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Fish4Brains

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Joined
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Hello all, Been a long time lurker and decided its time to do some work to my husky 55. The reason is not wanting to spend cash on a new saw, yet wanting a touch more poop from this one. I started with the muffler. I pulled the baffle and the screen also added one 3/8 hole richened up the top end and I notied a small difference in power (and noise) ok going in the right direction. Now having been a tool and die maker as well as machine builder Im thinking its time to do a bit more. I understand the degree wheel concept deck height and port timing but I do not understand what squish is, I also am wondering how you set up the jug (like bolt it down with no head) to do the degree measurements. It sounds like I wouldneed to widen the ex and intake ports as well as cutting the cyl base to up compression a bit. Not to sure where to go with timing of the ports but am definatly looking for sugestions.
Im thinking this is going to be as bad as my other habits
Thanks Brian
 
Lots to read about the basic questions you asked. Search for 'Degree' and 'timing' and '650' by user 'gypo logger' that will give you a good start.

When you degree a saw, the jug and piston have to be installed, intake and exhaust ports visible with carb and muffler removed. You need to measure when the intake, transfers and exhaust opens and closes. You will also need to measure squish, and your cranking compression. Once you have figured out how exactly to go about things, report back with your numbers and we'll give you some guidance.

Josh
 
Fish4Brains said:
Hello all, Been a long time lurker and decided its time to do some work to my husky 55. The reason is not wanting to spend cash on a new saw, yet wanting a touch more poop from this one. I started with the muffler. I pulled the baffle and the screen also added one 3/8 hole richened up the top end and I notied a small difference in power (and noise) ok going in the right direction. Now having been a tool and die maker as well as machine builder Im thinking its time to do a bit more. I understand the degree wheel concept deck height and port timing but I do not understand what squish is, I also am wondering how you set up the jug (like bolt it down with no head) to do the degree measurements. It sounds like I wouldneed to widen the ex and intake ports as well as cutting the cyl base to up compression a bit. Not to sure where to go with timing of the ports but am definatly looking for sugestions.
Im thinking this is going to be as bad as my other habits
Thanks Brian
Click to expand...


Squish is the distance from the piston to the head at top dead center. You can measure squish by inserting a piece of soft solder through the plug hole and slowly turning the engine over by hand. the piston will come up and crush the solder, then you can remove the solder and measure it. here is a printable degree wheel.
 
Last edited:
I measured where my ports opened with the degree wheel before I made any changes, then after I decked the cylinder I knew how much to raise the ports to return to stock timing. My exhaust port opened at 109* after top dead center before decking and opens at 109* after decking. (or whatever timing you want;) )
 
Thanks guys for the replies I have a bit of cutting this wekend then I think it will be teardown time. I am "new" to the internal workings of a twostroke for the most part. however I have done a bunch of machining and die work so my metal and precision work skills are definatly up to the task. I wil post back with my degree measurements as well as squish height.
Any body done one of the 55's pre rancher style?
Thanks Brian
 
Just incase you didnt know yet, another important factor along with squish height is the profile of squish....
 
blis said:
Just incase you didnt know yet, another important factor along with squish height is the profile of squish....
Click to expand...

yes.. many taper, so you need to measure it at multiple points around the piston crown AND make sure the solder reaches the cylinder wall. Remember also that skirt wear can cause inaccuate readings in the inlet and exhaust directions (piston can rock back). Sometime I'll draw some cad pics to show this and other issues with squish.. I just need more time than I have..
 
Lakeside53 said:
yes.. many taper, so you need to measure it at multiple points around the piston crown AND make sure the solder reaches the cylinder wall. Remember also that skirt wear can cause inaccuate readings in the inlet and exhaust directions (piston can rock back). Sometime I'll draw some cad pics to show this and other issues with squish.. I just need more time than I have..
Click to expand...
Yep, I use two pieces of solder 180deg apart to compensate for piston rock,,,, if you have a decom port put one in from that side and one in from the plug hole, just make sure they reach the cylinder wall if you have to bend them and make sure they reach before you put the cylinder back on. Thats the way I do it and it works every time..........
 
Use the smalest diamiter solder you can, this required less pressure to squish and gives the closest reading, Electrical lead solder is softer and beter than harder plumbing or silver solder.

Once I have squished the solder once I cut the squished tip in half and re squish it (takes almost no force to squish the second time), sometimes it does drop the reading by 1 or 2 thousandths.
 
An easy way to postion the solder and measure squish is just take the rings off the piston (you're going to take it to pieces anyhow!). You can then slide the cylinder on and off at will. Use heavy grease or chewing gum to hold the solder - put a blob in the middle of the piston (where it won't get "Squished") and run the solder to it. Torque down your cylinder each time. Be aware that an old gasket may be slightly compressed (if paper).
 
Lakeside53 said:
An easy way to postion the solder and measure squish is just take the rings off the piston (you're going to take it to pieces anyhow!). You can then slide the cylinder on and off at will. Use heavy grease or chewing gum to hold the solder - put a blob in the middle of the piston (where it won't get "Squished") and run the solder to it. Torque down your cylinder each time. Be aware that an old gasket may be slightly compressed (if paper).
Click to expand...

andy, u always have the best ideas!!!!

wood like to c your mouse trap though;) ;)
 
Thanks for the replies. I get the piston rock problem. Nice Method with the greese I think I will give that a try. Lots to learn.....Gordon Jennings tuners handbook is going to get some time this weekend. Thanks for all the input and the degree wheel.
I will keep you posted.
Brian
 
Ok I tore it down last night and am going to degree it now. the piston looks pretty bad so Im thinking I will put her back together for now.then order a piston and ring and do a light clean up hone on the bore and thats when "and if" I do a bit of porting on her. Right now i have to get it off my bench. I will post degree wheel results.
Thanks Brian
Oh to fill you in three years ago my brother in law put straight gas in it. My fault I didnt make sure of the can he grabbed:bang: but he ran it untill it quit 3 times." I was watching from 100 yards away". Anyway put mix in it and it has run good since so no suprise on the wear..
I bet alot more saws get that treatment than we will ever know.
 

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