Greyhound Clone Build for a 2005 Ty-Rail Gokart

#81
Finally, pictures! The throttle for the GY6 carb is just about done. It came with two metal ends bent at about a 70* angle. I took one side and bent it straight with a vice and adjustable wrench. I also bent the other one to about 100*. This picture shows the little lengthener piece I had to print to get the cable to reach the pedal:

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I also had to put the cable bracket on the carb to the "underhand" position. I'll have to make a plate for it because it is only supported by one screw this way:

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Here's a picture of the hand choke conversion:

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Now I had to print the entire intake boot in Ninjatek Cheetah TPU (rubber in laymen's terms) because it needs to flex to get a seal around the carb outlet. This works completely fine for the carb end, but the rubber flexes at the flange bolting to the motor, causing vacuum leaks as the carb bounces. Not only that, but the TPU is only rated to 180*F. For now my solution was to mill the bowl vent channel out of the stock insulator, slap it between the boot and the head, and drown it in silicone. This "works" temporarily. I will have to get either Colorfabb PA or PA-CF (nylon or carbon fiber-reinforced nylon) that is a stiff plastic good to 250*F and dual-extrude it with the TPU to get a high-temp, rigid flange and a flexible boot.

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In stock configuration through about a stage 2.5 configuration, it would make it up my steep trail but SLOWLY, just about smoking the belt. I took it for another spin today and I spun the tires all the way up the hill. It also managed the first sustainable donut of its life. By far the GY6 carb brought the most power of all the upgrades in the engine!
 
#82
Today I got together with my neighbor and one of his friends from vo-tech. We blasted through some trails until the main bolt for the rear suspension sheared. That bolt was a 3/4"grade 8 bolt that can handle about 26 tons of tension before breaking! When it sheared, the gas tank sat down on the engine and the header put a nice burn mark in it. I got a ratchet strap just to hold it together and my neighbor's ATV towed it back home.

But the big take away is that my turd actually impressed somebody today. He loved the power to hammer down and drift through corners.

Also, as I am typing this, I wanted to add that the bolt was a fine thread, but I can't put the cursor anywhere but at the end of the post. If I try to put the cursor back, using mouse or arrow keys, it just highlights the nearest letter and replaces the previous letters as I type. Has anybody else had this problem on a PC?
 
#83
Figured out the computer problem. I must have hit the INSERT key by accident.:rolleyes:

I got my new PA-CF filament and made the intake I wanted...but it didn't last long. Maybe 10 awesome minutes of riding in the dark. It was pretty much the same design as before but I started printing it with the PA-CF then about halfway through the print I swapped the filament to the flexible TPU for the carb boot. I did this so I could have a rigid, high temperature flange and a flexible carb boot. I thought the two materials would bond a little better than they did. The potato pics explain it all:

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The plan now is to step back and sort-of copy what the pros do to adapt a flange-less carb to a flanged intake port. They use an aluminum piece that bolts to the head and has a nipple for a hose to connect to the carb. I'll make the nipple out of the PA-CF and the hose will be the TPU. This way I can rely on a mechanical joint instead of a chemical bond of two completely different materials.

I'll admit I'm a little angry at how complicated this stupid adapter has gotten. By now I should've just bought the Chikuni kit but I am really liking the throttle response of this CVK carb. Is it worth it? Probably not. Is it cool? Yes.
 
#84
I got it running, hopefully for good, tonight. I caved and bought the NRR intake for a 24mm flatslide Mikuni and it actually fit this 24mm Keihin CVK carb perfectly. If only I had known this before!
I upped the timing from 29* to 31* and I think I might actually do 32* next time I'm under that shroud. Also, I swapped out the NRR 230 0611 cam for a Dyno MOD2.

Cool thing about this new cam, it proves the whole BS of backpressure in 4 stroke engines. The exhaust I have on this engine is about 3 feet of 3/4" EMT conduit with a homemade glasspack silencer on the end. I have a butterfly valve in the center of it so I can either open or close the "straight through" path for the exhaust. With the stock and 230 0611 cams, the engine really didn't care if that valve was open or closed, it just got quieter or louder. Now with 245* duration and 108* LS, both adding up to more overlap, the engine loses power when the valve is closed. This is because closing that valve adds a restriction in the exhaust, increasing backpressure, hindering the scavenging effect. With the valve open though, the engine gains about 400rpm at WOT and pulls harder with less backpressure.
 
#85
I recently checked the timing on the engine. I expected it to be 31* with the PVL flywheel (28*) and a 3* timing key. I printed out a degree wheel, duct taped it to the flywheel, and scratched a mark on the flywheel just in case the paper wheel moved when I started it up. I was very surprised to find it was EXACTLY 31*. I ended up moving the ignition coil down with the slot I ground in it and that took me to 32* timing. It doesn't feel nearly as "lazy" as it did before and I think I'll leave it as I'm running 87 octane.

Right now I'm experimenting with the TAV2 to get a low engagement yet keep the high rpm shift. I'll be sure to include more pictures with the good camera because even I'm getting bored reading all this text with no eye-candy. That's a post for another time!
 

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