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Yamaha compression

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Seadoobuddy

Seadoobuddy

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My nephew's 1995 -Yamaha RA:cuss: 1100 is running on 2 cylinders. i checked compression in the manual it says 134 PSI. the front one is at 120, the back one is at 118 but the middle one reads ZERO. I tested it twice. so it needs a rebuild. Would just a bad ring cause it to read zero or must it be a huge hole in the piston, loose connecting rod at the crank????
Any other suggestion? :cuss::cuss:
 
I'll let you know later as my friendly PWC mechanic is looking at it tonight with a scope camera. Should all 3 rings be replace at the time of rebuild?
 
Yes its smarter to just buy the rebuild kit it has 3 of everything and is well worth it in the long run. If im not mistaken those have three individual cylinders correct? those are fairly easy to rebuild on your own so go for it and do it all at once because all your readings were pretty low
 
testing compression

Seadoobuddy said:
My nephew's 1995 -Yamaha RA:cuss: 1100 is running on 2 cylinders. i checked compression in the manual it says 134 PSI. the front one is at 120, the back one is at 118 but the middle one reads ZERO. I tested it twice. so it needs a rebuild. Would just a bad ring cause it to read zero or must it be a huge hole in the piston, loose connecting rod at the crank????
Any other suggestion? :cuss::cuss:
Click to expand...
one thing u can do is squirt about a tablespoon of oil in the bad cylinder and check it 2 see if the compression goes up if it does u got piston ring comp loss
 
We checked the piston thru the plug hole. All 3 move up/down but the middle one wiggles a lot more than it should. He said maybe the skirt broke off. he won't know for sure until the head comes off and such.

Poor nephew...more repairs.
 
He pulled it apart on Sunday. No real damage except that the middle piston has a broken skirt.

Buying new piston and gasket kit.

Should all 3 rings be replaced...he said that it's not necessary.
 
well, u got a 7 yr old ski, and u say comp should be 134, other 2 cylinders are little low, and seein that u have it apart, personally, i would, cause if u dont, they will be weaker than center 1, sorta like buttering cold corn .... but, i would be more intrested in finding broken off piece of skirt


wheres the pic, u posted compression -- wheres the pic ?????
 
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thanks griz, actually it's 17 yrs old.

He took it apart without me being there, so no pics yet.

We will be finding any broken pieces for sure, thanks for the reminder.
 
Since the compression on the other two cylinders is low, I would at least do a top end rebuild. In fact if your nephew can afford it a rebuilt engine would be better. I just checked SBT a rebuild is $945.00.

Lou
 
All the parts are now in, He was In INdiana picking up a motor and gear boxes for Hydro Plane boat. U-5.
We will put all together when i get back home.
 
Just curious, you know how you always say, we like to end threads with a conclusion. How did this come out? Did the ski ever get fixed, how is it running? What was the final resolution?

Lou
 
a tombstone may be in place here lou, RIP i heard one of those prison shank screwdrivers is trapped in the lower part of case and cut the crankshaft in 2:seeya:
 
My friend called me in late March saying he fixed it while I was in Florida. I waited for 3 weeks for him to tell me the cost and now the problem is getting my nephew to bring the ski over here so that the motor can be dropped in. My friend is now working on the Hydroplane boats + his own full time job. I'll keep you posted as things happen.
 
It is not likely that a ring would cause you to have zero compression but that does not absolutely mean there is a hole the piston either but make sure you check the crank when you disassemble it.
 
The mechanic now has the ski at his house. the piston lost a good portion of both sides of it's skirt. i showed it to Dr. Honda and he said that it looks like the ring moved around and the gap caught the port and ripped it apart then kinda melted together. The jug was not damaged so he said.

IMG_0486.JPG IMG_0483.JPG IMG_0484.JPGIMG_0485.JPG
 
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I find it REALLY hard to believe that the cylinder is OK. On second thought, I don't believe it at all!!
 
Seadoobuddy said:
The mechanic now has the ski at his house. the piston lost a good portion of both sides of it's skirt. i showed it to Dr. Honda and he said that it looks like the ring moved around and the gap caught the port and ripped it apart then kinda melted together. The jug was not damaged so he said.

View attachment 12013 View attachment 12010 View attachment 12011View attachment 12012
Click to expand...

You might want to check the other pistons for cracks along the skirts.
Why is the blue butt in focus and not the piston?:D

Chester
 
OK, I didn't know what you meant by blue butt so i looked again. It's a back pillow for sitting upright in bed or on a couch......just got done with a 2 day garage sale....(the BB didn't sell)
I guess I was too close to the piston ....will retake pics later.
 
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