38mph Sears!

7

71demon340

Active Member
#1
#1
Faster than I thought it would be ! Hssk50 with the bigger exhaust valve. Governor removed, oil hole mod in stock rod, ported intake and exhaust, ported stock intake manifold, PZ20, carb body smoothed and polished, 92 jet. Straight through 7/8” exhaust with 3/4” sausage muffler, muffler baffle removed.
12.5 diameter tires
60 tooth sprocket
12t clutch
38 mph = about 5,100 rpms
Slightly cutting out at the top of the rpm so maybe still lean or valve float..
DC0FF849-4B2A-4DC7-86C3-67983AED1CC9.jpeg
 
Minimichael

Minimichael

Well-Known Member
#2
#2
71demon340 said:
Faster than I thought it would be ! Hssk50 with the bigger exhaust valve. Governor removed, oil hole mod in stock rod, ported intake and exhaust, ported stock intake manifold, PZ20, carb body smoothed and polished, 92 jet. Straight through 7/8” exhaust with 3/4” sausage muffler, muffler baffle removed.
12.5 diameter tires
60 tooth sprocket
12t clutch
38 mph = about 5,100 rpms
Slightly cutting out at the top of the rpm so maybe still lean or valve float..
View attachment 293095
Click to expand...
Such a good looking bike! Incredible design and details. Looks fast just sitting there.
 
creia

creia

#3
#3
How is the handling at that speed? It has been my experience (Sears Roper) that some of those Sears/Bird bikes get kind of squirrely at higher speeds.
Michael
 
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7

71demon340

Active Member
#5
#5
creia said:
How is the handling at that speed? It has been my experience (Sears Roper) that some of those Sears/Bird bikes get kind of squirrely at higher speeds.
Michael
Click to expand...
Handles fine, I have new shocks and kenda tires, more of a street tread. New wheel bearings also.
 
GustoGuy

GustoGuy

Well-Known Member
#7
#7
71demon340 said:
Faster than I thought it would be ! Hssk50 with the bigger exhaust valve. Governor removed, oil hole mod in stock rod, ported intake and exhaust, ported stock intake manifold, PZ20, carb body smoothed and polished, 92 jet. Straight through 7/8” exhaust with 3/4” sausage muffler, muffler baffle removed.
12.5 diameter tires
60 tooth sprocket
12t clutch
38 mph = about 5,100 rpms
Slightly cutting out at the top of the rpm so maybe still lean or valve float..
View attachment 293095
Click to expand...
Govenor removed. Tecumseh engines usually don't do well at high rpms. Plus stock flywheels can be dangerous at high rpms. Billet connecting rods and Billet flywheels are recommended if removing the govenor. However the oil hole mod should help to prevent oil starvation and possible seizing on the connecting rod where it connects to the crankshaft.
 
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Bobscooters

Bobscooters

Active Member
#8
#8
that looks Sharp i had the purple sears puncher as a kid i think only difference it had front suspension . little governor story when i got my minibike two brothers also got sears minibikes the red ones with the 2 1/2 hp motor mine had the 4 hp anyways the first day they both removed the governors on them and raced me and i thought dang i'm pretty skinny how they beat me that's when they said they removed the governors . a week or two later they had made push scooters out of them blowing both motors . back then in the 60's i doubt they had many mods for a mower motor like they do now .
 
joshua. c.

joshua. c.

Well-Known Member
#19
#19
The billet rod for the ohh55 from arc racing fits this motor and the cam can be re ground by dyno cams for more lift and better duration, if you do that and add some stiffer valve springs that top end will increase quite a bit. also buying and installing the h50 motorsports coil it increases the timing to around 32 degrees btdc and gives the motor a noticable boost.
 
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