Inside the Exploded JMS 064

[Keith Gandy]

+1. When I see your posts, all I can think of is JMS giving you all that crap about your 390xp.

I know what that 390 did against this 064/066 we r discussing here. Theres a reason I still have my 390!!

 

[astnmacgto]

May I present another question to the whole, "to lighten or not to lighten, that is the question" thing we've got going on here.

Is there a certain ratio of rod/piston weight to crank bell weight that the manufacturer has in mind or are they casting the piston and letting the design dictate how much that particular piston weighs.

Obviously the different manufacturers have slightly different weights.

You don't want the piston to be too heavy as that will cause extra stress on the rod bearings Right?

Premature needle failure cause it's too heavy?

Why couldn't a person take equal amounts off the piston as well as the crank until they were happy?

Has anybody ever had a saw crank balance checked to find vibrations?

Or had a crank in one of these checked for trueness and then had it adjusted for smoothest operation.

What about the parallelism of the big and little rod ends?

Won't all of these factors destroy a lightened piston not because it's too light but because there's too much vibration in the crank assembly itself?

All just questions worth answering IMO only, before you can decide how light is too light.

 

[MustangMike]

It seems, despite the high RPMs, that chainsaws are just "over built" instead of carefully balanced, so you can get away with doing things like putting a 460 piston on a 440 crank & rod, etc. Things you would never do with a car engine!

I'm sure a correctly balanced engine would last longer, but these things generally hold up very, very well already!

 

[paragonbuilder]

Common sense tells u if u take too much out it will fail? How much is too much? Not sure. Take enough until it fails. If somebody tells u that u can lighten a piston and it doesnt weaken the structure somewhat Id say they r full of it. Just because it hasnt failed doesnt mean the makeup of the casting hasnt been compromised to a point? Id agree that taking enough out to smooth and contour the windows and edges would be fine but theres definetely a factor of too much but not sure where thats at and the small amount it will make on a worksaw isnt worth ruining a saw IMO

I didn't intend to get your hackles up Keith, I was merely curious how you came to the conclusion that It was bad to lighten Pistons, and that TSS lightened his too much? I agree that on a worksaw it's probably not worth any gains. And of course from a physics standpoint, any material you take away is weakening it. But I'm wondering how over engineered they are.

 

[Keith Gandy]

I didn't intend to get your hackles up Keith, I was merely curious how you came to the conclusion that It was bad to lighten Pistons, and that TSS lightened his too much? I agree that on a worksaw it's probably not worth any gains. And of course from a physics standpoint, any material you take away is weakening it. But I'm wondering how over engineered they are.

No problem brother. . As to how much is too much I would guess no one knows the tipping point and would have to say its a gamble

 

[Deets066]

So what do you think about performance lightweight pistons? Like these

066 piston







372 piston


They have much wider skirts but are also much lighter than OEM. And a even that much more lighter than a meteor. Are they compromised because the don't have they structure to support themselves?

 

[astnmacgto]

It seems, despite the high RPMs, that chainsaws are just "over built" instead of carefully balanced, so you can get away with doing things like putting a 460 piston on a 440 crank & rod, etc. Things you would never do with a car engine!

I'm sure a correctly balanced engine would last longer, but these things generally hold up very, very well already!

For being pretty basic two stroke technology, they work pretty well. We get to see the tip of the iceberg with ported saws. Just imagine if all the technology that gets put into 2 stroke bikes and other things got put into chainsaws.....

 

[Keith Gandy]

So what do you think about performance lightweight pistons? Like these
View attachment 87765
066 piston






View attachment 87766
372 piston


They have much wider skirts but are also much lighter than OEM. And a even that much more lighter than a meteor. Are they compromised because the don't have they structure to support themselves?

Id say its supported totally different than a stock piston? Wouldnt u think?

 

[Deets066]

Id say its supported totally different than a stock piston? Wouldnt u think?

The 066 piston has far less "meat" than a meteor, maybe I'll get some pics tomorrow for comparison.

 

[Keith Gandy]

The 066 piston has far less "meat" than a meteor, maybe I'll get some pics tomorrow for comparison.

Id say Wiseco engineers the structure for less weight and reliabilty. Pretty sure they dont randomly give a hack like myself a foredom and a burr and say have at it??!! Big difference

 

[Deets066]

Id say Wiseco engineers the structure for less weight and reliabilty. Pretty sure they dont randomly give a hack like myself a foredom and a burr and say have at it??!! Big difference

The weisco has a full bottom. I believe they are tried and true.

The blue custom 066 piston has no R&D it was designed for all out performance, we shall see how it holds up

 

[astnmacgto]

The weisco has a full bottom. I believe they are tried and true.

The blue custom 066 piston has no R&D it was designed for all out performance, we shall see how it holds up

Who built that one?

 

[Deets066]

Who built that one?

 

[Deets066]

It was designed by a few members and myself

 

[astnmacgto]

It was designed by a few members and myself

Good good

 

[astnmacgto]

What's the coating on that? Did it begin it's life as a meteor?

 

[Keith Gandy]

The weisco has a full bottom. I believe they are tried and true.

The blue custom 066 piston has no R&D it was designed for all out performance, we shall see how it holds up

Id feel far more safe with thoso than one I sat down and guessed at

 

[astnmacgto]

How long before we start incorporating scatter blankets into our saw builds hahaha

 

[Deets066]

Id feel far more safe with thoso than one I sat down and guessed at

Not doubting your judgement at all Keith. You are the one that ground on it and know what it is. You were most likely in the right if you took that much off.

 

[Deets066]

How long before we start incorporating scatter blankets into our saw builds hahaha

My brother and I discussed that earlier today. Lol