Help performing leak down test

So I'm trying to do a leak down test on my '06 Husky SMR 510, and had a few questions....

1. How much PSI do you pump into the cylinder for a leak down test on a bike? Seems like cars use 100 PSI, same for bikes?

2. I had it at TDCC and sat on the bike in 6th gear, held down the foot brake and I could only put in about 35 PSI before the bike starting walking forward on me..... HOw do you keep the motor from cranking when pressurizing the cylinder??

3. I have the American General leak down tester from Harbor Freight which is the 2 gauge type. So I set my air compressor regualtor to 100PSI, then I attached it to the gauges, then I screwed the other part of the tester into my spark plug hole, and then once I was at TDCC and sitting on the bike with brake on, and I connected the gauges to the hose in my spark plug hole. Then I turned the regualtor knob on my leak down tester to start flowing air into the cylinder. It says to turn the knob clockwise until the gauge on the right (leak down percentage gauge) reads "0" problem is, the gauge goes down to 0 when I have only put in about 25 PSI into the cylinder, if I pump more PSI into the cylinder then the gauge goes way past 0, and becomes unreadable... What am I doing wrong? Seems like the gauge on the right should reach 0 at the same time that the regualtor gauge on the left puts 100 PSI into the cylinder right???


Thanks in advance for any help

nevermind, think I got this figured out thanks to youtube! You have to 0 out the leak down percentage gauge before connecting it to the cylinder, which is the opposite of what the instructions say.

Luigic81; What results did you get?
How many miles on the machine?
What is your course of Action?
is it too late to video the operation for posting?

I'm still at work so I won't be able to test it until tonight. I will post the results. Not much to video tape, once you have the CORRECT instructions it's pretty straight forward
The bike has 8600 miles, I am the 3rd owner so I don't know if it has ever been rebuilt, I have no problems with the bike, I had to shim the intake valves once last year. This is more of a preventive measure for me, I want to be ready for a full supermoto season come March without having to rebuild mid-season so I'm doing all work now.

So I just did the test, This tester is kind of weird, so once the tester is hooked up to the air supply, you turn the regulator knob on the tester until the gauge on the right (leak percentage gauge) is at 0, then you wait to see how much it leaks, well I tested it 3 times and my average was about 15%. Thats all well and good except I'm not really sure if the amount of PSI affects the percentage at all. When I turn the regulator on the tester to achieve "0" on the right gauge , the left gauge only shows like 15 PSI...... (The left gauge is supposed to tell you how much PSI in going into the cylinder)
If I add more PSI the gauge on the right goes waay beyond 0 so I cannot get a reading, not to mention that at about 35 PSI the motor cranks over.

So 15% is good enough for me, I did not hear any air escaping from the airbox, nor from the oil fill hole, or exhaust pipe, so thats good. I didnt think there was any problems with the bike, it runs strong, this was more preventative. But I'm gunna call Harbor freight tommorrow and see if I can get their tech guys on the phone, to make sure my 15% reading was accurate.

I have a couple of LD testers and one is a HF. The left gauge on mine is the supply pressure gauge and the other the cylinder pressure.

I would turn the regulator on the compressor up above the test pressure before starting. Next connect the tester and adjust its regulator to the test pressure. Now connect the tester to the hose on the sparkplug adapter. One school of thought is to now readjust the left gauge to test pressure before reading the cylinder gauge and the other to just read the cylinder gauge. I belong to the former.

Fifteen percent isn't good at all. If the bike is running good I don't think it is that high. Make sure you have a good seal at the sparkplug adapter.



I put a ball valve on the inlet of the testers so I can "ease" the pressure to the cylinder and prevent (usually) the piston from moving . I have not tested a Husky but I know the piston has to be exactly at TDC on the things I've tested. Usually I try to put a wrench on a crank nut to make slight adjustments and to help hold it.

I hope this helps a little. A better job of explaining would have been good, but its late and I'm tired.

What model HF leakdown tester do you have? I have their model 94190 and found it to be useless. Never called HF for help though. Here's a link that helps to understand how they're supposed to work. I don't think the HF one I have has the "damper" orifice sized properly to make it useful.

http://www.motorcycleproject.com/motorcycle/text/leakdown.html

The best way to use one is to baseline your engine when new and use the same exact procedure to check it over the life of the engine. What is 15% on one leakdown tester might be 35% on another. And a bad leak on a big cylinder might yield a 20% leakdown number while a bad leak on a small cylinder might yield only 10%. And if you use 50 PSI as the input pressure, the leak % reading will be half of what it would have been at 100 PSI. At least this is my understanding. I have never had a working LD tester so am basing what I say on reading up on the internet rather than personal experience.

Okay, I just did some more reading about this HF tester (at least the 94190 that I have). It turns out that it works a bit differently. It's apparently designed to work with an input pressure of only 15 psi and the instructions are wrong. What you're supposed to do is set the regulator so the gage on the right hand side reads zero --before you hook it up to the engine. The left side gage will read only about 15 psi. Then you connect it to the engine and read the % leakage on the right side gage. That's it. Please post your results and if you hear anything different from HF tech support.

Thats exactly right, and thats the procedure I used
It's the US general brand. HF tech confirmed thats how the test hsould be done. So I'm happy with 15% for now, should get me through another season, or atleast I can avoid a rebuild until I begin to hear the rod knocking (common on 510's) and then just rebuild it once, opposed to replacing the piston now, and then having to shotrly there after replace the rob and rebuild the crank. I will continue to monitor it and do a leak down test throughout the year whenever I check my valves.