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KFX80 top end rebuild

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  #21  
Old 08-22-2016, 04:48 PM
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Umm...WTF?!?!

I think I missed a whole lot of something...but if you're sending national motors to Utah at no cost, I'll take one!
 
  #22  
Old 08-22-2016, 05:17 PM
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LOL..
dirtdevil mentioned that the cylinder slid down on easy.
Then I went on and on with a story about a guy and a hammer...
FYI: I sent that motor to Tennessee and it's taking 2nd place 300' drag racing.
I'll gladly ship you the motor free....ROFL
That motor is out there. Larson sold it to a guy. We were in contact but then disappeared. He was using the CT extended axel pipe.
It doesn't perform well. No bottom end.
Call Tom @ Larson Crane and ask who has it. Don't mention my name. He won't return my calls..
 
  #23  
Old 08-23-2016, 07:25 AM
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I found a china kit in the garage. I can't see any marking on the rings.
However I can feel the difference in the ring. Maybe that's just experience.
 
  #24  
Old 08-23-2016, 07:49 AM
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feel the difference? Please explain!!
So you are saying there is a top ring and a bottom ring, even though there are no markings. I culd not tell a difference between the two rings at all in any way shape or form! But I have mechanic hands which are burned calloused and numb

A sledge hammer to install piston into jug??? Oh boy!!! now that is some compression!!!
 
  #25  
Old 08-23-2016, 08:29 AM
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Top and bottom are the same ring.
I can feel the top/bottom of the ring. One side is cupped, the other raised. Cupped side up.
 
  #26  
Old 08-23-2016, 11:47 AM
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LOL...I love your stories Jack!!! I like 410's "compression" comment as well!!!


If the cylinder is well lubed and the rings on right/pins aligned...it should just slide down when you compress the rings...personally, getting those tiny c clips in for the pin was a PITA...everything so damn tiny...and they just love to fly!!!!!!!!!!!!!!!!!!!!!!
 
  #27  
Old 08-27-2016, 04:21 PM
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I had some time to work on this bike again. Put the new top end on it. OEM cylinder with Pro-X piston kit. Things went much better this time...at least I think.

Again I saw no marks on the rings, but following advice given here I noticed the "springiness" of the rings and it was noticeable one way vs the other. Also cylinder slipped on much easier this time when compressing the rings.

After putting all the plastic cooling parts back on I nervously started it up. All seemed good. I ran it gently on a stand for 20 minutes than gave it about 20 minutes of put-put around the yard. By then it was pretty dark, put it away for the night. Today rechecked the head bolts torque was still good. Compression at 110psi. Ran it gently around the yard for a little over an hour. Cleaned up some ghetto electrical work the previous owner did.

Maybe tomorrow I will have a bit of time to get it on an easy mountain trail.

Hopefully it stays together. Thanks for the advice and help from everyone!
 
  #28  
Old 08-27-2016, 05:03 PM
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I knew you could do it.
 
  #29  
Old 09-10-2016, 03:18 AM
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I finally got round to rebuilding the LT80 top end this week, (farmers quads take priority as they need them for work). Anyway, was a bit disappointed that it still would only run if given a squirt of butane gas into the filter box, as this was the fault it came in with, but added fresh fuel and it starts OK now. Main reason for the update is I fitted one of those cheap Chinese fuel taps (£6.25 from Hong Kong), as the old one had got so that it would only work on prime. I had to fit an in line filter as the fuel pipe outlet is in a different place and the existing pipe was too short to reach it, but it works great, shuts off when the engine stops on RUN, like it should. Time will tell how durable they are.
 
  #30  
Old 10-10-2016, 04:09 PM
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As an update, it seems all is holding together well. I've had the new bike on a couple mountain rides and just this past weekend made a trip to our local dunes, Little Sahara.

The kids kept the mini quads running all weekend. Must have went through at least 4 tanks of fuel playing in the sand.

The plug on both my 80's seem to show a bit rich. Now I'm trying to decide whether to leave well enough alone, or drop a jet size or two. I have new 87.5 and 90 jets in the toolbox, but likely I'll leave them as-is rather than worry about leaning them out too much.

Thanks again to all those who prodded me along!!!
 


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