Finding the Leak

As the last entry shows, the engine had a bit of a hard week.  I was so afraid I had ruined the engine that I put this post on four forums: 

I started this Red Devil Enduro restore with my father a year and half ago. Sadly, he passed away last May, but I kept the project going.

http://kartrestoration.blogspot.com

Today was the first time to start up the rebuilt MC91b1. Don't want to be long winded...just letting you know the facts.

After getting some gas in the cylinder and case, I set the LO needle to 4 half turns; HI to 3 half turns

Cranked it over to get fuel line full and it popped. Hit it again and it started. it ran slow for but changed to higher pitch and settled. Reved it a couple times all seemed well. I choked it to shut it down, but had to pull the plug wire.

waited a few minutes. Set the needle to the same place, cranked it, but it did not even pop. thought it was flooded, so waited a bit.

Cranked it over, it started and ran faster than the other times, then quickly went "super screamer"!! I pulled the plug wire-NOTHING; choked it-NOTHING; finally turned off the low speed and it shut down.

I have not changed the idle in the restoration. 

IT IS MY FIRST TIME STARTING/RUNNING A MAC. I have been gleaning info on this and other forums. You guys are a wealth of info. 

ANY THOUGHTS/HELP/ENCOURAGEMENT IS MUCH APPRECIATED. post here or PM me.

Thanks a ton!

Thankfully, there is a very active community of vintage karters with tons of knowledge being shared on a few discussion forums online ( http://www.ekartingnews.com; http://www.vintagekarts.com; http://vintagepowersport.com/vka; http://www.rearenginekarts.com )

I spent a couple hours last night reading replies and doing searches on the forums for info on air leaks, pressure checks, carb testing, etc. 

Today, I did a pressure check and it held 12lbs pretty steady for 15 minute ... maybe loosing 1-2lbs. 

One of the forum moderators suggested (with caution) dunking the engine in water while doing the pressure check.  So... this is how you never want to see a Mac engine: UNDER WATER!   No bubbles, until I turned the crank a bit and a few came up from from behind the shroud and flywheel. See the video below.

I blew the engine dry so none of the steel parts would be harmed.  But I didn't grab Dad's wheel puller so wasn't able to check for the leak or dry behind the flywheel.  (Yes, I tried to use the screw driver and brass hammer technique, but it did not work.) the bubble was coming from around the points. 

OH Crap!  Electronic parts... made of ferrous materials... OH Crap!  Later I checked for spark... NONE... GRRRRRR (more on that later)

After the first rebuild, I did a pressure check and found the original seals were toast. Rebuilt and added new seals and added silicone. 

Will pull the flywheel and check/reseal all the screws/bolts on that side.

here is the carb with reed cage at the top

When I rebuilt the carb (first time doing it... and without Dad)  it all seemed very easy.  We had sealed the crank case with copper coat on the gaskets, so I put copper coat sealer on the paper gaskets between the intake/reed cage and reed cage/carb.   That meant removing the carb would destroy the gaskets.

the reed cage

intake manifold - the rod and crank can be seen inside

Here is the destroyed gasket.  Copper coat can be seen.  AND I found out there are these little holes in the end of the carb.  They are called pulse holes and it is MANDATORY they be open and clean for this carb to run correctly.  Rookie Mistake :-(

Next will be doing some more research and figure out the next steps.