Aeromagic Posted April 14, 2012 Share Posted April 14, 2012 I bought an old Shadow to work on during the winter in my garage. It had a cracked head, so I bought another off of E-bay. The seller says it came from a running bike (maybe it sat too long). I got everything back together today, but that cylinder doesn't have much compression - it won't fire. The compression leaks back through the intake valves and carbs. I know I'm grasping at straws, but is there any way that the valves and seats will begin to seal or am I facing an engine removal and disassembly? Anyone have a magic pill to cure valves and seats? It's no VFR!... Link to comment Share on other sites More sharing options...
Guest Posted April 14, 2012 Share Posted April 14, 2012 Try a teaspoon of oil down that cylinder, sea if the compression comes up a bit- will point to worn rings. GL Link to comment Share on other sites More sharing options...
Aeromagic Posted April 14, 2012 Author Share Posted April 14, 2012 I thought of that too. Right now there is no compression to speak of - all the cylinder pressure is coming out of the intake tract. I think the donor bike probably sat with the valves open and rusted - man, I wish I'd checked more closely. I let some oil sit on top of the back sides of the valves, but so far no luck... Link to comment Share on other sites More sharing options...
Member Contributer Cogswell Posted April 14, 2012 Member Contributer Share Posted April 14, 2012 You might double check the cam timing - that should be fairly easy to do without much dis-assembly. A longer shot would be the valve adjustments - you never know what someone else might have done to them (wrong shims, etc). Link to comment Share on other sites More sharing options...
Aeromagic Posted April 14, 2012 Author Share Posted April 14, 2012 Thanks for the suggestions. Valvetrain is hydraulic adjusted - maybe I didn't bleed the lifters properly. I'll check the timing too. Going to work on it another day... Link to comment Share on other sites More sharing options...
Member Contributer hondalover Posted April 14, 2012 Member Contributer Share Posted April 14, 2012 Typically a valve doesn't rust open, and if it does it is most likely not going to make it through the next time the piston comes to TDC. Being it's only the intake valves, I would venture to guess you have a set of bent valves. And with the descrpition of the eBay ad, "came from a running bike" can still be correct. My VFR ran on two cylinders after I dropped the rear cam chain. It didn't run well, but it did run. Good luck. Link to comment Share on other sites More sharing options...
squirrelman Posted April 15, 2012 Share Posted April 15, 2012 You can do useful leak checks on the valves by filling the up-turned combustion chamber with fuel while the head is on the bench. Link to comment Share on other sites More sharing options...
Aeromagic Posted April 17, 2012 Author Share Posted April 17, 2012 I went out to the garage after leaving the bike sit for a day and it fired right up and ran smoothly! The only thing I can think of is that a lifter bled down in that time and allowed whichever valve was hanging open to close. There is a procedure for bleeding the lifters in the Clymer manual, but it's a little vauge so I must have done something wrong. Thanks for the suggestions guys - all is well. Link to comment Share on other sites More sharing options...
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