Engine Trouble Engine rebuild problem


Local time
2:53 AM
May 19, 2023
So my first bike decided to lose power about a month ago, didnt really have that much time to check it until now....
The engine has about 1000-1200km (put on a speedo a few weeks after building it) and it ran fine until now. Opened up the top end checked the cylinder and it was ok other then a few wear marks (cant feel it with your fingers) and ports also looked good. The piston however has seen better days because there are very big scores on the left side.
I said to myself that rebuilding the entire engine with a new piston and gaskets, seals... wouldnt cost me over 30 euros. I did find a 50mm piston however it has a 10mm wrist pin (i need a 12mm low hole) checked the websites that ship to me and none have the correct size!
I can however find LD100 cylinder, head and piston for about 40-60 euros but i can get just an LD100 engine for 85 euros so thats not the way to go.
Does anyone maybe know if any chainsaw piston would fit my YD100?
If i wont be able to find anything for it i guess im out of 80 euros.... i guess no more going to the bar everyday until pay day.


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If you have access to some thick aluminum stock you might just need to make yourself a spacer to get the height right. A 50mm with 12mm wrist pin is gonna be a little hard to find.

Maybe it's time for a phantom 85 jug lol
Well i decided to order a YD100 piston that has the 10mm wrist pin (all of the other dimensions match) for 12€ shipped on ebay. It will arrive in 2 weeks. I will try to either get a friend to make a shim for my 12mm conrod so that the pin will go in tight into the bearing or find a bearing that is the right dimensions for the conrod and wrist pin.
Anyone have an idea for what material i would have to make the shim out off?
I also went to my local chainsaw dealer and we spent about an hour searching for pistons but none would work without serious mods to the case/cylinder.
The same material as the rest of it which is aluminum. Maybe you can find a bushing that is 10 mm ID and 12 mm od. If you could find that size almost any material would do. I don't have much experience with your situation, I'm sure others will step in with better info.