The Kart Engine Thread

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AH-81 Update

Had time this am to pop the 81's jug. The weld repair was quite good on it, but there were other surprises inside.

Seems my decision to replace this jug was a good one, it was a ticking time-bomb. Sooner or later that piece was going to come loose and grenade the whole thing.

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You can better see the piece I am refering to in this shot. The cracks continue between the transfers.

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Cracked between transfers on the other side, too.

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Seems there are more pistons and cylinders beyond the 90deg. change in exhaust port relative to thrust of piston...

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The "old" piston is on the left, the "new" on the right. The corresponding transfer windows in the jug are also different. I port mapped the "old" jug and the exhaust and upper transfers are, for all intents and purposes, the same. The "old" lower numbers on the jug are .865 wide, 2.250 down to top and 3.140 down to bottom. On the piston, the "old" windows are .625 crown to top of port and .930 dia. While the old one's are significantly larger, I'm not porting out the "new" jug. This thing is quite thin and, apparently, brittle enough. I'll just be happy with it running rather than being a monster.

Lastly, the transfer ducts cannot be used as there is no place on the case to feed the charge to them.

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"New" piston and cylinder are on the 81. Any idea what the torque spec is? I have it at 55 in/lb right now.

Also, the kill switch lead was flapping around behind the flywheel. I have no idea where it attaches. Could it be on the blade at the 4 o'clock position shown here?

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Waiting on the bar tensioner and I have to go through the carb and get the oiler freed up and this one'll be ready.
 
Not sure on the torque spec's, I usually
tighten till good and snug.
The kill wire will go to the stud the condenser
wire is on from the points.



Lee
 
Thanks again Lee. I guess, ultimately, I'm less concerned with an actual number, but really want to be sure they are all equal as these seem to have a reputation for shaking loose (as the old jug is evidence of).

I seem to recall Mac head bolt specs in the 65-85 in/lb. range, FWIW.
 
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<iframe title="YouTube video player" width="640" height="390" src="http://www.youtube.com/embed/3xHPkv5LyUs" frameborder="0" allowfullscreen></iframe>
german outboard, came as a single too.

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another view of same race.
 
Last edited:
You guys are gonna get me in trouble... I got a bunch of slightly rusty angle iron laying around and a welder... and a 18 HP V-twin Briggs sitting in the barn... I might build my own kart!!! :D
 

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