also, i forgot about taking the gasket out....doh!..easiest mode there is!
personally i use a gasket maker sealant, but i've heard good things too about the brown bag special version....


brad,
i meant using a small file to get a much flatter edge at the side of the ports...did it sound like something else or are the radio waves getting on the wrong frequency???

jordan

pull one:greenchainsaw: out before that was in there for atleast 4 years and still in good shape

 

[Brownpot Deaton]

also...

blood on ice, those are really good pics...im impressed!

and also an update,

on the porting book in pdf format, can anyone downsize these files if i send them to them, i've only sent it to one person, and its already maxed out my email, yet there are quite a few who still want a copy of this.

also. i have a copy of perf. tuning and tuners handbook i found through a link somewhere, but dont remember where...

jordan

 

[canopyboy]

Sent you a pm, I'm pretty sure I can downsize 'em for you.

 

[BloodOnTheIce]

Porting Stage 1:

I tackled the exhaust and by the time I had gotten all the carbon cleaned I didn't have time to do a whole lot of work.
Removed material from exhaust port, widened by about 1mm per side.
I cleaned up the piston also, but I need to pick up some different bits, the ones I have are to course to get a good polish.

Exhaust:

Piston fitted in Cylinder:
You can see the permanent marker is where I started.
I need to clean up top right corner

Cleaned Up Piston:

Inside of cylinder:

 

[stihlboy]

Lookin good bud i hope it screams

 

[troutfisher]

Looks good, are you adjusting squish at all?

 

[Brownpot Deaton]

dido, looks good..just wanna check all you did was take out the carbon deposits on the exhuast right, because you do not want to raise the roof of that port at all...even a millimeter can all but kill an engine this size.

never mind, can see the diference in texture now. good shape and all. now just get it wider. also like your piston for being first one..

jordan

looks like you may have not rounded out the edge much on the window closest to the screen and to the left, but could just be me...but then agian you say youonly have stones....

 

[troutfisher]

you do not want to raise the roof of that port at all...even a millimeter can all but kill an engine this size.

yes it will, If I raise an exhaust it's very slowly and meaured with a degree wheel. Maybe to compensate for milling the jug to set squish, even then I do compression tests often to keep from going too far. If you raise a port say 10 degrees, you just added 20 degrees to total duration......it'll open 10 degrees early and close 10 degrees later. 20 degrees is a HUGE change.

 

[Brownpot Deaton]

agree trout fisher, i do the same, but i was speaking in context of this particular build, which, he hasn't stated anything about lowering the jug, and even smoothing it out will microscopically raise it..but my fault for not being clear...anyways, sorry and back to the build...opcorn:opcorn:opcorn:

 

[CHEVYTOWN13]

Nice attention to detail BOTI.

This should be a fun build. Good luck.

 

[BloodOnTheIce]

The only work I did to the actual port was from the red lines outward, as shown by my awesome MS Paint diagram.

-I didn't stick the dremel into the cylinder at all touching the top or bottom. Out from the port on the roof and floor of it I ground enough to clean the carbon off, and sanded it some 200 grit wet/dry sand paper.

-For most of the grinding I'm using the round stones used to sharpening chainsaw chains, these are too course for final polish so I have to pick some more bits. The ones that came with the dremel are about useless.

-I have didn't have a chance to put a bevel back on the side of the port opening

-I haven't taken much material off the piston, I'm just cleaning all the casting marks, then I'll go back through and get it smooth.

-I need to get some solder so I can measure the squish, what is ideal squish for a saw like this?

-Squish, I plan on reducing it. When you make a gasket, do you use Derko or other sealant on it to get a better seal or put it in without sealant?

 

[troutfisher]

I like to have the cylinder cut on a lathe and then use the stock gasket, I have also used yamabond wich worked well.