Engines for Sale

Thursday, March 29, 2012

JON 0.3 cc Rebuild Project

JON 0.3 cc Rebuild Project
Circa 1996

Design History:
Design and produced in the Czech Republic, by J Garcice. There is also a 0.5 cc version of this engine; both engines were sold as glow and diesel configurations.

Design Features:
Front through the shaft induction;
cast iron piston with ball and socket top end connection;
crank shaft supported by plain journal bearing; and
steel cylinder liner 

displacement 0.35 cc;
bore 7.3 mm;
stroke 7.3 mm


This engine was acquired with almost no compression and lots of free play in the internal mechanism: further inspection revealed that the original piston was missing completely and a substitute one installed in it's place

After a difficult and lengthy rebuild project the little JON is back together again: 
At this stage the engine must be turned over by hand after oiling well to work in the parts and have them seat properly before attempting a run 

Using a fuel mixture with extra oil added and a big high pitch propeller mounted we are ready for a test run

This is a time of high stress: will it work; was all the work justified??

He fires readily but tight fit adds up to a lot of hand cranking and adjustments before we get a good run

It's always worth it when we can turn a useless relic into a sweet running rare vintage model diesel engine 

Uploaded by valic000 on Mar 28, 2012
A small engine, but a long repair story!
Lovely little engine from the Czech Republic, designed by J Garcice. I have no info about the year, but I guess arround 1990. It looks to be very well made. Nice castings and all the tiny parts are made with great precision.
When I got the engine, it had almost no compression and a lot play in the connecting rod somewhere. After an examination it was discovered that the internal parts were not all there, I saw that the original piston was not present anymore. I got some info about the original piston. It was same as the COX engines, with a ballend attachment at the top end. As the piston is made from cast iron, the chance it will come off was very high. I made up my mind to change my plans about doing a ball-end connection and made it with a regular wrist-pin setup.
As everything is very small, it was more difficult than with the other engines. With some setbacks I finally managed to get him back in working condition. Many thanks again to John from Australia, for a lot helpful information on this issue. It was a great help. As I must improvise a lot things, it was a long project, but finally we have a runner in the end and that's what counts after all.
Don't want even to think about a repair job to a 0.10 cc diesel!...
Thanks for watching! I hope you enjoyed this story. More stories and diesels on my channel. Valic000
Ratings and coment welcome!


Read all the details of this Rebuild Project

JON 3 Czech Rebuild Project

Table of Contents

ItemTitlePage Number
2Making new connecting rod6
3Making a new piston19
4Setting and securing the wrist pin35
5Lapping the piston37
6Engine assembling38
7Engine running-in procedure39

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