5HP Briggs pulsating

Cliff_Johns · May 28, 2004

( Sounds like the governor and linkage may need adjusting. Have you checked this out?
Ken /forums/images/graemlins/smile.gif )

Can you give me a clue as to what the governor and linkage look like and what adjustments that would be? Is it related to the long piece or stiff wire with the loop in it that appears to be controled by a oval loop on the end of a spring?
Cliff

slowzuki · May 28, 2004

I've got 2 briggs that surge like that, it is something to do with the governor. I unhooked the one on the tiller so I could do the garden. The tractor I just don't let it idle any more because the surge ends up stalling it.

For a guy who likes tinkering I sure hate little IC motors! It is probably a dry linkage, missing spring or something like that.

Ken

jlbota · May 28, 2004

Is this a fuel tank mounted carb or one that mounts on the side of the engine? It sounds like the side mount type if it vertical. On the Carb mount type it is usually one of two things. Those type of carbs use a rubber pump diaphram that sometimes get a pin hole in them and causes surging and they also have a small siphon type tube in them that clogs and can cause this.
On the side mount type it is usually a clog in the low speed siphon that feeds off the bowl. If you take this carb off and clean every little hole with carb cleaner it usually takes care of the problem.
Just make sure in either application you have fresh fuel. If it is varnish smelling...get it out of there as it will gum up everything and even ruin the rubber fuel line making it gummy feeling. An out of spec governer will cause this also but if you haven't messed with this setting I would guess its a fuel delivery problem.

Oh and wear safety glasses when spraying that carb cleaner /forums/images/graemlins/smile.gif

Cliff_Johns · May 28, 2004

( Is this a fuel tank mounted carb or one that mounts on the side of the engine? It sounds like the side mount type if it vertical. )

You are right. It is mounted against the side of the engine.

( On the side mount type it is usually a clog in the low speed siphon that feeds off the bowl. If you take this carb off and clean every little hole with carb cleaner it usually takes care of the problem.
)

I was hoping to avoid taking off the Carb. It's unlikely I'll ever get it to run again. I'm rather bad with fidly bits. You know, tiny springs and levers all of which can be installed in a variety of ways.

Oh well.

Cliff

RobertN · May 28, 2004

I have a 6hp mower that pulsates sometimes. It is mostly due to my son filling the gas tank and oil fill with water, trying "to help out Dad". Something in the carb float valve seat is messed up. The gas leaks down, through the float jet/valve,, into the cylinder, past the rings, and into the oil.

It runs aweful when the gas is not disconected. It spits icky gassy-oil up through the vent into the carb,, as well as just being icky for the bearings. The oil is thinned out, so it does not seal up the rings, causing blowby which puts pressure in the crankcase. It then blow up into the carb courtesy of the crankcase venting.

fwc · Jun 1, 2004

As previously mentioned, it sounds to me like the carb idle area is plugged or out of adjustment. I have had the similar problems after leaving gas in the engine for long time - it kind of turns to varnish and will plug up passages - Your carb may have a high speed and low (idle) speed needle valve adjustments - if so you may be able to limp by, with an slight adjustment of the idle needle valve. Or clean them out might be better - lightly screw them in (one at a time..) until they bottom out - counting the # of turns - then back them all the way out until the hole is empty. take the little plastic tube of some good carb cleaner that says will remove varnish buildup) and spray good into the hole. Put the needle valve back in - screw in all the way and back it out the number of turns you counted when you first bottomed it. Be careful (light tough) on the bottom out procedure because you could drive the needle hard into the seats and malform some parts.

Also see the following - scroll down to the troubleshooting section - it lists several possible causes. You may need to tweak the settings slightly after getting the passages clean.

Small Engine Repair faq - carb adj

Good Luck
fwc

Cliff_Johns · Jun 1, 2004

Thanks for the link fwc.
Cliff

Nasty135 · Jun 4, 2004

Cliff, When idling do you see the linkage moving at the carb? Pulsating with the engine. If so My vote is for the govenor. The govenor is located off of a rod with a long tension spring and more than likely it has gotten loose over time and slipped on the shaft (going into the block) which is attached to the rod going to a pivot point in the block... Adjust the lever on the shaft (if everything else looks correct ) one way or the other about 3/16" too see if it helps or hurts if so go the other way that should do it.. My father has a snow blower that was doing same thing that fixed it so maybe thats your trouble too, Good luck ,Mark S.