theory--vented cap

amite

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My rear engine with 13.5 HP B & S stalls after it's been running a while, and especially badly on turns. I have a theory that I need a vented cap. Thoughts?
 

Rivets

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Good theory, but probably wrong guess. Better theory, you have a fuel delivery problem, dirt in the tank, bad fuel line, bad fuel pump, dirty carb, etc. Have no idea on how to help you, as you provide us with so little info to go on. We don't know which model of Briggs you have, age of unit, how long the problem has been around, how long it's been running when problem occurs, is it worse when turning left or right, does it clear up or get worse as you continue. You are asking us to use our ESP to help solve your problem, mine is down due to the freezing temps here in Wisconsin. You need to help us help you, or you are out of luck.
 

bertsmobile1

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:welcome:

Any idea which one of the 743 different 13.5Hp engine we are talking about ?
It sort of helps unless you came here to get confussed by being given the right answers for the wrong engine.
 

amite

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@bertsmobile1--model no. is 31R507, 500cc. can get Type if needed.
@Rivets--unit is 13 months old; has had problem since day one; yesterday I cut mother-in-law's front and back, and it never stalled once. Came to my yard, stalled every minute or so. Have always believed right turns were worse. Gets worse with time. Thanks.
 

bertsmobile1

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That narrows it down a bit there is only 37 different specs for this engine.
As it is a RER I am assuming it has a fuel tank that is part of the engine assembly.

Even if not, drain the engine and check the fuel outlet from the tank.
It is not uncomon to find a casting flash in there partially obstructing the fuel flow.
Even worse are the loose ones that open & close like a flapper valve.
Check the fuel supply line which looks from the few IPL's I looked at has some nastly tight bends that could be restricting the fuel supply
And yes the code number for the engine would be helpful and the model number of the mower will not obstruct things either.
You are there & we are here .
We have no idea what you got un;ess you tell us exactly
The USA factories make around 9,000,000 mowers a season and import nearly the same number.
There are only a few thousand subscribed to this entire site so the chances of some one having the exact same mower are not particularly high and the odds of some one with the exact same mower experiencing the exactly same problems are about the same as winning the lottery without a ticket.
 

amite

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Update: Cut grass yesterday--first I loosened gas cap so that it just sat in place. The mower never stalled or bogged down once. Furthermore, the grass was high, I had the mulching plate on, and was cutting in top gear. The owner of the shop where I bought mower doesn't believe venting has anything to do with my problem, either. Sure is weird how loosening gas cap helps! :thumbsup:
 

Psychlopath

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Shouldn't it come with a vented cap? Have you checked the parts catalog for the mower to check what should be factory installed? I thought most RER Snappers had a little screw-in vent so you can have air flow when it's running but close it so so it won't spill fuel when you upend it. Maybe it was swapped out before you got for some reason.

If it works well with the cap loose, you may have found the problem; in the past when you opened the cap, have you noticed any indication of vacuum in the tank? You've got to have SOME way for air to replace the fuel in the tank as it drains.
 

ILENGINE

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Non vented caps have been used since 2012 on most mowers. either is vented through a separate line attached to the carb intake, or a charcoal canister. If the there is no separate vent line then the cap has a charcoal element.

If the charcoal gets flooded with raw fuel it damages the charcoal and will prevent air passage through the charcoal. Have seen this problem on spraying with engine driven pumps that have been mounted in the bed of utv's when used for spraying over rough ground.
 

amite

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@Psychoplath--the owner of the shop where I bought the mower looked up the parts diagram and said no to vented cap. He also mentioned "canister". I have never heard that sucking sound when I loosen the cap which would indicate a vacuum.
@ILENGINE--would a vented cap hurt anything?
 

ILENGINE

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Wouldn't be emissions compliant, but won't damage anything.
 
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