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Compression test

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StevieG View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote StevieG Quote  Post ReplyReply Direct Link To This Post Topic: Compression test
    Posted: 25 May 2018 at 19:49
moto Guzzi V50II
What is the ideal compression for each cylinder?
I’m showing 125psi on the right, 110psi on the left which seems to have a leaky head gasket.
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motopete View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote motopete Quote  Post ReplyReply Direct Link To This Post Posted: 25 May 2018 at 20:34
Not sure how much difference capacity will make to the reading, but my 750 measures 210 -220psi.

Compression ratio would be similar I'd think...
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c13pep View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote c13pep Quote  Post ReplyReply Direct Link To This Post Posted: 25 May 2018 at 22:05
My V50/3 had a reading of 149 psi on each cylinder after lapping in all the valves and fitting new head gaskets.
I would worry if both cylinders read differently by any significant amount.
Did you have throttle wide open when doing test as 110 seems low
CHRIS
you can`t have any fun in a straight line

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StevieG View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote StevieG Quote  Post ReplyReply Direct Link To This Post Posted: 25 May 2018 at 22:08
No, plugs out, just turning over.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote c13pep Quote  Post ReplyReply Direct Link To This Post Posted: 25 May 2018 at 22:15
with throttle wide open maximum reading should occur within 4 or 5 revolutions of cranking.
Mine responded well to lapping the valves in and upped the psi reading on each cylinder
CHRIS
you can`t have any fun in a straight line

Monza
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StevieG View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote StevieG Quote  Post ReplyReply Direct Link To This Post Posted: 25 May 2018 at 22:17
thanks!! Will do just that plus head gaskets. Hopefully that will fix things.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote c13pep Quote  Post ReplyReply Direct Link To This Post Posted: 25 May 2018 at 22:27
Just make sure that you are doing the compression test correctly before you strip the heads otherwise you will not have a reference point for comparison once reassembled
I think the V50/2 has slightly higher compression than mine so would expect reading to be more than mine.
CHRIS
you can`t have any fun in a straight line

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Brian UK View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 25 May 2018 at 23:00
The important thing is the comparison between the pots.
The engine should be hot, and throttle held wide open. If this was the case, then 110 seems low.

Unless you have a head gasket chuffing, it's more likely one exhaust valve is pitted.

A leak down test tells you more but it's more difficult to do.
Brian.

Better 5 minutes late in this world than years early in the next.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GC888 Quote  Post ReplyReply Direct Link To This Post Posted: 29 May 2018 at 11:24
160 on my v35

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