So, at the track for the 2017 White Knuckle Scramble. Things are looking good, the kart behaved like it always does, and like it always did since the first build 2 years ago.
On the first practice things were looking good. I was keeping up with the duals without issues. Stuff started going south on the second practice session, ironically right after a group of people came in appreciating all the work that went into the dual carb system. I should have known better.
The engine started behaving erratically, with the midrange “moving”: I would have it, then I wouldn’t. Thinking it was just the motor getting to temp, I pull in to find the back of the engine drenched in fuel.
I’ve scrambled and tightened every nut and bolt on the motor, managed to make it to Heat 2 and the final. Kart drove like poop on heat 2, and on the final it just wouldn’t rev past 6K RPM.
I retired 2 laps in. There was something wrong and I had no idea what it was. When I came home I started taking stuff apart:
With several engine rebuilds under my belt since when I first got my K30 nearly 4 years ago, I was flabbergasted at the crappyness of my work back then. That head gasket looks terrible, although the cylinder wear looked decent.
Quite probably the main culprit: Base gasket blowout. The base gasket I had made 4 years ago looked terrible. The way I worked around my weird K30 case was by just trimming a stock K30 base gasket to fit. That left very little material around the transfer ports to actually seal.
Another view of that disaster of a base gasket.
I also removed the dual carb and accessory fuel pump systems. The pulse lines were full of fuel, with gas gushing out of the lines upon removal and making my entire house smell like a gas station (the wife was thrilled )
In conclusion: I believe loose head nuts in turn loosened the cylinder, allowing for a poor seal of the jug against the case. Retightening did nothing, especially with a now soaked base gasket with so little material around the ports.
I also believe the carb and fuel pump setup had to go. They looked neat and served me well, but I had to be able to do better then that.
The whole thing was delivering too much fuel, and doing so erratically. On top of that, having some real VKA competition at that weekend taught me that simple is good and Alky (methanol) is great, so I was now on the hunt for a single BIG 34+ mm carburetor.
In better news, the entire kart fueled up weighed at 127lbs, on the Intercomp track scales so that was pretty cool.
It was time for me to open up that bottom end, for the first time ever, and do a proper rebuild. Let’s take this project to a different direction!