Leak Down Test on GT550

[gdh12bike]

Hello,

I suspect that I have bad crank seals on my GT550 and therefore want to conduct a pressure test. Does anybody know if I should be doing the test on each cylinder separately or if I should be testing the whole crankcase at once? How do I test the middle cylinder if it's the later? Do I have a serious problem if the middle seal is bad, because it's a built-up crankshaft?

Thanks for any input.

Gary

[tz375]

Unlike Yamaha twins which use a labyrinth seal between the two cylinders, Suzuki use regular type oil seals and all three cylinders need to be tested for leakdown and "leakUP". i.e. for positive and negative pressure (vacuum). Test at 6psi and see if it holds. If not you will be able to hear the air leaking out into an adjacent cylinder of out of the ends or into the primary drive.

Testing is quite easy but tedious to set up. All the carbs and pipes need to be removed first and then plug all of the holes bar one with expansion plugs available from your local hardware store. Apply pressure/vacuum through teh remaining port or plug hole and see if it leaks out or holds.

[gdh12bike]

OK thanks. We have setup that will do the job, so i'll give your method a shot. I'm pretty sure that the seals are all bad. Is that the death nell for this engine if i'm right? Thanks - Gary

[tz375]

If th3 outer seals are bad, they just need to be replaced. If the inner seals are bad the crank has to be sent to someone like Bill Bune In MN to be rebuilt.

Some of the crank parts are becoming , shall we say, difficult to source, but Bill and his team are pretty good at working out details like that. usually I'd suggest sending the seals with teh crank, but if you can't find them, ask them first if they could get something that will work.

Good luck.

[gdh12bike]

Thank you - much more reasonable than i thought it would be.