Interpreting Leakdown Test Results

I've got a Kawasaki 1995 vulcan 1500 V-Twin that has been running rough
on uphills/accelerations.

I've done a leakdown test ont he bike and have a few questions I'd
llike to pose to the group for their comments/help to interpret.

The leak is 20%. Last year the leak was 15%. I fully suspect the leak
will be 25% next year. I feel it's time for a top end job. Is this
the right decision? I'll have all winter to do the job myself. Any
tips or suggestions would be welcome.

I had weird results that I think are my problem with getting the
cylinder to TDC. Aft3er positioning the cylinder and putting the bike
in gear, I connected the gauge. Teh leak gauge went directly to 90%
leak. As the compressor cycled on to refill the tank, the gauge needle
started to climb, then a slow whoosh of air would come out of the carb
intake filter, the needle dropped down, stopped, then it began to
climb, again. This cycle went on several times until the leak gauge
needle finally climbed to and stayed at a steady 20% leak. I could
then hear the leak through the oil filler orifice identifying the leak
(I think) as the piston rings.

I have a couple of questions about this: did I position the cylinder
just on the edge of the intake cycle and the pressure build-up finally
allowed the pressured air to escape around the valve? Or, would a
cracked piston ring somehow have these same symptoms?? TIA for any
help here.

Manjo 1500A9 Kawa Vulcan

 

Does the engine smoke for about 30 seconds or a minute on startup, then
quit smoking? Does the engine use oil with no apparent smoking while
you're cruising along the highway? Are you getting tired of adding a
quart of oil every 500 miles or less?

Bad valve guide oil seals would cause this. The intake valve won't seat
properly once a lot of crud builds up on it. It might even burn. And,
perhaps excess oil from the worn valve guide oil seals might make the
piston rings stick.

That scenario would satisfy the description where air pressure
apparently shoved the intake valve closed, and you still heard leaking
past the piston rings. (1)

In order to get a good seal from the piston rings, spring tension has
nothing to do with it, air has to get behind the rings and push them
outward. So, if the piston ring grooves are full of carburized oil,
making the rings stick, that might be what's causing your compression
problem.

Have you tried anything like Rislone to free the rings? And Techron
Concentrate might clean deposits off the valve heads. It won't replace
the valve guide oil seals, if that's what the problem is.

(1) Or, does that engine just have hydraulic lifters and they are
stuck?

 

The top end has about 80k miles after piston replacement to cure piston
slap, something this model year has too often.

Yes, there are hydraulic lifters; I agree it could very well be the
valve guides, too;

Regarding the piston rings, we were on a long ride this summer and
after the first few 300+ miles per day, I had to ADD a quart of oil.
Then oil consumption almost went way entirely. I suspect the hard
riding and the addition of Sea Foam to the fuel, freed-up the rings.

When accelerating, especially when going up hill, the engine runs
rough, but strong. I've replaced the spark plug wires, and have a set
of ignition coils to test with to eliminate a spark problem. But I
tend to agree strongly with your opinion: it's tiime for a complete
top-end job to replace the guides, lifters,a nd valves.

I really like the bike and have it set-up for long distance riding. I
get about 40 miles per gallon on a good run. I want to get as close to
50 mpg. I think a top-end job will get me there, I hope.

Thanks for your post. It's been ery helpful. Any additonal comments
or tips would be welcomed.

check twice, ride safe,

Manjo