212 hemi predator help

[MINI-BIKE-BASHER]

Is anyone in the Levittown pa area that will take a look at my hemi 212 predator engine? It has an arc billet flywheel,arc rod,dyno cs cam,intake,exhaust,.037 jet (I've tried many) 140 Etube,26lb springs, arc stainless steel keepers and retainers,chromoly rods, and I think that's it. I can't get it to run right. It runs the best with no intake on it and stumbles on the high end. When it does stumble it shoots what looks to be gas out of the carb. At first I thought it was rich so I leaned it out and it seemed to help,but the plug got white as can be (lean) and it started to worry me that I was going to destroy the engine. Now I am stuck because if I richer it the engine runs horrible on the top an and seems to backfire out of the intake and if I lean it the engine lean pops out of the exhaust and the plug turns ghost white. At this point I am at a loss. Eric from OldMiniBikes has been so helpful with this build and really has gone above and beyond. I just want to enjoy my new engine. Is there anyone that will take a look at it for me for a fee? I am so frustrated and I don't know what else to do. I'm thinking the timing may be off and that is what is causing this. The flywheel I have has the 8 degree advance timing I believe. I don't have the time to build often and I am desperate to get this thing to run correctly. Is anyone able to look at this engine for me? I would greatly appreciate it.

 

[EVOL Tweety Bird]

Not up in your area but, a couple of things. Let's look at the basics.

Timing would have been done when you installed the cam, simple as lining up the two dots, so more then likely that's correct. You did line up the dots, yes?

Now did you compare the new push rods to the old ones? Same length? They do do come in different lengths. Same thing for the connecting rod.

Intake? Do you mean air filter/adapter? Shouldn't have this type of affect on running other then leaning it out slightly. Ditto if you added a header. Or did you mean valves? If valves, were they the correct size and were they lapped in to match the valve seats?

New flywheel, did you set the coil gap to 60 thousands like it says on the papers that come with it?

Valve lash correct? Almost sounds like this could be a problem with it, spitting of the fuel through the intake/exhaust. With the compression release it can be a little tricky to get it correct, TDC is not really TDC like on a car engine. Set it without compensating for the compression release and your valve lash will be way off.

Lastly, and probably not really your problem, but if using the stock carb you are pushing the limits of it with all the other upgrades you did.
Now not saying you can't get it to run good, but it won't reach its full potential with the stock carb. It's too small. I know on mine I had to increase the idle jet size on both to get them to idle correctly.

Things can happen, and you get frustrated with them. What works for me is to walk away from it for a day or so, then go back and start from the beginning and recheck each thing. This from the guy who spent two days trying to figure out why his leaf blower wouldn't run after rebuilding the carb. I had that carb apart a dozen times trying to fix it. Only to realize on day three, after walking away from it, I had the intake and return fuel lines reversed. DUH!!!

 

[MINI-BIKE-BASHER]

valve lash is set at TDC at .003 per Eric at OldMiniBikes. Air filter is what I am referring to when I say intake. Car lingo is always stuck in my head. valves were lapped and seated and are the correct size. Rod bearing was seated properly and the rod is the correct size. Dots on cam were lined up to set timing (just wasn't sure about the advanced timing causing an issue). push rods are the same size as the originals and the correct ones for the engine. I did set the lash exactly at TDC with the piston at the highest point. I have read about others saying to go slightly past tdc for these engines, but I wasn't sure about that. my flywheel said to gap at 30 thousandths, but I did around 45 thousandths per Eric. if I go to a large jet on the stock carb it always idles great, but starts sputtering on the high end and spitting gas out of the carb. if I go leaner it runs a lot better, but the plug looks horrible after running it that way so I don't want to kill the engine. I put on a new carb and gaskets and that did nothing to solve the problem.

 

[DeadPixel]

When you lapped your valves what compound did you use and how did you check the seal?

 

[DeadPixel]

Are you running a stock idle jet? I see you only have mentioned a main jet and E tube.

 

[EVOL Tweety Bird]

Recheck your valve lash,be willing to bet it's way off. See what you have when the engine is up to temp. Run it for a couple of minutes, pop the plug out and bring it up to TDC, remove the valve cover and check your clearance.

When these engines get hot the lash opens up, so if your lash is off to begin with, once up and running it's going to get even worse.

I set mine COLD at TDC, 0 (zero) lash. You can still spin the push rod at zero. Once the engine heats up you'll be very close to a correct lash setting.

Too much lash can have the rocker slamming onto the top of the valve stem, not good.

 

[MINI-BIKE-BASHER]

I used valve lapping compound. Bought at advance auto. I never checked the seal and I do not know how to honeslty.

 

[MINI-BIKE-BASHER]

I changed the jet that comes out of the bottom of the carb along with the etube. I have never changed any other jets in any of my engines,but I didn't know there was another jet that people were changing.

 

[MINI-BIKE-BASHER]

The lash was opened up a lot after warming up. I have never heard of the 0 lash trick before.

 

[DeadPixel]

If its the purple tube it dose not work well. I have used it and it is hit and miss if I can get it to seal. I use the 600 grit clover compound now after talking to other guys on here and it works amazing. There is different ways to check seal but I stand the port up and fill it with penetrating fluid like WD40. I get it for free so its free for me to do. I let the head sit for about 5 minutes to see if it leaks past the valve. Water dose not work well and will not show leaks un less there super bad. It needs to be a thin fluid that will not evaporate. Its not a great picture but here is a head getting checked. You only need to fill the port a little past the top of the valve. There is better ways to check but this is the way I do it cuz I get the fluid for free and its quick and easy.

 

[EVOL Tweety Bird]

Under the idle speed adjustment screw you'll see a black washer with a flat on one part.You need to remove the idle adjustment screw and carefully lift up the washer.
It holds your idle jet. Doesn't take much at all to plug it up.