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Discussion Starter #21

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'84 CX650E that is evolving into a GL500
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What Mark is talking about is sometimes called a "Hamilton Tool" (named in honour of late forum member Hamilton who invented it). I made mine by tapping the inside of the steel part of an old spark plug to accept the pipe nipple (5" long IIRC) with teflon tape to seal the threads. I also replaced the plug's washer with an o-ring so that it will seal at not much more than finger tight (helps keep it from coming apart when you remove it)
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But before you attempt to check the compression you need to make absolutely sure that the valve clearances were set at TDC compression (as discussed in the thread linked below) because there will be nothing to compress if the valves aren't opening.
 

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That's just like mine except my air line fitting is the nitto type.

I did photograph mine but at the moment my computer blue screens every time I plug the card reader into it so I couldn't upload.

When using it put the bike on the centrestand and remove the seat, airbox lid , air filter, dipstick and the valve covers.

Rotate the cylinder being checked until all of the valves rattle. Screw in the Ralpho tool and pressurise with air line. I run full pressure from my compressor - @120 PSI.You may need to restrain the crank from the front but once you get it sitting under pressure it will usually sit still.

Rings always leak through the ring gaps but you don't want to hear a really loud hiss and have a hurricane coming from the dipstick hole.

The heads of course shouldn't leak at all. Listen at the airbox and exhaust pipe for hissing.

A length of fuel line or similar held next to {not in} your ear can be used to probe into the airbox and up the muffler for a better listen.
 

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'84 CX650E that is evolving into a GL500
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I save everything on a big network drive (backed up file by file every night) so I can access them from any computer in the house.
I've only used mine for finding leaking head gaskets (remove rad cap, set cylinder being tested to TDC compression, apply pressure, watch for bubbles). Last spring it told me that both of my GoldWing's head gaskets had failed on the first ride of the season ;-)
 

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1978 CX500 "The Grub", '83 GL650, '82 GL500 Project "AdventureWing", '79 CX500C, '78 CX500 Scrambler
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I built one of those to attach my compression tester. It works for leak down, too.
 
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