Super A engine "jams" when handcranking!

Sun Jul 17, 2011 12:43 am

Had some time to work on "Ol Whitey," my white demo Super A yesterday...finally got the mag hot, (long story) and decided it was time to try to start it. Rigged up a pony gas tank, and after a few pulls of the crank, it did "hit" a time or two, which got my hopes way up. After a couple more trys, it suddenly became impossible to turn the engine with the crank. I was able to turn the engine backward by pulling on the fan blades, and it released and seemed ok but after a couple more trys it did it again, and I couldn't get it to turn loose. So I decided to call it a night.

I've hand cranked this engine a number of times and it has never shown any problem like this.

Any ideas what's binding it? I pulled the starter off just to make sure it wasn't jamming the flywheel (although I don't see why it would since I was hand cranking it.) No change. Though I have been around Super A's all my life, I'm not much of a mechanic, but my notion is there's an issue in the timing gears. Of course, those "hoofbeats I hear may not be zebras." In other words, it may not be that exotic of a problem. What else should I look for? I had high hopes of being able to hear it run before I did more extensive engine work, but that possibility appears to be fading fast...

Al

thanks,
Al

Re: Super A engine "jams" when handcranking!

Sun Jul 17, 2011 12:58 am

Stickey valve(s) :!:

Re: Super A engine "jams" when handcranking!

Sun Jul 17, 2011 9:23 am

Bill E Bob wrote:Stickey valve(s) :!:


I don't think valves are the problem, though I could be wrong. They all will move up and down by hand. Someone has had the valve cover off though, there's no gasket under it....

thanks,
Al

Re: Super A engine "jams" when handcranking!

Sun Jul 17, 2011 6:32 pm

Will the engine turn freely when you pull the plugs? Do the plugs look wet?

Re: Super A engine "jams" when handcranking!

Sun Jul 17, 2011 6:45 pm

VinceD wrote:Will the engine turn freely when you pull the plugs? Do the plugs look wet?


No, and no. Plugs have a nice generous coating of dry carbon. Again not trying to make a bunch of wild guesses, but after looking in each hole with a flashlight yesterday, I remmeber one cylinder in particular that was up near TDC so you could see a little of the piston. It got me thinking, I wonder if there's a big piece of dirt dobber nest, carbon, etc. that is making a piston contact the head? I can roll it backwards, I don't try to make a full revolution because I am afraid of damaging the mag impulse. Then if I roll it back forward, I can sometimes hear a little "clunk." I just can't tell where that "clunk is coming from.

I think I may rig up an attachment for my shop vac that will fit in the plug hole and see what I can vacuum out.

al

Re: Super A engine "jams" when handcranking!

Sun Jul 17, 2011 8:21 pm

Well I figured it out! It was crap in the #2 and/or #3 cylinders. Flushed it out with my long-necked funnel and some gas. VERY relieved! I am going to pick up some new plugs tomorrow and see if I can get her to crank....


Al

Re: Super A engine "jams" when handcranking!

Sun Jul 17, 2011 9:07 pm

Good deal, Al. Glad it was so simple.

Re: Super A engine "jams" when handcranking!

Tue Jul 19, 2011 8:17 pm

Glad you found the problem and it was not more complicated. Could you identify the "junk" and any idea how it got into the two cylinders? :D :D

Re: Super A engine "jams" when handcranking!

Wed Jul 20, 2011 4:17 am

VinceD wrote:Glad you found the problem and it was not more complicated. Could you identify the "junk" and any idea how it got into the two cylinders? :D :D


Not really other than it wasn't metallic. I think it was carbon and other "junk" from sitting. THere wasn't a lot of it but just enough in the right spot. Also it was mostly in #2 and 3, don't they have the most "direct" path to the outside world through the manifold? That's what I was thinkning--if so they would get most of the dirt, etc. that "settled."

Al

Re: Super A engine "jams" when handcranking!

Wed Jul 20, 2011 6:25 am

I have seen carbon build up around a plug, then when the plug is removed, break off in big enough chunks to lock the engine.