Well I blew up my Briggs flathead, took it down a hill with too low a gear ratio and the connecting rod grenaded, even took a bite out of the plastic cam and put a huge crack in the front of the block. This was about 10 days ago. I searched for a briggs 5hp, but my buddy was swapping in a 212 and i wanted to keep up with him so...
Bought a 212cc HF 69727 Predator motor (non hemi dished piston). Removed the governor.. man what a pain in the a$$ to take off that little clip that holds the governor gear. I had to completely rebuild the motor mount and 2-speed. My buddy gave me an 8' length of 4"x4" 1/8" wall box tubing and I got to work with a brand new 5-pack of HF cutoff grinder discs.
Making the engine fit was easy, but there is only about 35 thousandths clearance between the valve cover and the double tubes. If I pound down the lettering on the valve cover I'll have a 3/32" clearance! When the motor isn't supported at the front the vibration causes it to hit the tubes. I added a small tab to support the left predator gas tank mount. My buddy made a Heim joint for his bike that connects the shroud mount up there to the downtube, and cut his gas tank mounts off completely citing a risk of breaking one along with putting a hole in the crankcase. I'll add a Heim joint pretty soon as well.
The 2-speed took me about 40 hours. Hole saw, welder, drill, and angle grinder only. Spacing was difficult. The flange bearings eat up about a 1.25" of shaft space each. The final drive chain is a quarter inch out.. but its a long chain with the frame stretch and the rear sprocket is a 44t kit type that's only an eighth inch thick, so it takes it like a champ with the chain moving around on it. With the pedal chain sprocket limitation there just wasn't a way to get the final chain perfectly aligned. (LIGHTBULB! what if I put the bearing outside the... nah.. it would be too far out.. f*** it...) but it runs, and doesn't jump, and as long as it runs I really don't give a damn about it. The bearing mount bolts on the bottom JS are actually through-studs with nuts on the inside welded to the box tube, so tightening them down doesn't squash the box. Also welded in a little strap on the outside of the box to support it to further prevent bending in case the welds on the stud broke. Had to grind down my bolts for the upper jackshaft and cut relief holes and slots for the 2nd gear clutch and output sprocket.
The frame was wire brushed to bare metal, sanded, and painted with rustoleum truck bed liner. Angle grinder wire wheels are serious stuff. I got bit many times. The finish is very strong, looks good, and is oil and gas resistant.
I made my own flanges from 1" OSH washers (the thick ones!! .190" not the .150" thick ones that come in the same batch!!) and used 1" OD fork parts for both the intake and exhaust. Exhaust was done by cutting pieces with angles and welding them all together for the curves.. it looks like boogers in the corner of the underside of a church pew so I wrapped it up. All I got here is flux core! I also got a welding tan from welding with my shirt off in 90 degree weather.... complete with helmet tan line...
My first gear is 9.3 and my top gear is 6.4. This is approx a 1.45 jump. A 1.45 to 1.5 jump is perfect in my opinion. I have put about 3000 miles on the old 2-speed with a 1.6 jump and while it worked; it was way too much and caused excessive clutch wear, even with throttle blipping on shift. It's much nicer to keep your engine in the power band when it shifts. The top gear of 6.4 is way too damn tall though, but it's all I had for sprockets and I didn't want to gear it too low at 7.7 for fear of over-revving the 212. Tomorrow or another day I'll go down to Grainger and get a smaller output sprocket to get the ratio to a 7:1, will still be pretty tall but better suited I think!
The predator engine is very fat with the shroud and all, so I decided to go with a rope start like I had on the briggs. Anybody considering this should note that you must cut down the plastic fan down to the diameter of the starter cup and use it; otherwise the rope gets stuck in the gap between the cup and the flywheel. I also shortened the cup by taking it just down to the edge of where the slots would be. It really narrows the predator engine down.
The carburetor is a PZ19 slide type Keihin clone. Works real nice and engine idles very smooth! Needs some tuning, have the needed on max fuel setting for the midrange (lowest clip position). Still have some small things to figure out, like getting matching bolts here and there, putting the license plate back on, etc.
I just rode my first 15 miles for break-in motoman style and MAN does this thing haul. Was passing cars that were doing 45-50.
I'm surprised nothing broke or fell off on my first 212 adventure. Guess I finally figured out how to build 4-strokes...
Bought a 212cc HF 69727 Predator motor (non hemi dished piston). Removed the governor.. man what a pain in the a$$ to take off that little clip that holds the governor gear. I had to completely rebuild the motor mount and 2-speed. My buddy gave me an 8' length of 4"x4" 1/8" wall box tubing and I got to work with a brand new 5-pack of HF cutoff grinder discs.
Making the engine fit was easy, but there is only about 35 thousandths clearance between the valve cover and the double tubes. If I pound down the lettering on the valve cover I'll have a 3/32" clearance! When the motor isn't supported at the front the vibration causes it to hit the tubes. I added a small tab to support the left predator gas tank mount. My buddy made a Heim joint for his bike that connects the shroud mount up there to the downtube, and cut his gas tank mounts off completely citing a risk of breaking one along with putting a hole in the crankcase. I'll add a Heim joint pretty soon as well.
The 2-speed took me about 40 hours. Hole saw, welder, drill, and angle grinder only. Spacing was difficult. The flange bearings eat up about a 1.25" of shaft space each. The final drive chain is a quarter inch out.. but its a long chain with the frame stretch and the rear sprocket is a 44t kit type that's only an eighth inch thick, so it takes it like a champ with the chain moving around on it. With the pedal chain sprocket limitation there just wasn't a way to get the final chain perfectly aligned. (LIGHTBULB! what if I put the bearing outside the... nah.. it would be too far out.. f*** it...) but it runs, and doesn't jump, and as long as it runs I really don't give a damn about it. The bearing mount bolts on the bottom JS are actually through-studs with nuts on the inside welded to the box tube, so tightening them down doesn't squash the box. Also welded in a little strap on the outside of the box to support it to further prevent bending in case the welds on the stud broke. Had to grind down my bolts for the upper jackshaft and cut relief holes and slots for the 2nd gear clutch and output sprocket.
The frame was wire brushed to bare metal, sanded, and painted with rustoleum truck bed liner. Angle grinder wire wheels are serious stuff. I got bit many times. The finish is very strong, looks good, and is oil and gas resistant.
I made my own flanges from 1" OSH washers (the thick ones!! .190" not the .150" thick ones that come in the same batch!!) and used 1" OD fork parts for both the intake and exhaust. Exhaust was done by cutting pieces with angles and welding them all together for the curves.. it looks like boogers in the corner of the underside of a church pew so I wrapped it up. All I got here is flux core! I also got a welding tan from welding with my shirt off in 90 degree weather.... complete with helmet tan line...
My first gear is 9.3 and my top gear is 6.4. This is approx a 1.45 jump. A 1.45 to 1.5 jump is perfect in my opinion. I have put about 3000 miles on the old 2-speed with a 1.6 jump and while it worked; it was way too much and caused excessive clutch wear, even with throttle blipping on shift. It's much nicer to keep your engine in the power band when it shifts. The top gear of 6.4 is way too damn tall though, but it's all I had for sprockets and I didn't want to gear it too low at 7.7 for fear of over-revving the 212. Tomorrow or another day I'll go down to Grainger and get a smaller output sprocket to get the ratio to a 7:1, will still be pretty tall but better suited I think!
The predator engine is very fat with the shroud and all, so I decided to go with a rope start like I had on the briggs. Anybody considering this should note that you must cut down the plastic fan down to the diameter of the starter cup and use it; otherwise the rope gets stuck in the gap between the cup and the flywheel. I also shortened the cup by taking it just down to the edge of where the slots would be. It really narrows the predator engine down.
The carburetor is a PZ19 slide type Keihin clone. Works real nice and engine idles very smooth! Needs some tuning, have the needed on max fuel setting for the midrange (lowest clip position). Still have some small things to figure out, like getting matching bolts here and there, putting the license plate back on, etc.
I just rode my first 15 miles for break-in motoman style and MAN does this thing haul. Was passing cars that were doing 45-50.
I'm surprised nothing broke or fell off on my first 212 adventure. Guess I finally figured out how to build 4-strokes...
