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Kioritz 40 cc two stroke conversion.

Old 12-27-2018, 02:00 PM
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Jim.Thompson
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Default Kioritz 40 cc two stroke conversion.

I was given this engine recently. It is in very good condition with signs of very little running.
Three ring piston, roller bearing crank top and bottom.
The bearings are super smooth. I will replace the seals as they might be dried out a bit. Although, they feel fine. I have already cut down the excess material off the front of the crankcase.
I plan to give the bolted up crankcase to my engine rebuilder buddy to take into the workshop and mill .015 inch off the block.
Then I will check to the port timing and adjust as necessary.So far, the only guidance I have found for adjust port timing is on this thread: http://www.rcuniverse.com/forum/engi...iques-how.html
I will be following that, unless I am advised otherwise.
Old 02-22-2019, 02:31 PM
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Default Engine now running.

Kioritz two stroke first run.

I got this little engine running this afternoon. I had some difficulty at first, but the problem turned out to be a simple ignition timing fault: too little advance.
It is starting easily and running nicely. Not tuned properly yet, but it is obvious it will have a lot of power. Under propped with the 20 x 8. I will fit a 20 x 10 to it and give that a go.
I spent half a day making a manifold adapter to fit this Walbro carb : https://www.ebay.com.au/itm/Walbro-C...kkF:rk:42f:0

It was time well spent. This carb has a primer bulb and an accessible choke. Also, the configuration of the throttle yoke made it easy to fit a servo pushrod etc.

I increased the compression ratio slightly (don't know how much), by milling .015 inch off the block. Also, I modified the intake port timing very slightly to suit (133 degrees total). The exhaust timing was already good @ 160 degrees total. I really should determine what the static compression ratio is, but I find it is too much fussing around with putty etc.

Running on 40:1 AvGas and two stroke oil. I will buy some Stihl Ultra when I get to town next, and mix a new batch with that @ 40:1

I have the carburettor pump impulse line tapped at the bottom crankcase drain plug; it was already available, so I just removed the plug and made a nipple out of a small bolt.
However, I notice it has started to fill with oil; this may or may not be a problem later on. If it is, I will have to make a take off tap point somewhere higher on the crankcase. It will mean a strip down to do it though.
Edit: The muffler shown in the picture is the original one off the agricultural sprayer. I will have to get innovative about making or finding a more suitable one when the time comes to fit it into the 1/4 scale Spacewalker that I am building for it.
I will pull it off the mount and weigh it next.

All looking pretty good at this stage though!

Jim.


Original muffler, shown here, will be replaced with something more suitable for aircraft application.
Old 03-01-2019, 10:14 PM
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Jim.Thompson
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I first ran this engine on AvGas and two stroke oil at 40:1.
I mixed a batch at 30:1 and ran it again for comparison.
The RPM was about the same for each fuel. 7100 RMP.
So, in future, i will use the 30:1 ratio. AvGas and Stihl Ultra two stroke oil.

Jim.
Old 10-05-2019, 12:54 AM
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Engine running and flying in my 1/4 scale Spacewalker:

Great engine!

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