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One more thing on leak down. On the Yammie, I had to plug the powervalve vent tube they have to keep pressure in the case. I don't know if there would be leakage into the kips. The YZ spews spoo out that tube constantly.

""Tim the tool man" would super glue your crescent wrench wheel, grease your hammer handle and spit in you measly lil under stuffed tool chest for talk'n like that."



I'm sure he would. Then again, MY bike is still running....

How does the amount that I add, not accurately measure what I am losing, if I am setting the level to the same each time? Thanks for the help on putting a leak down tester together I will give that a try and see what percent lost I am at. I dont have time to disassemble for no reason so therefor I ask questions first! Trail time is more valuable than tool time for me.

Tschuss!

A question that may be an aside..but has to do with pressure testing anyway...

What is the design of a KDX crank seal? Generally, seals are designed to keep 'something' specifically in OR out. Is there an angle to the seal lip itself? Which direction is it facing?

Point is there is likely more pressure INside the crankcase that there is pressure in the transmission. I'm using the word 'pressure' to mean both negative AND positive...'cuz both pressure and vacuum are in the crankcase.

My QUESTION in regard to pressure testing..is it possible to correctly do a pressure test..see pressure HOLD in the crankcase ('force' in the crankcase higher than 'force' in the transmission) and STILL have a RH seal leak transmission fluid?

...cuz the TEST is not putting the engine in the state of FAILURE.

OR...does a two-stroke pressure test INCLUDE a vacuum test? It's vacuum that matters 'cuz of what's being sucked in what direction, transmission fluid INTO the crankcase.


Seems it took an awfully long time to get to what my question/point is..hopefully because I was specific and/or explanatory as opposed to mindless and wandering.

..aimlessly even.

Thanks!

Oh...I'm sure there WOULD be leakage thru the KIPS if the exhaust was plugged only at the pipe fitting. I don't think the subport drums are THAT finely machined/matched to the cylinder.

CC wrote " Oh...I'm sure there WOULD be leakage thru the KIPS if the exhaust was plugged only at the pipe fitting. I don't think the subport drums are THAT finely machined/matched to the cylinder."

What CC said is why I believe it is generally acceptable to have 1-2 psig bleed off in 5 minutes on a PV equipped motor. The power valve mechanism o-rings and shafts passing into the cylinder area have changed the way I look at the bleed down test on a 2-stroke. The old air cooled 2-strokes would hold there pressure easily for 5-10 minutes without any bleed off if they were tight.

What you are normally looking for IMO on a bleed down test is leaking base or cylinder head gaskets or reed cage areas (use soap bubbles) and you can also check the left hand crank seal effectiveness. Remove the radiator cap an look for bubbles for a leaking head gasket.

I've haven't done this test for a while but what I liked to use was a mini-mite vacuum/pressure pump. You just needed to install a suitable plug plate on the carburetor manifold (hose) and then plug the exhaust with a rubber plug which has been tapped with a hose fitting to hook up the mini-mite pump.

P.S. Everyone should have a mini-mite type vacuum/pressure pump IMO

CC wrote "OR...does a two-stroke pressure test INCLUDE a vacuum test? It's vacuum that matters 'cuz of what's being sucked in what direction, transmission fluid INTO the crankcase. "

My Ans. Don't know how you would determine where the vacuum leak was coming from. Not going to be able to see the oil entering the crankshaft area.

My thought is that the pressure test 'may' help indicate a right hand seal leak but that some of the pressure lost may be coming through the KIPS actuating shaft down into the right hand case and out the vent tube. So how to you determine what is what?

I would be focused on the periodic 'routine amounts of oil' be added to the transmission without any apparent leaks from the crankcase or vent tube as proof enough that I needed to look at the right hand seal and bearing. Should be able to run the bike 500+ miles without any need to add oil to the transmission.

Getting off in the weeds here..but something to take note of: Depending on what it is you want to test, the position of the piston will matter.

If head gasket integrity is what you're concerned about, you will not be applying any pressure/vacuum to it if the piston is @ TDC (or close to it).

Other testing intentions will be befuddled with other piston positions AND where you apply the pressure/vacuum.

There is no point in saying any of this to anyONE who understands 2T engines and knows what they're doing.

For someone that does NOT understand 2T engine basics, let alone knows what they're doing, using (let alone MAKING one)a leakdown tester isn't likely to tell you anything but, 'The User Now Has a Severe Headache'.