Woods Porting The MS660......Tricks And Tips

[indiansprings]

Once again, great contribution and thread, the owner should be pleased. Stock off the shelf they are so restricted it's a shame.

 

[Mastermind]

So then, question. It has been mentioned that you dont lower the intake side. That's fine, but what if the intake is lowered, could you drop the jug still?

I wouldn't want to go past 85 atdc.

 

[tree monkey]

the saw will run fine with over 170 dur but you will need a gastruck folowing you

 

[Scooterbum]

Did you get much gain in RPM at WOT?

 

[tree monkey]

Did you get much gain in RPM at WOT?

a little but not worth the extra fuel for a work saw
also a little slugish throttle responce

 

[Mastermind]

Did you get much gain in RPM at WOT?

If you mean on this saw Steve......it's tuned to 13,800.

 

[bryanr2]

In Mastermind we trust!

 

[Trx250r180]

too wierd ,i was just eyeballing my 660 last night ,and it didnt have a sticker on it ,then i see this thead today , great work as usual randy

 

[Mastermind]

too wierd ,i was just eyeballing my 660 last night ,and it didnt have a sticker on it ,then i see this thead today , great work as usual randy

We can cure that problem ya know.

 

[Naked Arborist]

Questions to Randy. One metal hacker to another...

Not to high jack but, I have a few questions that I hope will fit here and have some merit to the build.

1. What did you do to the piston on this MS660 build? Is it a stock factory piston in stock form?
I know they make popups but that is not the direction I'll be heading in.

2. Have you ever compared piston window ports from one manufacturer to another?
Please be specific if possible.

3. Does anybody have an average weight for the factory Stihl MS660 bare piston? Have not weighed mine yet.
That might seem pointless to most but it will be a huge factor for my build.

4. Does an 066 flat top no de-comp have a different piston?
Have not torn mine down yet to check.

5. Do you think window porting pistons improves the flow in this saw to produce more mid range torque?

6. Do you think a longer and wider piston skirt would be of any benefit to this build?

Thanks in advance

 

[tolman_paul]

I've only got ten saws to port in the shop.........

When i first started trying to figure this stuff out most guys were real careful about telling too much. That caused me great amounts of frustration.......I may be wrong but I think that being completely transparent is a good thing. People tend to want to know what is going to be done to their engine.......if I don't post pictures of my work they won't have a clue what I'm doing. The engine in this thread is a typical woods port for me. I almost always increase compression by cutting squish because I gain more control over the port timing......many times the saw leaves here with less exhaust duration or lower transfers than it had stock.

On the other side is helping out the guys that want a ported saw but really can't afford the expense of shipping it across the country and shelling out 250 clams. I understand that completely.....and will gladly share what little I know.

When I found this site I was in a bad state of health.....and money was very scarce. The info I found here helped me to have something to do while I was recuperating, without it I would have went crazy. The first saw I did any port work on was an 026 that was given to me.......it was cold outside, the shop was full of construction tools without heat. My wife insisted that I sit at the kitchen table and work on that saw. That gave me something to do with my hands.....at the time I really needed that. The incentive I needed to get started was found on this site. In my mind I owe this group of guys and gals.......I try to give some back whenever I can.

As anyone who's worked on two smokes knows, it takes much more than a degree wheel and a moto tool to make an engine builder.

But it's not just the investment in various hand pieces and burrs, it just takes time to learn how to layout a cylinder to port it, how the burrs behave in the cut, and no matter how many ports you've ground you'll have an oh sheep dip moment when a burr gets away from you and ruins a cylinder you've spent hours porting.

Honestly I've found one of the best additions to a grinding outfit is a foot pedal so you can turn the darn thing on and off quickly. I'm using a makita die grinder to power my foredom flex cable and a variac to control speed. But the foot pedal on off is highly recomended.

If anyone is secretive about their porting it's probably because they are embarassed to show how ugly the grinding marks are that they leave.

 

[Mastermind]

Not to high jack but, I have a few questions that I hope will fit here and have some merit to the build.

1. What did you do to the piston on this MS660 build? Is it a stock factory piston in stock form?
I know they make popups but that is not the direction I'll be heading in.

2. Have you ever compared piston window ports from one manufacturer to another?
Please be specific if possible.

3. Does anybody have an average weight for the factory Stihl MS660 bare piston? Have not weighed mine yet.
That might seem pointless to most but it will be a huge factor for my build.

4. Does an 066 flat top no de-comp have a different piston?
Have not torn mine down yet to check.

5. Do you think window porting pistons improves the flow in this saw to produce more mid range torque?

6. Do you think a longer and wider piston skirt would be of any benefit to this build?

Thanks in advance

The piston in this build is the stock piston and is completely unmodified, with the exception of the casting flash being removed from the windows. I realizing that the windows in the piston are not as critical to transfer flow as I once thought......having a smooth surface is more important in my opinion than sheer size. If I was trying to get everything I could from an engine I would use the windows and other areas to lighten the piston and enhance flow into the transfers......

I've not spent much time studying piston weight and it's effects......I build work saws for my bread and butter and tend to be conservative when altering a piston.......better to leave a little on the table than to lose durability.

The early 066 piston doesn't have the "wings" and would be lighter but also less stable in the bore compared to the 660 piston.

I have done two engines with work done on the windows of the piston in one and untouched in the other (MS460). I couldn't tell any difference in the two saws when bucking 20" rounds of oak. A stopwatch might have found a tenth in a cant.

A longer and wider skirt would add weight, we were attempting to lose weight in the piston a few sentences ago.

Whether the intake duration being shorter would help I'm not sure, but I think not. The ports being a bit wider might hurt in this instance, you must consider that width adds time/area and we just lowered the jug to get the exhaust down.......

Remember.........I'm just a guy feeling my way along.....I could be way off here.

 

[young]

bigger high side jet in the carb? :smile2:

 

[blsnelling]

What kind of compression did you end up with?

 

[tree monkey]

around 200

 

[Mastermind]

around 200

Yeppers.

 

[Naked Arborist]

Nice! I always like to leave something on the table for durability.
This is just where I want to go with one of my 660's.
I do like the idea of a more stable piston in the bore. I guess the ol 066 will be kept aside for a fun saw. Wait till you see the crazy muffler we are making for it.
The 200 psi compression is right where I'd like to be so running pump gas should be fine.
I would like to drop the piston weight a bit so it will smooth out the engine some on the top end. There are plenty of places to lose some weight off of it without hurting the durability or balance. Window porting the piston is something I don't like to do anyway. I know it crates stress in the pin wall area. It screws up the counter balance and is hell to get it back centered. I want the piston to be right as rain. Most of them are within a half gram from center on out.

Thanks

 

[blsnelling]

I ended up with 210 PSI on this 395XP with only a .035" popup and .020" squish. Needless to say, I was shocked. I was expecting significantly less than that.

 

[Dan_IN_MN]

I've only got ten saws to port in the shop.........

When i first started trying to figure this stuff out most guys were real careful about telling too much. That caused me great amounts of frustration.......I may be wrong but I think that being completely transparent is a good thing. People tend to want to know what is going to be done to their engine.......if I don't post pictures of my work they won't have a clue what I'm doing. The engine in this thread is a typical woods port for me. I almost always increase compression by cutting squish because I gain more control over the port timing......many times the saw leaves here with less exhaust duration or lower transfers than it had stock.

On the other side is helping out the guys that want a ported saw but really can't afford the expense of shipping it across the country and shelling out 250 clams. I understand that completely.....and will gladly share what little I know.

When I found this site I was in a bad state of health.....and money was very scarce. The info I found here helped me to have something to do while I was recuperating, without it I would have went crazy. The first saw I did any port work on was an 026 that was given to me.......it was cold outside, the shop was full of construction tools without heat. My wife insisted that I sit at the kitchen table and work on that saw. That gave me something to do with my hands.....at the time I really needed that. The incentive I needed to get started was found on this site. In my mind I owe this group of guys and gals.......I try to give some back whenever I can.

Sounds like you have a very good and caring wife!

I've had saws on the table, the only thing that was complained about was the smell. I don't understand! Isn't that a good smell? :msp_biggrinit can get to me too)

OH, Nice build thread!

 

[Naked Arborist]

I ended up with 210 PSI on this 395XP with only a .035" popup and .020" squish. Needless to say, I was shocked. I was expecting significantly less than that.

That sounds like it would be one very strong runner.