14 replies to this topic

[KurtM]

I bought a new, cheap compression gauge from autozone to psi test my 500ss, my buddy's 600 mxz, and my wife's venture 600 triple before putting getting them ready for the off season this weekend.

Did all three sleds stone cold 1st. My bud's mxz has the same base powerplant as my gsx...his has over 7k miles as its a 99 and my 04 has just under 4k miles on it. The readings on the 99 were 136 and 137(repeated twice for accuracy) on one cylinder and 141 and 142 for the other.y 04gsx registered 148/149 on left and 150/150 on right. My wife's yammi triple got 135/135, 135/136, and 136/137 on the 3 cylinders. I did have to start my buddy's 99 up to move it and after warming up the readings were pretty much the same.

At this point, i'm figuring all 3 have at least another season before I have to retest and maybe crack em open, but wanted to make sure there isn't any other testing I should do.....any advice?
tia,
kurt
mathman

[Yamadoo500]

Those readings all sound pretty good, especially the 500ss. They should all have a few seasons left in them, those Yamahas will go forever.

[KurtM]

Those readings all sound pretty good, especially the 500ss. They should all have a few seasons left in them, those Yamahas will go forever.

thanks! I figured all sounded ok. That means maybe I can use my off-season savings plan to get at the shocks of my gsx, hopefully!
\kurt

[Rev SDI]

I'm not a expert on this, but from what I've read on diff threads you should do a cold test and then a warm test to see what kind of drop off you have, not hot.... just warm maybe five minutes not much more. If I remember correctly more than 10% drop would indicate need for rings. now this is what I've re-searched and am logging at the beginning of the riding season and end of the season.

Good luck,

[grover]

You can also do a leak down test to check the rings also. Easy to do to check condition of the rings.

-Grover

[TwoRevs]

You can also do a leak down test to check the rings also. Easy to do to check condition of the rings.

-Grover

I think he meant "leak down test to check the crank seals". It will also test y-pipe and carb boots for leaks. Compresion test does rings.

[grover]

I think he meant "leak down test to check the crank seals". It will also test y-pipe and carb boots for leaks. Compresion test does rings.

Not quite true, there is a leak test to check engine/seal leakage like what you're reffering to. This uses the compressed air thru a guage and into thru your spark plug hole and you bring up the piston to tdc and you measure the pressure the cylinder holds vs. the leakage past rings as a precentage(above 15% would be a concern), can be used to check other leakage issues in the upper end as well in other applications. You can use this test to see if the rings have seated in a rebuild or worn in a older motor. Not a expensive setup(there were some posts from a few years ago on making your own) JEGS has them for a reasonable price.

-grover

[DOO_TINT]

Not quite true, there is a leak test to check engine/seal leakage like what you're reffering to. This uses the compressed air thru a guage and into thru your spark plug hole and you bring up the piston to tdc and you measure the pressure the cylinder holds vs. the leakage past rings as a precentage(above 15% would be a concern), can be used to check other leakage issues in the upper end as well in other applications. You can use this test to see if the rings have seated in a rebuild or worn in a older motor. Not a expensive setup(there were some posts from a few years ago on making your own) JEGS has them for a reasonable price.

-grover

that is for 4 stroke engines

[grover]

that is for 4 stroke engines

Its also used on two strokers. Ask Kelsey,& Cudney especially back when we were having ring flaking issues(do a search) with the 'Doo rings pre '04's. This a good tool to check if the rings were starting to go even with so called good compression with just checking with your compression guage. I had a DI kit from RKT and was ask by Kelsey to keep an eye on the leak % rate to see if the rings had seated when he knew I had a tester. He had a change from a supplier and wanted to see if the rings were seating, mine were not and sent me another set. So yes this type of tester is used on the two strokers and a very good way to test fitness and catch subtle issues(especially rings) that you wouldn't with "just" checking compression .....

Also remember there "alot" of variables in just checking compression

Here:


http://www.dootalk.c...h=1

http://www.lafishmag...DownTester.html






-Grover

[blueracer]

Its also used on two strokers. Ask Kelsey,& Cudney especially back when we were having ring flaking issues(do a search) with the 'Doo rings pre '04's. This a good tool to check if the rings were starting to go even with so called good compression with just checking with your compression guage. I had a DI kit from RKT and was ask by Kelsey to keep an eye on the leak % rate to see if the rings had seated when he knew I had a tester. He had a change from a supplier and wanted to see if the rings were seating, mine were not and sent me another set. So yes this type of tester is used on the two strokers and a very good way to test fitness and catch subtle issues(especially rings) that you wouldn't with "just" checking compression .....

Also remember there "alot" of variables in just checking compression

Here:


http://www.dootalk.c...h=1

http://www.lafishmag...DownTester.html






-Grover

It's called a differential pressure test. It is measured as a percentage of input pressure (usually 80 psi). I have never used this test on a 2 stroke before, but it works great with 4 strokes. I can't see why it wouldn't work to check the integrity of the ring seal in a 2 stroke. A leak down or pressure decay test is always a good idea to check the overall sealing ability of the engine (gaskets, crank seals, head seals etc.). Oh, and the OP's numbers look good on his comp. test.

[DOO_TINT]

Its also used on two strokers. Ask Kelsey,& Cudney especially back when we were having ring flaking issues(do a search) with the 'Doo rings pre '04's. This a good tool to check if the rings were starting to go even with so called good compression with just checking with your compression guage. I had a DI kit from RKT and was ask by Kelsey to keep an eye on the leak % rate to see if the rings had seated when he knew I had a tester. He had a change from a supplier and wanted to see if the rings were seating, mine were not and sent me another set. So yes this type of tester is used on the two strokers and a very good way to test fitness and catch subtle issues(especially rings) that you wouldn't with "just" checking compression .....

Also remember there "alot" of variables in just checking compression

Here:


http://www.dootalk.c...h=1

http://www.lafishmag...DownTester.html






-Grover

the 1st link is from 2004 when the moly ring thing was going on,,and they did not hold good compression very long and a good compression guage will let you know or my sled went down to 7.5mpg from 12-15mpg in 2004 from bad rings=150psi to 120psi/cold both

the second link shows how to make a leakdown tester for a 4 stroke eng/nothing about 2 stroke in that post

[grover]

the 1st link is from 2004 when the moly ring thing was going on,,and they did not hold good compression very long and a good compression guage will let you know or my sled went down to 7.5mpg from 12-15mpg in 2004 from bad rings=150psi to 120psi/cold both

the second link shows how to make a leakdown tester for a 4 stroke eng/nothing about 2 stroke in that post

Seemed to be used for checking two strokes and other motors as Bill indicates back when we had the ring issues and it indicated issues before it showed up with compression going down and you would have caught that with yours prior, I also remember finding quite a few with it here in the shop and yes the tester can be used for four strokes also.......

-Grover

[DOO_TINT]

Seemed to be used for checking two strokes and other motors as Bill indicates back when we had the ring issues and it indicated issues before it showed up with compression going down and you would have caught that with yours prior, I also remember finding quite a few with it here in the shop and yes the tester can be used for four strokes also.......

-Grover

the sled still ran great,,but when i cleaned the power valves and seen 1 ring pistons and buddy told me he read on this "dootalk" site about the rings,so i went to dealer as my warr was about over and they reringed it

but if you put 100psi in a 2 stroke,,you wont need to spray soapy water to find air leaks/lol

[djm]

"bring up the piston to tdc and you measure the pressure the cylinder holds vs. the leakage past rings as a precentage(above 15% would be a concern)"

You have me chuckling.. as we used to be concerned when leakage was 2.5 to 3.5% on our NHRA stockers...

This is why I never typically used my leak down checker on my sled engine, the single ring with large two cycle gap was lucky to leak less then 7 to 9 % when sealed well. Bill and I always disagreed on the advantage of using the leak down test back when we had the flaking rings issues. Always felt I could find a bad one using a compression test. I always ran a base line after a hot and cold test using a few drops of oil to estabish a perfect ring seal.

And yes we typically used a 100 psig dumped in the cylinder when running a leak down as it make it easy to figure % based on 100 psig equaling 100%. No calculations required. Ha ha when I first got back into sledding, when I heard leak down test, I didn't realize that they were really doing a 5 psig pressure decay test on the case seals.

Yes the leak down test is another way of testing ring sealing capacity. But it is a test you have to learn to run, have to know what percentages are typical with a sealed vs non seal two cycle engine. And they are different then the typical four cycle engines with two sealing rings and a three piece oil ring. But you have to have a compressed air source. Tough for most of us to do in the field.

[DOO_TINT]

the 100psi in a 4 stroke topend will find if the intake or ex valves or head gasket or rings are bad,,depends were the air is going

i read a hp test from a smallblock V8 and looser end gap was X hp? and a tighter ring end gap was 20hp more and gapless rings was 20 more hp or so

Doo not attempt tight ring end gap with 2 strokes