I am doing a valve adjustment on an '87 CBR 600. Manual has the procedure. However, they use numbers to determine which valves to adjust without presenting any picture I can find or what valve set (cylinder) is what number? Since they are asking me to look at the cam lobes for #4 from the side of the bike where the T mark is adjusted, I assume the cylinder numbers are 1-4 going left to right, but just want to confirm before I destroy this thing. Thanks.

 

So far the exhaust valves seem too tight, assuming 1-4 left to right facing forward on the bike. Is this unusual for valve clearance to be too little? I would think things would wear and get loose. From the valve cover gasket condition I assume no one has touched this in 10 years.

 

When you get your cover off and the cams set to the #1 TDC marks, #1 will be on the heels of the lobes while #4 will be toes down on the valves. Then you will know where #1 is and go from there.

 

And 2 and 3 are in order between 1 and 4, I assume. So that makes sense.

My numbers show that all of the IN valves are at .005 (except 4 that is at spec .006) and all of the EX valves are at .007 (vs. spec at .008). I would guess this is not enough to explain poor acceleration performance and inconsistent idle as the bike starts to warm up.

 

The valves get tighter as they wear. As the valve and seat pound on each other over the years, they sink in closer to the head and the stem will get closer to the lobe. As the clearance reduces, the time open increases, eventually having the edge of the valve exposed when that cylinder fires. That results in a burned valve, then engine failure....

Moral is: loose is better than tight. Set them on the loose end of spec where possible.

 

Ok. I can do that; for a learning experience if nothing else. But I don't think this deviation will explain the engine ticking as it warms up or the lurching idle and fluttering acceleration (unsolved by one major carb rebuild and one used carb install, as well as new plugs, filters and more). So I am guessing this bike is going to be parted out or sold for parts. It has been a major time sync and the fundamental problem remains unsolved. Without new replacement parts; not sure I see it getting fixed. At 32 years old; every single part is suspect and buying more used parts is just a guessing game. Plug wires for example; they looked awful and I did my best to repair them (disassembled, cleaned and sprayed with contact cleaner; but I still have no confidence they really work.

I appreciate the input.

 

Maybe the ticking I am hearing is not mechanical but is a result of the exhaust valve slightly open when the cylinder fires as the bike warms up and my low mechanical tolerance increases due to the heat (aka. my .007 exhaust valve gap becomes .006, .005 as the metal expands). Just hoping I guess. I also experience improvement at higher RPM; perhaps due to mechanical advance, perhaps completely off base but again, just hoping.