Has anyone seen this engine problem?

I have bought several McCoy 35 engines on ebay I am getting close to a dozen. Several of the engines run fine but some have minor problems like the piston is in backwards, no head gasket, spray bar hole is pointed up instead of down, nothing that can't be fixed. Another engine came in the mail today and I have been trying to make it run. It has lots of compression, starts real easy, comes up to full RPM in about 1 seconds, then dies like it ran out of fuel. Over and over the same problem. If I screw the needle out the engine still starts and revs up but not like before because it is running rich and it still dies. I took the engine apart and checked all the clearances and gaskets. This engine must be close to brand new the clearances are all close. Crankshaft busing clearance .001". Cylinder and piston clearance .001". Compression is excellent. Glow plug is new and runs fine in a different engine. I swapped fuel tanks and also tried a bladder fuel tank the engine still comes up to full RPM and dies like it ran out of fuel. The engine will restart very easy each time it dies. After restarting the engine over and over probably over 100 times I noticed each time the engine comes up to full speed it blows a spray of fuel out of the venturi and then it dies. It apears to me that when the engine comes up to full speed crankcase pressure increases, the pressure leaks past the crankshaft and bushing, and blows out through the venturi. That is why the engine runs out of fuel each time it starts. I notice the crankshaft can be slide in and out about .030" if I pull back and forth on the propeller. This seems to be a little bit loose compaired to my other engines. The plastic thing that is stuck in the end of the crankshaft and rubs against the crankcase cover is wore down flat thats probably why the crankshaft pulled in and out so much. When the engines starts the propeller pulls the crankshaft forward so I decided to push the crankshaft back by pushing the tip end of the crankshaft with the tip of my finger while its running. It is interesting the engine will now run without stopping but it runs rich and fuel is blowing out of the venturi all over the place. When I remove my finger from the tip of the crankshaft the engine revs up to full speed and dies. Has anyone seen this problem before???

Gary:
Had an identical problem with a Super Tigre on Contest Day. Later found a HAIR in the spraybar...

LAST EDITED ON Mar-20-04 AT 10:40 AM (CDT)
 
Check and make sure the sleeve is not in backwards. Fuel is not supposed to be spraying out the venturi, unless someone modified the timing. Usually the only time you will see fuel spitting out the venturi is when the engine starts backwards. Or on some radical timed racing motors you will see it happen until the motor comes up to it's racing RPM's.

I go with GARY,S guess.
General rule of thumb; the exhaust port opens before the intake port
easy enough to check in this engine.
just remove the cylinder head ,turn the engine piston down from top dead center and see which port is uncovered first and weather it is on the exhaust side or not.
Please let us know what you find

The McCoy 35 engine runs like a brand new engine. It starts easy and sounds good. This is a very nice engine probably one of my best running McCoy 35 engines. I took the entire engine apart again. I examined all the parts. The only thing I could fine wrong was that tiny plastic thing that is stuck in the end of the crank shaft that seems to be for keeping the rod on. That plastic thing was worn down to almost nothing. I made a new one out of brass. I got the clearance very close within .002". I notice the crankshaft has a smooth bearing surface that runs against the tip end of the crankshaft bushing. I assume this surface is suppose to seal off like a valve and the plastic thing keeps the crankshaft all the way up against the seal. I put the engine back together with the new brass part and the engine runs perfect.

LAST EDITED ON Mar-20-04 AT 06:22 PM (CDT)
 
PERFECT IS GOOD ENOUGH, Although I would still consider making the plug in the crank out of "teflon" as opposed to brass. The brass will eventually ware on the back plate after a few runs and if this engine is as good as you say it is now is the time to prevent unecessary problems.

Gary,
That bearing surface you mention on the crankshaft is probably the thrust bearing which supports all the forward pull induced on the crankshaft by the prop.
I believe the button in the crankpin is a spacer to prevent the conrod from rubbing against the backplate. It may have been worn down by someone using an electric starter on it.
As previously suggested you might want to make the button out of a plastic or fiber material. The brass will probably wear and the filings might do a number on your piston/cylinder fit.