author
45CommentsMidwest USA

Tell us about yourself!

Complete Your Profile
  • Homemade Exhaust for Your Old Lawnmower

    It could well be a 70's or 80's mower. Not as many self propelled mowers like today, and really no honds to speak of. Simplicity, the "cadillac" of mowers had a self opropelled mower that used a knurled roller on larger back wheels to drive it. MTD was not a huge player, and there were still lots of Montgomery ward, Sears, Coast to Coast, True value, and mom and pop stores that sold pretty generic mowers like this.

    DISCLAIMER: UNDER NO CIRCUMSTANCES DO I ENCOURAGE ANYONE TO DO OR TRY ANY OF THE THINGS I MENTION BELOW EVER ANYPLACE!! I am sharing this information only to illustrate the extremes bored farm kids will take to amuse themselves!RE: Horsepower, Depends on "what else" you do to the motor. On a horizontal 3HP Briggs (old water pump motor turned minibike engine) we planed the head(ourselves), replaced the head gasket with high temp silicone. Ported the intake and exhaust (we called it a Y head instead of L Head), ground the sides off the cam lobes and welded a bead on the top (using nickel rod) to increase lift and decrease duration. Advanced the timing (pretty far) by moving the crankshaft detent for the points ahead. We also ran Dads "racing gas" (125 octane sprint c...

    see more »

    DISCLAIMER: UNDER NO CIRCUMSTANCES DO I ENCOURAGE ANYONE TO DO OR TRY ANY OF THE THINGS I MENTION BELOW EVER ANYPLACE!! I am sharing this information only to illustrate the extremes bored farm kids will take to amuse themselves!RE: Horsepower, Depends on "what else" you do to the motor. On a horizontal 3HP Briggs (old water pump motor turned minibike engine) we planed the head(ourselves), replaced the head gasket with high temp silicone. Ported the intake and exhaust (we called it a Y head instead of L Head), ground the sides off the cam lobes and welded a bead on the top (using nickel rod) to increase lift and decrease duration. Advanced the timing (pretty far) by moving the crankshaft detent for the points ahead. We also ran Dads "racing gas" (125 octane sprint car fuel". Also tried 60/40 Gasohol in the same setup, and Methanol (with a Harley Davidson Carburetor). With the Harley carb, it would carry 3 boys and spin the rear tire using the cheesy centripetal clutch. All this without the governor of course. We were told we were likely getting 10-15 hp out of it. (WE WERE VERY VERY LUCKY the flywheel didn't explode....but like Wile E. Coyote, we didn't know how many RPMs it was turning, so we survived. If ANYONE is going to go that extreme with a motor, you definitely need a billet flywheel and metal shields around the flywheel (not tin), and steel angle irons or metal bars above the head and below the block all-thread rod-ed together) to hold the engine together.

    My thoughts as well. if you put that in "loose" it might baffle it pretty well, though I think that would be outside the pipe with the holes in it.

    View Instructable »
  • How to make a racing lawn mower (Updated!)

    yeah, unless you use a turbo (or smog air pump I.e. "poor man's" supercharger), definitely want the intake turbulence, especially if you run methanol) not sure for high rpm If a tunnel ram style intake might work? never tried that but who knows. seems a dyno would be a great thing for these engines to really tune them. we had a 3hp Briggs on a minibike in high school that with centripetal clutch and no trans would do almost 40. had a Harley carb AND burned 60/40 125 gas / ethanol mix though, HAH! crazy days.

    really great Instructable and comments. Few things I'd add, anybody try sprint car gas? my father used to tractor pull with multiple big block engines and he used 125 octane gas(seriously it durometered as that) the performance jump from that in small engines(from Briggs to dirt bikes) was incredible. the engine has to be built for it (bottom end) so crank, rods, billet flywheel, etc, as in the Instructable but it's almost like a supercharger in terms of extra HP. another thing would like to agree with porting comment. I'd natural aspirated(carb or injection) you want the intake slightly rough to mix air fuel, exhaust as smooth and unobstructed as you can. we used die grinder with carbide cutter tip (cross section screw looking oval shape) same as big blocks. took flathead brigs ...

    see more »

    really great Instructable and comments. Few things I'd add, anybody try sprint car gas? my father used to tractor pull with multiple big block engines and he used 125 octane gas(seriously it durometered as that) the performance jump from that in small engines(from Briggs to dirt bikes) was incredible. the engine has to be built for it (bottom end) so crank, rods, billet flywheel, etc, as in the Instructable but it's almost like a supercharger in terms of extra HP. another thing would like to agree with porting comment. I'd natural aspirated(carb or injection) you want the intake slightly rough to mix air fuel, exhaust as smooth and unobstructed as you can. we used die grinder with carbide cutter tip (cross section screw looking oval shape) same as big blocks. took flathead brigs "L heads" and made "y heads" hah! also ground the cams on them (decreased duration by grinding g lobes thinner and increased lift by welding a bead on the top of the lobe and grinding down. seems we advanced the timing a bit too from the crank. with higher octane it tends to run drier so you have to fatten up the fuel mixture. again great Instructable thanks, very detailed and thorough. btw anybody use comet differentials or clutches? seems differential might give you better handling, also since it's circle track, do you stagger wheel size left to right like sprints do? seems some of the camber and steering issues might be addressed with that.

    View Instructable »
  • ProfessorJWN followed mowerracer3 years ago