Saturday, October 3, 2009

Pressure Chart for GX 200 Clone Valve/Spring/Retainer Combinations

The following chart will help you select the correct valve/spring/retainer combination for your GX200 or Clone engine by providing the spring pressures and installed heights achieved with the various combinations. This chart is going to continue to provide further information. So check back!

Updated 10/3/09: Added Pressures for DJ-1055T Trick Stock Spring, BP Spring, and Dual Spring (Installed height for Dual Spring Retainers is not yet included.

The coil bind figures DO NOT necessarily mean you can run that much lift with the corresponding valve/retainer combo. YOU MUST check for clearance between retainers and valve guides, and clearance between valves and the piston.

Friday, August 21, 2009

Unconventional engine break-in theory.

This is not "MY" break-in program. But it is basically what I believe. What I do is rooted in Motoman's Break-in procedure. He's a smart guy and his procedure, adapted to a kart engine, works for me.

The theory is that with the hard chrome faced rings, tight piston to wall clearances, and fine crosshatch found in cylinders today, you have a very short time to get the rings to seat right before the peaks of the cross hatch become worn too much to finish the job right.

I use 16 oz of 30wt non detergent oil (Shell ND 30wt)and I cover up the vents in the pull starter cage to build heat. Remember, we don't have oil filters, so we have to change oil often to remove the debris from the oil.
I break mine in on the dyno with several long, wide open throttle, hard runs after I get the engine up to temp.

Jetting a clone carb

Here is what I have seen on my dyno:

If you are still running the stock air box:
A .029" is slightly better than a stock .028" If you are allowed to run the valvecover vent tube to a catch can and plug the hole in the airbox, do it.

If you are running Box Stock rules, only the main jet can be changed:
.037" to .039" seems to be the ticket at low altitude. .038" being my "go-to" jet.
When the engine is cool, a .037" makes more power on the top end and can help the engine turn more RPM, but most times, it is at the expense of HP at or about 4800 RPM. (you won't see that on anything other than a water-brake dyno)
A .039" almost totally gets rid of the mid range dip in HP, but it costs you on top end. A .038" is a compromise and once the engine gets good and hot, seems to run better than the .037"
Side note- On the road courses where we are running them 30 minutes wide open, we also drill the low-speed jet. to .019"-.020"

If you are running BP or Superbox, The etube and both jets can be changed:
I like the 140 etube, .036 jet and .019" to .020" low speed jet.

These have been my observations on on my dyno with the Yellow engine and the New Greyhound HF engine. My on-track experience has only been with the yellow engine.

Wednesday, July 29, 2009

Poor Man's A/C

It is really hot right now, and I thought I'd share a method I use to keep cool at the racetrack.

Get a small 6-pack cooler and fill it with ice. Pour in: 1 regular bottle of rubbing alcohol, 1/2 bottle of the green (menthol) rubbing alcohol, and 1/2 bottle of ammonia spirits (about 1/2 to 1 ounce). Add enough water to make it slushy so you can dip rags in it.

Dip in a rag, wring it out good, and wipe down your neck, face, arms, and legs. You can wrap the rag around your neck after that. Re-dip as needed.

Basically, the alcohol evaporates very quickly and cools you down faster than your sweat can, especially when it is very humid.

You may have to go to the pharmacy counter to find the amonia spirits (aka spirit of amonia).

I learned this trick at Suicide Circle Speedway from my buddy "Strolin" Jerry Nolan.