gt 550 crank seals and leakdown testing

[stlrocker]

i have a 72 gt550. it is not starting, and everything else checks out fine. so i did a leakdown test. i understand leakdown test on singles, but i want to make sure i did it right for a triple and get some thoughts on the results.

what i did was seal up all of the exhaust and intake ports. on one intake i put a shrader valve and a gauge. pumped it up to about 6 psi and waited. it held for a minute and slowly leaked down. so that seems bad but i want to redo this and make sure i have everything sealed up tight.

heres what i dont know about. if i am pressurizing the left cylinder and remove one seal from either the exhaust or intake of either of the other two cylinders, then i cant get any pressure to hold. it comes out as fast as i can pump it in. is that normal, or does that mean that my inner seals are bad? i am thinking that the crank seals between the cylinders should hold pressure to just the left cylinder.

it is confusing because i was told that all ports need to be sealed off, but that seems like it would only test the outer seals. pressure could flow freely inside the crankcase between all three cylinders and you wouldnt see a pressure drop at the gauge. shouldnt the crankcase be separated for each cylinder?

[tz375]

Unlike say a Yamaha twin with a central Lab seal, in a 3 cylinder Suzuki, all three cylinders should hold +ve and -ve 6 psi. If you are losing pressure from the left to the center then the seals between the cylinders are shot and need replacing.

[Suzsmokeyallan]

Maybe Richard, but what about the SRIS valves, did he check those to see if they are leaking? Test each cylinder separately and block off the SRIS valve ports to confirm each one holds both pressure and vacuum..

[Buffalo-guy]

As Allan said, the SRIS valve has to be blocked, because under 6 pounds pressure, it will bleed off internal pressure to the adjacent cylinder, as it does with excess oil when it is running. Hopefully, that is all it is. Doing crank seals is a little more complicated. Cheers.
Fred

[tz375]

Duh.

I always block those off for testing and forgot to mention that. Good catch guys.

[stlrocker]

thanks guys. i didnt even think of that. i'll give it a try and report back.

[stlrocker]

i pulled and plugged the sris. i got the same results.

with all ports plugged it holds some pressure but leaks down in about 1-2 min. i didnt time it cause it is obviously leaking way too much. if i have any one port open it will not hold any pressure at all. just as before.

i guess this means all seals are shot.