[Warrencl224]

Hi guys. Any tricks and ideas on how to pressure test a crf250x head after installing new valves? Want to make up so sort of jig so i can do it in the future.

[JimDirt]

If the valve seats were correctly cut then there should be no need to pressure test , unless of course you are wanting to pressure test the fresh head with a worn one to determine or compare the difference in loss if any , if that is the case then i would say do it like they do with automotive heads and make a plate out of thick lexan (1 inch or so thick) and stud it or use nut/bolts , use either with large washers on the plate side with O-Rings to assure sealing thru the threads/holes , so you can tighten it down to the head and assure the combustion chamber is sealed (you could if you find it leaks , add a head gasket , and/or you could also use a 1/4" or thicker Steel plate , but the Lexan would be easier to drill and cut down to size) , then thru the spark plug hole , insert/screw in the adapter hose from a Leak Down Tester (you will need a Leak Down Tester to be accurate) , and use the Leak Down Tester as your guide , as they are made to test from the plug hole , and find any leakage , you can then accurately monitor any pressure loss either immediately or over time (24 hr , etc) from the valve seats ....

I use my Snap-On Leak Down Tester at about 100 P.S.I. on my bikes with the head on the bike/completely assembled and ready to run , as i can then tell if there is any ring or gasket leakage as well as valve sealing issues ...... same way it is used in automotive applications , but if your wanting to "bench test" then you will need a plate of some sort to seal the combustion chamber

[Aussiecrf230]

I have always found that with the head inverted, to fill chamber with alcohol. If that doesn't leak out through to the ports you are good to go. Checking with prussian blue prior to assembly shows where the contact patch is located an confirms it is evenly mates across the seat. I am talking methylated spirits not wild turkey to do the checking.