Originally Posted by old motorbike
I'm a retired Master Tech also. I always wanted to build a motorized bike and opted for a cheap China deal. It wouldn't start for a day and Finally found that the plug was intermittent. I've only been riding it for about a week and not too far, just in case it decides to lock-up. Using 16:1 oil and running it for all it can do. I figured I'd try to get it to lesser oil mixtures before trying to recalibrating the carb or using another. It starts quicker and runs better than last week. Also I found out it's only a 70cc rather than the 80cc I wanted. It runs ok with quite a bit of vibration for a small engine. I'm also reading that some of the newer ones have roller rod and wrist pin bearings?? I want to install a shifter kit before I inspect the engines internals, If it runs that long? I seem to have a good one after reading some of these posts, but I'm still skeptical.
I'd go to 24:1 now, then re-calibrate the fuel/air mix.
You will find these are all just under 70cc, none are 80's.
The ones with wrist pin needle bearings were sold for awhile, don't know how they turned out....the one (needle upper) I have (new) is supposed to be a 60cc.
I can say I have had engines from thatsdax, livefast, and another undetermined seller...they are all pretty much alike. You can get good ones and bad ones, the majority seem to be somewhere around the middle.