Poulan Pro PP-335 Weed Trimmer

fayjim2

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It might start but won,t stay running. Removed tank n cleaned replaced lines and filter. still the same. Replaced fuel primer, seemed like the bulb was loosing its mojo.,. I then removed carb WTA-28 Dissasembled (looked clean but let soaked 24 hours in carb cleaner. Removed from cleaner and used air to dry all passages.. Reassembled with original items and still won,t stay running. Now when I squeeze the primer after 3 pumps it stays collapsed. Is there someone who has had this ailment prior, Thanks Jim
 

ILENGINE

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Carb cleaner will cause the check valves inside the carb to swell and either not open which is most likely the situation that you have, or will not close in which the carb won't draw fuel and therefore doesn't prime.

which are the main reasons most repair shops don't rebuild those carbs any more because there is a 50/50 chance that it won't work after rebuild.
 

bertsmobile1

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Pull the fuel intake tube off.
It is the one furthest away from the primer.
Pump the primer bulb.
If fuel squirts out of the carb, you took the wrong tube off.
If the primer pops up quickly then the filter is clogged or line is pinched off.
If it stays down the carb is clogged

If the latter there are 2 possibilities
1) you assembled it incorrectly
2) as per previous post the carb cleaner has destroyed internal parts
The only stuff you should ever use to clean a cube carb is fuel , soapy water or Walbro's carb cleaner that will not swell seals & check valves.
 

fayjim2

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Just where are these seals and as far as a checkvalve the only item I saw was a small alum plate that covered to small holes? I have taken many carbs apart but never have I been told the cleaner will hurt the parts. Is there a good breakdown of this carb, and also what do you suggest for a replacement carb? Thanks Jim
 

bertsmobile1

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Item 17 in the diagram below
View attachment Check valve.pdf
There is also 1 or 2 under the primer bulb

There may be more than 1 check valve in the carb body itself depending upon which carb you have.
I can't be bothered to track down the parts breakdown for exact carb you have and you have not made the effort either or you would have found the parts break down showing the check valves.
It is on the Walbro web page along with the proper way to clean & diagnose their carbs.
They used to come in the overhaul kits. I have a couple of very old kits I inherited with the business.
The new kits do not have them but you can order them direct from Walbro, or Zama.
You can not get them for Ruzing or any other Chinese carbs as the only parts available for them are diaphragms & gaskets.

If you really want to know exactly how the carb works there is a really good series called "two stroke carburettors theory & operation" or something similar on You tube.
It is presented by an very well informed but utterly boring UK presenter.

Next best is the series by Joe Pace ( ex Husqvarna Service School ) called "Two stroke Diagnosis "
Taryl & Donny Boy might have some good videos but neither present much in the way of theory of operation.

Most everything else is just ego food for monkeys who watched some one make a video & post it then "monkey see - monkey do "
 
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