Compression

[Lewes96]

Any thoughts on what compression check for 3 1/2 Strada should be?

[Glennh]

Do you mean psi reading on a compression test gauge?
Strada 10:1 compression ratio would give 161 psi reading according to various conversion websites. A Sport at 11:1 would give 184psi. Does this help?

[George 350]

Compression readings can have a lot of variables. Hot or cold engine? Speed of cranking (difficult to know with a kickstart only bike)? Camshaft type? (Sport cams have quite a late inlet valve closing point, good for top end but will definately lose compression compared to a Strada cam), so being realistic, as long as you can see over 135-140psi, you should be ok. That is with the throttle wide open.
Most important is that both cylinders are similar values.
Regards, George.

[Lewes96]

Thanks re PSI suggestions. Not sure I get the throttle open bit as surely this is just done kicking it over?

[BumbleBee]

Totally agree with George. Also note that you should turn off the fuel supply and drain the float bowls before the compression test, because the more fuel gets sucked into the cylinder the more it progressively increases the pressure and gives you a false reading. As a basic test, if you can push down the kickstarter by hand and the compression is "perfect" then you should find it feels blooming hard to push down. If it's very easy to push down then it's worn past its service limits.
Yes you have to open the throttle fully to ensure the air can easily fill the cylinder otherways you would get a false measurement as less air would be available to compress.

Gary

[Lewes96]

Thanks for the clarification.

[Lewes96]

150 PSI on both