Leak down test, sort of

[MPittma100]

Leak Test

There is one way to do the leak down test (as has already been suggested) and that is with the proper tool. Any other method is simply a guess of what is leaking.

Get a tester. The piston is to be up with valves closed. You can expect 15% leakage max past the rings on a warmed up engine. If you have a valve leaking, the leakage will be as much as 100%. Also, if a valve is leaking, make sure that there is some lash. If there is none, make some and check it again.

By doing this test properly, you will make one repair - the right one - the first time. Otherwise you may end up tearing it down several times.

MP

[LoHo]

Well, the only way for me to get it warmed up is to light it on fire, which has crossed my mind several times.

[DGXSER]

Oh, I recall several days of thinking I should just roll it down a hill and set it on fire. Look at it this way, the victory is just that much sweeter after that long of a fight.

[Rasputin]

lol thats not what u said in ur first post
but all good.

I have been wrong before and will do it again just cause I am wrong most of the time. I just had to elaborate on why I thought it was wrong and why I would like to see the test done properly the first time.
The way I was taught was the way I posted. Simple as that. I saw my wrong in the posts and adjusted to the consensus.
A test is a test no matter how you shine a light on it and it must be done correctly to get the right results. I do it my way, and then add different positions to do the job I intended in the first place.
You are more than welcome to do it your way...just know that if you are in my garage you will do it my way. I am kind of a dink that way.

[skids]

Well, the only way for me to get it warmed up is to light it on fire, which has crossed my mind several times.

That was funny as hell! I have started a bike that would only run on 3 cylinders. Something else must be wrong than just low compression in that cylinder if it will not start and at least run sh$tty.

[MPittma100]

Well, the only way for me to get it warmed up is to light it on fire, which has crossed my mind several times.

It is not a big issue if you do not or cannot warm the engine prior to the test. The results (% of leakage) will be more on a cold engine, but the ability to determine the source of leak is the same.

If you determine that you have excessive leakage into the crankcase (rings), add a few shots of oil to that cylinder and retest.

MP

[LoHo]

Skids, did you catch the part where I realized that I'd set the cam timing to "C" last time I put her together? The bent valve/low compression was a result, not a cause.

I've ridden her for a few miles on two cylinders (vacuum to petcock came off), and off a tooth or two (new ACCT didn't extend fully), so I know she wants to run, and would run if I didn't keep interfering with it.

[LoHo]

Just to put this to rest, let me say that I fully realize that what I did was not a leak down test (hence the "sort of"). You guys have gotten after each other over how to do one, and I believe that each of you knows more and can do better than I can and have.

As I stated, all I wanted to do was confirm that my compression was leaking out of the intake on #3, and I did that. It wasn't warmed up, I didn't have all of the components attached, I didn't gauge it or measure loss as the piston traveled, which are all components of of a proper leak down test. Mea culpa.

On the other hand, when more experienced mechanics start these pissing contests, I always learn a lot, as they explain why some other guy is full of it and the other guy counters with why the way he learned in 1964 is STILL the most reliable method and blah blah blah.

[skids]

I'll bet you would have good results by replacing the valve, lapping it, resetting the camchain/timing etc. or by replacing the head with a known good one...either way.

[LoHo]

Oh yeah? How much you wanna bet?

[skids]

I'll bet you a beer, but you have to do all of the work (correctly this time).

[petejw]

I have been wrong before and will do it again just cause I am wrong most of the time. I just had to elaborate on why I thought it was wrong and why I would like to see the test done properly the first time.
The way I was taught was the way I posted. Simple as that. I saw my wrong in the posts and adjusted to the consensus.
A test is a test no matter how you shine a light on it and it must be done correctly to get the right results. I do it my way, and then add different positions to do the job I intended in the first place.
You are more than welcome to do it your way...just know that if you are in my garage you will do it my way. I am kind of a dink that way.

hey ras,
i was just messing around,
ive been proved wrong more than once on here,
is all good, its the only way to learn. :-)

[LoHo]

"(correctly this time)."

There, Skids, is the Achilles heel of your argument...Newcastle Brown Ale, please, and keep 'em coming!

[petejw]

On the other hand, when more experienced mechanics start these pissing contests, I always learn a lot, as they explain why some other guy is full of it and the other guy counters with why the way he learned in 1964 is STILL the most reliable method and blah blah blah.

i didnt see any1 here having a pissing competition,
just a few blokes with differing opinions and thoughts,
no one was arguing about it,
was good u achieved what u were after,
its also good to recieve the correct information, and a
way to learn, also why not take advantage of the mechanics
on the board, its those little things that can make all the difference.