Stratto saw life

maowwg

maowwg

ArboristSite Lurker
Joined
Nov 8, 2020
Messages
32
Location
Wisconsin
Without too many details or a long boring story, my young son started a chainsaw repair business during Covid. Business is a loose term. Basically he bought a few saws, fixed them, and resold. In addition to learning about the mechanics, he learned about inventory, keeping customers happy, and finding a niche in which a profit could be attained and especially the value of a dollar.

Believe it or not, we have stayed away from Sthil chainsaws and huskies, because of the cost to get in and the risk of getting stuck with a bad unit and the ease at which we can part out little consumer saws can’t be fixed. So, he did a lot of Craftsmans and Poulans, which sell well if clean and rebuilt.

Having helped him tune the carburetors, we find it signi easier to tune a non-strato saw than the newer ones. Hitting that sweet spot where the saw essentially accelerates into the cut is just flat easier.

So here’s the question: The life of a saw motor is tied to how well it is tuned while running assuming no other abuse. Do the older saws last longer because they’re easier to tune and keep tuned properly?

The sample size for that statement about tuning is over 30 and less than 40 saws. So, I’d also be interested in seeing if folks have that same experience, and whether there are any tips or tricks for more efficiently tuning a strato saw with the Zamas vs the simple box Walboro box carbs.
 
huskihl

huskihl

Addicted to ArboristSite
Joined
Dec 26, 2014
Messages
3,062
Location
Northern Michigan
Zama or walbro doesn’t matter, as they both make standard and strato carbs.
A strato saw typically won’t last quite as long because of the heavier piston hammering on the bearings. But for the stuff you’re fixing, if it’s mostly off brand homeowner stuff, I doubt you’d see the above statement true as they usually get straight gassed or burned up from running too lean long before the bearings wear out.
As far as difficulties in tuning the strato saws, I’d wager that there is very little fine tuning in the manufacturing stage to actually make sure the jetting and air flow is perfect in a sub $200 saw where the owner won’t know the difference anyway, vs someone knowledgeable running a $1000+ saw that would know if things weren’t quite right
 
maowwg

maowwg

ArboristSite Lurker
Joined
Nov 8, 2020
Messages
32
Location
Wisconsin
Yeah. Had not thought of the heavier piston. More mass changing direction thousands of times per minute.

You're right, I'll never know how long they last, because we never hear back from the buyers. I was just wondering more than anything.
 
esean

esean

ArboristSite Operative
Joined
May 20, 2020
Messages
105
Location
SE Ohio
No answer to the longevity issue, but I find it easier to tune my Stihl 362 strato than my Echo 2511T non-strato. Might be due to the difference in sound level between the two. The idle's a bit more finicky on the little Echo too.
 
huskihl

huskihl

Addicted to ArboristSite
Joined
Dec 26, 2014
Messages
3,062
Location
Northern Michigan
No answer to the longevity issue, but I find it easier to tune my Stihl 362 strato than my Echo 2511T non-strato. Might be due to the difference in sound level between the two. The idle's a bit more finicky on the little Echo too.
The little Echo is tough. Almost gotta run a half tank through it and make an adjustment one way or the other and try it again
 
Slotracer577

Slotracer577

ArboristSite Operative
Joined
Sep 2, 2020
Messages
104
Location
Cos
One thing I noticed is my non strato saws all have catalytic converters. Strato saws do not. So for that alone I would suspect my strato saw to run longer as it has less heat. Now remove the cat at it could easily switch.

makita 6100 vs4300, 5000, and 7900. I really like the 6100, bigger better air filter, open muffler stock, runs and cuts well. You can tell it was designed more recently than some of my other saws.
 
tomalophicon

tomalophicon

ArboristSite Operative
Joined
Apr 28, 2020
Messages
484
Location
Canberra, Australia
One thing I noticed is my non strato saws all have catalytic converters. Strato saws do not. So for that alone I would suspect my strato saw to run longer as it has less heat. Now remove the cat at it could easily switch.

makita 6100 vs4300, 5000, and 7900. I really like the 6100, bigger better air filter, open muffler stock, runs and cuts well. You can tell it was designed more recently than some of my other saws.
I have found the 6100 to be more challenging to tune than my other saws. I find it harder to discern the burble vs what might be the limited coil cutting in.
 
m21bmr

m21bmr

ArboristSite Operative
Joined
Aug 20, 2009
Messages
103
Location
Alabama
Over the past several years, I have refurbished quite a few Poulan homeowner saws. Mostly just fuel lines, carb cleanups, diaphragms, etc.

In my experience with those saws, the non-strato versions from the 1990s-2004 rarely had piston/cylinder damage. In 20 or more saws that I worked on, I don't remember but maybe one saw having a scored piston. In the dozen or more strato versions that I've worked on (which were made from 2005 and forward), it seems 50% or more of that series of saws have scored pistons. I'm not sure if it mainly the factory tuning becoming significantly leaner, but the likelihood of scoring in my experience is much higher in the Poulan strato saws.

As far as tuning on the Poulan series, I do find it harder to tune the strato saws in general. I would definitely prefer to work on the older non-strato saws.
 
sean donato

sean donato

Addicted to ArboristSite
Joined
Aug 3, 2014
Messages
2,575
Location
Eastern, PA
I can't give a carpet statement for which is better in non pro homeowners saws. I've worked on about every version of Poulan I can think of. The only consistent thing I've found is they all are very lean from the factory. Stratto or normal. Seen just as many stratto saws burned up as as regular ones. Don't think the stratto has a significant difference in reliability out side of heavier piston and cheap materials. I've had good and bad of both to tune.
 
Northerner

Northerner

ArboristSite Operative
Joined
Dec 13, 2010
Messages
340
Location
Alberta, Canada
I dont have a whole lotta love for the stratto saws yet. Supposed to be more environmentally friendly I assume, seems so useless when you see jets going overhead burning unreal amounts of fuel, and here we are on the ground trying to save the world with a little 4hp engine.


Sent from my iPhone using Tapatalk
 
tomalophicon

tomalophicon

ArboristSite Operative
Joined
Apr 28, 2020
Messages
484
Location
Canberra, Australia
I dont have a whole lotta love for the stratto saws yet. Supposed to be more environmentally friendly I assume, seems so useless when you see jets going overhead burning unreal amounts of fuel, and here we are on the ground trying to save the world with a little 4hp engine.


Sent from my iPhone using Tapatalk
From what I have read, the advantages are lower fuel consumption as the air fuel mix can be leaner and a higher compression ratio (presumably allowing an increase in power).
Maybe the disadvantages are the leaner air fuel mix (reduced lubrication?) reduces engine life.
 
Slotracer577

Slotracer577

ArboristSite Operative
Joined
Sep 2, 2020
Messages
104
Location
Cos
My understanding is they are not necessarily leaner, it just stacks air on top of the air/fuel charge in the transfers so that less fuel is pushed out the exhaust during overlap. Less unburned hydrocarbon, no need for a cat. Now that doesnt mean that the oem is tuning them leaner. That wouldn’t surprise me as the epa likes engines to be lean to reduce unburned hydrocarbons. thats why they have non adjustable screws. But if you can adjust it richer, the strato part should not make the engine run lean.
 
sean donato

sean donato

Addicted to ArboristSite
Joined
Aug 3, 2014
Messages
2,575
Location
Eastern, PA
I don't buy the stratto is junk or will wear out faster because it's a stratto engine. Since 2012 I've owned a 562xp, 10+ cords a year and it took till 2019 to loose enough compression that it had low power. Rebuilt and back at it again. They just work differently then a std cylinder and let's face it they don't have a tuned pipe to help with keeping fuel in the cylinders so anything that can move the exhaust out before the fuel/air mix enters the chamber is a plus, not just for the epa but fuel economy and power. I'll 100% admit im not nearly as comfortable with them as a standard cylinder, but the results speak for them selves, but then again I'm not talking a $100.00 walmart special either. The problem with the home owner saws is just that, they are made cheap to throw away.
 
huskihl

huskihl

Addicted to ArboristSite
Joined
Dec 26, 2014
Messages
3,062
Location
Northern Michigan
My understanding is they are not necessarily leaner, it just stacks air on top of the air/fuel charge in the transfers so that less fuel is pushed out the exhaust during overlap. Less unburned hydrocarbon, no need for a cat. Now that doesnt mean that the oem is tuning them leaner. That wouldn’t surprise me as the epa likes engines to be lean to reduce unburned hydrocarbons. thats why they have non adjustable screws. But if you can adjust it richer, the strato part should not make the engine run lean.
In a non strato, some (25-30%) of the fresh charge purges out the spent exhaust. On a strato, fresh air purges out the spent exhaust. That’s 25-30% less fuel and oil going through the bottom end. So basically everything below the crown is leaner by that amount
 
sean donato

sean donato

Addicted to ArboristSite
Joined
Aug 3, 2014
Messages
2,575
Location
Eastern, PA
In a non strato, some (25-30%) of the fresh charge purges out the spent exhaust. On a strato, fresh air purges out the spent exhaust. That’s 25-30% less fuel and oil going through the bottom end. So basically everything below the crown is leaner by that amount
No i don't think you understand how strato saws work, the fuel air charge in the crankcase has more fuel in it then a std design, since you just using fresh air to purge the exhaust mix. You have to have more fuel in the crankcase to make up for the air that's already in the cylinder. Hence the reason your not loosing mix going out out exhaust like a std cylinder. If all you changed in the system was to add more air and not compensate the engine would just run lean as heck all the time. The fuel improvement isn't from extremely lean ratios, it's from a more efficient cylinder evacuation process.
 
bwalker

bwalker

Tree Freak
Joined
Jun 3, 2002
Messages
10,085
Location
Montana
No i don't think you understand how strato saws work, the fuel air charge in the crankcase has more fuel in it then a std design, since you just using fresh air to purge the exhaust mix. You have to have more fuel in the crankcase to make up for the air that's already in the cylinder. Hence the reason your not loosing mix going out out exhaust like a std cylinder. If all you changed in the system was to add more air and not compensate the engine would just run lean as heck all the time. The fuel improvement isn't from extremely lean ratios, it's from a more efficient cylinder evacuation process.
No. Less pre mix moving through the motor, the less its lubricated.
Keep in mind that once pre mix enters the motor in fine droplet state the fuel changes phase and the oil is deposited on the internal parts. Less fuel passing through the motor= Less oil the motor sees.
 
Top