#2 and # 4 cylinders no compression

Joined
Oct 26, 2006
Messages
26
2 stroke v4 engine. # 2 and # 4 cylinders have 0 compression. Pistons are good, rings are good, head gasket shows no signs of worn spots or leak. cylinders are in good shape. I'm lost and have no idea what could be the problem. oh the heads are good. any ideas i'm up for them at this point. I spent to much time and money to be where I'm not and that's on the water.
 
Joined
Oct 26, 2006
Messages
26
Re: #2 and # 4 cylinders no compression

got it ! it's a 1987 yamaha 115 v4 precision blend. sat for a year ran it a few times a year just to run it. had a bad coil replaced it. the next day it would not start. had the motor looked at by mech. he said it had a bad piston. took it to another mech he said pistons and all were fine. that he would need to dig deeper to find the problem. my question is ; if the pistons rings and heads and head gaskets are all good on a 2 stoke engine what else could possibly be the problem giving it 0 compression.
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
9,092
Re: #2 and # 4 cylinders no compression

The only things I know of to cause no compression at all would be a hole in piston, broke rod not moving piston, hole in cylinder,or a real bad blown head gasket.

Even cracked rings and stuck rings should show some compression.

Did you take the compression readings or someone else and they just told you there was none?
 
Joined
Oct 26, 2006
Messages
26
Re: #2 and # 4 cylinders no compression

both mechs said there was none then when i got it back i checked it myself. I also pulled the head myself to see what was going on everything looks pretty much new I am as lost with this as a can be.
 

waffles1

Petty Officer 1st Class
Joined
Jul 15, 2008
Messages
260
Re: #2 and # 4 cylinders no compression

When you said everything looked good did you see the pistons moving up and down as they should? I agree with 99yam40 about the busted rods or maybe cam bearings bad and spinning. Good luck.
 

rodbolt

Supreme Mariner
Joined
Sep 1, 2003
Messages
20,066
Re: #2 and # 4 cylinders no compression

you either have some seriously stuck rings,the sleeves have rotated or the head is warped.
all are easy to check.
 
Joined
Oct 26, 2006
Messages
26
Re: #2 and # 4 cylinders no compression

i'm having the heads checked tomorrow. piston rings stuck on both cylinders that bad do you really think that could be the case. how can i check and how can i fix for cheap. I have a guy the will rebuild the power head for $995 with a 3 year warranty. I' a little skeptical though. do you think I should go ahead and have the power head rebuilt and be done with it. he said he'll even pull it for that price.
 

rodbolt

Supreme Mariner
Joined
Sep 1, 2003
Messages
20,066
Re: #2 and # 4 cylinders no compression

for that price I am a bunch skeptical.
takes 18 hours or so labor to remove,strip,clean and reassemble it.
takes about 225 dollars to bore,hone and chamfer the ports.
pistons are easy 50 each, gasket kit is about 120.
then rodbolts,pins pin bearings,bottom crank bearing at a minimum.
myself I would have run a leak down test on it before pulling the head.
 
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