5hp FlatHead B/S Build-up

[ed1380]

great article. although $600 for 9hp? ut:

 

[Kenny_McCormic]

great article. although $600 for 9hp? ut:

Thats why flathead racing is nearly dead. You can get 6 for free.

 

[go kart mozart]

just throw a used 4 HP head on ther and ur good

 

[Kenny_McCormic]

just throw a used 4 HP head on ther and ur good

The 4hp head slow them down. Shave the eyebrows, weld the head in the thin spots and mill it to look like a heart. That will let it breathe.

 

[jr dragster T]

I would just do a light port job on the head.

 

[Jerryburger]

Except for the cam-change, the motor (5hp Flatty) seemed to live right around the 5000 rpm range. With the exhaust pipe change and the port-work (both very cheap!) they gained close to a full hp.

Now imagine doing the same simple mods to a clone and keeping it within 5000 rpm for safety reasons..... probably a really nice gain for not too much $$ !
...makes you want to try all the "cheap mods" on the clone and see what rolls out.

 

[Kenny_McCormic]

The first cheap mod a clone needs is a billet flywheel.

 

[Russell ATV]

What's a real eye-opener is how the stock exhaust chokes the engine of 1/2hp, even at 3600 rpm... where the engine is supposed to run!

If I ever find such a well-documented article on the Honda GX200/Harbor Freight clone, I'll post it. I get the feeling it's going to be the next "Flathead Briggs" among karters.

Ask and you shall recieve. I just posted a great HTML page I found in 4 Cycle forums. Clones are good.

Russ Barrow
Russell ATV

 

[Jerryburger]

You rule, and I humbly bow before you! Now I'm eyeballing those poor inocent clones in the back yard....! (Eyes glowing red.)

 

[Russell ATV]

You rule, and I humbly bow before you! Now I'm eyeballing those poor inocent clones in the back yard....! (Eyes glowing red.)

IF you think that is good, I think I have a source for a 7.5HP (208cc, 14.3 N.M/2500 RPM) engine that is exterior identical (dimensions) to the 6.5HP clone. Same engine basically, just a larger Bore (from 68 to 70mm). Only 1 pound heavier. Ultimate cheater engine in Box Stock class if you are into that, but should make getting 9-10HP out of the engine very simple and at 36lbs, we are almost talking about 2stroke power to weight....almost.

I am currently evaluating their 6.5HP engine (196cc, 13.2 N.M/2500 RPM). Stronger (more torque) than the Lifan (12.6 N.M/2500RPM). Engine appears solid and has a better fan on the flywheel.

Russ Barrow
Russell ATV