Carburetor Internal Parts Identification And How To Be Certain Which Ones To Use

[watsonr]

do you have the carb PDF from Walbro, Zama and such. Maybe a cut away view would show a picture to close the gap. Trying to explain without a picture is sometime hard to visualize for me and I may be not doing a very good job either.

 

[mikedennis0586]

the great grand coulee dam...you sell carb kits you told me earlier do you have a website?

 

[stihl041avhog]

sub two

 

[mikedennis0586]

no i don't have any of those pdf files...where would be the best place to find such a thing?

 

[watsonr]

email me at [email protected] and I'll hook you up. Cool place, I'm from Lewiston and know where that's at.
website is the link in my signature

 

[stihl041avhog]

I once had a box full of left over gaskets and such. it is now in the burn pile. just get the right kit for your carb. I know you think it should work like in your #1 pix but its just wrong . but I like the way you think. cheers

 

[mikedennis0586]

Ahh yes the famous weed eater man... been to your site a few times and heard you mentioned a bunch...never saw the link in your signature but also I wasn't looking either....I was fairly focused on what I was researching... I've been to Lewiston a few times myself... when I was still working out of the hall with the millwrights I was dispatched to potlatch a couple times... pretty area but boy was that mill stinky... I'll shoot ya a email tomorrow

 

[watsonr]

here is the manual on the WT- series carbs. It shows why you need a fuel pump and why there needs to be separation.

 

[mikedennis0586]

randy - got a few updates here...so i had the saw ready for return to it's rightful owner but i couldn't get in touch with him today so i had it at home one more time. it was killing me all day thinking about the issues that i was having so i took the carb apart one more time. i have figured out why the saw was flooding with the first diaphragm installed. once i had a good understanding of the passages and looked at the cover closer it all made sense. the impulse port was in direct access of the fuel inlet and metering supply passages. but now i'm stumped again. with the proper fuel pump diaphragm installed the large cavity is completely sealed off from the impulse passage. after looking at the carb and the cover for a while i still don't see how the impulse works. once the diaphragm and gasket are installed the impulse passage goes no where. it comes in through the carb, through the diaphragm, through the gasket and into a cavity located inside of the cover which sits directly over top of the large fuel cavity in the carburetor body. i see how the fuel flows in and out of the carb i just don't see how the impule works now. it appears to me that once it's inside the carb it can't go anywhere because it is sealed to the cover by the gasket.

 

[watsonr]

the pump is activated with every stroke of the saws piston. The down stroke pushes fuel into the metering needle and into the saws case. As the piston travels up, the impulse is reversed and sucks the fuel from the tank and deposit's it in the fuel chamber opposite the metering needle.. ready to be pushed in by 10psi needed to overcome the spring. Ultimately, the fuel just flows from the tank because of the negative pressure in the chamber, the impulse just pushes it home and the H/L needles control the amount of flow.

that little area created by the gasket (between the cover and pump) is all it needs because its moving so fast. Remember it moves with each stroke... 12K rpm. Of course it probably stretches a little, why it looks bubbled out in pic #2

Did you look at the WT pdf carb manual I attached to that last reply last night.

 

[watsonr]

and when its worn out becomes stiff, ethanol does that to it over time. I've never seen a pump worn out, just damaged by ethanol or gummed up from fuel just sitting and turning to varnish.

 

[mikedennis0586]

so their's no actual connection between the impulse cavity and the fuel cavity...impulse moves the section of diaphragm that separates the 2 cavities just enough for it to move fuel....got it now!

yes i did look at it but just kinda glanced...i haven't had a chance to really give it a good look

 

[watsonr]

the cavity is divided by the pump, that's it. One side is fuel, the other is impulse.

And welcome to the site... lesson one complete!

 

[mikedennis0586]

thanks a million randy...i sure do appreciate you taking the time to help out

 

[watsonr]

my pleasure