I'm gonna do a leak down test on my Pro this week. What would be an acceptable leak down percentage for this motor?
Leak Down Test?
- Thread starter SpeedWobble
- Start date
umm...I have never leakdown tested a 2 stroke..on a 4 stroke we normally tore them apart for repair if we saw anything close to 10% with oiled rings(squirting a little oil in to seal the rings)..normally a leakdown is more for testing valve seats/quides then rings(simple compression test is adequite for rings normally)..but it should show your ring leakage as well....
we have always leak down tested our motors to check our ring seal. dont know if its an accurate measurement or not, but its not unusual to see numbers between 10 and 15 percent on a freshly rebuilt motor.
yeah speed, without oiling the rings I would imagine you would see that much on a fresh engine...and I suppose if you did check on a fresh rebuild and periodically there after it would give a fair idea on the condition of the rings...we mainly used a leakdown to check valve to seat seal on our big block chevy race motors that we were zinging the rpms on..running very small stemmed titanium valves(11/32" stems on a 2.4" intake, 2.00" exhaust valves) on a big roller cam(.822" intake and .865" exhaust lift) we were on the constant look out for signs of light valve float(valves tapping a piston dome), stuff that you could miss on a compression test would show on a leakdown...it was a constant battle keeping the valvetrains in running so much rpm..
A buddy of mine used to work with some independent racers who worked out of some of the big name performance shops back East. One of the things he came back with from that experience was the importance of a leak down test versus a compression test to evaluate the ring seal. Can be a good indicator of worn or flaking rings.
Happy Sledding!
Happy Sledding!
The following was taken from out leak Down Tester instruction sheet:
Cylinder leakage on a new engine or good condition cylinder walls and piston rings should be
within the 5% to 15% range and is best for power. Good service from the engine can be as much
as 25% for average use. Over 25% would be recommended to install new rings and pistons if
needed. Check cylinder for excess clearance, out of round or taper, repair as needed.
Personally, I would not let a motor get to 25%. After 15%-20% I would be going through it.
Dustin
Cylinder leakage on a new engine or good condition cylinder walls and piston rings should be
within the 5% to 15% range and is best for power. Good service from the engine can be as much
as 25% for average use. Over 25% would be recommended to install new rings and pistons if
needed. Check cylinder for excess clearance, out of round or taper, repair as needed.
Personally, I would not let a motor get to 25%. After 15%-20% I would be going through it.
Dustin
SLP leak Down Tester link:
http://www.slp.cc/catalog.cfm?pageID=detail&view=description&catalogID=3&catID=24&productID=237
http://www.slp.cc/catalog.cfm?pageID=detail&view=description&catalogID=3&catID=24&productID=237
I
Let's not forget that crank seals can compromise these numbers so the seals should be inspected and observed during the test.
Hopefully I will get a chance to leak down test next week. Sled is currently at dealer awaiting new injectors and TPS.
W
I don't think the crank seals have anything to do with a cylinder compression leak down test.
