Suggestions for 3.75 hp B&S push mower?

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Ok I know it sounds silly but this little thing deserved attention too. It's about 4 years old and runs great. I got tired of the auto-throttle-thingy and how it would allow it to bog out them rev up, etc so I sortof redneck'd it to where it runs much faster and I love it. I did that during the first season. Yeah, it will probably last half as long but no more bogging out and it sortof cracks me up
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The manual specs the 30 weight and I have always ran the B&S oil because of the container goes on about some special additives, etc. I have also added some Lucas Oil Treatment (don't laugh) because frankly I figured it needed something extra due to the higher rpm's I'm running it at.

Truth be told, could I run a good 30 wt synthetic motor oil, or does the mower really need the B&S oil with its marvelous, magic additives?

I pulled the plug and looked at the piston while ago - it's got I'd say just enough buildup to cover the surfaces, a few silver spots left but not many.

So, two questions really:
Could I run a good automotive syn oil and benefit?
What's the best way to clean it, apart from rebuilding it? Chevron Techron? A good blast of brake fluid through the plug hole?(LOL but seriously...?).

Thanks for any thoughts.
 
I use the same oil in my mower ( 4.5 B&S) as I do all my cars and change the oil every 10 hrs of use.

Looks like the piston has carbon buildup.

I change the plug often,every month or so and run a few ounces of Seafoam in the gas every time.

To remove heavy carbon build up,remove the plug after you have run the mower a while and pour as much Seafoam in the plug hole as possible.

Put plug back in and let sit overnight.

Next day,crank it and let it run until all the white smoke goes away.

Do this about once a month.

BTW,I've been using the same ,cheap mower for 8 years and yep,I shortened the throttle spring so it would pull harder too.

\rv85
 
Thanks RV.

I just found this link which implies that all B&S engines use 30 wt and can use automotive oil, including synthetic 5w30. I guess you have it nailed with your process. I still wonder though if the auto oil gives the same performance, as B&S claims it's 'specially designed' for air-cooled engines that 'run hotter'. I don't know if that's true or not or if it is, if it makes any difference.

http://faqs.custhelp.com/cgi-bin/faqs.cfg/php/enduser/std_adp.php?p_faqid=1419
 
How much did you raise the RPM? I think the gov. limited the RPMs for safety (if you hit a rock). I've heard that's why the new mowers are rated by torque instead of HP. At lower RPMs the torque doesn't drop as much as the HP. If you're running it over 4k, I'd be more concerned about operator safety than engine life.

I use Pennzoil Platinum 5w30 in my push mower. $6/qt doesn't matter when I only buy 1 qt a year.

Did you run stale gas in it? The last few years, I don't put gas in any can without stabil in it. It raises the fuel cost by about 12 cents per gallon. For that, I'd rather not worry about if the gas is fresh or sliming the carb.
 
I gave it a good little kick. I have no idea what rpm it was at or what it's at now. It just got on my nerves one too many times and out came the needle nose pliers for a little re-engineering of the throttle spring.

I do run stale gas usually every season, but I saw need for this little mod shortly after I got it. I do need to buy a bottle of Sta-bil. I wouldn't be suprised if it isn't gummed up right now. I guess I'll find out tomorrow.
 
Originally Posted By: ksJoe
How much did you raise the RPM? I think the gov. limited the RPMs for safety (if you hit a rock).


The 4-horse and smaller Briggs engines have an uber-cheesy governor, and always have: the cooling fan blows on a flapper that balances against spring tension to govern the RPM. Simple, but not accurate. If the flapper breaks (I've had one that way) the engine will wind up to maybe 3800-3900 before it just can't breathe enough, so its not super dangerous. But it is better to have it governed down to where it should be.

That's part of the reason I don't even fool with those little Briggses anymore. The Quantum and Diamond/Commercial 6-horse and up lines have a real fly-weight governor that holds the RPM rock solid as the mower chews into grass.

Best mower engine oil in my book: HDEO. Rotella, Delvac, Mobil 1 Turbo Diesel Truck, VPB... any of 'em. I use Rotella T Synthetic 5w40 in my 6-horse Briggs because I also use it in 2 cars.
 
Those engines don't need of deserve anything special I have a 10 year old sears with a tecumse used 10 months per year cuts the lawn about once a week .I use what ever oil is left over from oil changes.I did 2 seasons with 5w20 oil. If I had a riding mower I would use a HDEO oil dino of syn.
 
Those engines don't need of deserve anything special I have a 10 year old sears with a tecumse used 10 months per year and it cuts the lawn about once a week .I use what ever oil is left over from oil changes.I did 2 seasons with 5w20 oil. If I had a riding mower I would use a HDEO oil dino of syn.
 
i have run these little briggs before on whaever i have had laying around and turned them way past there limits and never had a problem. i had an old push mower i attached a tongue to and pulled it behind one of my riders for brush hogging duty. oil is oil in my opinion
 
I started my racing career running karts.Most were modified Briggs engines.

These engine are ez to mod and are fairly tuff.The spring mod just shortens the spring about 2 rounds and makes the spring pull a little sooner & harder.

I probably change oil in all my machines more often than most folks,but it has served me well and I always recycle used oil.
\rv85
 
It really is funny watching these engines rev to 4000 rpm and beyond. They do scream. I would be a "little" worried about the blade coming apart or sending a rock flying into your leg.

When I was younger (14-15) I had a briggs 5 hp gocart. I couldnt leave well enough alone. I bought a race camshaft for like 10 bucks with extra power valve springs for abother 10 bucks to prevent valve float. My dad drilled out the fuel jet for more fuel flow. I beleve that engine would put about 4500 rpm. The oil slinger attached to the crankshaft broke apart at high rpm and went through the side of the block spraying me with hot 250 degree oil. We pulled the broken oil slinger out of the block, patched the hole in the block with some jb weld and continued to run that thing for quite some time after that.
 
Originally Posted By: bubbatime
It really is funny watching these engines rev to 4000 rpm and beyond. They do scream. I would be a "little" worried about the blade coming apart or sending a rock flying into your leg.

When I was younger (14-15) I had a briggs 5 hp gocart. I couldnt leave well enough alone. I bought a race camshaft for like 10 bucks with extra power valve springs for abother 10 bucks to prevent valve float. My dad drilled out the fuel jet for more fuel flow. I beleve that engine would put about 4500 rpm. The oil slinger attached to the crankshaft broke apart at high rpm and went through the side of the block spraying me with hot 250 degree oil. We pulled the broken oil slinger out of the block, patched the hole in the block with some jb weld and continued to run that thing for quite some time after that.


thats quite an impressive story bubba.so jb weld held up huh?
 
I would go with the Synthetic Rotella 5w40 that they sell at Walmart.
Those smaller engines only hold one pint of oil, so if you change it at the end of the season 1 quart will last you 2 seasons.
Also, my father has had good luck with high mileage oils in the smaller engines.
 
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