Predator 212 tossed a road

[Briguy35]

I fired my motor up after tearing into it ran great.... upgraded dyno cam springs etc....

Original carb got stuck and I had the front of the cart against a wall.... so It backfired and dIed.... not starting now so I took of the valve cover saw the road wasnt under the ( not sure what the part is called but it goes up with the rod pushed back with the spring)

Anyway I couldn't get my rod to drop back in place so I removed the head and was able to look where the rod went into and I noticed the where it went wasnt push pack inside of the motor....

I manage to get it all back together and it seemed like it works properly however I pulled the pullstring 5 mons ago and it yanks back to quick what should I do?

 

[jmaack]

wow.

 

[KartFab]

Easy, set your valve lash to .002-.003” with feeler gauges.

 

[Karttekk]

Agree with KartFab here. One of your pushrods popped loose from under a rocker arm. Readjust the valves. Are you familiar with how to do that?

 

[Karttekk]

Here's how to adjust your valves.

That engine has a compression release mechanism on the camshaft. Pop the valve cover off and remove the spark plug so you're not fighting compression. Turn the crankshaft or pull the rope slowly while watching the valves open & close. You'll see one valve open then close then the other valve will open & close then you'll see the exhaust valve just barely open then close, that is the compression release device opening the exhaust valve enough to allow easier cranking until the engine fires. Centrifugal force will "pull" the compression release back once the engine starts to keep it away from the exhaust valve. Put a screwdriver or something with a long stem on it in the spark plug hole and turn the engine over manually until the piston pushes the screwdriver up until it's at the very top of the cylinder while watching to make sure both valves are closed. This is what's known as Top Dead Center. Loosen both rocker arm jam nuts then loosen both rocker adjusting nuts until both rocker arms wiggle around and are loose. Grab your feeler gauge and find one blade with .004 on it. Slide it under one rocker arm where it touches the valve and turn the adjusting nut until there is slight drag on the blade. Tighten the jam nut. Repeat with the other valve. Manually turn the engine over a couple of times then check your clearances again. If both valves drag the feeler gauge properly put the valve cover back on, put the spark plug back in & see if the engine will fire and run normally. Unless you have a bent valve, a worn cam or an extreme lean condition, the engine SHOULD run normally. Report back with results.

 

[bgcrawford1983]

So do these engines come new with lock tite on the plug? I tried to remove mine for the first time and turned it about one full crank and it was still really tight.

 

[Karttekk]

I don't believe so. Take your time, turn it back in a few turns then back out a few more turns than before. Repeat the process until the plug comes out.

 

[madprofessor]

Spark plug tight: If the motor's on a bench, BOLT IT DOWN! Many a plug has been broken off by somebody struggling to hold on with one hand to the motor to keep it still and wrenching with the other. However you're doing it, just make sure you're using both hands to keep your plug socket perpendicular to and centered on the plug.
Setting valve lash: If your motor is a Predator, hemi or non-hemi, look for a lash cap that the valve rocker actually pushes down on, and not the valve stem itself. For example, my Predator 212 hemi motors have a lash cap sitting on the end of the valve stems of both intake and exhaust. I believe the non-hemi only has a lash cap on one of the stems. If you unknowingly push one of those caps off and it falls down through the pushrod passages into the case, it could totally destroy the motor.
If you do that (or already have): If your valve lash has been set correctly with a lash cap in place, then the cap falls out, that valve rocker will practically flap around. If so, the pushrod can jump out from under the rocker, and then get badly bent by the rocker.
Pullrope yanking back: Look for my post here on "How much pullrope are you using?" or something like that. At the end it will say to pull your rope out all the way and measure how long it is. Then do a normal pull like you do and see how much of it you're not pulling out. Stepping back a bit to facilitate my ability to pull out the entire 4 feet of my pullrope cured my yank-back problem immediately and ever since. A 15+ hp. modified Predator can practically rip your pulling fingers off if it fires backwards.
Motors ignite their fuel/air mix in advance of the piston reaching top dead center. If you've stopped pulling right there, then the combustion is going to push the engine backwards the way it came from. If you pull hard on through all the way past top dead center, the motor absolutely must combust in the continuing correct direction.

 

[Api]

Hi there. I am a new member here. Me and my 15 year old son have built a few go karts and mini bikes thru the last few years. Currently we have a mini bike with a Predator 212 that has the same issue as mentioned in this thread. The engine runs and throws the intake pushrod out. We have set the and reset the valve lash to .003 while following all the steps and engine at tdc. After we put her back together the engine will run but bogs out if we try to run it full throttle and same thing happens again.
We are running 22lbs valve springs. What am I missing here?

 

[madprofessor]

Api, here's how you can start your own thread to ask your questions................ Go to the home page of this forum, select "Go Kart Discussion", "Engines & Clutches", or whichever heading you want. When you click on it, the first line that comes up just before the existing threads under that heading will be a blank one that has "Thread title" at the beginning of it. Click on it, type in what you want to say, then click on the blue "Post thread" box to see your own thread up on the forum.
That's the best way to get some useful answers from the many experienced and helpful folks on this forum, and it won't impose on Briguy35's own thread here.