Piston weights

[Justin Taylor]

I’m waiting for parts atm but I have some questions. I’m planing on doing a Farmertec bb with a lil red barn popup 52mm it’s for my 440 clone. I know Farmertec isn’t Stihl quality but it’s cheap and less expensive to practice on. Should I make the piston weight the same as the 50mm piston or don’t even touch it. I have seen 1 thread saying more weight the more torque but less rpm is this true? This saw wears a 24in bar and I mostly cut pine. Thanks and try not to embarrass me too much

 

[Justin Taylor]

.

 

[1hander]

I have never done balancing with saw cranks and pistons... But based on building 20 or so Honda 4 cyls.. A few ls2s and ls3s.. You always do a rebalabce when changing pistons.. I don't know anyone who does chainsaw dynamic balancing. But if the flywheel and fan are zero balanced from factory who h they usually are.. .. Then rotating assembly should have either been dynamic balance or a calculated balance which is just a guess.. I doubt they are dynamically balanced.

So yes if you can try to remove weight from somewhere that is not critical..and match the weight to the original piston.. Maybe try it first.. The extra weight could balance it better.. Just depends on which way the factory imbalance was.. On wiseco pistons the material is removed if needed under the wrist pin mounts believe it or not.

Man it would awesome to be able to dynamically balance a saw rotating assembly and make up Bob weights for the process

 

[TheAMMIXman]

The furthest I have taken this process is removing the casting lines in the pistons underside surfaces, then polish my work a little. For air flow purposes.

I know that doesn’t really answer your question but that’s the most I’ve touched a piston on a saw. I’ve never aimed to change weight much, opposite really, cause I didn't know what you want to know either.

 

[cus_deluxe]

i would guess that youd seriously compromise that 52 mm if you were to try to get it to weigh the same as an oem 50mm...

 

[1hander]

im thinking the same thing, they just dont leave any meat on them at all other than whats necessary for function

 

[Justin Taylor]

i would guess that youd seriously compromise that 52 mm if you were to try to get it to weigh the same as an oem 50mm...

Good point won’t even touch it

 

[Justin Taylor]

Thanks everyone

 

[Jkstihl]

I have never done balancing with saw cranks and pistons... But based on building 20 or so Honda 4 cyls.. A few ls2s and ls3s.. You always do a rebalabce when changing pistons.. I don't know anyone who does chainsaw dynamic balancing. But if the flywheel and fan are zero balanced from factory who h they usually are.. .. Then rotating assembly should have either been dynamic balance or a calculated balance which is just a guess.. I doubt they are dynamically balanced.

So yes if you can try to remove weight from somewhere that is not critical..and match the weight to the original piston.. Maybe try it first.. The extra weight could balance it better.. Just depends on which way the factory imbalance was.. On wiseco pistons the material is removed if needed under the wrist pin mounts believe it or not.

Man it would awesome to be able to dynamically balance a saw rotating assembly and make up Bob weights for the process

Me likey k20a2's k24/k20's , b18c's, b16a-b's, b20's, lsvtecs, h22's, h23's, h2b's, dohc zc's d16z6's, y8s y7s d15b's and probably a few im forgetting...lol. Oh yeah and f20b but ive never had one

 

[1hander]

Lol my son is rebuilding his 95 civic currently.. We built the d16z6 and once the car is done we'll fabricate a system for the Nagasaki noise maker.. Should live a long life at 18 to 20 pounds boost

 

[Jkstihl]

Lol my son is rebuilding his 95 civic currently.. We built the d16z6 and once the car is done we'll fabricate a system for the Nagasaki noise maker.. Should live a long life at 18 to 20 pounds boost

Hell ya..i love honda's...maybe even more than saws lol.. Heres mine i have a 02 si and a 99ex

 

[Canyon Angler]

 

[1hander]

 

[Jkstihl]

View attachment 800672

Hell ya..i love eg coupes...probably the best civic chassis there was.

 

[Jkstihl]

Looks like a ef?

 

[1hander]

Haaaa.. I didn't see the huge can... I love inlines.. But.nothing compares to a v8 with a fat cam AND A healthy LSA..

Only one other sound compares... The same v8 with 2 hairdryers on it.. And the look on exotic car owners faces when they PECK EH FEIGHT and you let 1100 horsepower eat on em

 

[Canyon Angler]

1100 horsepower

 

[Westboastfaller]

Should I make the piston weight the same as the 50mm piston or don’t even touch it.

Don't even touch it. AM piston are generally lighter anyways and won't heat transfer nearly as well as it is. I have used fly weight open skirt pop-ups and ruined a good oem 50 mm cylinder. It was good for the first day when the trees were under 2.5ft The next morning I had a pile of bigger cottonwood close together all 3.5 to 4ft with a favourable lean. It made short work of the first 2.5 trees and then it said 'game over! Credit Zero! Play again! insert coin.
The sad part was I had a 266 xp OEM window piston in there that was just killing trees. I don't mess around anymore.
---------
I am assuming that would be a Looper style piston (open skirt?) If that's the case then it would be lighter than a solid piston I would think.

You can only blame the crank on those saws or youself if it falls apart.
You are dealing with a lower quality and you are beefing it up?
Some of those cranks may not be too bad but with the 372 they seemed to go together too tight with the case gasket they supply. That could have been about 6 years back though. The first one we tried on a ported 52mm and I punched it out on the second day also. I was going to sell it for him after trail. I did have one I ran for smaller falling and slashing with a ported 48mm. Then I used it with a ported BB on the coast and it held out. Probably 5-6 months on it then chucked it. That's right, she got f*ed & chucked.

I have seen 1 thread saying more weight the more torque but less rpm is this true? This saw wears a 24in bar and I mostly cut pine. Thanks

That comes from rotational mass
The larger body of rotating mass = greater inertia. The bigger the rock the harder the stop, in theory. I would think more in terms of a bigger flywheel: rotating mass on an axis. and all other things equal (equal as can be) including RPM then It would be harder to slow down. Inertia = rotational mass. Torque= rotational force. A piston has a reciprocating motion and a little more or little less weight, one ring or two, my be more relevant/ noticeable to a few other things Imo but it's neither or the two mentioned above.
A generated flywheel has a magnetic ring and weighs a bit more but it's closer to centre of mass which travels a shorter distance per revolution. Maybe these things help a bit. It's a lot different if you had that same mass spread on the outside creating a greater centrifugal force opposed to being closer to a neutral centre of mass.

In chainsaw layman's terms.
It's all about the angle of the dangle that will stop thAt c*** dead.

 

[Sepia]

Don't even touch it. AM piston are generally lighter anyways and won't heat transfer nearly as well as it is. I have used fly weight open skirt pop-ups and ruined a good oem 50 mm cylinder. It was good for the first day when the trees were under 2.5ft The next morning I had a pile of bigger cottonwood close together all 3.5 to 4ft with a favourable lean. It made short work of the first 2.5 trees and then it said 'game over! Credit Zero, To play again insert coin
The sad part was I had a 266 xp OEM window piston in there that was just killing trees. I don't mess around anymore.
---------
I am assuming that would be a Looper style piston (open skirt?) If that's the case then it would be lighter than a solid piston I would think.

You can only blame the crank on those saws or youself if it falls apart.
You are dealing with a lower quality and you are beefing it up?
Some of those cranks may not be too bad but with the 372 they seemed to go together too tight with the case gasket they supply. That could have been about 6 years back though. The first one we tried on a ported 52mm and I punched it out on the second day also. I was going to sell it for him after trail. I did have one I ran for smaller falling and slashing with a ported 48mm. Then I used it with a ported BB on the coast and it held out. Probably 5-6 months on it then chucked it. That's right, she got f*ed & chucked.

That comes from rotational mass
The larger body of rotating mass mainly = greater inertia. The bigger the rock the harder the stop, in theory. I would think more in terms of a bigger flywheel: rotating mass on an axis. and all other things equal as can be including RPM then It would be harder to slow down. Inertia = rotational mass. Torque= rotational force. A piston has a reciprocating motion and a little more or little less weight, one ring or two, my be more relevant/ noticeable to a few other things Imo than create any kind of inertia to speak off. PfffffT. You gain here, you lose there. A generated flywheel has a magnetic ring and weighs a bit more but it's closer to centre of mass which travels a shorter distance per revolution. Maybe these things help a bit. It's a lot different if you had that same mass spread on the outside creating a greater centrifugal force opposed to a neutral centre of mass.

In chainsaw layman's terms.
It's all about the angle of the dangle that will stop thAt c*** dead.

You should save this and use it as the preface for that book your are writing

 

[1hander]

1136.. 37 pounds boost.. 427cid..e85.. Not my car unfortunately I only got to build it.. I can't afford that much motor but it was fun tuning it.. My car would be lucky if it's 650 at the tires..