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Equally low compression on all 4 cylinders

  • Thread starter Thread starter Tanerrx
  • Start date Start date
Tanerrx said:
I ......And wouldn't both valves be closed automatically if it were at TDC?
Click to expand...

Nope, this is a 4 stroke, it's at TDC twice in cycle ,once for the compression stroke and then at end of exhaust stroke when exhaust is open (and intake a wee bit)
 
tom203 said:
Nope, this is a 4 stroke, it's at TDC twice in cycle ,once for the compression stroke and then at end of exhaust stroke when exhaust is open (and intake a wee bit)
Click to expand...

Well ****. I just figured it I were on the T mark that everything would be closed up. I'll give it another try this afternoon when I'm doing a couple other tests.
 
Tanerrx said:
Well ****. I just figured it I were on the T mark that everything would be closed up. I'll give it another try this afternoon when I'm doing a couple other tests.
Click to expand...

just curious, why not use a compression tester instead of your compressor and feel?
 
mvalenti said:
just curious, why not use a compression tester instead of your compressor and feel?
Click to expand...

Did the test again with the pistons and valves in the compression stroke instead of the time around that the exhaust is open and there was no leak coming out of the other spark plug hole. I need to take the carbs and exhaust pipes off with the oil cap off too and do it again to try and listen for leaks properly but I'll save that for another day.

The reason I just did it by feel was because if I can feel the air shooting out of the other spark plug hole I know there is a leak (or thought there was). At that point it wouldn't really matter how much the leak was leaking. It would need to be addressed no matter what it read on the compression gauge. I hope that answers your question. I did use the compression gauge to test the compression earlier and it read low. That's why I went to the air compressor, to find where it was leaking. If that's what you were asking.

Also, my compression gauge suddenly won't hold the needle to the highest amount of compression. So I'm wishfully thinking that my compression gauge if faulty.
 
When you pressurise the cylinder do you lock the crank, cause otherwise she'll turn and start shifting valves.
I reckon/hope it is the tester - the readings are too even.
There is an old RFC preflight check list round here somewhere. It says that if you don't get the full revs against the chocks the inexperienced pilot sends for the mechanic to check the motor, the experienced pilot asks the tacho be changed.:)
 
Brendan W said:
When you pressurise the cylinder do you lock the crank, cause otherwise she'll turn and start shifting valves.
I reckon/hope it is the tester - the readings are too even.
There is an old RFC preflight check list round here somewhere. It says that if you don't get the full revs against the chocks the inexperienced pilot sends for the mechanic to check the motor, the experienced pilot asks the tacho be changed.:)
Click to expand...

The gauge is for sure not working properly. One attachment lets the air back out cause the needle to just bounce up and down and the other leaks air at the rubber part near the head causing it to not get the full pressure. I'm putting some gasket seal around the rubber part and letting it set over night. Hoping it stops the leak. We'll see, just because the gauge isn't working right doesn't mean the cylinders are so I've got to figure something else out.
 
Do you have an Autozone/Pep Boys/NAPA nearby? They might have programs to loan out tools...
 
stetracer said:
Just wondering do you have C/V carbs on the bike
Click to expand...

I don't think so. Not really sure what constitutes a C/V carb but it looks like it has something to do with a diaphragm and my carbs don't have diaphragms. The only marking on the carbs says Mikuni. Does this tell you anything?
 
Ok you have your stock carbs. If you had c/v carbs you would have to remove the carbs to do a proper compression test instead of just holding the throttle wide open
 
stetracer said:
Ok you have your stock carbs. If you had c/v carbs you would have to remove the carbs to do a proper compression test instead of just holding the throttle wide open
Click to expand...

I'm not sure I follow you here. How do you figure that holding the butterflies open with the throttle does not constitute a proper test?
 
BigD_83 said:
I'm not sure I follow you here. How do you figure that holding the butterflies open with the throttle does not constitute a proper test?
Click to expand...

On c/v carbs even when you hold the throttle open all the way the slides will not lift if the bike is not running
 
BigD_83 said:
I'm not sure I follow you here. How do you figure that holding the butterflies open with the throttle does not constitute a proper test?
Click to expand...
When you twist open the VM carbs the slide comes fully up and the bore is wide open. Doing the same with CV the throttle plate/butterfly is open but the slide is not fully up, restricting the supply of air to the cylinder.
 
True enough, but I'm not sure you aren't splitting hairs, though. If I'm not mistaken, the Suzuki service manual gives numbers for compression testing with the carbs on...
 
BigD_83 said:
True enough, but I'm not sure you aren't splitting hairs, though. If I'm not mistaken, the Suzuki service manual gives numbers for compression testing with the carbs on...
Click to expand...


what are the the compression numbers the manual calls for with the carbs on? It would have to be a low number. That is why I asked him if he had c/v carbs because some guys switch to the newer c/v carbs or the flat slide c/v carbs like on the Bandit 1200's
really not splitting hairs there is a big difference in cranking compression with carbs on as to off with c/v carbs
 
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