Leak Down Test

When a leak test is done, I am assuming that the cylinder needs to be at TDC?

What are some of the better testers available?

This is the one that I want too!

http://www.summitracing.com/parts/otc-5609/overview/

I hate that when that happens.

LOL, once you break the seal,it's 1 leak every 2 beer

Also show if you have an intake or exhaust valve leak...

Leak down test is a great way to find poor sealing valves and ring issues. I know on a car you test from about 75psi to 100, putting compressed air into your cylinder when it has been rotated to TDC compression stroke. On a bike with less reciprocating mass in its engine maybe 55-80psi? with a steady flow of regulated air you listen and feel for air at your throttle body, exhaust pipe, or breather tubes. I use a MAC tools CLD200M and it works fine, with directions and expected results on inside label. BaggerPaul or that Prodrag guy could likely nail down the proper air pressures for a bike engine. MAKE SURE BIKE IS IN NEUTRAL! If the engine rotates from too much air it might fall off stand. Hope this helps.

I am thinking about using about 90 psi and it was suggested by BaggerPaul that I back off both off the pushrods completely so I have no doubt that both valves are closed. As far as my bike falling off the stand, that won't happen as I have alift table. LOL, but I will put it in neutral. Check the link above, that is is the one that I am going to get. FWIW, the 10 psi difference is in the front cylinder and is the low one. Also there is something that I am seeing that is alarming me to do this. I am being thorough. Thanks for the advice dude!

FWIW...Pump it to 100psi,that way makes it easier to read the % leak down,no gazinta's to figure out

Here's a how to JB...

http://www.dansmc.com/leakdown.htm

lol, I was going to, just bullshitting you.. LOL

Another idea if you do find something amiss is buy or rent a boroscope to inspect the valves, seats and pistons visually. They have really come down in price the last few years and with some you can download their vids to your computer to email your builder. Good luck with it. Lucky you have that kickass Sportster to ride in the meantime!

BTW, if you back off the pushrods, won't that be not a true representation of the engine in running condition? I understand why you would, but if you had a misadjusted pushrod causing your issue and you backed em off before you test, you would never find the source of the leak? JMO. Not trying to step on ideas from proven builders, just wondering.

I am all for having cool toys to play with but that seems to be a stretch for me to justify something like that. LOL thanks, I like my Sportster too!

The whole point of collapsing the pushrods is to leave no question that both valves are closed. Remember a thing called valve overlap? There is no way to really ensure that you are truly at top dead center by doing it by hand. Also, I am not trying to emulate actual engine running condition with a leak test, simulating running condition was done with the compression test when I actually spun the engine. If I do a leak test and I have backed off the valve adjustment and I am hearing air escape from somewhere, (i.e. carb or exhaust, case), I then know where the issue is and then can fix it.

You are right, BaggerPaul is awesome. He knows his stuff and he has taken the time to fill my head with a lot of no bullshit straight information. He took the time to come here to Minnesota and help me with this project. Hell did yolu read my build thread? He thinks that I am going about this in the right way, although he doesn't think that there is anything really wrong, but again, we really do not know considering I have no baseline to work from.

There is a quick way to ensure TDC by hand that I use, use your compression tester hose with no Schrader valve in it, put a balloon on the end, turn motor until balloon inflates itself, then when almost at TDC, remove "balloon gauge" and find TDC with an indexed steel rod. I've been reading Baggerpaul's posts since I joined here, he really sounds like he knows his stuff, this Harley bike stuff is recent to me, sorry if some posts sound uninformed. I'm learning as I go. He flew out to your place? That is very impressive!

Yes, I flew him up here to Minnesota and him and I put this bike together basically with hand tools in the cold. LOL. Paul and I talk pretty close on a daily basis either via text or talk. I trust him very much as he has never steered me wrong.

Check this out. It is long but a lot of good information there. http://bike-talk.com/threads/88-ci-to-98-ci-upgrade.17848/

Many of us learn as we go - I'm still learning, too. I haven't done a compression test on my shovel since the heads were totally rebuilt & the cylinders honed and Hastings rings installed. It runs better and hits hard for a 36 year old motor and . . . that's good enough for me.

Hope you find out what the problem is . . .