Over size piston

[joe_indi]

Yes Joe!!  They call them "Supers" !!

Rockfarmer
If those are called  Supers, what are Magnums?

[Rockfarmer]

Yes Joe!!  They call them "Supers" !!

Rockfarmer
If those are called  Supers, what are Magnums?

I wish I knew Joe!  I have a couple 045 Supers and the only difference between them and the 045 is 2mm on the pis/cyl. The 045's were 49,50 + 52mm, the supers were 54mm and the mag was 56mm. They all use the same case, crank and rod. I think there were some small differences on the intakes as well with the mag but I really dont know.

Funny story Ian 

[Al_Smith]

   .
In auto techie lingo, would I be correct in stating that the engine develops a broader power band with the maximum rpm trimmed off a bit?
 

 

In a manner of speaking . Depends on a lot factors not just bore size .

For example a Ford 300 cubic inch I6 develops max power at most likely 2800-3400 rpm . An old John Deere 70 gaser only runs at around 1100 rpm max but puts out max power at around 800 .

In my opinion it's rather pointless dealing with saw engines to worry weather it cranks out another 600 rpm's or so because they are going to run wherever they run at with regards to speed .

[Dave Hanny]

   .
In auto techie lingo, would I be correct in stating that the engine develops a broader power band with the maximum rpm trimmed off a bit?
 

 

In a manner of speaking . Depends on a lot factors not just bore size .

For example a Ford 300 cubic inch I6 develops max power at most likely 2800-3400 rpm . An old John Deere 70 gaser only runs at around 1100 rpm max but puts out max power at around 800 .

In my opinion it's rather pointless dealing with saw engines to worry weather it cranks out another 600 rpm's or so because they are going to run wherever they run at with regards to speed .

They may run whatever they're gonna run, but the RPM or it simply running doesn't seem to be the question here - is it running 'better' at whatever RPM it is now running (i.e. is it developing an appreciable increase in either the amount, or the usable range, of torque to make the saw more useful when in whatever range it likes to run).

The I-6 was an great motor the way it came from Ford (the power range was already 'broad' due to them choosing the right cam).  But I've seen the same 300 I-6's made for specific applications that are cammed to run at one RPM, period, to develop its power.  The latter motor would be frustrating and nearly useless in an automobile or truck. 

What joe is wondering is if he was able to take the saw and make the usable range broader, which does seem to mean it will be easier to work with when felling all day long.

I, personally, don't know how to figure it beyond just using a saw pre and post-joe.  Usually increasing the overall weight of the rotating parts (simply put: increasing the weight of the flywheel - but any weight that needs rotated by a motor will have the same effect) creates the effect that joe_indi is suggesting he got (a more usable range, and the ability to stay in that range when working).  But joe went the opposite direction in weight... he's using a lighter piston.  If he went for a ligher piston than stock, alone - without increasing bore, the saw should feel as if it revs up (and down) faster, but it would lose some usability in its range of power.  But he did two things: lightened the overall 'flywheel-effect' AND increased the bore size a bit.  The two could cancel each other out in as far as the effect to the usuable power range for all I know.

[isawlogs]

  I dont know how to mesure any of the modes you made and tranfer that to energy, but I sure do like reading this thread.      I am also glad you posted pics on how things got done    Thanks .

[Dave Hanny]

I take back what I said about the piston's weight being the same as a flywheel - the piston stops and changes direction a lot, so a lighter piston can (in my mind) only help improve the saw's performance.

Still don't have a clue as to what the effect would be on usable torque range - but since the lower weight is one less thing the saw has to overcome when actually sawing a log... it would seem that it would help it to stay at its peak torque a little longer.

[Cut4fun]

If you have a piston that is 1mm to 2mm bigger and it works in the saw you want to use it in.
You can take and send the piston with the cylinder to a shop up north and they will bore and fit the piston and then re-plate the cylinder for a fee $$$.  Dont see any reason to do that in a work saw.

If this has already been answered I am sorry, I ain't going back to read 4 pages.

[joe_indi]

I've added some images of the oversize piston, the new chrome rings and the sleeved cylinder.

http://www.forestryforum.com/gallery/thumbnails.php?album=2273

I've also uploaded pictures of an air filter that came on a 046 in 1999 (??).
Does anybody know whether they are still available?

joe

[Cut4fun]

If you are talking about the 1605 air filter in the pic Stihl HD type, 1605 was replaced with alot better HD 1654 flocked and 1653 wire mesh. Now my numbers could be off, so hopefully someone in the know will chime in.

[Rocky_J]

I don't have the part number either, but the current MS460 air filter will fit that saw. There is the main air filter element as well as a prefilter wrap that fits over the filter. The prefilter keeps the vast majority of dirt from ever reaching the main filter, so it doesn't need cleaning as often and will last almost forever.

[Al_Smith]

I've added some images of the oversize piston, the new chrome rings and the sleeved cylinder.
 ?

joe

The work looks good Joe . As I said before though that type of rework is cost prohibitive in this country .

About the only resleeving or re-plating that is done is for restoration or racing which really could be classified as experimental .

That stuff,restoration ,racing falls under a different catagory than rebuilding a working saw . For the later the price of a new cylinder and piston may equal about half the price of a new saw .Often the saws may only get one top end rebuild then they are just parts saws or scrapped out .

After that guys like me end up with them and nurse them back to health .However guys like me do not depend on a saw to make a living with either .I can afford for one to take a fit on me now and again .Pro loggers and tree service workers cannot .

[Rocky_J]

What Al was trying to say (before he got sidetracked talking about his old saw collection  ) is that we have environmental laws here which make it prohibitively expensive for anybody to set up a shop doing that type of work. That, and we can buy aftermarket pistons and cylinders so cheaply that there just isn't any market for it. For the cost of doing all that custom work, you can buy factory replacement parts and have money left over.

[Al_Smith]

Well now all are  not really moldy oldies .Most of them are though ,I'll grant you that .

That aside a pro saw user can't be fiddley ---around trying to get somebody to make an oddball 1/2 mm sized piston to keep his or hers saws operational for them to make a living with .

Not saying in any way it's not a worthy cause just not expediant in the broad scope of things .

Now granted some missfit gearhead like myself might endeaver to do that stuff but good heavens if I charged my shop rates for that stiuff you could get a thousand bucks in reworking a 300 dollar saw .That would fly about as far as a lead balloon .

[joe_indi]

Okay Folks,
Here is the latest on my endeavor.
I finally got the diameter corrected for the sleeve.
This put an end to hours of buffing down pistons.The solution was so simple, and it was right there from the beginning.
My first mistake was in thinking that the 046/MS460 piston had a diameter of 52mm.
It does not! It is the cylinder bore that is 52mm!!
Here is what I for when I measured an original piston:
 Diameter at the top of the piston was  51.75mm and at the skirt was 51.95mm.
This goes into a cylinder with a 52mm bore.
I measured the oversize piston.
Diameter at the top was 52.25mm and at the skirt 52.45mm.
An overall increase of .5mm.
All I had to do was to machine the bore to 52.5mm.
This worked wonders. But then the honing marks were not considered.
Within a week, when the bore was polished during the run in, the bore diameter had increased to nearly52.65mm.
So to compensate, the machining was limited to 52.48mm.
During the machining, the tool kept impacting on the cylinder top.These marks were smoothed off, but at the cost of reduced compression.
A kindly soul from this forum advice me on how to measure the squish and take necessary corrective action.
The same kindly soul also recommended a slight port advance at the exhaust.
The correct squish and the port advance have worked wonders.
Saws with the latest sleeves have completed more than a month without any problems.
I have no idea how, but fuel consumption has decreased by a good 15%.
Output from the saws have increased.
Outside the cut the rpm does not climb to 13500 or 14000.It stays at a respectable 13000.
But in the cut, the rpm does not drop as much as a regular saw.

I am thinking of trying out a 53mm piston soon, that is if my friendly neighborhood piston manufacturer agrees to make me some.

Al,
I do understand that doing all this might not be possible in your part of the woods.But then you have many other thing going f.
Like a leg of ham, good bacon, a juicy hamburger,.......
Joe

 

[rebocardo]

On  a V-8, 4 stroke, running 1 hp per1ci, torque and HP equalize/cross about 5200 rpm, at what RPM does that happen on a 2 stroke engine?