I turned my Kawasaki 19HP into a 25HP with nothing but a hand grinder.
Anyone "soup up" their lawn mower engine?
- Thread starter daves66nova
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Over the years, I've modified more engines than I can remember. Lawn mower engines are no exception. Often, they are so restricted, the HP can be doubled with ease.
My 6HP Briggs Intek pressure washer was a prime example. I was very disappointed with it's performance. So I replaced the muffler with a long (tuned ? ) pipe and non restrictive large muffler. I then ported the intake and exhaust ports. They were horrible, with a very nice, intentional casting restriction blocking about 1/3 of the intake port.
I modified the carb too, by streamlining the throttle plate, choke plate and minor cleanup.
I then adjusted the governor to 5500 RPM, instead of the stock 4000. Yes, I know the engine was rated for 3600, but for what ever reason, Generac had it at 4000.
It rocked! Other than the fact that it used an awful lot of fuel per job.
My current 13HP Honda pressure washer is not significantly more powerful. But it can finish a roof job on one gallon of gas. Something the hot rod Briggs could never do.
The Briggs engine is still running. But the pump is shot (what a surprise! )
My 6HP Briggs Intek pressure washer was a prime example. I was very disappointed with it's performance. So I replaced the muffler with a long (tuned ? ) pipe and non restrictive large muffler. I then ported the intake and exhaust ports. They were horrible, with a very nice, intentional casting restriction blocking about 1/3 of the intake port.
I modified the carb too, by streamlining the throttle plate, choke plate and minor cleanup.
I then adjusted the governor to 5500 RPM, instead of the stock 4000. Yes, I know the engine was rated for 3600, but for what ever reason, Generac had it at 4000.
It rocked! Other than the fact that it used an awful lot of fuel per job.
My current 13HP Honda pressure washer is not significantly more powerful. But it can finish a roof job on one gallon of gas. Something the hot rod Briggs could never do.
The Briggs engine is still running. But the pump is shot (what a surprise! )
Originally Posted By: Malador
Originally Posted By: TMF
I turned my Kawasaki 19HP into a 25HP with nothing but a hand grinder.
How?
I was looking through my manual and my mower was offered with three different Kawasakis FH601, Fh680 & FH721 and according to the specs in the manual they were all the same displacment. I search around online and found that people were modding the engines to 25hp. lawnsite.com
All the engines are exactly the same except for the carb, but all the carbs are the same (even the jets) except for the throttle shaft which has a different stop on it. The 25hp throttle valve opens all the way.
I took my carb apart and the throttle valve only opened about 3/16" at WOT. I ground the ear on my shaft until it would open about 100% You can't tell a difference until your in a situation where you need the extra power and its there.
The FH721 25hp did come with a oil cooler and its more of a heat sink. I did add one to mine and it was under $15.00 for everything needed.
Originally Posted By: TMF
I turned my Kawasaki 19HP into a 25HP with nothing but a hand grinder.
How?
I was looking through my manual and my mower was offered with three different Kawasakis FH601, Fh680 & FH721 and according to the specs in the manual they were all the same displacment. I search around online and found that people were modding the engines to 25hp. lawnsite.com
All the engines are exactly the same except for the carb, but all the carbs are the same (even the jets) except for the throttle shaft which has a different stop on it. The 25hp throttle valve opens all the way.
I took my carb apart and the throttle valve only opened about 3/16" at WOT. I ground the ear on my shaft until it would open about 100% You can't tell a difference until your in a situation where you need the extra power and its there.
The FH721 25hp did come with a oil cooler and its more of a heat sink. I did add one to mine and it was under $15.00 for everything needed.
try , methanol or nitro.
Originally Posted By: SOHCman
What, no forced induction? c'mon people...
I have only tweaked the governor so far but I think Ill be getting out the dremel after reading this.
I totally agree. I need to tear mine down to replace a probable bent crank key, it would be a great time to smooth out the intake port and do some carb tweaking.
The worst that can happen is I junk a mower that I hate already....
What, no forced induction? c'mon people...
I have only tweaked the governor so far but I think Ill be getting out the dremel after reading this.
I totally agree. I need to tear mine down to replace a probable bent crank key, it would be a great time to smooth out the intake port and do some carb tweaking.
The worst that can happen is I junk a mower that I hate already....
Originally Posted By: river_rat
That looks brutal combined with the dark paint. I have to repaint some areas on my red Snapper anyway; this picture does tempt me to try a "murdered-out" (utterly black) look.
But for now, I'd be happy just being able to lower this snapper..
It's a self-propelled Hivac, though I've started to mostly mulch because I've now got Bermuda grass.
Even though there are already a few uneven spots where the deck scrapes the dirt, it's mostly too high on the lowest setting.
At least for the last/first bagging mow to cut down the yellow grass to get the new green started low down, I'd like to get it quite a bit lower.
There are "drop spindles" for some cars where the stub axle is higher on the steering knuckle so that the car sits lower with unchanged suspension position, but I'm unconfortable doing anything with the rear drive axle in that regard. For the rear, it would at least have to swivel only on the usual adjustment axis in order for the belt to work without changes.
Are the front wheels actually on the full-width front axle, or is that just a connector between the adjustable parts?
Since I need to do this only once a year, lowering only the front axle and moving a little slower to ensure all gets cut by the lower front (much like one sometimes mulches with the rear lower) ought to work.
I've not tried putshing the adjustment arms past the lowest notch. Is there something there to keep them from going further?
That looks brutal combined with the dark paint. I have to repaint some areas on my red Snapper anyway; this picture does tempt me to try a "murdered-out" (utterly black) look.
But for now, I'd be happy just being able to lower this snapper..
It's a self-propelled Hivac, though I've started to mostly mulch because I've now got Bermuda grass.
Even though there are already a few uneven spots where the deck scrapes the dirt, it's mostly too high on the lowest setting.
At least for the last/first bagging mow to cut down the yellow grass to get the new green started low down, I'd like to get it quite a bit lower.
There are "drop spindles" for some cars where the stub axle is higher on the steering knuckle so that the car sits lower with unchanged suspension position, but I'm unconfortable doing anything with the rear drive axle in that regard. For the rear, it would at least have to swivel only on the usual adjustment axis in order for the belt to work without changes.
Are the front wheels actually on the full-width front axle, or is that just a connector between the adjustable parts?
Since I need to do this only once a year, lowering only the front axle and moving a little slower to ensure all gets cut by the lower front (much like one sometimes mulches with the rear lower) ought to work.
I've not tried putshing the adjustment arms past the lowest notch. Is there something there to keep them from going further?
Originally Posted By: 01rangerxl
This old beast has been running without a muffler since 2009.
The muffler rusted off my old 3.5 briggs on the rotor tiller. I wear ear plugs so its not too bad and its a bit odd to be able to see the valve stem when you look in there. Makes it easy to add ether for that first start if its been a hard winter!
This old beast has been running without a muffler since 2009.
The muffler rusted off my old 3.5 briggs on the rotor tiller. I wear ear plugs so its not too bad and its a bit odd to be able to see the valve stem when you look in there. Makes it easy to add ether for that first start if its been a hard winter!
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