# B&S primer bulb Q's 6hp vertical shaft



## 440s-4ever (Feb 23, 2010)

I hope one of you can enlighten me. I'm working on an 80s/90s era 6 horse briggs and am thinking I've got a mismash of parts. It has 2 primer bulbs. 

Primer bulb #1 is mounted in the air filter housing and the air filter has ports against the carb flange to move fuel. However, my carburetor has no ports there, just flat surface. 

Primer bulb #2 is in the side of the gas tank and has a tiny rubber line running to a port on the carb, it looks like it's the proper primer bulb for this carb/engine. The catch is I can't verify it because the bulb top is missing. 

The mower only runs when you shoot cleaner/fuel into the primer hole, it won't stay running. I've cleaned the carb out but no luck, still doesn't flow fuel thru the carb primary circuit. 

So this is really a 2 part question, is that air filter bulb necessary. And will a bad primer on the tank-mount style cause them to not run???

thanks


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## geogrubb (Jul 28, 2006)

Post the engine model, type and code usually found on the metal shroud just above the spark plug. You can go to the briggs site www.briggsandstratton.com and see an IPL for the engine, sounds like someone replaced the air filter cover for some reason. Have a good one. Geo


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## geogrubb (Jul 28, 2006)

The primer bulb will not keep it from running, it just forces air into the fuel bowl which in turn forces fuel up the nozzle and into the engine. You probably have a dirty carb, remove the bowl and see how much junk is in it which will give you some indication how dirty the rest of the carb is, if it isn't too bad clean the holes in the bowl nut put it back together and see if it runs, if not you will probably need to remove the carb and give it a good cleaning. Have a good one. Geo


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## 440s-4ever (Feb 23, 2010)

The carb is spotless, had it apart today. Aerosol carb cleaner flows thru all the passages. When I unhook the fuel line at the carb it pours out unrestricted. Hmmmmm.


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## justin3 (Apr 10, 2007)

Sounds like someone installed the newer carburetor and air cleaner assembly on your engines, older ones has the primers mounted on the gas tank. Check to make sure the primer on the air cleaner is working. You should see gas shoot out of the main jet when you push it.


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## 30yearTech (Sep 14, 2006)

justin3 said:


> Sounds like someone installed the newer carburetor and air cleaner assembly on your engines, older ones has the primers mounted on the gas tank. Check to make sure the primer on the air cleaner is working. You should see gas shoot out of the main jet when you push it.


If it has the new air filter base mounted on the old carburetor, the primer on the air filter base will not do anything. The older carburetor had a small nipple on the side that a hose from the external primer bulb mounted to. The old carburetors are not ported on the front for primer operation. These carburetors usually had a metal air filter base, like the older units with a manual choke.

Something is restricting fuel flow either the nozzle or main jet is the likely cause.


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## 440s-4ever (Feb 23, 2010)

30yearTech said:


> If it has the new air filter base mounted on the old carburetor, the primer on the air filter base will not do anything. The older carburetor had a small nipple on the side that a hose from the external primer bulb mounted to. The old carburetors are not ported on the front for primer operation. These carburetors usually had a metal air filter base, like the older units with a manual choke.
> 
> Something is restricting fuel flow either the nozzle or main jet is the likely cause.



I think you've hit the nail on the head. The air filter primer is just a cruel trick.

Guess I'll be taking the carb apart again, sometimes it helps to hear somebody confirm what common sense is telling ya! Thanks!


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## 440s-4ever (Feb 23, 2010)

Update for those who care. And those who don't but are already reading this!

Turns out the carb wasn't clogged, had a ton of water in the gas. Drained & refilled, fired right up. But 30yeartech is still accurate about the bulb situation. Quick shot of carb cleaner into the broken tank mounted primer bulb tube and it starts right up. 

Runs great with one exception. Revs up and down continuously. A buddy says I've got the governor spring in the wrong hole. I don't remember multiple options but will look and try.

This mower is a composite of my neighbor's old mower plus 2 freebies off the curb. Engine from one, deck and handle from number two, wheels and controls from the third. Recycling at it's finest, made possible by things like this forum.

Soon it's off to craigslist to see if it's tradeable for something I care about, such as RC or slot cars  Hobbies Rule!


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## 30yearTech (Sep 14, 2006)

440s-4ever said:


> Update for those who care. And those who don't but are already reading this!
> 
> Turns out the carb wasn't clogged, had a ton of water in the gas. Drained & refilled, fired right up. But 30yeartech is still accurate about the bulb situation. Quick shot of carb cleaner into the broken tank mounted primer bulb tube and it starts right up.
> 
> ...


Tank mounted primer is available Briggs # 394281S

You drained the fuel tank, did you take the carburetor back apart and clean out all the water from it as well?

Water is much more dense then gas and will not meter through the jets, effectively restricting the flow of fuel through the carburetor, much like dirt or build up. Fuel tanks can harbor water in the tank and need to be carefully dried out, simply draining and refilling may not do the trick. A small amount of water in the carburetor can cause an engine to hunt. If it's not over speeding then the governor spring may not be the problem. If the governor spring is hooked up properly, then the tension may need to be adjusted, or the static governor adjustment needs to be performed.


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## 440s-4ever (Feb 23, 2010)

Thanks for the tip on the part number!

Update 2, it hunts for speed. Rev Rev Rev Rev Rev Rev

I drained the tank with it removed from the engine, then stood the mower vertical and drained the carb bowl thru the fill lport. The position of the port seemed to effectively drain the bowl. Then I filled it and mowed for 15 minutes plus test run time. I'd expect it to have passed the water, especially considering the new fuel is ethanol blend.

The speed hunt seems governor related. If I over ride the governor and hold the throttle blade/arm with my finger it holds speed perfectly at all throttle positions. 

There are no spring position options, at least on the carb end.

Tips? What's causing the governor mechanism on the back of the motor to do that? Everything seems to move freely when I move the rods manually.


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## 30yearTech (Sep 14, 2006)

440s-4ever said:


> Thanks for the tip on the part number!
> 
> Update 2, it hunts for speed. Rev Rev Rev Rev Rev Rev
> 
> ...


You could try performing the static adjustment on the governor, but I suspect you still have some water in your system. Ethanol blends may help with a tiny amount (such as a couple of drops) but an ounce or more will still stop up a carburetor, the orifice in the main jet is very small for this engine. I have removed tanks with water and drained them and then have to blow them out with compressed air for several minutes in order to get all the water from the tank. Any water at all in the tank will make it into the float bowl in short order once the engine is running. If you do not remove the float bowl and blow out all the jets, you will still have moisture in the carburetor and even just a little bit will cause the engine to sputter and surge.


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## 440s-4ever (Feb 23, 2010)

Is that because the governor is more sensitive than my ear? To my ear it runs smooth and fine when I hold the throttle manually, which makes me wonder about water versus the governor. I don't know jack about small engines but have a healthy automotive hobby and my ears "know stuff"  But still, a governor may be reacting long before ears could detect a problem. 

Per the throttle cable, it surges at all rpms. But over-ridden with a finger on the governor, smooth and perfect at all rpms. 

Yesterday after posting I gave it a super dose of heet (2 glugs in a half tank) then mowed a half acre. At times toward the end of that tank it ran without surging, then I refueled and surging returned. Which lends credence to the water theory I suppose. But the governor was also allowed to return to it's off position during refueling.

Once again, thanks for your help and advice. Gonna try another half acre with super-dose heet this morning before taking the carb off again.


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## 440s-4ever (Feb 23, 2010)

Not water. Mowed another half acre with heet, ran it out of gas, let it sit in the sun for 3 hours to warm/dry, pulled the float bowl and drained/inspected everything. Added fresh gas, still surges. 

Guess it's time to investigate the governor. 

Weirdly, if you push it aggressively so it shakes around, especially uphill, the surging seems to stop for 30 seconds.


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## 440s-4ever (Feb 23, 2010)

SOLVED.

So after much looking at the governor and deciding it looked right......realized I'd been using the mixture screw setting the mower came with. You know the drill, count the # of turns to seated before taking it apart. 

Today I did a proper mix adjustment. Guess what? There's about a half turn of adjustment where the surging stops and the governor goes stationary. Runs perfect now.


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