ok guys this is really weird ,,,

[pythonz281]

I have posted the other ski of mine that most have helped on ... about the 96 gtx ,,, front cylender 110 psi and back 0 psi with most of yall have seen the pics of the piston that burned tru ...

ok now i have 2 of these skis 96 gtx 787 motor so i decided to test the compression today 155 psi in front and 0 psi in rear .. but this one runs !!what the hell is going on here an i doing this test wrong i

1 remove both spark plugs
2. installl compression tester
3.hold trottle wide open
4 do this at least 3 times to get a good reading

please help does this mean i am rebuilding this motor too


Kenny

 

[kustomkarl]

Here is info on a compression test Kenny. It covers all the basics.
To test compression, remove both spark plugs. Place spark plug caps on the plug cap studs near the cylinder head to ground the empty caps. This completes the circuit of the ignition electrical system and prevents any electrical problems from the caps being un grounded. Using the correct adapter for the threaded end of the tester,( same length of the spark plug threads length)screw in the tester in one plug hole. Hold the throttle wide open. Push the start button. Watch the compression gauge, when it peaks out at the most compression, let go the start button. Read the psi number. I would do it 3 times to be sure it is accurate. Check both cylinders the same way. The ideal compression is 150 psi per cylinder. If it is less, it's not a problem as long as they are close to being the same. If the psi is less than 90 it might need be time for a tear down and a rebuild. If the psi in 1 cylinder is say 140 psi and the other is 80 psi you need to tear down and repair. This difference is a lot then there is a problem. I hope this helps you.
Let us know how you make out.

Karl

 

[timmyboy76]

Yeah, thats weird, it runs..on 1 cylinder.
If thats the case, put both good psi cylinders and pistons on one motor, so, ur only rebuild'n one...?

 

[pythonz281]

Here is info on a compression test Kenny. It covers all the basics.
To test compression, remove both spark plugs. Place spark plug caps on the plug cap studs near the cylinder head to ground the empty caps. This completes the circuit of the ignition electrical system and prevents any electrical problems from the caps being un grounded. Using the correct adapter for the threaded end of the tester,( same length of the spark plug threads length)screw in the tester in one plug hole. Hold the throttle wide open. Push the start button. Watch the compression gauge, when it peaks out at the most compression, let go the start button. Read the psi number. I would do it 3 times to be sure it is accurate. Check both cylinders the same way. The ideal compression is 150 psi per cylinder. If it is less, it's not a problem as long as they are close to being the same. If the psi is less than 90 it might need be time for a tear down and a rebuild. If the psi in 1 cylinder is say 140 psi and the other is 80 psi you need to tear down and repair. This difference is a lot then there is a problem. I hope this helps you.
Let us know how you make out.

Karl

Thanks karl !!

I did it agian no pressure in rear i guess i am doing a top rebuild on this to !!!

Kenny

 

[timmyboy76]

Yeah, thats weird, it runs..on 1 cylinder.
If thats the case, put both good psi cylinders and pistons on one motor, so, ur only rebuild'n one...?

typ'n atsame time...

 

[pythonz281]

typ'n atsame time...

:agree:
trust me i thougt of that but the on the other motor was only pushing 110 psi so hay i guess its rebuilt the top on both i am doing the work myself so at least i dont have the labor to worrie about except the head workl i found a kit that only cost about 220 a piece to rebuild the top end ...

thanks for reply
kenny

 

[timmyboy76]

:agree:
trust me i thougt of that but the on the other motor was only pushing 110 psi so hay i guess its rebuilt the top on both i am doing the work myself so at least i dont have the labor to worrie about except the head workl i found a kit that only cost about 220 a piece to rebuild the top end ...

thanks for reply
kenny

110lb aint bad, you got nuth'n to lose, even though you have 150lb in other, but hey, will work for now...:cheers:

 

[robin savell lloyd]

I have posted the other ski of mine that most have helped on ... about the 96 gtx ,,, front cylender 110 psi and back 0 psi with most of yall have seen the pics of the piston that burned tru ...

ok now i have 2 of these skis 96 gtx 787 motor so i decided to test the compression today 155 psi in front and 0 psi in rear .. but this one runs !!what the hell is going on here an i doing this test wrong i

1 remove both spark plugs
2. installl compression tester
3.hold trottle wide open
4 do this at least 3 times to get a good reading

please help does this mean i am rebuilding this motor too


Kenny

It sounds as if you are probbly doing the test right. the reason the one does not run is because the pulse line for the fuel pump is conected to the side of crankcase that has low compression. [wich means no cylinders are geting fuel] Now on the engine that runs the cylinder that has compression has the pulse line also so both carbs can get fuel. It may start and run like a race car on dry land but it will be a dog in the water if it will even start in the water. I can allways be wrong so good luck. Robin :cheers:

 

[PWCdoc]

You can get a motor with zero compression on one cylinder to run...but only out of the water. Put it into water and it'll die. It's normal for this to happen. And yes, looks like not one...but two rebuilds are in your future.

 

[dghal]

Always check and clean the fuel filter in the carb "WHEN" doing the top ends,, Lean conditions hurt top ends,, if those are dual carb motors pay close attention to the carb on the cylinder that was cooked,,