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Way too high compession...

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gcha1727

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I just reassembled a 787 motor, top and bottom. Im getting compression around 250 from mag cylinder... My pto is kinda high too...around 155-160...I checked gauge on other motor and shows 140-150 so i know its not the gauge... Anyone know what I have assembled wrong????
 
oil fillng motor

well, I guess that could be the high compression cause. Im not sure yet how to make it stop flowing... Ive pinched the lines for now. Why would oil flow into motor without it running???
 
Compression?...

Usually, when your compression is over 150, you have oil or gas that is sitting inside the motor. If this is an older crank, your oil can be coming from a leaky rotary seal. Which, if this is the case, will eventually need to be replaced. Or, if you can get it to slow enough to run the motor, sometimes, the heat will reseal the rotary seals.

Pinch the bottom oil line from your tank to the rotary chamber. If necessary, drain the oil from the chamber till you can determine that it where your oil is coming from.

Before doing this, I would pull the pulse line off your casing to your fuel pump on the carbs and make sure you dont' have a hole in your fuel pump, gravity draining fuel into your crankcase.

But, anytime your compression is that high, it's from trying to compress a liquid.......
 
I agree.

ALSO...

The safe thing to do is to check your squash band gap. if it's in spec... you will be fine after the engine is started.
 
Its def. oil flooded

Thanks for the responses. I probably lost a couple quarts into the motor over 1-2 hours... I blew most of it out yesterday... I just had this motor completely apart, top and bottom... Due to a screw off carb into motor...I replaced complete rotary shaft with a used one that was seemed to be in good shape...along with RV...new pistons... inspected crank(best I could)...no previous problems with crank...but pulled it out ,cleaned case...everything seemed to go back together well...MAYBE I REASSEMBLED WRONG??? It seemed pretty straight forward...I didnt pull anything loose from crank...The thinkness of the wheel (the part the RV locks to) on RV was a little bigger than my old one...Everything else on it is identical...I was told this wouldnt matter...Dr. Honda Im not sure yet what it is you suggested to check, but I will look into it...THANKS AGAIN FOR ALL THE HELP
 
why would this motor pull oil from tank

Any ideas on why this motor will continue to fill with oil?

Is there anything I can check before pulling it back out and totally disassembling it?

Can I cheat and just install some kind of shutoff valve inline?
 
Thx dr honda for your input

I had leaked a quart or two in an hour in the motor. Could I lose that much with a bad seal?

I started a new thread with alot more info about this problem since its kind of a new problem. Its titled oil flooded and engine vibrating. If its not too much trouble can you give it a look to see if anything else might come to mind??

Thank you dr. honda and anyone else that may help!!!
 
changing seals...

Hey dr honda...how do I check/replace the seals on the crank?? Someone else told me the seals are part of the crank and are not replacable...and the whole crank gets replaced... Are they just trying to sell me a new crank???

Was I suppose to seal this crank somehow during assembly??? Its weird that I went from no known leak to the floodgate opening...

Any chance It could be something with RV shaft...I replaced my bad one with a used one that appeared to be in good condition..

Im just tryin to get into this with a better sense of direction...Thanks
 
Yes and no.

Yes the seals are replaceable... but if you don't have the equipment to do it... then you replace the entire crank. (you have to press it apart, and back together) I own the equipment to do it... and I won't do it most of the time because normally when the seals are bad... it's time for a crank rebuild.

If you have a freshly rebuilt crank, then it's worth changing the seals.


You can loose that much oil thought the RV seal, which is replaceable by a home mechanic.

As I read back though your posts... the info is a little broken. Since your RV shaft was set too deep... did you damage the gears?


Honestly, if you are loosing that much oil into the engine... I would take it apart and check everything again.

I will look for your other thread and read it too.
 
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