Performed a leak down test tonight and it's failing. I plugged all exhaust and intake ports, I'm pressurizing through the left side spark plug and here's what happens. The gauge sits there stable for a moment or two then drops a tick, then sits there a moment again, then drops another tick. It loses a psi in about 30 seconds. The frustrating part is that I can't tell if my test is flawed because I haven't found any clue as to where the air is going but it has to be going somewhere. Plugging the left side intake is difficult as there isn't much room for the plug and I tried also putting the boot on that side and plugging it. Same thing. I can't hear air hissing from anywhere. I sprayed some WD-40 around the gaskets with no luck.
I'm not ready to call it definitively bad crank seals because there's multiple possible points of possible failure in the test itself and no idea where the air is actually leaking yet.
At any rate, I feel like more money out the window and I've learned nothing after several hours trying.
Put some water in an almost empty washing up liquid squirty bottle and squirt that around, then watch for bubbles.
Better than wd40 for finding leaks as the bubbles stay there for ages.
Think of how stupid the average person is, then realise that half of them are more stupid than that.
Thanks, I'll give that a try. My girlfriend just said "I told you so"...
I haven't tried it from the right side either. Should I be performing the test on all three cylinders or perhaps give the middle a shot if I can get to it? Now that I think about it, it seems like if trying to determine if the crank seals are bad or not, testing the middle might make the most sense...?
Don't put more than 4 psi or you will DAMAGE your crank seals!
If your pressurising the left cylinder you are only testing the left cylinder. They are not connected and each must be pressurised and tested seperately.
Welp, take two for identifying where the air is escaping was as successful as take one. Not. At this point I have zero confidence in the validity of the test as I have little confidence that it isn't just leaking around the expansion plugs in the exhaust ports which don't work well, regardless of being the proper sizing. I could make plates but I'm also not all that confident that it isn't leaking around the spark plug adapter where I'm pumping the air which does have an o-ring but who knows.
At this point I'm giving up on the leak down test as "inconclusive" and will finish up the rebuild of the front disc caliper once the last part arrives and then do the carbs this fall. If it still runs less-than-all-that-great I'll have to make the decision to live with it or sell it because I don't really want to pay to have the motor rebuilt nor really want to attempt it myself.
Thanks, I did submerge the connections in a bowl of water and no bubbles. I could dunk the bike in a swimming pool and look for them...
For now it's going back together and between now and whenever I do the carbs I'll come up with a more definitive way to seal the ports and will give it a go again down the road. Thanks guys for the help!
