08-02-2022, 05:50 PM
Chapter 112
OH CRAP! HOLD ON STEVE! Forget everything we just talked about. What the heck was I thinking? That adapter is supposed to space out the pyramid reed. I dont think it will work like I thought. If just using it as a spacer for the carburetor would be perfect. But I didnt think all of this thru well enough.
So let me rehash this one more time. Dang it! It is right. I was picturing the Westbend Vee reed in my head for some reason. Even a four petal pyramid reed wont work either. These wont rotate like the six petal reed will. So we are good. Well I think we are good. Go ahead and drill them out Steve. Drill the first one out and we double check to make sure this all works. I wont do anything to the second one until everything fits like pictured in my head right now. Then it should work out after figuring for what I didnt think out well enough on this one. You got it Steve?
About 20 minutes later Steve was satisfied he had done a fantastic job counterboring the holes using a reamer. The bolts sat just below flush on the face of spacer. I bolted it on the stock manifold and could now envision the completed assembly like it would be on the engine. Basically a quick check using some of the spare parts on the work bench. By rotating the carburetor just enough to clear those counterbored holes, needles could be adjusted a lot easier now.
The diameter had already been scribed for what size to make the center line of carburetor mounting holes which worked out to be 1.800". I went ahead and marked a radius that is perpendicular to the bolt diameter. Can you actually do that on a radius? These lines were scribed using the sharp edge of my vernier caliper far enough from each of the counterbored holes so they could be drilled and tapped without interference.
First a center punch mark, then using a number 7 drill bit, following up with a 1/4-20 tap. These are the steps Steve used to finish the other two holes. One small issue is drilling the pulse hole. It is going to be at a funky angle, but should not be too difficult.
With the carburetor gasket a mark was made where the pulse hole goes. I first left a dimple using the drill press with 3/32" drill bit. Then with a hand held drill, the angle was eyeballed and penetrated about half the way thu spacer.
From the bottom side I did the same trying to intersect that first hole. So long as the two small holes sort of lined up and drilled slightly past each other, there should not be any problem. Since it is only drilled 5/16 inch deep from both sides, not much chance of complete failure.
I probably dont need to bother so much with a pulse hole, since we are still gravity feeding the fuel with stock gas tank mounted on top of the engine. But I was curious and wanted to find out how much trouble it would be to drill this out. Sometimes the pulse hole is just drilled past the reed cage into the manifold. I was trying to carry it back to the original location on stock manifold. This way it is fed directly from the crankcase instead of being less effective if only drilled thru only the reed cage flange.
Originally Steve had fabricated, for lack of a better word more specifically describing his efforts, a small bracket from sheetmetal. It bolts to the manifold and sticks out under the carburetor. The throttle shaft arm lines up with that bracket. So this is how we set up the linkage. I had to slightly alter this bracket when trying out the one modified carburetor and Palmini intake manifold for our second practice day.
With the carburetor now angled, rotated, or indexed so many degrees, Steve went ahead and made another bracket. Actually ending up just by cutting off some material, then rotating the old one so it now lines up with the offset carburetor. Drilling another hole and he can bolt back on the manifold like it had been.
So when all the parts are bolted on the engine, the carburetor is slightly rotated off being square to the engine. Now we can easily tweak the needles out on the track without any problem. Well that is the plan.
I remember back when I first drove the kart when still belonging to Mr Cates. He made sure I could make adjustments to the carburetor while driving out there on the track. He gave a quick explanation in the pits, then when I was making laps, he gave me a hand signal after listening to how the engine was running.
I acknowledged this, nearly screwing up letting go of the steering wheel with one hand coming out of a turn. Then made an attempt to adjust the high speed needle while driving one handed on the carburetor. At that time, I never realized the low speed needle was not adjustable since being so close to the engine side cover. Tonight I have taken care of that problem. Now it should be easy enough adjusting both needles while running on the track.
I always adjusted the engine, usually when still cold in the pits first. Getting the low speed needle opened up enough for it to sound slightly rich. A deep throaty, not a hollow gasping sound when hitting the throttle quickly. I made sure the idle screw was nearly backed off all the way too.
But this causes the engine to load up and die fairly quickly when off the throttle for only a few seconds. Most of the other karts I have watched are running and just idling sitting on the grid waiting to be released out onto the track. To me this is not set up for racing. It is fine for a lawnmower or even a minibike.
But you need a good rich mix of fuel when the kart is set up going thru a hard turn on the track. I found this out by a quick choke with my hand sometimes out here practicing. After the engine warms up it can get lean for a split second when under a lot of load exiting any of the tighter turns. This also helps keep the engine from running too hot after a lot of consecutive laps.
I set my engine up this way and Steves was left alone. His engine was adjusted more like the other karts I had checked out at the track that first night we got a chance to see the races. After we both ran a bunch of hard fast laps, my kart would always have a slightly better run out of the turns. Even with the smaller axle gear. When back in the pits, you could feel a temperature difference by holding your hand close to each engine.
This got me to thinking about something else too. Is there an optimum engine temperature that could be monitored out on the track? I wonder what type of gauge we could come up with to do this? Right now I richen up the high speed needle until it just starts to four cycle, then screw it back in until the engine clears out.
So far this has been a good way to properly adjust the carburetor. But the low speed needle has to have some affect on the whole range of rpm. If it is too rich, then I might end up with the high speed needle pinched down just a little too much that could make the engine run hot and slow down slightly.
What if the low speed needle was too lean and I had the high speed opened up more to compensate for that? It might end up running hotter, but still could be too rich on the top. Wow this gets complicated really fast.
Getting a grip on adjusting the carburetor is one of the things I had managed to figure out from the two times we did go to the track for practice. Even with all of the distractions, like Frank to be more specific, and his magic super duper special Dart prototype A-Bone wannabe chassis. So the practice days were not completely useless for testing some ideas that have proven to work when we made it out for our first race.
OH CRAP! HOLD ON STEVE! Forget everything we just talked about. What the heck was I thinking? That adapter is supposed to space out the pyramid reed. I dont think it will work like I thought. If just using it as a spacer for the carburetor would be perfect. But I didnt think all of this thru well enough.
So let me rehash this one more time. Dang it! It is right. I was picturing the Westbend Vee reed in my head for some reason. Even a four petal pyramid reed wont work either. These wont rotate like the six petal reed will. So we are good. Well I think we are good. Go ahead and drill them out Steve. Drill the first one out and we double check to make sure this all works. I wont do anything to the second one until everything fits like pictured in my head right now. Then it should work out after figuring for what I didnt think out well enough on this one. You got it Steve?
About 20 minutes later Steve was satisfied he had done a fantastic job counterboring the holes using a reamer. The bolts sat just below flush on the face of spacer. I bolted it on the stock manifold and could now envision the completed assembly like it would be on the engine. Basically a quick check using some of the spare parts on the work bench. By rotating the carburetor just enough to clear those counterbored holes, needles could be adjusted a lot easier now.
The diameter had already been scribed for what size to make the center line of carburetor mounting holes which worked out to be 1.800". I went ahead and marked a radius that is perpendicular to the bolt diameter. Can you actually do that on a radius? These lines were scribed using the sharp edge of my vernier caliper far enough from each of the counterbored holes so they could be drilled and tapped without interference.
First a center punch mark, then using a number 7 drill bit, following up with a 1/4-20 tap. These are the steps Steve used to finish the other two holes. One small issue is drilling the pulse hole. It is going to be at a funky angle, but should not be too difficult.
With the carburetor gasket a mark was made where the pulse hole goes. I first left a dimple using the drill press with 3/32" drill bit. Then with a hand held drill, the angle was eyeballed and penetrated about half the way thu spacer.
From the bottom side I did the same trying to intersect that first hole. So long as the two small holes sort of lined up and drilled slightly past each other, there should not be any problem. Since it is only drilled 5/16 inch deep from both sides, not much chance of complete failure.
I probably dont need to bother so much with a pulse hole, since we are still gravity feeding the fuel with stock gas tank mounted on top of the engine. But I was curious and wanted to find out how much trouble it would be to drill this out. Sometimes the pulse hole is just drilled past the reed cage into the manifold. I was trying to carry it back to the original location on stock manifold. This way it is fed directly from the crankcase instead of being less effective if only drilled thru only the reed cage flange.
Originally Steve had fabricated, for lack of a better word more specifically describing his efforts, a small bracket from sheetmetal. It bolts to the manifold and sticks out under the carburetor. The throttle shaft arm lines up with that bracket. So this is how we set up the linkage. I had to slightly alter this bracket when trying out the one modified carburetor and Palmini intake manifold for our second practice day.
With the carburetor now angled, rotated, or indexed so many degrees, Steve went ahead and made another bracket. Actually ending up just by cutting off some material, then rotating the old one so it now lines up with the offset carburetor. Drilling another hole and he can bolt back on the manifold like it had been.
So when all the parts are bolted on the engine, the carburetor is slightly rotated off being square to the engine. Now we can easily tweak the needles out on the track without any problem. Well that is the plan.
I remember back when I first drove the kart when still belonging to Mr Cates. He made sure I could make adjustments to the carburetor while driving out there on the track. He gave a quick explanation in the pits, then when I was making laps, he gave me a hand signal after listening to how the engine was running.
I acknowledged this, nearly screwing up letting go of the steering wheel with one hand coming out of a turn. Then made an attempt to adjust the high speed needle while driving one handed on the carburetor. At that time, I never realized the low speed needle was not adjustable since being so close to the engine side cover. Tonight I have taken care of that problem. Now it should be easy enough adjusting both needles while running on the track.
I always adjusted the engine, usually when still cold in the pits first. Getting the low speed needle opened up enough for it to sound slightly rich. A deep throaty, not a hollow gasping sound when hitting the throttle quickly. I made sure the idle screw was nearly backed off all the way too.
But this causes the engine to load up and die fairly quickly when off the throttle for only a few seconds. Most of the other karts I have watched are running and just idling sitting on the grid waiting to be released out onto the track. To me this is not set up for racing. It is fine for a lawnmower or even a minibike.
But you need a good rich mix of fuel when the kart is set up going thru a hard turn on the track. I found this out by a quick choke with my hand sometimes out here practicing. After the engine warms up it can get lean for a split second when under a lot of load exiting any of the tighter turns. This also helps keep the engine from running too hot after a lot of consecutive laps.
I set my engine up this way and Steves was left alone. His engine was adjusted more like the other karts I had checked out at the track that first night we got a chance to see the races. After we both ran a bunch of hard fast laps, my kart would always have a slightly better run out of the turns. Even with the smaller axle gear. When back in the pits, you could feel a temperature difference by holding your hand close to each engine.
This got me to thinking about something else too. Is there an optimum engine temperature that could be monitored out on the track? I wonder what type of gauge we could come up with to do this? Right now I richen up the high speed needle until it just starts to four cycle, then screw it back in until the engine clears out.
So far this has been a good way to properly adjust the carburetor. But the low speed needle has to have some affect on the whole range of rpm. If it is too rich, then I might end up with the high speed needle pinched down just a little too much that could make the engine run hot and slow down slightly.
What if the low speed needle was too lean and I had the high speed opened up more to compensate for that? It might end up running hotter, but still could be too rich on the top. Wow this gets complicated really fast.
Getting a grip on adjusting the carburetor is one of the things I had managed to figure out from the two times we did go to the track for practice. Even with all of the distractions, like Frank to be more specific, and his magic super duper special Dart prototype A-Bone wannabe chassis. So the practice days were not completely useless for testing some ideas that have proven to work when we made it out for our first race.