angus67
Welder's penetrate deeper!!
you can rent at most auto part stores, and you can use a comp tester too. Some have a fitting like a shrader valve you can pump some air into, the gage will read, and theres your tester.
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Top end rebuild (inquiry)
- Thread starter cobrasneverdie
- Start date
cfdfireman1
XS650 Member
Compression tester with a 1 Tbs. of oil on the second try will do pretty much the same thing as a leak down tester.
NONclow
Confirmed Laquer Breather
Used in conjunction with a long piece of hose, one end near your ear, and the other probing for leaking air noted by % psi drop: at the intake, the exhaust, and the crankcase. It can also narrow the prob to a single, sticky, carboned up valve, which cannot be located with a tbsp. of oil.
This thread has already degenerated to usual 650.com mix of good advice from experienced hands and rookie bullshit, so I'll keep this short. 1. When you're using a leak down tester on a twin cylinder motor, LOCK DOWN THE CRANK. 2. If a leak down tester doesn't enable you to compare inlet pressure to outlet pressure accurately, it's useless. 3. When using a leak down tester you are well advised to use a water separator and filter in the line; you don't want moisture and garf blown into your cylinder any more than you'd want it in your paint. 4. Will those who have not actually used a leak down tester please STF up on that subject.
Just a "few" thoughts on leak down .
My gauges are 3" in diameter .
You should seriously consider checking at various points before and after TDC .
Use leak down testing to verify break in . I use time to temperature from cold iron then verify with leak down at temperature as well as cold iron . As time to temperature increases and leak down decreases then all is well .
One quick note on bore finish . I bore to within .00125-.0015 , hone to SIZE +-0 with 220-240 , hone to CLEARANCE with 320 . This leaves a plateau for the rings to seal and slide on and a slightly deeper scratch/groove for oil retention . Do what ever your little heart desires but this has served me well . Again this is opinion and should be taken as such . I keep telling you that I could very well be full of shit . Are you paying attention ?
Leak down can be a very useful tool . As jargon its fairly useless .
~kop
My gauges are 3" in diameter .
You should seriously consider checking at various points before and after TDC .
Use leak down testing to verify break in . I use time to temperature from cold iron then verify with leak down at temperature as well as cold iron . As time to temperature increases and leak down decreases then all is well .
One quick note on bore finish . I bore to within .00125-.0015 , hone to SIZE +-0 with 220-240 , hone to CLEARANCE with 320 . This leaves a plateau for the rings to seal and slide on and a slightly deeper scratch/groove for oil retention . Do what ever your little heart desires but this has served me well . Again this is opinion and should be taken as such . I keep telling you that I could very well be full of shit . Are you paying attention ?
Leak down can be a very useful tool . As jargon its fairly useless .
~kop
sevens0n
XS650 Member
I tried a leak down tester once. I thought I would make it simple to calculate % leakage so I set 100# pressure on the input regulator. Then the other gauge would read the percent "Keep-age" I figured... easy. Put a breaker bar on the rotor nut and bring it up on compression, Well I couldn't hold it tight enough, breaker bar kept trying to throw me on my can. 
It didn't dawn on me at the time, so I gave up on the test. Would I be correct in thinking that was way too much pressure? I'm thinking that if you used maybe 10-20# pressure you might be able hold it hard enough to do some diagnostics on any leaks...
In other words... Lock the crank!
It didn't dawn on me at the time, so I gave up on the test. Would I be correct in thinking that was way too much pressure? I'm thinking that if you used maybe 10-20# pressure you might be able hold it hard enough to do some diagnostics on any leaks...In other words... Lock the crank!
No, 100 psi is not too much pressure. Low pressure testing would yield questionable results. Your mistake was trying to hold the breaker bar manually. Just put a cheater on the breaker bar and brace it against the floor. I made my tester with a shut off valve on the output end so that pressure can be applied slowly and I can turn off the air if anything looks like it's going to do a comealoose.
3" gauges, Kop? Jeez, I thought I was AR!
3" gauges, Kop? Jeez, I thought I was AR!
...and oil filled .
~kop
~kop
sevens0n
XS650 Member
Thanks Kop & Griz. Good info and insight. I'm learning something here! A valve on the output side is a very good idea indeed. Wouldn't want to have an out of control "comealoose" Have this vision of bike jumping up in the air, flopping down on it's right side, and a 4 foot cheater pipe whipping around and smacking me in both knee caps. ....
Maybe one could fabricate some fixture to hold the tranny output sprocket ? Or even just the rear wheel somehow? Would allow you to index the crank BTDC & ATDC easily, as Kop suggests.... Just got me "a-think-in"
Thanks again guys....
Have this vision of bike jumping up in the air, flopping down on it's right side, and a 4 foot cheater pipe whipping around and smacking me in both knee caps. ....Maybe one could fabricate some fixture to hold the tranny output sprocket ? Or even just the rear wheel somehow? Would allow you to index the crank BTDC & ATDC easily, as Kop suggests.... Just got me "a-think-in"
Thanks again guys....
If you google "Lycoming leakdown test", you'll see the FAA procedures, and others.
I would put a cylinder at TDC, then place my prop blade on my padded shoulder, and clamp down on it with my hand. Other hand would work the tester. Moving the prop up/down a few degrees would give an idea of the condition around that critical TDC position. Gotta be vigilent though, 100 psi on a 5" piston is about a ton of downforce on the piston.
100 psi on an XS650 piston puts about 700 pounds of downforce on the piston. You'll want something solidly clamped to the crank, perhaps a wood/leather form-fitting clamp around the exposed rotor, with a 3' arm. Or at least a long, snug-fitting no-slop rotor nut wrench.
I would put a cylinder at TDC, then place my prop blade on my padded shoulder, and clamp down on it with my hand. Other hand would work the tester. Moving the prop up/down a few degrees would give an idea of the condition around that critical TDC position. Gotta be vigilent though, 100 psi on a 5" piston is about a ton of downforce on the piston.
100 psi on an XS650 piston puts about 700 pounds of downforce on the piston. You'll want something solidly clamped to the crank, perhaps a wood/leather form-fitting clamp around the exposed rotor, with a 3' arm. Or at least a long, snug-fitting no-slop rotor nut wrench.
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Rotor bolt? Come on, 2Many, you know better than that! Socket on rotor nut, breaker bar on socket, cheater pipe on breaker bar, cheater bar against floor; it doesn't get simpler. BTW, you want to set the crank just a little bit off TDC so you'll know which way it will try to move when the pressure hits the piston.
sevens0n
XS650 Member
Did some homework...
http://www.lycoming.com/Portals/0/t...I 1191A (09-28-1998)/Cylinder Compression.pdf
http://www.dansmc.com/leakdown.htm
I'm learning a few things. Not the least of which is that " I.D.K.S."
I played around with my with my Dad's leak down tester once. He had Lycoming engines in his homebuilts. so I suppose that's what my (inherited) tester is designed for.
I'm taking the best advice, going to STF-UP on the subject until I get some more hands on experience.
Will be trying some of this stuff with my new motor break-in.
http://www.lycoming.com/Portals/0/t...I 1191A (09-28-1998)/Cylinder Compression.pdf
http://www.dansmc.com/leakdown.htm
I'm learning a few things. Not the least of which is that " I.D.K.S."
I played around with my with my Dad's leak down tester once. He had Lycoming engines in his homebuilts. so I suppose that's what my (inherited) tester is designed for.
I'm taking the best advice, going to STF-UP on the subject until I get some more hands on experience.
Will be trying some of this stuff with my new motor break-in.
Attaboy! That 60° orifice inlet angle is simply the countersink opening into the orifice, similar to the cone-shape countersink opening in your idle jets.
We'd use 100 psi inlet, with 80 psi outlet as the limiting criteria. If a Lycoming or Continental came up with less than 100/80 on any cylinder, then the engine would fail inspection for 'fly-for-hire' commercial operation. For private, non-commercial operation, the owner would be strongly advised to get at least a top end overhaul, for at least that cylinder. 100/60 was definitely a no-go...
cfdfireman1
XS650 Member
OK.... I did the compression test and the numbers are low. I added oil to the cylinders and repeated the test and the numbers are still low. Should I source a leak-down tester rent a compressor and test further or just bite the bullet and pull the head?
Why not?
I'm pulling it anyway at this point.
Why not?
I'm pulling it anyway at this point.
Jw801
XS650 Member
I am trying to get to my cam and i have removed all of the nuts on the top of the cover, it wont budge, so i got the motor hot (let a hair dryer blow through the cam shaft for about an hour) still wont budge. I (gently) tapped into the space where the cover meets the rest of the motor with a flathead to break up any liquid sealer and i can see all around the bottom of the cover, but it still wont slide up off the bolts... Any ideas?
I am Carbon
shade tree mechanic
remov all 8 nuts and 7 bolts
if you haven't loosened the valve tappets just turn the engine over and the valve springs probably will push the cover up. that has worked for me.
