Hey Everyone,

I’m wondering what the conscious is on the right way to do a leak down test. With the engine warm or with the engine cold, and why?

Thanks in advance and Merry Christmas.

 

Why not just do both and compare the results, keeping in mind parts will expand and clearances typically diminish when hot.

 

I plan on it. I was just after the opinion of those who know such things in a effort to continue learning about my bike.

 

I'm using the leakdown tester from Jims. Have a look a the instruction page from JIMS. Even it's not explained why you shall do it hot, it's a very comprehensive guide.

Hope it helps!

 

I've found over the years, Harleys have a high leak down rate (compared to automobile engines) Still seem to run ok...

 

True. The service manual on late model bikes say up to 25% is OK.

 

I always did it cold. Sometimes it’s a non run situation or new engine pre-install so warming up isn’t an option at best slightly warm. It sucks pulling plugs on a hot plug. Most specs you find should be cold numbers.

 

Damn, that's a lot! I seem to recall seeing between 5 and 10 percent on my Evo.

 

Yep. I have a screen shot of the 2018 service manual somewhere. If I'm lyin' I'm dyin'!

Edit - found it in the 2020 service manual:

 

That's crazy.....

In my 2001 & 2003 Service Manuals it calls for a max of 10%....