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bob58o

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Not really great for straight lines, is it?
The rounder tire with larger circumference will want to steer the kart in the opposite direction, right? Always kinda pushing left?

19” diameter vs 18” is like 6% increase, so the ground moving under the larger tire is moving 6% faster than the ground under the smaller tire.

At 30 mph kart speed, 1” difference in rear tire diameter means there’s a difference of about 2 mph between each tire. One wheel trying to move 30mph, one trying to go 32mph.

Not sure how much this matters in practice?
maybe can adjust tire pressure?
I just keep thinking circle racing set ups.
 

Whitetrashrocker

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Ohh. Engine p○rn.
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This is the exhaust port. Major restrictions going on here. Let me just take some weight off too. I heard it makes you go faster.

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PPOV.
Pistons point of view.
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Man, this camera really picks up the rough surface. It looks and feels smoother than it shows here. I'm still gonna go at it some more with some sand paper and a finger. 👉.

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Did you see my oopsie?
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I was just saying I'm done here. Get to polishing and quit hogging.
Made a new exhaust leak.

Now I gotta head to my dad's and use the TIG.
Hope I can get it patched without having to pull the valve guide.
 

Whitetrashrocker

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Glued some aluminum back on the head. Yeah it's ugly. My sharkfin was a first attempt for me. Roast away, but I'm sure it will flow better than it did.

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Did a little cc calculation. Bore and stroke came to 193cc. Funny cause the case stamping says 171FFM. Which translates to a 71mm piston. This one is 63mm. I thought I had a 250cc but got a 200 instead.
Head came to 22cc and the domed piston was 11cc. Gasket was .9cc.

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Here's the new cam on the right and the one I removed on left.
This had the same size lobe from center to peak but they removed material from the base circle. This makes it +2mm lift. The duration is more too. I'm not breaking out the degree wheel. I'm just gonna roll with what I have.

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Good old hillbilly press.

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Whitetrashrocker

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Putting the cam in wasn't hard but I had to sneak peek the dots. The seal has to be removed to see the dots. I wasn't gonna mess with it.
So some paint and a mirror. Works for ugly girls. Why not.
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Next up is arts and crafts.
Gonna get clay and measure the piston to valve clearance. That 2mm of lift is gonna make it close. I've read guys getting 1mm decked and are ok but I don't know if they did a cam or not.
1mm is real close to .040 freedom units. Or a banana slice for scale.
 

bob58o

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What kind of clearances are needed for comfort? On the 212 engines I’ve played with I think I aim for about 0.030” piston to head clearance and maybe 0.065” exhaust valve to piston. 0.050” intake valve to piston? I don’t remember what basic guidelines are.
 
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Whitetrashrocker

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Glad you asked Bob!

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Twiddling the slide rule a bit i got 8.5:1 compression ratio.
If I deck 1mm or .040" I'll be real close to 10:1
After milling I'll be at 4mm or .160" roughly. As you can see by my dollar store calipers, I'm at the utmost of accuracy.

Notice the quench ring? On the outer edge of the combustion chamber. That's about the 1mm deep and will remove a considerable amount of volume. Maybe 1.5 to 2cc.

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Whitetrashrocker

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Today's quiz everyone. No cheating, keep your eyes on your own paper.

Progressive springs. On a valve, which way is the proper orientation.

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Please explain your reasoning and show your work.
I'll will check in with your answers later.

Free refreshments and centrum will be held in the cafeteria afterwards.
 

Whitetrashrocker

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Ended up taking .035" off.

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I had .040 in my head but I was getting close to the valve seat. So I just stopped there.

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I have a 12x12x1" bullet proof glass panel i use as a surface plate. You can see where some one took a few rounds to it. That's on the bottom. Top side is perfect.

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All pretty and smooth.
CC'd the head again. Got 19.5cc

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I don't estimate very good. I was shooting for .040 off and about 1.5 - 2cc lost.
I got .035 off and 2.5cc lost.
It is what it is.

Dug my abacus out of the drawer and figured my new compression ratio to be up a little over a full point.
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Lapped the valves in and put it all back together last night.
Gonna do some vrooming later.
I'll let you know.
 

Whitetrashrocker

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I might get a nibbi carb for this.
The pz27 i have on it has no adjustments. Basic needle clip adjustments and a throttle slide stop for idle control. That's it besides jets.
Might also go with a 28mm carb. The air flow out the exhaust is noticeably more.
In fact, in the video, I had to pause because the idle stop was too closed for the new air flow. I had to screw it in like 2 turns just to get enough air to idle.
 

Whitetrashrocker

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Went for a ride. Well tried to.

Not enough carb. It will idle. But as soon as you try to give it any throttle under load it just boggs. Tried moving the main jet needle up and down a notch. Worse.

If I feather it and limp it into the main jet, holy cow! This engine woke up. It runs like crap and I can tell it's got more beans.

I need to adjust the slow jetting. I don't have any jets for this carb so nibbi , here comes my order.
Now just to decide flat or round slide. The flat is more tunable but it's also costs a bit more and I don't see a flange mount style.
The round type has a flange mount up to 28mm. The 30mm goes to a slip fit. I'm thinking just go with the 28mm flange. If it's a little under carbed I don't think it will hurt performance too bad. I'd rather be slightly under sized than over. Faster air velocity makes better fuel atomization.


Or





It look like Denny is the only one paying attention in class.
 
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