Briggs flathead engine speed help

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CopperheadJK

New Member
#1
#1
I'm building a mini for a 6 year old. I only want the top speed to be around 20 mph. Right now he has an electric mini which tops out at 14 mph so I only want it to be a little faster for now. I will be using a Briggs flat head engine I believe is 3 or 3.5 hp. What's the best way to do this?
 
tyleryamaha

tyleryamaha

Active Member
#4
#4
CopperheadJK said:
I'm building a mini for a 6 year old. I only want the top speed to be around 20 mph. Right now he has an electric mini which tops out at 14 mph so I only want it to be a little faster for now. I will be using a Briggs flat head engine I believe is 3 or 3.5 hp. What's the best way to do this?
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Limit the throttle , you want the bike to be slower than you can run just in case you need to stop it.
 
electrathon

electrathon

#5
#5
Adjust the governor. If you limit throttle you will still have top speed, it will just take longer to get there. Limiting the governor you will still have acceleration, just not as many RPM.
 
The.MiniTard

The.MiniTard

Member
#6
#6
Tall gear. I have a worn out 3 hp with a vaccujet, so really probably only 2 .5hp with a 5.3:1 gear ratio and it got me up to 25 with a leaky carb and no tuning knowledge. I am gear it for low speed. Limiting throttle, I've heard, isn't good on clutches.
 
H

Havasu Dave

Moderator
#7
#7
Because you said Briggs, gearing is your best choice.

Adjusting the governed speed on these, "if" you even have the complete governor is tedious, and requires pulling and reinstalling the shroud each time to check. Setting the governor is accomplished by setting the rod in different holes on the wind vane beneath the shroud.

You didn't specify which machine, but a 10t clutch going to a 72 tooth drive sprocket will get him slowed down. 17 MPH on a six-inch wheel based mini bike running at 3600 RPM. (Full throttle)
 
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