stihl weedeater wont prime - HobbyTalk
 
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post #1 of 14 (permalink) Old 07-27-2008, 12:16 AM Thread Starter
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stihl weedeater wont prime

I have several stihl weedeaters they are the newer ones zama carbs on them i have done everything i know to do i cant get them to prime changed fuel lines and filter rebuilt carb, changed gas cap, new primer ball it will crank with starting fluid but dies soon after it is building up pressure in the tank what else can i check
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post #2 of 14 (permalink) Old 07-27-2008, 01:51 AM
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loosen the cap & try it. if it runs you've found the problem. now why on several Stihl weedeaters?
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post #3 of 14 (permalink) Old 07-27-2008, 02:08 AM Thread Starter
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just got a few with the same kinda carbs rotary they belong to a customer and all three are doing the same thing ill check the cap when loose
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post #4 of 14 (permalink) Old 08-07-2008, 11:29 PM Thread Starter
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it still wont prime i know the carb is clean been over it several times nothing seems to be clogged do these carbs need the welch plugs changed what else can go wrong usually dont go no further than new diaphram gaskets you know the regular stuff dont know a whole lot about the rotary carbs they seem to be pretty simple although they have no adjustments on them(sux) not to much there to get stopped up someone told me there is an ajustment screw where the throttle hooks up just a plate to me holding down the throttle took it all apart i could not see where to adjust anything dont know just open for suggestions thnx
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post #5 of 14 (permalink) Old 08-08-2008, 11:10 AM
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I would suggest going to;
www.zamacarb.com
Select - Service/Aftermarket
Select - Technical Guide
Close to the bottom of the .pdf it covers the rotary carb.
Hope this helps. Have a good one. Geo
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post #6 of 14 (permalink) Old 08-08-2008, 03:10 PM
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I have rebuilt 2 stroke carbs for the past 2 years in my shop that I do as a side business.

I have yet to get a rotary carburetor to work right , I've rebuilt them, cleaned them and adjusted the metering levers, they would never work. both the Zama's and the Walbro's.

I have sat and read the service manuals on them several times, no help.

If it's a rotary carb , I just buy a new one and be done with it.

I know this dont help your problem , but dont feel bad, your not the only one having problems with them.

Mark
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post #7 of 14 (permalink) Old 08-08-2008, 08:33 PM
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I would check or replace the high speed check valve, if it leaks the primer will not work and you will not be able to get the engine to run. They will start with a bad check valve, but as soon as you take the choke off, they will lean out and die.
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post #8 of 14 (permalink) Old 08-08-2008, 08:40 PM
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I would check or replace the high speed check valve, if it leaks the primer will not work and you will not be able to get the engine to run. They will start with a bad check valve, but as soon as you take the choke off, they will lean out and die.
is that the governor (sp)
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post #9 of 14 (permalink) Old 08-08-2008, 09:02 PM
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is that the governor (sp)
No, the high speed check valve in the carburetor prevents back pressure from the engine from entering the metering chamber of the carburetor. 2 cycle engines tend to have quite a bit of back pressure flow back out through the carburetors when they are running, if the pressure enters though the main jet and into the metering area of the carburetor, it will prevent fuel from flowing into the metering side and the engine will die.
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post #10 of 14 (permalink) Old 08-09-2008, 03:08 AM
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No, the high speed check valve in the carburetor prevents back pressure from the engine from entering the metering chamber of the carburetor. 2 cycle engines tend to have quite a bit of back pressure flow back out through the carburetors when they are running, if the pressure enters though the main jet and into the metering area of the carburetor, it will prevent fuel from flowing into the metering side and the engine will die.
i need to tare into a few more carbs i guess
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post #11 of 14 (permalink) Old 08-12-2008, 09:33 PM Thread Starter
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thanx for all the help i took carb apart one more time and looked it over real good the small oblong welch plug was missing put a new one in and put it all back together primed right runs like a champ appreciate the info
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post #12 of 14 (permalink) Old 08-13-2008, 04:38 PM
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What is a rotary carb.?

I just started a short time ago tinkering with 2 cycle engines and I read messages about rotary carbs. and don't know for sure what they are.
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post #13 of 14 (permalink) Old 08-13-2008, 05:11 PM
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I just started a short time ago tinkering with 2 cycle engines and I read messages about rotary carbs. and don't know for sure what they are.
i don't think i have worked on them myself
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post #14 of 14 (permalink) Old 08-14-2008, 10:34 AM
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I just started a short time ago tinkering with 2 cycle engines and I read messages about rotary carbs. and don't know for sure what they are.
Go to www.walbro.com and look up any wy, wyk, wyl series carburetor and you will see what is being referred to as a rotary carburetor. It's the type of throttle valve that is being used on a particular carburetor.
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