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General Category => General Discussion => Topic started by: Beavis on May 13, 2023, 08:09:53 AM
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Hi to all , waiting for my compression tester to arrive , can someone tell me what results should i expect ( PSI ) from a healthy V7 lll Stone 750cc engine?
Thx in advance.
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Do it after a ride, warm engine. With plugs out & wide open throttle. 180-200psi under 80 won't idle.
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Do it after a ride, warm engine. With plugs out & wide open throttle. 180-200psi under 80 won't idle.
Many thx . Will do that. :thumb: :thumb:
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Hmm. Got me curious now…
There are easy to follow instructions if you do a Google search. Make sure you take into consideration your elevation from sea level.
This Motortrend article spells it out fairly simply: https://www.motortrend.com/how-to/engine-diagnosis-leakdown-compression-test/amp/ (https://www.motortrend.com/how-to/engine-diagnosis-leakdown-compression-test/amp/)
Atmospheric pressure at sea level is approximately 14.7 psi. A 9:1 compression ratio cylinder is compressing the air and fuel mixture to about 132 psi at sea level (9x14.7=132.3)
The Guzzi V7 III’s manual states a compression ratio of 10.5 +/- 0.5 :1, same as the VII Stornello variant (but not the rest of the VIIs are a hair less for some reason), so at sea level, it should read around 154-162 psi.
Now, last time I read mine, it was in 170s. Something else going on?
Regardless, these newer small blocks are higher compression machines—one reason why I argue against people calling them “agricultural”.