Cam Chain Guide - How far should I go?

cfinn1

I was in the process of replacing a small spring that had broken on the shifter that was causing the bike to jump out of gear and I notice lots of black debris in the oil filter Sad

so.. it looks like I have a cam chain guide replacement in the near future.

Million dollar question is how far should I go while I'm in the process? The bike is an 1981 with 20K miles on it. Bike runs great so I wasn't planning on tearing into it but I guess I'm now forced to.

Just change the chain and the guides?? Rings, valves etc... ???

xsjohn

If it were mine with 20 thou....I would replace the chain and guide and run it.....

Could check endgap on the rings and skirt clearance......would suspect the way you say it runs that I wouldn't even hone it..........Valve seals might be worth the time....they are cheap........hand lap the valves while you are there........

With no noises or other wierd soundsthats the way I would go unsess you see something strange.....

John

cfinn1

Thanks!! This will be new territory for me so it will be an educational experience. Always interesting

Joseph · Full Member Joined: May 22, 2007 Posts: 767 Location: NY

What is valve laping?

xsjohn

Hand lapping involves applying lapping compound (an abrasive paste) to the valve face or seat, and then using a suction cup on the end of a short stick to rotate the valve back and forth while slight pressure is applied. This smoothes off any imperfections on both surfaces and results in a near perfect seal.

John

5twins · Full Member Joined: Aug 05, 2006 Posts: 1616

Test the valves first for leaks before you tear them out and lap them. If not leaking, then you don't need to lap them. Turn the head upside down and with some old plugs installed, fill the combustion chambers with some sort of solvent (I use kerosene). Now some guys just peer into the int. and ex. ports and look for any liquid leaking by the valves. This isn't good enough. It will show a really bad leak that way, but not minor ones. You must blow compressed air in the int. and ex. port and watch the edges of the valves for bubbling.

I just did my top end this spring. This compressed air test showed both ex. leaking but both intakes good. No liquid leaked by them just sitting there. I cleaned the ports up so all the valves were coming out anyway. They all had pitting on the seats so they all got lapped. The ex. were pretty bad and I thought I might have to take the head somewhere and have them cut. About 3 lappings cleaned them up, though. Testing afterwards showed all the valves sealing tight as a drum.

xsjohn

Still need to release the springs to change the 25 year old basted seals if you feel the need....might as well just lap them while you are there.....doesn't hurt anything....just an hour or two of your time.....does require valve spring remover....fashioned mind from a long c-clamp.......almost a two man job to get the keepers back in..........with some cussing......well at least then the head is right.......valve seat erosion can hurt things later... especially after finding lean epa settings and unbalanced mixtures that work bad things on the valves and everything else..........been there and done that.......

John

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