You are most welcome Anastasie,
Judging by the You Tube Video you have uploaded here your beautiful Grillo 2 wheel tractor has seen many row miles of tilling and mowing.
You need a bushing/sleeve whether it is made from steel or bronze to take up the space between the outside diameter of the mounting stub and the collar portion of the handle bars and that would help you.
If you own a micrometer you can obtain the Inside Diameter of the tiller handles tube and the outside diameter of the tiller handle mounting stub base record the measurements and take the handle bar to a machine shop in your area to have them make a bushing
for it.
To be prepared for this you need to have the height measurements of the mounting stub below the machined groove and as well as the
correct assembly height of the spline/star washer and flat washer in relation to the mounting stub and the Grillo 2 wheel tractor handlebar.
If you have a machine shop nearby you should take the tiller handle bar to it to have them double check your measurements make sure you have the right size sleeve machined for it If employing a sleeve top take up the worn space is possible and in so doing you will have the tolerances closed and have a much stronger handlebar mounting on your Beautiful Grillo 2 wheel tractor.
I am sure that Joel will be happy to help you with your beautiful 2 wheel Grillo Tractor and its repair and send you a copy of the Owners manual and a repair manual for your Beautiful Grillo 2 wheel tractor as well.
About me, I am greek orthodox by birth and as a lay person I have for years been researching the battle between the Greek Orthodox Church and the Catholic Church. As I was told the last permanent rift that has been in existence to this day was that one of the bishops of the vatican got into an argument with the archibishop of the Eastern Church about he should cross himself and they have been at a standstill since them.
I am a fellow hobby gardener of the soil and I use lime, gypsum, sand and a bit of man made fertilizer and a lot of sand to overcome the black clay I have here. I hope to do more vegetable gardening this coming year and build a flower bed for my wife as well as it is long overdue as I am doing much better now.
I am blessed to have my beautiful father inlaws "original" Garden Way Inc. 1980 Troy-Bilt rototiller (and the manuals for it) that needs some tender loving care this spring and painting once the weather warms up.
I also have an original Graden Way Inc. 1996 2 stage snow blower that my brothers gave me when they bought the 45 inch snow chewing 2 stage monster they have now.
My mother's younger sisters husband escaped stalin's grip on Ukraine after World War 2 before the iron curtain went up and enlisted in the United States Army in Europe.
After Theo Michaels his dedicated service to the United States Army he became a United States Citizen and then he entered college on the GI bill in the United States and later became a school teacher for the cities of Syracuse, New York and Dunkirk, New York. Sadly we lost him to Suicide in 1975 and he left behind my aunt and three young children. He left a sister behind in Ukraine at the time as well.
Theo Michael spoke very little of the famine caused by stalin and the pain his family lived with.
Leon