TRX250R.ORG

Workshop => Engine and Bottom End => Topic started by: aberegg05 on March 08, 2014, 07:14:35 PM

Title: leak down test?
Post by: aberegg05 on March 08, 2014, 07:14:35 PM

Is it better to do a leak down test on a fresh motor or after the initial break in?

Title: leak down test?
Post by: Morse250r on March 08, 2014, 07:58:17 PM

Fresh !

Title: leak down test?
Post by: 4WHLr on March 08, 2014, 09:07:29 PM

Yes, pressure test it before it comes off the work bench, for a fresh build

Title: leak down test?
Post by: Langbolt on March 09, 2014, 10:40:13 AM

The reason you do a leak down test is to see if all the seals & gaskets are doing their job....if you have a leak and don't know it, you might not make it through the break-in! (too lean)

Title: leak down test?
Post by: aberegg05 on March 09, 2014, 01:06:43 PM

I got ya. I thought  if the motor got warm the seals and gaskets got hot they would seal better after the very first heat cycle. Thanks. Will wait to fire it up until I i to the leak down test. Ill have to yank it back out of the frame.

Title: leak down test?
Post by: Jerry Hall on March 10, 2014, 09:58:58 PM

If you have an air leak that is severe enough to hurt your engine you will know it when it runs.  Very small air leaks will cause the engine to have the Ring-Ding-Dings as the RPMs decelerate after blippng the throttle.  If the air leak is more severe, the engine RPM may hang at a high RPM or the RPM may continue to climb even though the throttle is closed.


The above statement is only true if you carburetor's low speed jetting is in the ball park.

Title: leak down test?
Post by: Jerry Hall on March 11, 2014, 10:49:11 AM

Quote from: aberegg05;28323

I got ya. I thought  if the motor got warm the seals and gaskets got hot they would seal better after the very first heat cycle. Thanks. Will wait to fire it up until I i to the leak down test. Ill have to yank it back out of the frame.

I have seen crank seals that are worn on the "suction lip" of the crank seal leak when the engine is cold and seal when the engine is hot.  I have not observed temperature affecting a gasket's ability to seal.

Title: leak down test?
Post by: Rupp250 on March 11, 2014, 11:37:49 AM

You don't have to remove it from the frame to do a leak down.

Title: leak down test?
Post by: aberegg05 on March 11, 2014, 11:44:57 AM

Well I just did my leak down. Started at 7 1/2 lbs and only went to 4 lbs in 8 mins. Good or bad???

Title: leak down test?
Post by: Tbone07 on March 11, 2014, 12:41:35 PM

That's probably a little more of a loss than you want. Is this a PV cylinder?

Put some pressure in it and get some dish soap and warm water to find your leaks

Title: leak down test?
Post by: F-Red on March 11, 2014, 12:49:02 PM

^^ Agreed. Too much of a loss. Right now, dish soap is your best friend.

Title: leak down test?
Post by: rablack21 on March 11, 2014, 01:30:29 PM

Also make sure it is not leaking from your actual pressurizing device in the intake boot.

Title: leak down test?
Post by: aberegg05 on March 11, 2014, 01:58:00 PM

I checked the Intake boot. Im leaking around the base gasket. Im gona use a little sealer and see what happens. Thanks everyone.

Title: leak down test?
Post by: supernutt on March 11, 2014, 06:42:52 PM

Had a tough time with my base gaskets also.  Also my spacer plate was not even close to flat.   Used 3 bond 1211 on my base gaskets and the center crankcase gasket.  Mine held 7psi for 3 days when I was done!!!

Title: leak down test?
Post by: aberegg05 on March 11, 2014, 09:09:31 PM

Put some rtv blue on her. Will try another test tomorrow.

Title: leak down test?
Post by: aberegg05 on March 13, 2014, 12:01:16 PM

Leak down test successful! Held 7 lbs for over six minutes. No more leaks at base of cylinder. One tiny leak on my tester. My 344 is air tight. Thanks for the help guys.
Matt

Title: leak down test?
Post by: rablack21 on March 13, 2014, 12:35:50 PM

Quote from: aberegg05;28802

Leak down test successful! Held 7 lbs for over six minutes. No more leaks at base of cylinder. One tiny leak on my tester. My 344 is air tight. Thanks for the help guys.
Matt

Awesome! Now you are good to go, and you learned something. Good job.

Title: leak down test?
Post by: johnny22 on March 13, 2014, 06:15:33 PM

that 3 bond stuff on the base gasket is a pain in the butt when you go to take it off again. I hit my self in the face with the studs on the top trying to get it off once haha it sucked