Hello all! I would like to start this post off by saying I am trying to get a go kart build rolling. I bought a harbor freight engine (predator 212cc) after researching and seeing the great price and users positive feedback. I have run the engine a few times to break it in but here is where my dilemma begins. Just last night I was fooling around and took off the exhaust and ran the engine (I know not a smart decision). It made a bubbly noise untill I turned it off. When I put the exhaust back on and tried to start again I noticed that the pull cord would snap back and was hard to pull every few pulls. I have been looking around and seen that it may be a timing issue with the flywheel and woodruff key may be sheered. I am getting the tools to take off the flywheel to check. In the mean time I wanted to ask if anyone has any other ideas on what could be happening. Thankyou!
Welcome to the forum.
Predator engines are entry level, budget based engines that are known for things not being properly assembled or for bolts left loose. The ones for the crank and the rocker arms seem to be left loose occasionally.
You can usually see if the flywheel key is sheared without pulling the flywheel - just remove the nut and see if the flywheel and crankshaft keyways are still lined up. Good time to make sure the coil bolts are snug too.
There is a compression release mechanism on the camshaft that helps make the cord easier to pull during starting. A movable lobe on the camshaft opens the exhaust valve slightly on the compression stroke, then it retracts once the engine starts and it sees about 500 RPM. These can cause issues in a couple ways.
A common reason that the cord pulls hard and/or kicks back is loose rockers. If the exhaust rocker was set too loose or the adjuster wasn't tightened, the compression release won't work correctly, causing hard starting. Always a good idea to check the rockers after a couple run cycles to make sure they are set correctly. You don't mention Hemi or non- Hemi - there are many you tube videos showing how to check and set valves on either.
Occasionally the compression release portion of the camshaft will stick or fail. If it sticks "working" the engine can make an odd popping sound in the exhaust when running, because it is cracking the exhaust valve open on the compression stroke. Sticking in the "not working" position will make it hard to pull.
Hope this helps. Willie