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leak down test help needed
Posted: 12:20 am Aug 18 2018
by kdxdazz
so finally got my DIY leak down tester made up,started pumping and the needle wouldn't even move,sprayed soapy water everywhere and noticed bubbles coming from the carb boot where it joins the reed cage,pulled it off and noticed somebody has ground away the plastic in the reed cage so much that the carb boot has nowhere to seal,my bike is a kdx220sr and i assume the plastic in the read cage was ground larger to allow for the now 36mm carb but obviously no consideration to sealing was given,i made a gasket from 3mm industrial rubber which worked well. i started pumping again and the needle on the gauge finally moves but won't hold air for more than 10 seconds,sprayed again and saw and could hear air leaking from the right hand side powervalve cover. my question is how do i get this to seal so i can continue to check crankcase seals. i know i will have to take the top end apart at some point but would like to know the condition of the seals before i do this
Re: leak down test help needed
Posted: 01:36 am Aug 18 2018
by KDXGarage
Is there not a seal on the power valve?
What PSI?
Re: leak down test help needed
Posted: 06:06 am Aug 18 2018
by kdxdazz
There is a seal on the power valve but it leaks. How critical to jetting is this. I made my leak down tester from a blood pressure testing kit so I think only goes up to 5psi but as stated right now the engine won't hold anything
Re: leak down test help needed
Posted: 07:38 am Aug 18 2018
by John_S
5 psi should be fine once you can get it to pump up. Try checking the tester itself for leaks. It's not easy but plug the end with the palm of your hand and squeeze as hard as you can. Pump it up to 5psi and submerge it. Make sure even the pump bulb goes underwater. The smarter thing (which I didn't do) would be to get a rubber cap that you can clamp on and plug it, then test it underwater.
If that power valve seal is leaking that bad you don't have many options. It's time to tear down the top end for at least new gaskets. I've had good luck with the $16 Tusk top end set. It includes those two seals for the kips shaft that you're talking about. Jetting it with an air leak is a waste of time. It might leak worse when the engine is cold or hot so the jetting is all over the place.