What would happen If you plugged strato ports?

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Tinman204

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I have a question for anyone in the know.

I have a 576xp here that I'd like to try and put a different carb on.

The idea is I find the zama carbs on 576 saws are too lean, so Id like to try mounting a different carb. I've already put a new zama on my saw and its once again being picky.

The only thing I can think of is either make a new intake manifold or plug the strato ports and hook up a normal carb..

I know guys hack open the intakes on X-torxs and basically put fuel into the strato ports, what about the other way around and just get rid of them?

Anyone know is this is a silly idea or not???

I'm just brain storming and want to know if its even possible to block the strato inlets and not harm the saw?
 
If you plug the strato ports greta would get mad......
6a585419a169afd231cc2969505e4ffa.jpg



Sent while firmly grasping my redline lubed RAM [emoji231]
 
In all seriousness after dealing with my 576 and hearing my buddies thoughts on how his runs I think those zama carbs on those saws are junk.

Ive had 3 on my saw and they all run and tune like $5 ebay Chinese carbs except they are $200 or so.

They never idle right and tend to lean after a big cut.

I'm going to figure this out!!
 
You probably won't have the top end because of the strato airflow absence. I have done it on a Stihl TS700 of mine before as a test because the strato reeds on that peticular model were broken. I used epoxy putty and plugged the ports closest to their entrance in the cylinder. This variation of strato is an early design, not like yours, though the end result is the same. It introduces the "strato air only" charge in an external transfer tube with a reed check valve to prevent backflow, which enters in the top of the intake transfer port. It doesn't require the air charge to pass through a cavity designed in the piston to transfer the air portion like your saw.
It worked fine, but lacked a minor amount of power at wot, and had to be leaned down on the high speed needle to run right.
On the TS700, the strato portion of the carb is only designed to open above half throttle.
 
Im going to try and make a walbro off a 441c fit.

My buddy is going to dig one out from his spares.

Winter is long and I got notjing but time.

To be continued.......
 
Im going to try and make a walbro off a 441c fit.

My buddy is going to dig one out from his spares.

Winter is long and I got notjing but time.

To be continued.......
Although I applaud your need to explore; you will probably sober up once you actually see the impracticality of what you are suggesting.
Are you considering throttle linkage, impulse port location, and air filter fitment issues?

You may well end up with a useless saw, or a pile of parts.
If you go modifying things that you can't revert back to it's origional configuration, that's likely.

Chainsaws aren't like old cars you can get a blowtorch, and a saws-all to "shoe horn" another engine into.

I have substituted a Stihl 076 carb onto a Pioneer 62 series before, but that was just a matter of changing the impulse port location by means of drilling a hole, and using a carb fuel pump side diaphragm cover with an omitted impulse nipple.

Try an easier approach.
See if your strato carb has a "screw in jet" on the high side.
On models without a high side adjustment, as the saw wears, it can get out of the 14 to 1 sweet spot mixture range.
I've had (accidental) luck before on re-jetting a Stihl MS170 "no adjustment" carb in the past by rejetting to a slightly larger jet.
The carb had an accelerator pump that was not functioning though, so it was just a work around, and didn't fix the actual issue.
There again, if you or someone else corrects the issue causing the origional lean condition, you've got to change the jet back, or it's a no-bueno hack job.
You will need dead donor carbs to rob from that have jets that are about two jet sizes bigger to make a difference.
If you go too much, the auto-tune won't be able to tune the richness out.
Your saw may have some other issue that's causing the lean condition, or it may not even be a lean condition at all.
If you you were dealing with a lean condition, and were using the saw anyways, you would probably have scored the piston by now.
It could be as simple as a wet air filter from a worn piston skirt.
It could even be fuel quality/grade, altitude, or temps the saw is having trouble coping with, even being an auto tune saw.
Have you ever had it reset by a tech with a computer?
 
Although I applaud your need to explore; you will probably sober up once you actually see the impracticality of what you are suggesting.
Are you considering throttle linkage, impulse port location, and air filter fitment issues?

You may well end up with a useless saw, or a pile of parts.
If you go modifying things that you can't revert back to it's origional configuration, that's likely.

Chainsaws aren't like old cars you can get a blowtorch, and a saws-all to "shoe horn" another engine into.

I have substituted a Stihl 076 carb onto a Pioneer 62 series before, but that was just a matter of changing the impulse port location by means of drilling a hole, and using a carb fuel pump side diaphragm cover with an omitted impulse nipple.

Try an easier approach.
See if your strato carb has a "screw in jet" on the high side.
On models without a high side adjustment, as the saw wears, it can get out of the 14 to 1 sweet spot mixture range.
I've had (accidental) luck before on re-jetting a Stihl MS170 "no adjustment" carb in the past by rejetting to a slightly larger jet.
The carb had an accelerator pump that was not functioning though, so it was just a work around, and didn't fix the actual issue.
There again, if you or someone else corrects the issue causing the origional lean condition, you've got to change the jet back, or it's a no-bueno hack job.
You will need dead donor carbs to rob from that have jets that are about two jet sizes bigger to make a difference.
If you go too much, the auto-tune won't be able to tune the richness out.
Your saw may have some other issue that's causing the lean condition, or it may not even be a lean condition at all.
If you you were dealing with a lean condition, and were using the saw anyways, you would probably have scored the piston by now.
It could be as simple as a wet air filter from a worn piston skirt.
It could even be fuel quality/grade, altitude, or temps the saw is having trouble coping with, even being an auto tune saw.
Have you ever had it reset by a tech with a computer?

Yes I'm considering throttle linkage, impulse line and air filter location and space.

I already have a useless saw so I'm where im at.

This saw is non auto tune, and even if it was first gen auto tunes are not plug and play like my 2nd gen 562 is.

I've been inside this saw enough times to rule out the "simple stuff" its a matter of these zama carbs seem to be junk no more no less. If I could get a zama to run right ( I'm on carb 3) i would simply run a zama and call it a day.

I cut at 600 feet altitude and only that atltitude so its not that. Pressure and vac have bever yielded anything. I use premium hugh octain and optimol at 45:1, all my other saws run sweet on that.

Hell I even rebuilt the saw around a new set of cases to rule out an airleak that may not be detectable.

This is simply an excercise in "can I" and if it don't work I will be the first one to admit it.

576s are great saws but in my oppinion new zama carbs are of low quality and most saws that run through my shop with zama carbs always have tuning issues, poor idling and or a scored piston..

I rarely experince that with a walhbro or tilly.
 
In all seriousness after dealing with my 576 and hearing my buddies thoughts on how his runs I think those zama carbs on those saws are junk.

Ive had 3 on my saw and they all run and tune like $5 ebay Chinese carbs except they are $200 or so.

They never idle right and tend to lean after a big cut.

I'm going to figure this out!!

Thats not the first time iv heard that about those carbs. Im here to listen. I cant help you here sir.


Sent while firmly grasping my redline lubed RAM [emoji231]
 
Yes I'm considering throttle linkage, impulse line and air filter location and space.

I already have a useless saw so I'm where im at.

This saw is non auto tune, and even if it was first gen auto tunes are not plug and play like my 2nd gen 562 is.

I've been inside this saw enough times to rule out the "simple stuff" its a matter of these zama carbs seem to be junk no more no less. If I could get a zama to run right ( I'm on carb 3) i would simply run a zama and call it a day.

I cut at 600 feet altitude and only that atltitude so its not that. Pressure and vac have bever yielded anything. I use premium hugh octain and optimol at 45:1, all my other saws run sweet on it.


Hell I even rebuilt the saw around a new set of cases to rule out an airleak that may not be detectable.

This is simply an excercise in "can I" and if it don't work I will be the first one to admit it.

576s are great saws but in my oppinion new zama carbs are of low quality and most saws that run through my shop with zama carbs always have tuning issues, poor idling and or a scored piston..

I rarely experince that with a walhbro or tilly.


Zama must be sabotaging all carbs headed for Husky.
Stihl does own Zama after all.
They make all Husky run like ****.
They're doing a very good job, imho.
HaHaHaHaHaHa
 
Zama must be sabotaging all carbs headed for Husky.
Stihl does own Zama after all.
They make all Husky run like ****.
They're doing a very good job, imho.
HaHaHaHaHaHa

I find 99% of saws that I work on with carb issues have a zama under the hood.

Maybe stihls clst 20% more to pay for the good carbs they have???
 
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