Huskyboy meets the 572xp

[andyshine77]

IMHO some saws will not last as long with lots of compression in a true work setting. Often real high compression isn't needed anyway, and if you go too far the saw won't run free and you start going backwards. I have actually discussed this with several other saw builders. For instance I really see little need to push a 372 over 180psi of compression, some of the best running 372's I've ran had less than 180. The 390xp is another example, the big end is a bit weak and you don't want real high compression if you want the saw to last. Obviously you can push smaller saws much farther when it comes to compression without the negative effects.

Stihl's typically can take the compression better than husky saws, and some saws like the Dolmar 7900 come from the factory with 180+psi of compression, one reason they run so well.

And yes more oil is a must when you start pushing compression. Oil isn't just there for lubrication it can also act as a cushion.

I will say many of the so called woods ported work saws at gtg's likely wouldn't last a week on the job, if that long IMHO. At the same time others would surprise you how long they would last, it really comes down to how the saw is built. I personally wouldn't want finger ports in a work saw either, even though many have had great success was finger ports.This is just my opinion remember.

So to say a strong ported saw won't last is false IMHO, as is saying every ported saw will last just as long a stock or mm saw.

The few who actually took the time and documented the difference in the field, saw a significant increase in production with a properly modified chainsaw.

[emoji111]

 

[huskyboy]

372’s have a 6202 bearing on both sides. They probably did it to keep the weight down if I had to guess. Stock or light mods I think it’s probably fine. But mod them heavily turned up way past stock rpm or even just abused, sure I can see that failing. A 7900 or 461 have a 6202 on the flywheel/6203 pto side by comparison. It was a smart idea to go with 6203 size bearings on both sides on the 572 imo.

 

[Spike60]

I think there would be a lot more variables than just oil Mike. Many many more.

One of them being that Mike sharpens his chains with the care of someone tuning a piano. Many guys file at strange angles cause Uncle George did it that way. Some guys file the depth gauges real low, or OFF. You're right, the list of variables can get pretty long.

 

[RI Chevy]

Yes sir. One could probably come up with 100 variables. Then find 1 more to add.
Some users are harder than others. Hardness of the tree, location, maintenance, etc. The list goes on.

 

[~WBF]

Yes sir. One could probably come up with 100 variables. Then find 1 more to add.
Some users are harder than others. Hardness of the tree, location, maintenance, etc. The list goes on.

You must be talking to me???
No what I was saying was...
The Bruins are going down in '6'
Aaaaahhhaaaha
Truth of it is...the Bruins are straight up Scarry; could go all the way if they get game 6. Experience!!!

 

[RI Chevy]

Wrong thread sir.

 

[~WBF]

Wrong thread sir.

That's ridiculous? No off topic content in this thread so far??? (Sure you engaged in it) No off topic threads in the saw sec that you are aware of?
H-ll, there was just a thread in the saw sec
to create thread ideas and organization..
Did you jump on any of that chit? ..ever?
No you played part. Go all on one side or the other but don't play the middle sir.
So the Bruins got beat?

 

[RI Chevy]

Well. There is a hockey thread going. And this thread. Seemed to me like maybe you posted tim the wrong thread. You can do whatever you want, whenever you want, however you want. Knock yourself out.

http://opeforum.com/threads/2019-nhl-play-off-thread.16369/

Bruins tied the series at 3-3. Back in Bean Town for the finale.

I was actually referring to the post directly above mine when I posted, so no, I really wasn't referring to you regarding the 100 reasons post.

Now back to the thread... [emoji6]

 

[MustangMike]

Lots of good points being made here … and then we presume that if you get 100 bearings that one of them is not a bit flawed …

But I think that it is fair to say:

- Avoid Excessive Compression
- Properly Vent the Heat
- Properly maintain and tune the Saw, Bar + Chain
- Use quality oil mixed at a good ratio for your saw and conditions
- Operate in a reasonable manner

All will usually contribute to longevity of a saw.

 

[andyshine77]

372’s have a 6202 bearing on both sides. They probably did it to keep the weight down if I had to guess. Stock or light mods I think it’s probably fine. But mod them heavily turned up way past stock rpm or even just abused, sure I can see that failing. A 7900 or 461 have a 6202 on the flywheel/6203 pto side by comparison. It was a smart idea to go with 6203 size bearings on both sides on the 572 imo.

RPM really isn't the cause of most premature failures as long as you have the fuel IMHO. It's compression that will wipeout the big end bearing before the crank bearings. Bearings like oil! True some saws that weren't "let's just say" designed just right, may be a little more fickle when it comes to rpm's. Heavy pistons small bearings is a bad combo.

To me personally a good mm, setting squish and some timing goes a long long way with most saws.

 

[shadco]

You must be talking to me???
No what I was saying was...
The Bruins are going down in '6'
Aaaaahhhaaaha
Truth of it is...the Bruins are straight up Scarry; could go all the way if they get game 6. Experience!!!

Let's go Caps, maybe they will get their heads outta their asses tonight.

.

 

[MustangMike]

Agree with you on the compression, but not so sure on the RPMs.

There are a # of factors going against the saw:

1) A single piston engine is never ideal for high RPMs.

2) Chainsaws are not truly balanced, and are over built to make up for it.

High RPMs generate additional centrifugal force and additional levels of stress, and are especially tough on both ends of the rod bearings. Heavier pistons magnify this stress. It is a wonder that our Hybrids (and Big Bores) hold up as well as they do, and a reason I always use an OEM piston pin bearing.

 

[MustangMike]

RPM really isn't the cause of most premature failures

Think of it, 15,000 RPM is 250 RPM a second, or 500 stop and starts for the piston going back and forth in the cylinder!

It is amazing they last more than 5 minutes! The force of acceleration and deceleration increase greatly with increased RPMs, so I respectfully disagree with you on this point.

 

[andyshine77]

Think of it, 15,000 RPM is 250 RPM a second, or 500 stop and starts for the piston going back and forth in the cylinder!

It is amazing they last more than 5 minutes! The force of acceleration and deceleration increase greatly with increased RPMs, so I respectfully disagree with you on this point.

Most motorcycle engine of much larger displacement spin that fast or faster now, I must disagree with you here. The piston velocity and energy/inertia depends on the stroke length. The longer the stroke the graeter the piston velocity, the shorter the stroke the lower the velocity, this is what's critical. Plus they are not turning that under load.[emoji111]

 

[Spike60]

You guys ain't gonna start gettin technical on us are ya?

 

[andyshine77]

You guys ain't gonna start gettin technical on us are ya?

Lol how you doin' Bob?[emoji16][emoji111]

 

[mdavlee]

You must be talking to me???
No what I was saying was...
The Bruins are going down in '6'
Aaaaahhhaaaha
Truth of it is...the Bruins are straight up Scarry; could go all the way if they get game 6. Experience!!!

You didn’t kill any bottom ends with those 75cc jugs did you? They were pushing 190-200 lbs. I know Shane’s 71cc was 225 or so after break in and it was probably the best running one I ever built with a stock piston.

 

[MustangMike]

Most motorcycle engine of much larger displacement spin that fast or faster now, I must disagree with you here. The piston velocity and energy/inertia depends on the stroke length. The longer the stroke the graeter the piston velocity, the shorter the stroke the lower the velocity, this is what's critical. Plus they are not turning that under load.[emoji111]

Generally, the higher revving motorcycle engines have more pistons, making it easier to even the load on the crank.

Re: bore/stroke for the same cc … it is a catch 22, the shorter the stroke the larger the bore and the heavier the piston … inertia is inertia and reversing it results in stress. The higher the RPMs, the higher the stress. Building with the right components is key … but increasing RPMs, all else being =, will shorten the engine life. In addition to reversing the direction of the piston there will be more side force (due to inertia) on the P + C and it will wear faster … there is no getting around it. (Until you invent the oil that increases viscosity under load).

 

[RI Chevy]

How about full circle cranks? Better, less wear or worse, more wear?

 

[MustangMike]

Weather it will help the crank or not I don't have a clue, but will not reduce the stress on the rod, piston and cylinder created by addl RPMs.