Recent content by KartFab

You can get most realistic numbers from the off the shelf engine descriptions from NR racing

.039-.041”

Yerf dog runs a 7” driven. Run the sprocket on the outside of the jackshaft and relocate axle sprocket.

Compression on a compression release engine means nothing. look up summit racing compression ratio calculator.

Easy, set your valve lash to .002-.003” with feeler gauges.

If I remove governor, then I’m putting a cam in it. Stage 1 adds like 10-25% more hp, and a cam adds a crap ton more.

You should get a billet rod, advance timing by 4 degrees, and get an NR racing 280 cam, torque grind.

The gx390 Mano I have was stock stage 1 believe it or not. I upgraded a few things on it like 280 cam and connecting rod, but other than that it was stock. It actually was a very mild build.

Mild modified big block was floating the valves at 65 mph in under 300 ft, where higher stage small blocks were barely able to hit 55 mph in the 1/8th mile. This was at a drag race a few months ago.

this is about right but yours will make less because the carb is more restrictive than the stock appearing 24mm http://www.nrracing.com/product-p/eng-rac-420-pack2.htm

Hmm so what you really mean to say is the following? Q: Why are you replacing the clutch? A: Because I keep burning through clutches. Q: Why do you keep burning through clutches? A: Because my gear ratio is either 4.1:1 or 5.0:1 Q: Why is your gear ratio like this? A: Because it was modified...

Claims Some people say you can take a 5-6.5 stock engine and then bolt on a stage 1 kit and you get 10-12 hp. I am not one of those people because I have tested stages 1-4 on my dyno. Real Numbers On a briggs flathead, you see about a 0.5 hp with a "stage 1" mod. On ~200 cc small block OHV...

Remove the jackshaft. Place the driven on a vise, but don’t crank it down all the way, then use a metal punch (awl) in the center of the jackshaft and beat it out. Do not hit the jackshaft with a hammer or you will mushroom it out. ---------- Post added at 07:21 PM ---------- Previous post was...

I wouldn't let it idle above 13.2:1 FYI. Try blipping the throttle to 1/8" open. you will get a better response if you are idling at 12.5-13.2 MAX AFR. I wouldnt be too worried about the low 11s on gas, but you will get optimal hp around 12.2-12.5 AFR. Main jet is the only thing you need...

dont forget spark plug to piston clearance too. You can check that with a little bit of math and a striaght edge over the mating surface of the head with the head off. I had a head milled .030 and the spark plug was protruding into the piston if turned too far one way or the other. just FYI.