boosting compression?the cheap way?

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dmartin1

New Member
#1
#1
well,after a longgggg dam time i got my 1971 arctic cat mini bike goin,,,,,but i only had a 2hp briggs.it just doesnt have enough UMPFF to take off good enough with my butt on it.

sooooo
i go the motor for free.muaha.

i want to boost the compression,
now,i know i can mill the head,and have seen a few home-done ways to do it,but is there anything i can like do something to the head gasket to bost it,or somehting?
anything i can work magic with gasket sealer?
lol lol.
i have piece of pantyhoses as the air filter as it filters very fine and lets a ton of air through.

anything i can do with exhaust for more power?

any help would be appreciated
 
Jay Wrix

Jay Wrix

New Member
#2
#2
Hello,

Before starting, realize that you cant get a super lot of horsepower out of the 5 horses, but free is free.

Most power produced from flatheads is from Flow and not compression, too high of compression will hurt the flow and loose power.

You can get thinner head gaskets from some motors, and this will boost the compression,

The gasket sealer will not work too well, You can make copper head gaskets out of thin sheets of copper. Milling the head is the easiest, just dont go too thin. or you risk damage.

Get an air filter. the panthose wont work that good. and the good K&N aircleaners will work much better.

A proper tuned header will produce the most power, but your limited by the motor.

Personally I would try to find a briggs and stratton 5 horsepower, get the power without playing with it.

Id just cut the head a little and leave it there...
 
125ccCrazy

125ccCrazy

Well-Known Member
#5
#5
with a little 2hp engine you are not gonna gain enough power by milling the head to justify the cost of machine work, you may gain 1hp max with milling, airfilter, carb..... Do like Jay said and look for a 5hp, you can do a few simple mods carb and gain as much hp as your engine puts out now.... Unless you are trying to keep the bike original a Honda clone 6.5hp is about as cheap as your gonne get for quick power and then those engines have so many upgrages and performance parts available that you can get them up over 15hp easy..
 
65ShelbyClone

65ShelbyClone

Well-Known Member
#6
#6
Jay Wrix said:
Most power produced from flatheads is from Flow and not compression, too high of compression will hurt the flow and loose power.
Click to expand...
Milling the stock head to increase compression is what kills flow. More compression is still good for efficiency and power and race flatheads have smaller chambers that still flow well.

However, making a 2hp engine comparable to even a stock 5hp is going to be a battle you can't win. That would be a 250% increase in power; no east feat. :eek:ut:
 
ttapa207

ttapa207

New Member
#7
#7
125ccCrazy said:
with a little 2hp engine you are not gonna gain enough power by milling the head to justify the cost of machine work, you may gain 1hp max with milling, airfilter, carb..... Do like Jay said and look for a 5hp, you can do a few simple mods carb and gain as much hp as your engine puts out now.... Unless you are trying to keep the bike original a Honda clone 6.5hp is about as cheap as your gonne get for quick power and then those engines have so many upgrages and performance parts available that you can get them up over 15hp easy..
Click to expand...
i would say that the briggs 5hp is the best bang for your buck. people build em over 30hp for the jr. dragsters. and all the performance parts are pretty cheap. never drop a clone in, you dont wana destory a perfectly good mini like that, try and get a briggs 5hp flathead
 
Jay Wrix

Jay Wrix

New Member
#9
#9
Dont grind it off the cam, its too much of help to get rid, plus its so small that at operating RPMs it doesn't even make a difference in horsepower, most racing cams have them

I would definitely leave them
 
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