What is a "good" leak down ratio for a monster 2V?
I'm getting around 20% on both cylinders @50 psi, which I'd consider "good enough" if it was my 65 Galaxie. My hunch is that ducati engines should be closer to 10%.
Thanks!
-Jordan
Hot or cold? Anything coming out of the intake or exhaust?
Cold (well, warm at most), and I didn't hear anything at the exhaust or intake.
I know the valves are tight because before I put the heads on I poured gas in the intake and exhaust and didn't see any drips out of the valves.
I also lapped the heads to the cylinder bores. I used fine grit (~400) compound, but the mating surfaces didn't come out polished looking - rather they looked sort of matte. I'm concerned that I have bits of the polishing compound embedded in the aluminum causing a leak around the head.
Accuracy at less than running temperature is questionable. Pistons are slightly oval when cold so blowby can reduce when hot even more so with an air cooled engine I am not aware of any official cylinder leakage spec for a Ducati, but 20% on a cool engine would not concern me. Left over lapping compound would scare me though. Disassemble, wash with soap and water until all grit is gone (white cloth stays white).
Find out where the air is going before you disassemble.
Ok heres where I'm at:
I brought it to local shop to get balanced, and they said compression was too low on horizontal cylinder and was at the bottom of spec for vertical.
I took it home, took it apart, lapped the valves*, lapped the heads to cylinder bore, checked/adjusted valve clearances, and checked/adjusted timing with dial indicator.
* I did the gasoline test on the valves, and it failed but I didn't know it at the time. I thought gas "seeping" around the edges was ok. I know better now.
Got it back together, warmed it up, and the compression was ~70 psi in both cylinders :(
I then discovered that my valves were leaking.
I took the heads off (I left the cylinder bore/pistons in place) and had the valves and seats professionally ground with a Newen Contour. I redid the valve clearances and did the gasoline check - no seeping the valves fit like corks.
I put the heads back on. I didn't check timing this time - I assumed that as long as neither the cams nor the cylinder head spacing has changed, the timing would be unaffected by valve clearance.
Got everything back together, warmed it up, and now the compression is like 80 in both cylinders.
I got a leak down tester from harbor freight and I saw 20% on both cylinders (it wasn't 50PSI, more like 15 I was reading it wrong), but I think I still had oil in the cylinders from a "wet" compression test.
I took the horizontal head off, and when I do a leak down test on the vertical I'm getting 30psi. All the noise appears to be coming from the crankcase where the horizontal cylinder fits.
This indicates piston rings or bad cylinder bore, right?
My piston rings have like ~100 miles on them, and a local shop that specialized in ducatis looked at the cylinder bore and said it looked ok.
I have a macro photography setup which I usually use for taking pictures of bugs... below are some shots of the cylinders and piston rings.
Do these look damaged or too worn to the experts?
Thanks for reading such a long post!!!
Horizontal cylinder:
(http://i28.photobucket.com/albums/c235/FurrorNos/xhatch2_zps39bc9289.jpg)
Horizontal cylinder close-up:
(http://i28.photobucket.com/albums/c235/FurrorNos/xhatch_zpse223e480.jpg)
Horizontal rings - edge:
(http://i28.photobucket.com/albums/c235/FurrorNos/rings1_zps6e5cff1b.jpg)
Horizontal rings - sides:
(http://i28.photobucket.com/albums/c235/FurrorNos/rings2_zps0b16b2c2.jpg)
Also: its been pointed out in a couple other posts I've read that I haven't "seated" my piston rings in such a short amount of time.
I get that, but it seems like new piston rings should at least be in spec, albeit low, without having been "burned in", etc.
I've been wrong a few times, though.
What kind of compression should I expect on newish rings prior to break-in?
When you're doing the leakdown, what pressure are you applying?
Have you checked the two gauges on the leakdown to see that they read the same?
Rings that new may not give good leakdown or compression readings.
What valve clearances have you set the engine to?
Quote from: Speeddog on September 16, 2013, 07:23:07 PM
When you're doing the leakdown, what pressure are you applying?
I read about 2 methods with my Harbor Freight gauge.
Method 1: with tester disconnected from cylinder, turn knob to all the way off and then rotate until you get to zero. Then connect to cylinder and observe drop. Heres what I get that way:
Before connection
(http://i28.photobucket.com/albums/c235/FurrorNos/method1_pre_zps653d9505.jpg)
After connection
(http://i28.photobucket.com/albums/c235/FurrorNos/method1_post_zpsb5886224.jpg)
Method 2: With tester connected to cylinder, turn knob to all the way off and then rotate to a known % (like 40%). Then disconnect from cylinder and observe increase. Heres what I get that way:
before Disconnect
(http://i28.photobucket.com/albums/c235/FurrorNos/method2_pre_zpse5171785.jpg)
after disconnect
(http://i28.photobucket.com/albums/c235/FurrorNos/method2_post_zps7bea086b.jpg)
Quote from: Speeddog on September 16, 2013, 07:23:07 PM
Have you checked the two gauges on the leakdown to see that they read the same?
I answered that above, right? The harbor freight device doesnt have 2 gauges; you calibrate 1 to the other via a pressure valve.
Quote from: Speeddog on September 16, 2013, 07:23:07 PM
Rings that new may not give good leakdown or compression readings.
Would it be so much lower that I'd get ~80PSI with a hot compression test? I read in a few places that piston ring break is should be done on a dyno with a specific sequence of RPM/load. If I didn't do that, does it mean my rings are wrecked? They were really expensive
Quote from: Speeddog on September 16, 2013, 07:23:07 PM
What valve clearances have you set the engine to?
All closers are such that if I press on the closing rocker I can rotate the shim with my fingers, but theres no appreciable difference in opener clearance.
H and V intake openers are .003 to .004, H and V exhaust openers are .004 to .005.
One thing I noticed is that I get smaller opener clearances with the black spacer clip in by about .002", so I sort of split the difference.
Also:
ThankyouThankyouThankyou! Theres a dealership in my city but theyre not that helpful - I get a blanket "bring it in" whenever I ask a technical question. They also stopped their shim exchange, which is frustrating.
I have a Harbor Freight leakdown tester, it's been several years and my memory is hazy as to exactly what I had to do, but basically the thing was a complete POS and wasn't even designed right. Not sure whose leakdown tester they copied but they copied it wrong. I had to modify it to make it work correctly. I'm on the road and can't go out to my shop to look at it and jog my memory as to what I had to do. Maybe they've fixed the problem by now, but I wouldn't base any decisions or come to any conclusion based on a HF leakdown tester.
Bob
I discovered at least part of the problem...
I thought that the cam nut held the timing plate, but I was wrong: the 3 small bolts through the pressure plate are what keeps the timing setting in place - 10Nm each means the plate has 30Nm total holding the timing (seems light, but thats the spec I guess).
So after getting my timing right on with a dial indicator and degree wheel, the timing was shot within a few revolutions after starting up the engine because the sprocket was maximally retarded.
Not sure if I've totally fixed the compression issues at this point - I want to put a few miles on it before I do another leakdown.
-Jordan
I <3 Harbor Freight. That's all... :)