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Yamaha 140hp v4 2stroke compression test

Frank Carroll

New member
Hi guys
Just ran a compression test on my v4. I'm just wondering if anyone knows what ballpark i should be in, I have a feeling my tester is faulty.
 
The most important thing is that they are even between cylinders.-----Likely 120 PSI--------Just curious as to what year your Yamaha 140 was made , as most only list a 115 and 130 HP V-4.
 
I'm not entirely sure what year it is to be honest, haven't done my research just yet, my guess is late 80s/early 90s going by the colour and stickers. It would appear the 140 wasn't offered in the north american market from the brief read up I have done. This one was originally purchased in England going by the dealer stickers and made it's way over to Ireland ten years ago or more from what the previous owner told me. Although his credibility is looking shady at the minute!

Yeah I was expecting something in the 120psi region but the (borrowed) compression tester I'm using is showing figures in the mid forties, with less than 5psi variance between cylinders. This seems unlikely to me though given that it starts and runs reasonably well, it is suffering from a slight miss-fire but I'm inclined to think that's an ignition issue having noticed the (my terminology fails me here) arm which advances and retards the spark under the flywheel is sticking, I would guess due to the engine being unused for some time.
 
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The 140 was available from the early 80's thru to the mid 90's in the european, asian and australian markets... possibly elsewhere too..
Compression is usually in the 120 - 135psi range... I would be doubting that compression tester if it shows a steady mids 40's all round..
 
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