pressure/vacuum test via spark plug hole?

[kevin j]

rotate the crank, or make sure the piston is down far enough to open the transfers.

The rings don't seal totally if up, but if you pump up either crankcase or spark plug hole, the needle will drop and drive you crazy looking for a 'leak' that is air leaking in or out of the cylinder into the crankcase.

PUtting piston at BDC or anywhere the transfers are open makes it all one volume to pressure/vacuum.

 

[turbo885]

Thanks for all the replies. I was expecting someone to tell me I'm a dork and do it a different way.
I did see the eternabond thread as well. I just figured I'd like to make something. I'm a tinkerer. I was thinking of breaking an old spark plug and welding a barb on there. I agree with making it as simple as possible to rule out any connections.

you can get the fittings in the auto parts store they come in a two pack for 2 different size spark plugs. they have 3/8 pipe thread on the other end you can put a hose barb there. used to put air in cylinder to hold valves when you change valve seals i think mine were made by lysle i think they were 6 or 7 bucks BILL

 

[Don Ens]

What does the leak down tester look like, any pics? Someone mentioned using a brake bleeder pump. Can someone list the exact process using either or both?

 

[heyduke]

this is a bit sloppy looking but works great. the plate is a scrap of aluminum with quarter inch pipe threads and a brass barb. one could probably find an 1/8" barb too. there is another aluminum plate on the exhaust side. used some kind of gasket compound to help seal the threads. epoxy would work too. gaskets are standard blue fiber from autozone. found the leak on the flywheel side crank seal. used windex for bubbles.

 

[Don Ens]

Thanks! Now can you show the rest of the apparatus, as not sure what the rest looks like. I assume the exhaust port is blocked with similar plate.

 

[heyduke]

Thanks! Now can you show the rest of the apparatus, as not sure what the rest looks like. I assume the exhaust port is blocked with similar plate.

yes there is a similar plate on the exhaust side. the case is pressurized with an air compressor set to 5psi. here's a youtube vid:



the operation was a success and the patient lived. hope this helps.

 

[Don Ens]

Great video of the operation! Especially liked illustration of the bad seal using the spray. Thanks!

 

[cruxmon]

A comprehensive kit using the MityVac 8500 with sealing plates and a spark plug adapter is available on eBay...search "2 Stroke Pressure & Vacuum Leak Down Engine"