Acceptable leak down numbers

[brewops]

I'm finishing a rebuild on an XLT 1200 and which I had to split the case. Replaced a ton of stuff including crank, all new seals and gaskets, OEM Etc. I've got everything back together and I'm doing a leak down test and am wondering what acceptable numbers are. Found a few things that said no more than one psi per minute. Do a pressure to 8 psi for 10 minutes and measure. To a pressure test to 6 psi for 5 minutes of measure. I went headed to both and came up with the following numbers. For the 6 psi test, I ended up at 4.5 psi after 5 minutes. For the 8 psi test, I ended up at 4.5 psi after 10 minutes. Are these numbers acceptable? I'm having a hard time tracking down the leak otherwise, been spraying soapy water looking for it without success.

[brewops]

I sprayed pretty much everywhere I can reach with the exhaust manifold and carbs on & blocked off. No bubbles on the output side of the crank, I have the flywheel on so I guess that's going to come off next. Really hope it's not that seal since it's new and all back together. Any other ideas? I did also block the exhaust off on the output side of the exhaust manifold originally and it had the same result, so I'm thinking that it's not bleeding from the exhaust to water side...

[RamblinGPR]

I don’t really have an answer for you. I’m testing mine now. Actually it failed the first tests colossally. Easily found the bad leak at the rear crank seal. It’s the only one I found at that time and thought I checked well.

just yesterday I installed the new crank seal, resealed the case and wet at it again this evening. Pressure test resulted in 1 psi drop in 3 min so it was just a little worse than yours. I was ready to just call it good but finally found the #1 TB boot plate leaking. I’ll have another go tomorrow.

check good between the boot plate and the balance plate it bolts up to. I missed this the first time concentrating more on the VF3 adapter plate.

Sorry not good answer, it’s not terrible, and mine wasn’t either but at this point i want near perfection.

[Jonesyfxr]

Did you seal the reed cages?? Did you grease all gaskets during the build, this aids in sealing

[RamblinGPR]

Yep greased them all. Or at least I think I did. Gonna find out.

[Team Bilford]

I test at 6 psi and you should have no loss for 3 mins. That's minimal acceptable. The 2 stroke engines that I build hold the 6 psi for several hours. You must make sure that the leak is not on your test rig as well.

[RamblinGPR]

Thanks, that’s inline with other threads I’ve read, near zero drop for several minutes. I knew I had something going on and kept looking.

I hope th OP finds this gets it figured out.

[RamblinGPR]

I test at 6 psi and you should have no loss for 3 mins. That's minimal acceptable. The 2 stroke engines that I build hold the 6 psi for several hours. You must make sure that the leak is not on your test rig as well.

thanks for the info. I called it after 2 hours and the pressure actually crept up the width of the line when it got hot in the shop.

this thing is tight.

sorry for the hijack, Good info for others, keep looking for leaks. Zero drop is attainable.

[Myself]

I always go 15psi for 15 minutes looking for zero pressure drop.

[brewops]

Digging this up again since things have slowed down enough for me to get back to it. Still not finding it, checked the gauge and such in a bucket of water and if it leaks, its very tiny almost imperceivable bubbles. Reed cages were sealed, new oem gaskets/seals everywhere, grease what I thought was appropriate. This is driving me nuts. Checked both sides of the crank at the seals and it seems fine. Tried even checking the bottom case bolts and dont seem to see it there. Some spots are hard to spray into or see, must be something around there. I might just have to unbolt things and reseal. Not sure what else to do.

[RamblinGPR]

I initially used grease on all intake gaskets. I eventually found the leak at a throttle body boot plate. Looking closely the rubber ridges molded into the flange were kinda chewed up. I resealed with 1211 and that did the trick. It took me a surprisingly long time to find it. It was the worst leak I had. The slight bubbles at the test fitting were insignificant. Once I fixe the crank seal and boot it held with zero loss for 2 hours.

hang in there bud!

[Jonesyfxr]

What was used to seal the crank case halves?

[brewops]

Finally got back to trying to find the leak. I sealed with 1211 and that looks great. I used the same method that I did with a recent trans rebuild for my Polaris side by side. Apply sparingly and spread on the mating surface to ensure it coated. I split the carb spacer apart, cleaned it all up and put new gaskets in but still had a leak. Out of frustration I basically coated the motor in my dish soap spray solution and just listened as hard as I could. Unfortunately/fortunately I found the leak. Under the starter there is a small crack in the case where the soap spray barely touched and I had to use a flashlight to find. It's not near a mating surface, so I'm going to have that welded up locally. That did mean pulling the whole motor apart, but I'm this far in now so I might as well do it right. Glad I didn't just call it good or I'm sure I'd be right back here in short order.

[Jonesyfxr]

If you use some type of grease.. we use wheel bearing, it aids in sealing and prevents leaks. We used Permatex ultra grey seal t on the carb spacer plate to seal it up… it’s impervious to oil and the like.

[jeffg426690]

Glad the op found his leak. Just going to add to this for future folks who go searching. I had an uncommon leak yrs ago on a gpr rebuild that had been un salt and not taken good care of w flushing. The leak was on the water jacket on exhaust manifold, was leaking internally into the water jacket. I had exhaust mani bolted on and sealed where u-pipe mounts. Found the leak by plugging the water in fitting on exhaust mani w my finger and holding there while watching my gauge for cpl minutes and it held then. Found corrosion had found a home on cylinders where exhaust mani mounts. Fixed w JB weld (dremeled corrosion away to good metal, filled in and built up high, took it down w a file and then block sanded for nice flat surface). Held together just fine for yrs. Finding the leak was frustrating to say the least, soapy water all over showed nothing.