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Is this a low cyl pressure for a corsa? (pic inside)
Posted: Fri Apr 13, 2012 12:18 pm
by dv/dt
Does this seem low? The guage is one i rented from O'reilly and i DID use the small adapter that came with it, which would seem to lower the pressure reading due to adding volume to the cylinder.
I used the same tester with and without the adapter on a friends Rattler 110cc and the results without the adapter were 150 psi and without ~145.
My scoot thus far seems to top out at 64mph at about 9100 with the corsa bore and PG short pipe, 8.44 gears and breathing through an oko 24. Some of you guys are hitting 70, but i spose you have pipes that are geared more towards peak power.
Re: Is this a low cyl pressure for a corsa? (pic inside)
Posted: Fri Apr 13, 2012 12:22 pm
by fastplastic
well first tell us more how you did the testing, but yes it does seem a lil low....
the guys going 70mph have pg longs 7.5 gears and sing around 10900 to 11300 rpms... so it sounds more like a tuning issue....
Re: Is this a low cyl pressure for a corsa? (pic inside)
Posted: Fri Apr 13, 2012 12:27 pm
by dv/dt
fastplastic wrote:well first tell us more how you did the testing
The engine was warm when i hooked the guage up. After it was on i used the electric start to spin the motor for a few seconds until the reading peaked.
Re: Is this a low cyl pressure for a corsa? (pic inside)
Posted: Fri Apr 13, 2012 12:31 pm
by fastplastic
kick it till it peaks while holding the throttle wide open and while its cold, give that a shot...
Re: Is this a low cyl pressure for a corsa? (pic inside)
Posted: Fri Apr 13, 2012 12:36 pm
by dv/dt
fastplastic wrote:kick it till it peaks while holding the throttle wide open and while its cold, give that a shot...
OHHH i did forget to hold the throttle open. WELP, time to go rent that guage again haha.
Re: Is this a low cyl pressure for a corsa? (pic inside)
Posted: Fri Apr 13, 2012 12:38 pm
by fastplastic
dollars to donuts says you will be in spec when you retest... now on to the turning you should be able to get more rpms out of the pipe... whats your setup from head to toe...
Re: Is this a low cyl pressure for a corsa? (pic inside)
Posted: Fri Apr 13, 2012 5:39 pm
by Wheelman-111
Greetings:
I simply popped the carb off the mani to test compression. When I did mine, the used Corsa I bought from CustomX22, I got like 115PSI. The same gauge accurately predicted the sure demise of Flash 4.1 with compression over 150, so I believe the numbers. The Corsa's exhaust port closes very late, so the PSI compression isn't all that high. It relies on a good chamber pipe to stuff that last escaping gasp of mixture back in and raise the dynamic compression. 8.44 gears might be a reason why you hit "only" 64 - which really ain't bad for 72cc, if you think about it. I got 69.9 with 7.58s and stupid-rich jetting, but sometimes I wish I had faster take-off instead of the top speed. You can't have everything...
Re: Is this a low cyl pressure for a corsa? (pic inside)
Posted: Mon Apr 16, 2012 12:26 pm
by veedubh20
get a pg long/28 oko can get 70 plus and sell the pg short!
Re: Is this a low cyl pressure for a corsa? (pic inside)
Posted: Mon Apr 16, 2012 12:49 pm
by dv/dt
veedubh20 wrote:get a pg long/28 oko can get 70 plus and sell the pg short!
Nah, top speed is fun BUT i live in a pretty dense city and that means lots of stop/start type riding. Need the midrange!