CB360 - Clean and simple
- Thread starter tnum
- Start date
Leak tester came today
Torqued the head down
Checked the left cylinder
Looks good
Right (scratched) cylinder
However a lot of air was blasting out of the intake port so I thought maybe I had another bent valve or something
Pulled it all back apart to check the valve
The valve and seat both looked fine and not bent. Wiped everything clean and put it all back together.
Checked the right side again
Success!
Must have just had something between the valve and seat?
So the numbers are ~10-11% loss on the left side and ~11-12% loss on the right (scratched) side. Keeping in mind I did these checks at bottom dead center, I'd say they are very acceptable and the scratch is going to be a non-issue.
Also cleaned up the spark plug threads when I had the head back off
Torqued the head down
Checked the left cylinder
Looks good
Right (scratched) cylinder
However a lot of air was blasting out of the intake port so I thought maybe I had another bent valve or something
Pulled it all back apart to check the valve
The valve and seat both looked fine and not bent. Wiped everything clean and put it all back together.
Checked the right side again
Success!
Must have just had something between the valve and seat?
So the numbers are ~10-11% loss on the left side and ~11-12% loss on the right (scratched) side. Keeping in mind I did these checks at bottom dead center, I'd say they are very acceptable and the scratch is going to be a non-issue.
Also cleaned up the spark plug threads when I had the head back off
The best way to test for leaky valves is to fill the chambers with isopropyl alcohol and look for seepage. There should be none. A little wetting of the edges of the valve is okay (not ideal), but no drip should be seen. And a leak down test is supposed to be done at TDC. That's where compression is important.
irk miller said:
Interesting, does it matter what grade of isopropyl alcohol you use?
Agreed that the leak down test is supposed to be at TDC but since I scratched the cylinder and it only goes half way up, but is visible at bottom BDC, I wanted to check to see if there was any significant blow-by when it was involved. Then of course I checked the other cylinder at BDC to have an accurate comparison. Plus I don't have the cam in yet so the valves weren't open regardless and trying to do the leak down test at anything other than BDC would have resulted in ending up at BDC very shortly after applying pressure.
I don't think it matters much. I use 90% Isopropyl, but some people use denatured because it lacks water. Others use acetone.
cardinal said:
Thanks!
I looked into used lathes but they were either outside of my price range or outside of my size range.... I think this cheap one is a pretty decent foundation as long as your willing to invest a bit more time and money (mostly time) into it once you get it. The motor mount definitely needed work and overall it pretty much needs to be completely disassembled and reassembled as soon as you get it to make sure everything that should have grease has it and all the bolts are tight (a surprising amount of them were not even finger tight on mine)
The real test will be trying to turn a new 4130 axle 8)
This handle unscrews when using it, and is a little hard to grip...
So I made this one to replace it:
It has a bushing (which I also made) to let it spin without loosing the screw:
Fits extra nice:
Anyway, makes the lathe nicer to use and gave me some practice creating knurled pieces (handle bar grips? foot pegs? who knows? : )
So I made this one to replace it:
It has a bushing (which I also made) to let it spin without loosing the screw:
Fits extra nice:
Anyway, makes the lathe nicer to use and gave me some practice creating knurled pieces (handle bar grips? foot pegs? who knows?
: )
I love how you just bought a lathe and got stuck in! Fantastic stuff. Loving the work you're turning out too
The biggest issue with the cheaper Chinese lathes is usually the way the ways are designed and made.
crazypj
Split personality, I fake being smart
irk miller said:
The 'correct' way to do it is fill port not chamber. Filling chamber really doesn't show anything other than major leak, having head 'on end' and filling port shows even the slightest weep around valve. I use acetone, if it doesn't leak, you know it's 'good'
Nice work on the brake adaptor
crazypj said:The 'correct' way to do it is fill port not chamber. Filling chamber really doesn't show anything other than major leak, having head 'on end' and filling port shows even the slightest weep around valve. I use acetone, if it doesn't leak, you know it's 'good'
Nice work on the brake adaptor
Do you think this needs to be done in addition to the leak test? or is that just a good way to do it if you don't have a leak tester?
crazypj
Split personality, I fake being smart
If you have the head off it's the correct way to check valves for sealing.
A leakdown tester is used before stripping motor to give customers an estimate or pinpoint where head is leaking. (intake/ exhaust valves, gasket or piston rings
For a DIY'er leakdown doesn't really matter so much as your either going to take it apart to fix or 'offload' to someone else. About the only time it's handy is when you know there is a problem but motor still runs, gives an idea if it HAS to come apart or could wait another month or two
A leakdown tester is used before stripping motor to give customers an estimate or pinpoint where head is leaking. (intake/ exhaust valves, gasket or piston rings
For a DIY'er leakdown doesn't really matter so much as your either going to take it apart to fix or 'offload' to someone else. About the only time it's handy is when you know there is a problem but motor still runs, gives an idea if it HAS to come apart or could wait another month or two
