briggs and stratton lawn mower issues

[pkrainert]

I have a 6.75 hp lawn mower that will only run if i put gas in the carb directly or in the cylinder. I took the carb apart and cleaned everything out. I didnt have a rebuild kit but tehre isnt much to the carb there is no diaphram it is gravity feed... After cleaning it out and putting it back on I had the same issue. So I took it apart again to try and re clean it and make sure everything was put together right... in doing this I broke the primer base... so now when i pump the bulb it does no good because where the gas used to be sprayed is a big hole.... My question is do I need to replace that base?? or will it run ok if I just rebuild the carb?

 

[v1_0]

Re: briggs and stratton lawn mower issues

I have a 6.75 hp lawn mower that will only run if i put gas in the carb directly or in the cylinder.

I'm interested: how are you putting gas directly into the carb?

If you are physically pouring gas into the carb... and that works... it would mean that there is some blockage between the carb and the gas tank. [As opposed to pouring gas into the cylinder through the carb's air intake] Or, that the gas in the gas tank is bad and you are using good gas when you pour it in directly..

So, if you know that the gas in the tank is good - check for clogs between the tank and the carb. You could disconnect the gas line at the carb and see if gas flows out from it.

 

[pkrainert]

Re: briggs and stratton lawn mower issues

If I poor gas in the face of the carb where you can see the butterfly valvle it will run. or if i take the spark plug out and put a tiny but of gas in there it will fire... I put a new gas line and the gas is all fresh. there was no gas in the tank when I got the mower... When I get home i will pull the fuel line off and see how free flowing it is. Thanks. I know that gas flows from the line but I am not sure how fast. When I pulled the carb apart there was gas in the bowl. so it is getting at least some gas.

 

[thefairlaneman]

Re: briggs and stratton lawn mower issues

I had one of those engines and it became a headache to start. The bulb must be replaced or it for sure wont run, You have to make 100% sure the carb is clean. Be sure and clean and inspect the float . If any water or trash gets in the gas it will settle at the bottom of the float bowl and cause it not to crank. Give me a 3.5 any day.

 

[pkrainert]

Re: briggs and stratton lawn mower issues

bowl is spotless as well as the float. tested the float no holes or dents. What does the primer bulb do when the engine is already running? Just wondering. also the primer bulb has a hole in the very center... but it looks like its supposed to be there. its not just a hole it sticks out more than the rest of the bulb.

 

[greasemonkeyjmj]

Re: briggs and stratton lawn mower issues

the primer bulb is supposed to have a hole in the center of it.does your breather base attach to the carb with 3 bolts ? if it does sometimes the plastic breather base housing gets warped and will not keep a airtight seal against the carb. the easiest thing to do usually is to take the base off and double up the gaskest that goes between the carb and base.when you tighten the 3 bolts, do not over tighten them, just snugg them good. and if this gasket is leaking, it will not pick up the fuel even after it has started. let me know if this helps

 

[pkrainert]

Re: briggs and stratton lawn mower issues

well I broke the plate. and i overtightened the screws!!! So I guess I will just have to order them. Parts i need are about 35 shipped. I guess that would be better than buying a new mower... unless this doesn't fix it.

 

[v1_0]

Re: briggs and stratton lawn mower issues

When I pulled the carb apart there was gas in the bowl. so it is getting at least some gas.

The first thing to do is to replace the broken part you mentioned.

Then replace your primer bulb. I have a B&S 4.5 model, and I absolutely need the primer bulb to start it when it's cold. Matter of fact, it takes several primings to start - each time it will run a bit longer until it stays running.

Once it warms up, it will start right away. I'm guessing your putting gas into the cylinder is doing the job of the primer bulb...

 

[greasemonkeyjmj]

Re: briggs and stratton lawn mower issues

the 6.75 works on a totally different primer setup than the 4.5 it is very rare that the primer needs to be changed on a 6.75 especially since the are made with a hole in the center to start with. the breather base housing completes the primer circuit, if it is broken or leaking, it will give the same effect as a leaking primer bulb on the smaller engines.

 

[Jeff-in-PA]

Re: briggs and stratton lawn mower issues

Since it runs when gas is poured into the carb, it's probably dirt in the small idle or mid range circuits.

Get some carb cleaner ( I suggest berkebile carb cleaner ) and disassemble the carb. Into each passge, spray the cleaner in with the small tube in the end of the nozzle. It should come out somewhere else. If not, that passage is blocked.

 

[greasemonkeyjmj]

Re: briggs and stratton lawn mower issues

this carb will only have one runner right in the middle of the throat with a jet at the bottom of the tube in the carb bowl.they dont have low,med,high jets. when the primer is pushed, it shoots the fuel straight into the front of the carb.

 

[pkrainert]

Re: briggs and stratton lawn mower issues

Ok so now I got the lawn mower to run about 20-30 seconds after cleaning everything. i let the carb soak for a bit but it still wants to die. I did notice that the rubber seat for the jet has a tiny crack in it would this cause that problem?

 

[KRS]

Re: briggs and stratton lawn mower issues

disassemble and use the rebuild kit you already purchased.

 

[pkrainert]

Re: briggs and stratton lawn mower issues

I never purchased one...

 

[getinmerry]

Re: briggs and stratton lawn mower issues

Check the compression. Small motors like this rely on good compression to draw the gas out of the carb and into the cylinder. I have seen B&S motors run well at 50lbs of compression, but the larger single cylinder motors are much more finicky. You may have a stuck valve or blown head gasket. Stuck exhaust valves are common.

 

[Splat]

Re: briggs and stratton lawn mower issues

If it's runnign for 10-20 seconds this is still a fuel issue. Still have a dirty carb.

Is this a VLV or EPA carb(plastic)? They are sometimes next to impossible to clean, and we used to just often replace them.

Bill

 

[thefairlaneman]

Re: briggs and stratton lawn mower issues

If it were to start blowing oil back into the carb I would say low crankcase vacuum . I agree its got to be the carb otherwise.You got to fix it or replace it. The main reason I gave up my little lawn mower service was because people with lawn mowers worth 75 bucks just WOULD NOT want to pay more than 10 or 15 bucks to have them fixed and there was no way I would spend an hour or more and chasing parts if I couldnt clear about 25 bucks on each one. I wonder what the pro shop repair bill would be to fix this threads mower issue.

 

[pkrainert]

Re: briggs and stratton lawn mower issues

I ordered the carb kit and the primer base... hope this solves my problem! especially since I saw a couple decent mower on craigslist for 50 dollars in my area lol. oh and btw its not a plastic carb.

 

[Mike722]

Re: briggs and stratton lawn mower issues

thefairlaneman - I wonder what the pro shop repair bill would be to fix this threads mower issue.

Assuming that the carb is the problem, I would try to clean by soaking, one time, and then we would price him a new carb. 30 mins to 45 mins labor and a few bucks new gaskets.

 

[pkrainert]

Re: briggs and stratton lawn mower issues

Got it running now. It mows great. All I did was spray some carb cleaner to get it started... at first it kept dying. But I would let it run then when it was going to die give it a small spray so it would stay running... I did that for about a minute and now it starts on the first pull. Runs very smooth. I am still going to rebuild the carb since I purchased the kit and I am also replacing the primer base.