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Sounds like a cyl head needs to be removed and look inside
 

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Discussion Starter #22
Rbarre, you sure u telling me right, with piston all way up I shouldn't be loosing air nowhere, cause I am
 

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Where are you loosing it? Are you sure you are on TDC ( which means both valve are closed)
There are 2 times the piston is in the top most position Compression stroke and Exhaust stroke.
did you try and turn the crank shaft 180°
 

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Discussion Starter #24
I'll try that, it was pouring out the carb with piston all way up
 

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If it still blows out the carb after moving it it is a intake valve problem.
The cyl head will still need to come off.
 

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Discussion Starter #26
Got to timing wheel, set it on T got air out carb, turned it a full turn got air out oil hole
 

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Discussion Starter #27
Y'all don't quit on me now, we in agreement pull head? Do I need to pull cylinder or just head first, if it's head do y'all have any recommendations where I can send to have it re worked?
 

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By all means pull the cyl. head.
But before doing that it would be wise to obtain a service manual or repair guide.
Some one here probably give some hints on which are the best ones.
 
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Discussion Starter #29
I redone the top of a Yamaha several years ago, so I'm not on strange ground, just trouble shooting is my problem..
 

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Do you know if it was hydro locked? I remember you saying the oil looked good after the kids sunk it some, took 5 changes to get mine clear after my submarine, but never knew how deep/bad the Yamaha was..
 

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Y'all don't quit on me now, we in agreement pull head? Do I need to pull cylinder or just head first, if it's head do y'all have any recommendations where I can send to have it re worked?
If you end up needing the head reworked contact Charlie at pro1racingheads.com I've used his services many times. Great work, pricing and fast turn around.
 

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Discussion Starter #32
I don't know how deep or if it hydro locked, I could see where some dirt got past breather, oil does look clean to me, have not drained yet, was waiting till tear down, what you think?
 

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Discussion Starter #33
If you end up needing the head reworked contact Charlie at pro1racingheads.com I've used his services many times. Great work, pricing and fast turn around.
Thanks BPS that's one thing I was really worried about, machine shops are a thing of the past around here
 

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Do you know if it was hydro locked? I remember you saying the oil looked good after the kids sunk it some, took 5 changes to get mine clear after my submarine, but never knew how deep/bad the Yamaha was..
I'm with whit, it just doesn't add up to me. It was running great, went into a deep "puddle" and now it won't start due to low compression. Also it's leaking past the intake valves.

If it was hydro locked there would have been water in the upper part of the cylinder which you would have had to come out somewhere (spark plug hole, exhaust or into the crankcase). It just feels to me that it already had issues.

In the end it really doesn't matter now. All of the problems just need to be found and addressed. Cylinder head needs to come off.
 

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A little air escaping from crankcase can be expected, a large amount could be a sign of cracked rings or hole in piston (I'll doubt that one) since you had some compression.
As others have said start with head removal and then we can go further with desk diagnostics.
 

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Discussion Starter #37
Here's what we got, head looks in great shape to me, I'll let y'all decide, cylinder don't look good at all, scratches down front and back, rings are melted into back of piston, I cannot get piston off and it's not floping on rod real easy, kinda stuff, have not worked with it alot, but pin definitely didn't just slide out, tell me what y'all think, head gasket looked good
 

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To me, from your description sounds like wrist pin is seized on piston which may have contributed to the cyl. scoring.
Can you feel the grooves in the cyl with your fingernail or is it very shallow?
Why that happened I'm not sure. Low oil pressure? or just lack of lubrication? IDK
I don't know if the cyl can be sleeved and get a matching piston or but a jug and piston as a fitted set.
 

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Well, we now know the puddle didn't do that. That engine was run low on oil or without oil pressure as rbarre said.

A quick search showed a top end rebuild kit with new piston, cylinder, gaskets, etc for about $450.

But, if there's an oil pump issue you're in for more work. I would put money on it just being run without oil at some point in its life.
 

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Discussion Starter #40
Yes u can feel it with nail, I was going to buy a cylinder and piston as long as we all agree that's the prob, cause rings are melted into back of piston, so how do I get that wrist pin out, could only get one clip out, other acts like it's welded in place
 
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