compression test gt 550

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bazit
On the street
Posts: 37
Joined: Wed Jul 09, 2014 6:27 am
Country: UK
Suzuki 2-Strokes: gt 380x2 gsxf cb 900 bmw funduro,KZ 650
Location: Macclesfield Cheshire
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compression test gt 550

Post by bazit »

Hi
Could any one point me in the right direction regarding the compression I should see ,at the moment I am getting 10.5 bar ,11 bar ,and again 10.5 bar thats with throttle wide open no air filters on .I know what the compression ratio is supposed to be on the GT 550 but are my readings about right .
There may well be a formula for working this out ,but cant find it ,any help would be appreciated.
One other question ,if the rubber boots on the carbs are shot would this upset the air fuel mixture and cause poor starting .
The bike has not been started for a long time and I am just running thru things .
Regards
Barry
yeadon_m
Road race school
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Joined: Sun Aug 05, 2012 1:18 am
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Suzuki 2-Strokes: GT380B, GT550B, GT750A, GSX1400

Re: compression test gt 550

Post by yeadon_m »

Barry,

I have 3 GT triples (with near new top ends) are all of them give 120-125 psi when tested as you wrote. As 1 bar is 14.5 psi, your numbers are fine, if not quite a bit higher than I'd expect. Numbers vary with the gauge used, so as a general approach its as well to look for major differences across the cylinders, and yours are fine. Has the motor been modified?

Yes, carb to motor boots must be airtight. Its not common for for the boots themselves to actually split right through though thats possible. It is common for them to harden and make it tough to squash seal them with the ring clamp.

Cheers,
Mike
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