atomsplitter
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The 2.3's ran 8:1 compression while the 2.5's run 10.8:1.
What I found using Co=Pilot:
If you’re asking for factory cylinder compression test pressures (e.g., PSI or kPa values for a compression gauge test), Triumph does not publish those numbers in any publicly available service documentation for the 2025 Rocket 3. Only the static compression ratio is provided.
However, based on the 10.8:1 ratio and typical behavior of large-displacement, low‑RPM, high‑torque triples, expected compression test readings (inference, not factory data) would generally fall in the 170–220 PSI range on a healthy engine — but this is not an official Triumph specification.
What I found using Co=Pilot:
If you’re asking for factory cylinder compression test pressures (e.g., PSI or kPa values for a compression gauge test), Triumph does not publish those numbers in any publicly available service documentation for the 2025 Rocket 3. Only the static compression ratio is provided.
However, based on the 10.8:1 ratio and typical behavior of large-displacement, low‑RPM, high‑torque triples, expected compression test readings (inference, not factory data) would generally fall in the 170–220 PSI range on a healthy engine — but this is not an official Triumph specification.
Kevin frazier
Widowmaker!
2.3s w 10:5:1 200ish, i would guess new 2.5s leave factory at 180ish but thats just a guess. Id think there is a lot of room for more on the 2.5s, stronger head, i cant wait till someone moves cams and gets some pressure on one of these new ones. 
TURBO200R4
stand up straight and grab the world by the a$$
i have seen threads that say the 2.5's have a compression release so taking a test might be a problem?
imcool
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someone saying that its 220psi
2.3s w 10:5:1 200ish, i would guess new 2.5s leave factory at 180ish but thats just a guess. Id think there is a lot of room for more on the 2.5s, stronger head, i cant wait till someone moves cams and gets some pressure on one of these new ones.
@Journeyman can you share insights, if one has to measure PSI with a guage, what would the correct procedure?
Journeyman
"And this one is just right" ~ Goldilocks
Sorry, I've not checked, but @TURBO200R4 is correct about the compression release ("decompressors"). I'm not sure if you would get an accurate reading, as the exhaust valves are held slightly open on startup, but perhaps with enough revolutions they would close and enable full compression. If you were to test and find it extremely low I would say that is what's going on.
and here...
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mo8414
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That would explain why Triumph has no published cylinder compression numbers
imcool
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but there are more complicated procedures in the factory manual for testing other stuff , why would they hide comparatively somewhat easier procedure to test compression of engine?
atomsplitter
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Old school engine were simple, you pulled the plugs, put in a pressure guage in the cylinder you wanted to test and then rotated the engine by hand until that cylinder was at TDC. Viola! Pressure reading. With the newer motors that doesn't necessarily work since at low RPM a compression release could be in play. To get the reading you first have to disable the release mechanism. Had a compression release on my 72 Yamaha XS 650 that was also the starter switch. If you didn't relieve the pressure the starter couldn't turn the motor over. If the starter was out, the kick starter could do the trick but a misfired would launch you over the handlebars on kick back if the release wasn't held.
TURBO200R4
stand up straight and grab the world by the a$$
just thinking
if you pulled one spark plug in each of the 3 cylinders and a compression gauge in one and hooked it to a good charger on crank assist that might crank that motor fast enough to disable the decompressors. probably necessary to disconnect fuel or wide open throttle so motor won't start.
or pull the wire on cylinder are checking.
if you pulled one spark plug in each of the 3 cylinders and a compression gauge in one and hooked it to a good charger on crank assist that might crank that motor fast enough to disable the decompressors. probably necessary to disconnect fuel or wide open throttle so motor won't start.
or pull the wire on cylinder are checking.
