proper compression testing

[2jugrider]

I recently purchased a custom banshee (my first one!) that has a Patriot racing built 350 dune port motor. It is supposed to only run 110 octane race gas according to Patriot. I recently checked the compression and am getting 120 psi at best, hardly race gas territory. It seems to run good but being new to banshees I don't know what to compare it to. I did the check with the motor cold and pulled both plugs and kicked it over as fast as possible. Tried it with carbs wide open, one plug in, etc... same results. So I guess its time for a rebuild? Can port work make compression reading difficult? If I ride it anymore before the rebuild should I just run super?

Thanks for any advice!

[sheefreak]

I can tell you that Dan from Patriot knows his shit. If it is set up for race fuel you better run it. You are either in desperate need of a rebuild, or your compression tester is giving you false readings.

[toytech]

I recently purchased a custom banshee (my first one!) that has a Patriot racing built 350 dune port motor. It is supposed to only run 110 octane race gas according to Patriot. I recently checked the compression and am getting 120 psi at best, hardly race gas territory. It seems to run good but being new to banshees I don't know what to compare it to. I did the check with the motor cold and pulled both plugs and kicked it over as fast as possible. Tried it with carbs wide open, one plug in, etc... same results. So I guess its time for a rebuild? Can port work make compression reading difficult? If I ride it anymore before the rebuild should I just run super?

Thanks for any advice!

 

wont hurt it to run the race fuel if your guage is rite, but no need,If it is supposed to run on 110 only it should have over 150 psi of compression, are you sre you guage is good? port work does not make a comp test any different to do, one plug in,throttle wide open, and kick until guage stops climbing.

Edited September 15, 2010 by toytech

[2jugrider]

edit

Edited September 15, 2010 by 2jugrider

[2jugrider]

The best I can figure is that it hasn't been rebuilt since it was done by Patriot 5 years ago. The only way to test my compression gauge is to compare it to a known good one or maybe an air tank with a known pressure in it. Can I pull the cool head off to check the dome cc and re-use the o-rings?

Thanks

[2001blackshee]

The best I can figure is that it hasn't been rebuilt since it was done by Patriot 5 years ago. The only way to test my compression gauge is to compare it to a known good one or maybe an air tank with a known pressure in it. Can I pull the cool head off to check the dome cc and re-use the o-rings?

Thanks

 

 

If its been 5 years since its been opened up.. Them O rings arnt going to be in too good of shape... Ive tried using mine before.. and they dont seem to hold there shape after sitting for a few days.... All in all. its your decision.. hyou can get new O - rings for 20 bucks....You dont need anti-freeze coming threw the head bolts!!!

[2jugrider]

Update! The special schrader valve in my sears/actron tester was bad. I took it out to inspect it and it fell apart. I suspected something was up when I tested it again and the compression jumped up to 140 and then dropped to 100, then to 0! Problem now is sears disco'd the part but it appears similar to what the other testers use. It has to be a special light spring, the bike or car ones are too heavy to let the compression by properly, or so I'm told.

 

I also pulled the t5's off to replace the o ring and took a look at the piston/cyl. Looks like new, no scoring, carbon on piston sides, etc.... will let you know what I find when I get the tester fixed.

Thanks