Leak Down Test Procedure

[Motorhead]

Engine on TDC, device for holding clutch from rotating while adding the 100 PSI on (warm engine), but for what length of time should I expect the PSI to hold for % rating ?

What defines a good % versus a not so good % ?

Where on case or engine do I find the TDC markings ?

I realize that I could rotate engine until compression stroke and then continue to rotate until piston is at it's top point, but I am hoping that this engine does have quick visual alignment marks without removing engine covers !

Thanks..

 

[Motorhead]

Nobody ? I have searched this site for hours and could not find the post where someone gave a length of time for each cylinder test for what I thought was out of the yamaha service or maintenance manual. I did find and download the manual but did not find a section pertaining to Leak Down Tests, and under this site's tech pages I did find the procedure for a 2 stroke Leak Down Test but again nothing about time duration for leak %...

I know this was covered under a previous post and I thought you had to leave the 100 PSI for 5 or 10 minutes, and then calculate the loss PSI for a % loss !

I shall continue searching, my leak down test set is scheduled for mid to end week delivery, so I have some time!

Thanks Mooseman, I did order the same unit that you had purchased through Amazon.

 

[BigDog05]

The following procedure is for a 2 stroke, but basically the same.

http://www.totallyamaha.com/snowmobiles ... 20test.htm

 

[Motorhead]

Thanks for the reply BigDog05. 5- 10 minutes it is then. I suppose that 5 minutes and then 10 minutes can be my reference times for leak down %. Hopefully they are much the same at both time intervals.

 

[BigDog05]

I test my turbo sled at the end of every season, but have not done so this year. If I remember correctly the amount of time does not really matter because you are constantly adding air from the pressure side.

The gauge gives you a percentage of leakdown relative to the amount of air put into the cylinder.

Just make sure on a four stroke all valves are closed. Listen for air coming thru the carbs, and the exhaust valves. You may have to rotate a little off TDC to get valves closed.

 

[Motorhead]

Thanks again, now I have it straight, makes much more sense that way !