# Pop Off Pressure- Do you know where yours is at ?



## OilHead (May 2, 2008)

Seeing as there is no information on the subject figured I'd post this question as it will eliminate nags on modified saws. The article can be found at - www.aerocorsair.com - Inventions Page - Pop Off Pressure By: Alex Varv Jan 2008. I wont be taking any question untill after the lecture. Your car or truck does not have a motor in it . It has an engine. Motors are electric.


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## OilHead (May 2, 2008)

If any one knows how to transfer the page over here then we'll have it for future referance should that site go down.


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## boostnut (May 2, 2008)

Why is this in the Arborist 101 section? By the way, both my car and truck have motors in them. The starter and windshield motors come to mind.:censored:


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## lxt (May 2, 2008)

boostnut said:


> Why is this in the Arborist 101 section? By the way, both my car and truck have motors in them. The starter and windshield motors come to mind.:censored:



LOL.

what is the purpose of this anyway? motor, engine, internal combustion power plant, etc... where are we going with this?


LXT...........


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## Kogafortwo (May 2, 2008)

Google Walbro+popoff and you will get about a zillion hits from the remote control airplane and go-kart crowds. I still don't understand popoff though. I just set the needle lever to the right height and leave the spring tension how I found it. Usually stuff runs good that way.


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## glenn31792 (May 2, 2008)

If you want to know my popoff pressure you should ask my wife
not me.


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## OilHead (May 3, 2008)

glenn31792 said:


> If you want to know my popoff pressure you should ask my wife
> not me.


 -  - OK 102 views & no yes votes. A member from another camp & myself have gone into the test mode to see if we can eliminate nags from saws after saws have been modifyed including just gutting the muffler & opening up the total exhaust area to as much as 150 % the size of the port it self. I have all my # but am waiting for our friend to show up here. You should have a clue by now what were lookin at.


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## glenn31792 (May 3, 2008)

modifyed including just gutting the muffler & opening up the total exhaust area to as much as 150 % the size of the port it self


If you need to go to 150%, that tells me that the muffler volume is to small.


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## OilHead (May 3, 2008)

glenn31792 said:


> modifyed including just gutting the muffler & opening up the total exhaust area to as much as 150 % the size of the port it self
> 
> 
> If you need to go to 150%, that tells me that the muffler volume is to small.


 - Were talkin about where the exhaust exits the muffler . Not a dime size hole that is less than 1/2 the total area of the exhaust port on the cylinder. I did hear back from the other camp today & so far results have been excellent . He is still workin on a tilly that is really out to lunch. It's being measured at 50 psi , a wonder the saw even ran with it or has'nt had a major seizure . Ultimately were trying to come up with a # we can call the defacto standard.


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## glenn31792 (May 3, 2008)

Were talkin about where the exhaust exits the muffler 

I am aware of that. I have worked on 2 stroke motors that are between 5.5 and 6
hp per ci and none of them were anywhere near 100% much less go to 150%.


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## OilHead (May 8, 2008)

Kogafortwo said:


> Google Walbro+popoff and you will get about a zillion hits from the remote control airplane and go-kart crowds. I still don't understand popoff though. I just set the needle lever to the right height and leave the spring tension how I found it. Usually stuff runs good that way.


 - If you perform an extensive muffler mod you will most likely experiance run on when returning back to idle. It is a dangerious situation that needs to be addressed with more than just richening up the L. Update we now have one other person that is fixin to lower the pop off pressure on a 441 . It has real bad nags I have seen the video. Running 10% alky he has allready opened up all the orfaces but still doesnt have enough fuel yet. Should have some results back on that one pretty soon.


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## ray benson (May 8, 2008)

I don't remember anyone recommending 150%. Around 100% is the upper limit.


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## timberwolf (May 8, 2008)

Are you talking 100% of the flange area, or 100% of the actual port area?

100% of the port area is no problem, even 150% is likely ok. But 100% of the flange area is likely approaching the maximum for a work saw.


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## Kogafortwo (May 9, 2008)

OilHead said:


> - If you perform an extensive muffler mod you will most likely experiance run on when returning back to idle. It is a dangerious situation that needs to be addressed with more than just richening up the L. Update we now have one other person that is fixin to lower the pop off pressure on a 441 . It has real bad nags I have seen the video. Running 10% alky he has allready opened up all the orfaces but still doesnt have enough fuel yet. Should have some results back on that one pretty soon.



Could this be why I can't dial in my little Craftsman with the muffler mod? And is there a way to modify pop-off by just stretching or compressing the needle lever spring, just guessing at how much tension you need? I would try that with my disposable saw just to experiment.


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## timberwolf (May 9, 2008)

Yes, to lower pop off, just shorten the spring a coil or two at a time, want to increase pop off streach the spring.


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## OilHead (May 9, 2008)

Kogafortwo said:


> Could this be why I can't dial in my little Craftsman with the muffler mod? And is there a way to modify pop-off by just stretching or compressing the needle lever spring, just guessing at how much tension you need? I would try that with my disposable saw just to experiment.


 -   Was waiting for the other guys before I posted my findings but here goes. 15-17 Psi seems to be the majic # so far. When cuttin off the spring take a turn off from the other side as you go. As time goes on think were gonna find a lot of saws that are at 20 or more which was the case on the walbro from a 310. Just get it off that high area but no lower than 15. It will be fat after the mod so be ready to adjust it right away or you will foul out the plug that or turn both the L & H back in 1/4 turn lean & set max rpm from there.


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## t613 (May 9, 2008)

Where is the dipstick on a motor to check the motor oil level??! Now I'm really confused. Sorry to derail the train even further...


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## OilHead (May 9, 2008)

t613 said:


> Where is the dipstick on a motor to check the motor oil level??! Now I'm really confused. Sorry to derail the train even further...


 - The reason you cant find the dipstick is because electric motors dont have them only engines.


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## OilHead (May 10, 2008)

*1 Week later.*

1 Week later & 334 views w/ 1 yes vote. Hmmmmmmm.


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## OilHead (May 11, 2008)

Kogafortwo said:


> Could this be why I can't dial in my little Craftsman with the muffler mod? And is there a way to modify pop-off by just stretching or compressing the needle lever spring, just guessing at how much tension you need? I would try that with my disposable saw just to experiment.


  If you have to cut more than 2 turns off each end it's probably better to stop by your dealer and have a look at his spring box & find one thats closer in length to where you need to be & still maintain 1 or 2 turns on either end for superior accuracy . Mine charged me $ .56 , so is basicly a 100 % free mod or 20 minutes in the shop if you have the carb off.


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## OilHead (May 14, 2008)

Update : An inquiry was sent to walbro in requards to the pop off pressure settings . Here is the responce : ***************************** Luis Salas Program Manager - Aftermarket Walbro Engine Management 6242-A Garfield Avenue, Cass City, Mi 48726 " The Bottom line to pop off pressure is that the inlet needle pops off at some pressure. With leaner calibrations, heavier or stronger metering springs, smaller seat orfices and other variables the pop off pressure can vary. We expanded our pressure tester to go from 0-60psi because of these variations. We do not have a set pop off pressure based on this information. The pop off pressure for consumer applications is not that critical . However, in professional or high performance applications such as kart racing and the like , pop off pressure is more critical.  Nope this is exactually what I suspected when first putting this thing under the microscope. No published specifications to be found anywhere. Boy we got the dogs on them now . Hi - What would be helpful though is readings taken from some old Macs prior to all this hog wash.


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