1973 TX650: No Compression

[Oldschool]

I picked up a '73 yesterday from FB Marketplace. It had been setting in a farm building since 1987. The owner passed and gave it to his BOL just before. The BOL found that it was beyond his abilities: I expect to do the same. But I have had a 1976 for these last 43 years, so I have a chance. A quick look tells me that the '73 has a compression release that the other doesn't. The '73 has absolutely no compression, and also no noise at all when cranked over by hand. If the release is stuck from setting that long, will there be zero compression? I thought there might be at least a bit. The other cable operated units are stuck pretty tight, as expected, really. I can't take it apart for awhile. So this is mainly to quench my curiosity mostly. I will respond with the answer at some point when I know. I had hoped to meet many of you in Arkansas, but I now have to make it next year as I don't have so many more. Thanks for any hints.

 

[5twins]

Well, the compression release only works one cylinder so that one would have zero compression if it was stuck open, but the other cylinder should have compression still. But from sitting, it's possible a valve is stuck open, or maybe the rings are stuck compressed in their grooves. Or, heaven forbid, there's a hole in a piston top, lol. If it is a stuck open valve, be careful turning the motor over or the piston may strike that open valve and bend it. You can often see a holed piston if you remove the plugs and look in the plug holes with the motor at TDC.

 

[Oldschool]

Great summary. I'll use your points faithfully. Thanks 5Twin.