Compression Test gone wrong!!

Discussion in 'Outboard Maintenance' started by AfterHours2, Jan 17, 2011.

  1. AfterHours2

    AfterHours2 Stripper in my own Mind!

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    Well after I finally got my motor put back together and running, I decided to put on the old tester for a test. Unfortunatly, I didnt notice the long adapter on the end and just screwed it in. Long story short, the fitting screwed too far into the cylinder head and when I turned the motor over it smacked the hell out of the piston top. It doesnt seem to run any different but was wanting opinions as to the damage that I might have today or somewhat in the future due to my stupidity. Thx :-[
     
  2. cutrunner

    cutrunner Cert. Yamaha technician

    Depends on how long you turned the motor over with the wrong adapter in and how much longer it is than the right one. If its a tenth of an inch and only a couple times i wouldnt sweat it to hard, but if its an inch longer i would further investigate damage. Pull the plug out an turn the motor so that that cylinder is at top dead and inspect the damage. But for reference changes in the piston surface affect quench in the combustion chamber
     

  3. AfterHours2

    AfterHours2 Stripper in my own Mind!

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    Thx for the info. Unfortunatly, the adapter was about a half inch longer. On a good note, maybe, I only turned the motor for a second and realized there was a problem. When you refer to the "Quench" of the piston, are you refering to needing more fuel for combustion? I know this is a newbie mistake, and a dumb one, but this is only a one time issue and I can deal with that. Thx again!
     
  4. levip

    levip I Love microskiff.com!

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    no hes referring to the distance between the bottom of cylinder head and the top of the piston its call quench height and if you only hit it for a second it might not have done any damage .... turn the engine until that piston is at top dead center and shine a light in the sparkplug hole and tell us what you see if its just dinged a little it shouldnt be bad
     
  5. AfterHours2

    AfterHours2 Stripper in my own Mind!

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    After further inspection, the piston top seems to have a slight impression on it but nothing major. This motor is a going to be a learning experience so I think I will just continue on and if need be rebuild it completely at a later time. The throttle gears have been a nightmare to replace financially so far as they were completely frozen and broke. I think I will just take it one step at a time. Beats the price tag of a new one however. Thx for the help fellas! Happy fishing. ;)
     
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