compression 100psi

angelo · Derestricted Danger Joined: 30 Jan 2006 Karma :

I have a off road 125, it is 2 stroke, it has a power valve and will make 27bhp acording to the manual, the rings are due for a change acording to the manual, ie 8000km. I did a compression test and found that the pressure reached with the power valve in the "off" or rest position was 100psi. is this bad ? good ?

puremagic72 · Brolly Dolly Joined: 15 Nov 2005 Karma :

Sounds a tad low to me, average should be 120 to peak at 145psi.

Baz.
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Make; cbr929cc blade Year; 2001
Gsxr 750 2000, alstare Corona, Current bike 1999 R6
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angelo · Derestricted Danger Joined: 30 Jan 2006 Karma :

can you explane what an average and peak reading is? is that with the power valve open? i just fixed up the compression gauge to the plug hole and kicked the start lever a few times, it pumped its way up to 100psi after about 4 kicks and then would go no futher.

swampy · World Chat Champion Joined: 04 Aug 2004 Karma :

I think that you should take the reading after each kick rather than pumping it up. IIRC you should kick it over and take the reading three times (starting at zero each time), then add them together and divide by three giving you the average reading. The peak reading would be the highest of these three. HTH.

Try looking here for some info https://www.dsmgrrrl.com/FAQs/compression.htm

Should give you an idea.
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puremagic72 · Brolly Dolly Joined: 15 Nov 2005 Karma :

excactly as above, but i would take about 5 readings then take the average.

Baz. Thumbs Up

____________________
Make; cbr929cc blade Year; 2001
Gsxr 750 2000, alstare Corona, Current bike 1999 R6
(1) Kids in the back seat cause accidents; accidents in the back seat cause kids.

angelo · Derestricted Danger Joined: 30 Jan 2006 Karma :

giving one kick the average comes out at 94 with a peak of 97, as the bike only has 8400kms it asume this means that the rings are going and it is time for new ones?

gsxrpeak · Trackday Trickster Joined: 06 Apr 2005 Karma :

make sure you put the choke on and the throttlefull open
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angelo · Derestricted Danger Joined: 30 Jan 2006 Karma :

I did not do that, i wil try it that way this weekend.

NSR Mick · World Chat Champion Joined: 26 Jun 2005 Karma :

angelo · Derestricted Danger Joined: 30 Jan 2006 Karma :

I thought cold motors have the best compression, cause the cylinder is smallest. bike alaways has more go for the first 10 min after puting the choke in.

gsxrpeak · Trackday Trickster Joined: 06 Apr 2005 Karma :

sorry. ment to say, make sure the choke isnt on and the throttle is open.

but warm it up as well. cold engine give bad readings

kris
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