My shop connected an air compressor / measuring device to the spark plug holes, pushing air into the cylinder at TDC.
The mechanic thought it was too easy to turn the engine over by hand and wanted to see what was going on.
We got 4% through the vertical and 10% through the horizontal cylinder.
My bike runs great and it doesn't use much oil.
It has been ~12,000 miles since my engine rebuild with HC pistons etc etc
What now?
That's generally called a leakdown check.
Did they listen at the intake, exhaust and crankcase to narrow down where it was leaking from?
Have the valve clearances been checked?
When you had the upgrade done, did they cut/grind the valves and seats?
Did they install new guides?
How many miles on the engine?
I wouldn't panic at 4% and 10%, but it's worth poking around to find out what's going on.
If t6he 4% and 10% is through the rings and not through the intake and exhaust all is good. Was the engine at operating temperature when they did the test? Temperature matters with rings. IMO, if it ain't broke don't fix it.
They listened, but they didn't tell me why or what they might have heard. I'm calling them Monday to ask.
Closers close to lower end of spec, both openers at .20. Didn't have the required shims (4.20 and 4.25 because of custom intake valves). We're aiming at .10
The top was port & polished with attention to squish edges, so my guess is that the seats were worked on. Yes to new guides.
~ 30,000 miles before rebuild, ~ 12,000 since. (stock cylinders with big bore and coating)
Test was done with the engine (oil) at about 140 F
They may have gone a little narrow on the valve seat, with more of a 'race' setup rather than 'street' setup.
But that's very much speculation on my part, until there's some definition on where the air is going.
Kaemna are not amateurs...
Did they use Ducati guides or bespoke units?
Closers....what are they at now?
I don't know which guides I have.
The closers were well within spec according to my mechanic and I can't remember what the measurements were.
I'll get back with info about where the air was going.
Thanks [thumbsup]
Nothing conclusive from my mechanic.
I'll keep you posted.
Quote from: stopintime on September 23, 2011, 02:24:02 PM
My shop connected an air compressor / measuring device to the spark plug holes, pushing air into the cylinder at TDC.
The mechanic thought it was too easy to turn the engine over by hand and wanted to see what was going on.
We got 4% through the vertical and 10% through the horizontal cylinder.
My bike runs great and it doesn't use much oil.
It has been ~12,000 miles since my engine rebuild with HC pistons etc etc
What now?
When they do that test, the air is metered through a small orifice before it goes into your cylinder. So,the 4% and 10% leakage rate doesn't represent 4 and 10% of the compressor's capacity, it is 4 and 10% of the air after it's metered through a small orifice. Ten percent may be toward the upper end of the range for a street engine, but it's still acceptable. It's good to keep an eye on your engine's condition, but it's running good and not burning oil and if it were mine, I'd just ride it and not worry about it.
Also...determining exactly where the air is leaking to (through valves or past the rings) is an integral part of a leak down test. If your mechanic didn't determine that, then I think it's reasonable to question him about it.
Bob
If Kaemna used stock ducati valve guides you could have leak on the exhaust valves.
The stock ducati guides are too soft.
have them check the play on the exhaust valves.
the shop I worked with uses a special harder material for the valve guides to avoid that issue.
Quote from: Langanobob on September 26, 2011, 01:50:06 PM
.............
Also...determining exactly where the air is leaking to (through valves or past the rings) is an integral part of a leak down test. If your mechanic didn't determine that, then I think it's reasonable to question him about it.
Bob
I did - he didn't have an answer and will do it again for free.
Quote from: Raux on September 26, 2011, 01:56:12 PM
If Kaemna used stock ducati valve guides you could have leak on the exhaust valves.
The stock ducati guides are too soft.
have them check the play on the exhaust valves.
the shop I worked with uses a special harder material for the valve guides to avoid that issue.
Thanks! I'll keep that in mind [thumbsup]
Quote from: Langanobob on September 26, 2011, 01:50:06 PM
When they do that test, the air is metered through a small orifice before it goes into your cylinder. So,the 4% and 10% leakage rate doesn't represent 4 and 10% of the compressor's capacity, it is 4 and 10% of the air after it's metered through a small orifice. Ten percent may be toward the upper end of the range for a street engine, but it's still acceptable. It's good to keep an eye on your engine's condition, but it's running good and not burning oil and if it were mine, I'd just ride it and not worry about it.
Also...determining exactly where the air is leaking to (through valves or past the rings) is an integral part of a leak down test. If your mechanic didn't determine that, then I think it's reasonable to question him about it.
Bob
Zakly, if the air isn't leaking past the valves, [Dolph]
The valve guides are called Pistal valve bags(?) on my invoice. Stock or better?
Had my shop do the test again - they had to turn it very carefully to close properly and got readings of 4% on both cylinders.
Good to know - other than a missed opportunity to get my ugly heads painted.
[Dolph]