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UPDATE Today I tried to take the minibike out for a proper test run. Did nothing from yesterday except relocating the breather filter, installing the air filter on the carb, shortening the fuel line a bit, and adding some gas to the tank (from the same gas storage tank that I used to fill it up...

I have seen people running 0.009" metal head gaskets on these Predator 212 Hemis with the head milled .050" running a .308 lift cam without issue. I'm only running .265 lift with no head milling so I think I'll be fine. When I had the engine apart I checked for any signs of piston to valve...

UPDATE I lapped the intake valve very well with Permatex valve grinding compound and assembled everything back together. I turned off all the lights in my garage and used a super powerful handheld flashlight to check that the valve was sealing. On a sidenote, the install height for the 26lb...

Couldn't be the compression release since I completely removed the rocker arms and pushrods.

Yes, how am I supposed to know anything for certain? Without access to a professional engine lab and extremely advanced tools none of us here can know many things for sure...engine building is sometimes more of an art than a science.

UPDATE I finally found the culprit. Out of all the most difficult problems to find in an engine, this is probably the hardest issue imaginable to find. I pulled the cylinder head and carefully examined everything. The bore looked to be in near-perfect condition, indicating that this likely...

I got perfect spark with the old plug and cleaned it off really well with a blowtorch. I also visually saw spark from it. I'll try another one but I highly doubt that could be the issue.

Nothing seems wrong with the shaft and keyway at all. Am still at a total loss for what could be wrong with this Chinese piece of junk.

Here’s a picture of the flywheel and shaft. Doesn’t look stripped to me, should I go ahead and pull it off completely??

Thanks a lot for the advice everyone. I replaced the entire spark plug coil and boot with a new coil wire/boot and it didn't make any difference. Saw nice bright sparks as well and I know this coil works since I used it on another engine. I checked lash again and there was .0025" on both valves...

I used the stock valves that came with the Hemi 212.

I torqued the rod to 15 ft/lbs as recommended by ARC (I did it exactly as they did) and I don't understand how it would be a lock-up since the crank wouldn't rotate if the rod was locked up?? I know heat could make it lock up but as I said it spins freely at idle so it should at least idle for a...

Hello All, I am fairly experienced at working with small engines, both 2 stroke and 4 stroke, but for the life of me I can't understand what's going on with 212 I just built for a minibike. Below is a list of the mods I did: Predator 212 Hemi, Stock Bore, Stock Stroke, Stock Valves, Stock...

Hello, This is my first post in this forum, so I apologize in advance for any mistakes I might make. I built a motorized bicycle (not a mini bike, an engine attached to a regular bicycle) a few months ago using a lightly modified Non-Hemi Predator 212cc (governor internally removed, upgraded...