Overheating inlet valves XS400SE SOHC ?

[thegrouch]

guys,

I was doing the yearly check on my XS400se and hit the wall when it came to inlet valves clearance check - I couldn't remove the caps covering the regulation screws. After using some not-very-smart-but-effective tools I managed to actually loosen them, but... I had the same issue last year and I was cautious to not overtighten them then. And yet - it happened again (good they are still available).

The head seems to pick up a bit of heat in this area, since it's colours are somehow different from the area of outlet valves and resemble the exhaust pipes - not like dark blue, but somehow reddish/copper like colours.

Is it possible that the inlet valves "leak" and heat up the head from inside or it's rather a matter of heat being transfered from the front of the engine?

thanks
oscar

 

[bcware]

Use anti-seize on the caps and they will not get stuck.

If your valves were leaking at the seal in the combustion chamber you would lose compression. If the valves are leaking at the oil seal they will leak oil and burn it.

The valves themselves do act as a heat sink transferring heat out of the combustion chamber, but I have never heard of them causing external signs of increased temperatures on the head.

Do you mean the color of the engine externally is discolored? Or are the valves discolored? Discolored valves might occur due to leaking valve seals; the oil will build up on them.

Maybe you could take a photo?

 

[thegrouch]

Well, I do loose compression... I was trying once to check valves using compressed air, but that didn't bring any luck since I didn't have a really good compressor and sparkplug attachment. The "oil test" didn't bring any solution either so I am not really sure which way it goes... I'll try to take a photo, but that'll be no sooner than Sunday/Monday.

 

[bcware]

Do you have a traditional compression tester? Like this:

 

[16VGTIDave]

The reddish/copper deposits on and around the intake valves are typically additives put in the fuel. Not to worry unless they are building up excessively.