Head/Cyl. stud size - 70cc vs. 48cc compare



I have a 70cc from dax. The top rod bushing gave out which resulted in destroying the whole upper end.

I thought about getting whole upper rebuild kit that is a 48cc. I think it would work but the only thing that I am not sure about is the stud diameter.

Is the stud holes in the case the same for all engines sizes? I was thinking maybe the diameter of the studs on a 48cc get smaller from the case treads on up. I not sure.

I know the 48cc has smaller stud size through the cylinder and head.

Any feedback in regards to this would be greatly appreciated.




engine incompatability

Hello, I see no-one has answered this post so I will. The hole in the top of the crankcase is larger. The studs are farther apart, the stroke mAY be longer. Do not try this it will not work, as a bolt-in part. Mike


Wow, I have noticed a lot of upper end rod bearings going out on people. Mine went out and destroyed the upper half also. Of course, I am new to running an engine on my bicycle and couldn't tell the specific noise while it was happening to me. I guess it takes some experience to tell the difference between muffler baffle rattle noise, engine mount noise, chain noise, the loose screw in the drive gear noise, the chain guard rattle, misc. bicycle parts vibrating loose noise, and of course.... the upper arm bearing going out noise. I guess if I had to stop and peddle or push my bike home everytime I heard a vibration or wierd noise, I might as well not mounted an engine on it!! I got some slack from someone telling me when I heard a wierd noise that I should have known it was my upper bearing and immediately stopped the engine and walked the bike home.

I have a grab bag used motor with a good upper half coming to me from Thatsdax. I am going to give the Motor-assisted bicycle one more try. With less than 300 Miles on my first brand new engine and all the things I found wrong and bugs I had to work out the first few weeks, then the upper bearing shredding on me while I am going less than 30MPH. Maybe it's bad luck.

Try sending Thatsdax an email. He might have some spare parts lying around to hook you up. You have my sympathies. I am going through the same situation. I figured 150 Mpg! Save money from not buying gas!! But it seems like I am just spending that same amount of money and more on new parts to repair these Chinese engines. Like I said, one more shot, I am going to do it by the book again when I get the engine put back together. If it fails again during normal operation. It's coming off and I start looking for a 250CC motorcycle built by the Janpanese!! :)



Thanks you guys for the info! I still have not purchased any parts yet. I'll get to er' eventually.

Thanks again,