Stiff engine

I bought and installed an 80 cc engine I found on eBay. I rode the bike maybe ten or so times on short trips then it became very stiff and I couldn't make it work. It would throw the chain and at first I thought there was something wrong with the chain idler. But after a few more checks I discovered the engine was very tight and was the reason the chain was coming off when I tried to start it. I was so happy with the bike and now I'm distressed and don't know what to do. An obvious cause is not enough oil in the fuel mix but I thought I was careful to make it twenty to one as suggested in the manual. Do I have a burned out engine? How can I check for this condition? Any ideas out there as to my next step?

hi; rog; pull the head fasteners, the head and the bbl. this way you can make sure. also dont rebuild with hardware from the kit. replace all hardware with american stuff. use red and blue locktite when reassembling. if you have a dremel its time to match the exhaust pipe with the gasket also replace spark plug and wire. sick bikes has an air cleaner that will let your engine breathe. i dont know why your engine would tighten up with the right gas/oil ratio unless you have a leaking gasket.

Make shure that the clutch shaft that the sprocket is bolted to isnt dragging.If it is you can remove the cable bracket that screws into the motor and spray some areosol greese into the hole this will help lube up the shaft from the inside it will also get rid of any squeeks caused buy being to dry.

Are you sure it's the engine and not the clutch dragging, bearings in the clutch shaft, or rear wheel of the bike.

Usually an engine won't "drag" as much as scrape, clunk or rattle when it's busted.

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