Why are these allan caps here?

[xswheels]

They are threaded into the cylinder head, adjacent  to the spark plug, and I guess allow access to the water jacket, but why?

[Lucky]

those are your head bolts

[nwrider]

Wish my bike was that clean....and new looking!

[xswheels]

those are your head bolts

No they're not. I'm talking about the cap with the allen wrench still attached.

[xswheels]

Wish my bike was that clean....and new looking!

Thanks, but it's only that clean because I'm working on it plus it's put away clean for the winter.

[Lucky]

ok, i was looking at it on a dim small monitor at work last night.  i forget what it is open it! i dare you!! :) :>

[xswheels]

I'm pretty sure if I remove it I will get a uncontrolled gush of coolant. I really don't need that.

[Brian Moffet]

I looked at the micro-fiche and Haynes manual (didn't go downstairs for the service manual in the garage) and I suspect you're correct. I couldn't find them in any of those places.

However, I think they are there as part of the casting process rather than for any useful thing.

Brian

[Jimustanguitar]

It is the "Awesome" control, adjust it as high as you can.



Just kidding, I couldn't tell you what it is from memory.

[Jimustanguitar]

Taking a closer look, there is no mention of that bolt in the yamaha parts manual that I can tell. I would imagine that the bolt in question plugs the passage that you can see the drill hole from on the face of the cylinder head.

That's my best guess.

Did you try removing it? I'm not recommending that you do, but I'm curious what it is in case you did.

[xswheels]

I would imagine that the bolt in question plugs the passage that you can see the drill hole from on the face of the cylinder head.

Nope, it doesn't do that. First off I am sure it's not a bolt, but rather a cap. Secondly the drain hole should always remain unrestricted. It's there to drain the spark plug well.
I'm convinced no good would come from trying to remove it.

[Brian Moffet]

To really test it, you would start the bike up, let it get good and hot, and then open it  ;D

(Warning, no user serviceable parts in here...)

[xswheels]

Hey you might have something there. You can turn old retired Visions into a fountain. :o

[musicweb]

It is a coolant plug....

I had to remove mine because of slight weepage.

Cleaned it up, applied a little thread sealant, and it seems OK now.

BTW...there is also a metal gasket in there....