Seeking New England USA Z1 mechanic

kawsakiman wrote:

i would suggest a compression and leakdown test before you rip the motor apart.
it could be a bunch of different things such as inproper cleaning of the carbs, carbs not synced right, valves out of adjustment, timing out of adjustment just to name a couple.
did they give you a reason why you need rings or are they just guessing?

smurphy777 wrote:

Hey kawasakiman,
Thanks. Here's what they told me:
======================================
Compression is 135 and 120 on the two weak cyl (middle cyl's) the leakdown is 11% and 19%. the leakdown is the real cause for concern. as typically anything exceeding 5% is a substantial leak.
======================================

Leakdown sounds more like valves than rings.

Are valve clearances within specs?

I second kawsakiman's advice.

Good Fortune!

Perhaps the advancer is sticking, and needs lubing, or both cleaning and lubing.

Easy to check function of advancer with timing light.
Should see it quickly move back and forth as rpm is varied by blipping throttle.

Also check ignition timing to assure F mark aligns with case mark at idle rpm.

Good Fortune!

[Click on image to enlarge view.]

I will disagree with 5% being a substantial leak. No way, a fresh engine built perfectly/ blue printed will have at least that after the break-in period. 19% is a bit high, 10-15% would be fairly normal on any used engine of a poppet valve design. Add some oil to the cylinders that are low and retest, if it comes up right away, then bleeds back down, this is rings. Probably a bit stuck or they are wearing and the gap is getting on the bigger side of the factory max.
Does it use oil? Did you do as suggested and check the valve clearances? If valve adjust was done, due to tight valve, I would suggest running for a few hundred miles before retesting, as you are not loosing enough for a rebuild yet. (Unless you race it)

EDIT: I almost forgot, these compression tests and leakdown tests should not be performed on a cold engine. Warm it up good first.

Good Fortune!

When setting ignition timing, always use the F mark.

Ignore the T mark.

Good Fortune!

A leakdown test injects air pressure through the spark plug hole to pressurize the combustion chamber.

Air heard escaping from exhaust port indicates exhaust valve not fully closing (perhaps too tight clearance or damaged valve or valve seat).

Air heard escaping from carb intake indicates intake valve not fully closing (perhaps too tight clearance or damaged valve or valve seat).

Air heard escaping from crankcase breather indicates loss of compression past rings into crankcase (perhaps worn piston rings or cylinders).

Air heard escaping from head gasket area indicates indicates loss of compression past head gasket (perhaps due to a blown head gasket).

Good Fortune!

GregZ wrote:

You can try the oldkawman,mike Coogan
If you want his number pm me. He is in Swansee Ma.

Request going easy with the silicone, as excessive application may break loose and clog lubrication channels.

This is the same reason not to use silicone when installing a cam cover gasket, except for an ultra-thin smear around the half-moons.

Good Fortune!