4hp Briggs......

[heyttown]

3 yrs old 4 hp B&S push mower.....Throttle keeps surging, Has fresh gas,clean air filter.Cleaned the plug.....<br />What would cause this surging when it surges it also drops well lower then the normal rpm and almost dies..Filter was filthy and was damp with what smelled like gas....This is all spring mechanism on the system.....ANy help getting this thing back running, grass is getting pretty tall.

 

[eurolarva]

Re: 4hp Briggs......

I would start by inspecting the governor spring for wear and clean that whole mechanizim with Carb cleaner or WD40. If that dont help verify the bolts to the carb are tight and all the fuel lines are tight. You may have an air leak in the fuel system. The carbs are junk but maybe cleaning it out will help.

 

[heyttown]

Re: 4hp Briggs......

Im not sure if it would help or not, but when it would bog down then speed up, on the speed up side, it would let out a puff of smoke....Plug looked black like alot of carbon on it.I ran out of daylight today, will get back into it tommorow night....<br /><br />I have 400 reasons to wanting a new mower,but lack the greenbacks to get one...

 

[one more cast]

Re: 4hp Briggs......

Running a lean fuel air mixture will cause that problem and I'm pretty sure there isn't any ajustment so I would be looking for an air leak. Possibly the screws that hold the carb on have loosened or the intake gasket may be leaking.

 

[SS MAYFLOAT]

Re: 4hp Briggs......

Might want to check to make sure your choke isn't closing and opening while its running. I had one engine do that. I ended up tieing the choke open. Took care of my problem. Good luck.

 

[dolluper]

Re: 4hp Briggs......

Try running it with the gas cap off vent could be pluged up, Take some carb cleaner and spray down throat of carb with it running at higher speed if you can Iam leaning towards the govenor as causing the problem

 

[heyttown]

Re: 4hp Briggs......

Ok bought new air filter,new plug, and changed the oil(it needed it) Pulled off the gas tank, cleaned what I could without taking primer and everything off......Put in clean/new gas and still have the same problems....My next move may be to drop the tank again and rebuild the primer/carb but since the carb appears to be plastic I dont think it can be dipped in the cleaner.....Looking for a online diagram on how to rebuild the carb...ANy suggestions?

 

[craze1cars]

Re: 4hp Briggs......

As others here have already suggested, I REALLY think it's a governor problem. You haven't mentioned that you've checked that yet. Make sure you don't have a spring that's missing, or stretched, or bent, or hung up, or a governor windvane that's cracked, or binding, or gunked up with oil/dirt, or lodged full of grass clippings.<br /><br />A carb rebuild certainly can't hurt anyway. They're simple. Just take it apart, remember how it goes back together (expecially count the number of turns on mixture screws, etc.) and soak/scrub everthing in carb cleaner. Carb cleaner won't hurt the plastic at all. A new carb gasket kit will cost about $5 or less, if you need it at all, many times they can be reused.<br /><br />But still...I think after you do all that to the carb, it'll still surge, and you'll eventually discover it was a governor problem.

 

[K Hultgre]

Re: 4hp Briggs......

If the carb is mounted directly to the gas tank go to the local and buy a carb kit (bring #'s)(it's the diaphram thats giving you problems). <br /><br /> Clean the area and use a straight edge to verify the tank has not warped or been bent (re-bend where appropriate). <br /><br />Install the gasket paying attention to make sure it does not slip. Check the oil, add gas, and go mow your lawn.

 

[heyttown]

Re: 4hp Briggs......

Its hard to tell how many springs it had on it but right now it has 2...1 long one about 3" and 1 short about 1" long.The windvane was cleaned and inspected today and it moved freely and no cracks. The Carb is mounted on the gas tank, I called today on a rebuild kit,picking it up tommorow.....I will post how it goes.<br /><br />Thanks for the help

 

[craze1cars]

Re: 4hp Briggs......

Sorry I didn't share this sooner, but if you continue to struggle with this, post your question here, or search the site for your problem:<br /> http://www.perr.com/forum/viewforum.php?f=2&sid=1921f3e4c1b8873272a4739f010cf449 <br />It's an outstanding forum designed for getting help on small engines like this.

 

[heyttown]

Re: 4hp Briggs......

Cool.....Got the Diaphram and gasket today,but had lots of errands to do...Looks like a project for tommorow unless the rain comes.

 

[heyttown]

Re: 4hp Briggs......

All is well, 10 minutes of taking the tank off and cleaning the gasket area and such replaced the gasket and Diaphram and it runs great......<br /><br />My only other problem is the mower wont throw the grass clippings to the back of the bag.....It throws the grass in teh bag maybe halfway and it doesnt take long to clog up and I have to empty the bag when its half full......<br /><br />Its been like this pretty much the entire time since Ive owned it... Changed the blade and really didnt make much difference......<br /><br />Any ideas.

 

[Xcusme]

Re: 4hp Briggs......

I had an older Sears mower do the same thing, half bag, then have to empty. Seems the smaller grass clipppings clogged the bag, which limited to amount of air to escape the bag. I powerwashed the bag, from the outside in. That fixed the problem. I did also clean the underside of the mower.

 

[K Hultgre]

Re: 4hp Briggs......

Is that a high lift blade or a mulching blade?<br />What happens if you mow more frequently, 4hp is not much power if your cutting more than an inch.<br /><br />Definitely wash the bag it makes a difference.