Help with Briggs engine

[archer1232]

I have an older briggs and stratton engine im fixing for a friend. I believe it is a 3.5 hp but im not 100% sure. So heres my problem, the engine only idles with the choke on and dies as soon as i take off the choke. And when i pull the throttle it does not want to rev high. BTW it has the governor removed and i cleaned the carb, changed the oil, bought a new sparkplug. It has a pretty bad air filter. The ones that have a whole bunch of hairs in a "can".
Any suggestions would be GREAT.
The carb looks like this one http://www.asecc.com/data/briggs/images/typl.jpg

 

[Oldsalt]

Often, if it is fitted with the common straight carb with the gas tank attached is the screen at the bottom of the dip tube is plugged. If it has a deep tank and two tubes going down into the tank the longest one has a tiny check valve at its lower end near the screen. If that little ball is not working the engine will starve for fuel. Lots of other things can be a problem but that is the most common on an old Briggs that has set for awhile. Another problem, if the engine has a lot of hard hours on it is that the exhaust valve, being very hot, will "sink" into the block which closes up the valve lash. The first symptom is sorta low comtression when you pull the rope. Take off the valve lifter cover on the side of the block and check that there is some clearance.

 

[5 Horse Fan]

Only running when choke is on, and not reving mean that there isn't enough fuel getting inside the engine.

I believe that is a Vacu-Jet Carburetor used on 2.5 - 3.5 HP engines.
Alot of times there is a restriction in the pick up tubes or the tubes may be leaking and need to be sealed or replaced. You have to unscrew the carb from the tank to view the pick-up tubes.

 

[archer1232]

Alot of times there is a restriction in the pick up tubes or the tubes may be leaking and need to be sealed or replaced.

I took the tank off the carby and the fuel filter pick up tube is damaged. Part of the end of it is broken off. Do you know where i can buy a new pick up tube? Or are there any alternatives like a weed wacker fuel filter that goes inside the fuel tank. But if the filter is too restrictive will the carb not be able to suck up the gas?

 

[Oldsalt]

I have removed the pick up tubes from one carb and stuck them in another but the best move would be to get another complete carb. The junk yards are a good source. A lawn mower shop, if they are of the friendly variety, will probably have some junk engines with a useable carb.

 

[5 Horse Fan]

If the pick up tube is not leaking, you can stick some fuel line on it and run a plastic filter inside the tank. It might be hard with a small gas tank, but I've seen it done with a 5hp engine.

 

[awkwardkitten]

Ok I think I am having the same problem. My 5 horse briggs flathead has a new sparkpul, fresh gas, and fresh oil. It does'nt start when I pull the cord, but when a LITTLE bit of starter fluid is sprayed in the carb, it runs like a champ for a second. I'm pretty sure the problem is that the engine isn't getting and fuel. I pulled off the tank and the tubes look ok from the outside, but how would I tell if something is clogged? I don't want to mess with the tubes without knowing what I'm doing.

 

[Tom S.]

Ok I think I am having the same problem...

Yours is most likely a similar problem w/potentially different fix. The carb in the pic above is a vacu-jet. It uses a single tube to suck fuel straight out of the tank and into the carb. Your 5hp engine probably has a pulsa-jet carb that uses a spring-loaded diaphragm gizmo and two tubes to move the fuel around. It can have the same clogging problems mentioned above, but it could also have a failed diaphragm. That part is easy to replace. Ebay has a wide selection of inexpensive carb rebuild kits. There are also lots of shop manuals for $10-$20 that will explain clearly how both carbs work and how to fix and adjust them. Here's a pic of a pulsa-jet.

 

[awkwardkitten]

Yes mine is definetley a pulsa jet carb. Ill have to find a shop manual, you are probably right.

 

[The Restore Kid]

Yours is most likely a similar problem w/potentially different fix. The carb in the pic above is a vacu-jet. It uses a single tube to suck fuel straight out of the tank and into the carb. Your 5hp engine probably has a pulsa-jet carb that uses a spring-loaded diaphragm gizmo and two tubes to move the fuel around. It can have the same clogging problems mentioned above, but it could also have a failed diaphragm. That part is easy to replace. Ebay has a wide selection of inexpensive carb rebuild kits. There are also lots of shop manuals for $10-$20 that will explain clearly how both carbs work and how to fix and adjust them. Here's a pic of a pulsa-jet.

Yup.. I was waiting for someone to say that.. The pick up tubes will get clogged.. but EVEN MORE often with a briggs diaphragm carb is the diaphragm is junk.. They are dirt cheap.. You just have to remember to save the spring and little cup because a new diphragm does not come with them...

When ya take that diaphragm cover off, you will be able to stick the little red tube on your carb cleaner can, in the passage ways and blow them out and make sure your pick up tubes are not clogged...

pickup tubes and passages get gummed up, but about %80 of the time, briggs carb problems are caused by the diaphragm being old and cripsy and curled up and junk.. If so you take it out and crease the flappers over so they close up again.... then put it all together and try it out.. It's not a permanent fix but quite often will fix the problem and lets you know that indeed the diaphragm is your problem... Briggs carbs are a nightmare...