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Radiator overflow tank behavior ?

7699 Views 12 Replies 7 Participants Last post by  Dirt_Dad
This was a new one for me. Riding 300+ miles home today from New York. Outside temps in the low 90s and I notice I'm seeing 3 bars on the temp gauge more than normal. I stop and I hear a gurgling sound. A check of the overflow tank shows the level about an inch or more over the full line.

About 3 minutes later I look again and the overflow tank is completely empty. Restart the bike and at speeds less than 50 MPH the gauge is always reading 3 bars. 50 and over it goes back to 2 bars.

I found some wet spots on the left of the crankcase and I assume my top hose is leaking. That's easy enough. I assume the gurgling is from air getting sucked into the hose.

The thing I'm confused about is the disappearing fluid in the overflow tank. Is that expected behavior? I witnessed this on two different stops. Is that just what happens when there is air in the system?
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I was having this problem since replacing the rad on my Vee and recently running it in hot weather.

The solution was to fill the overflow tank to between the lines, run the bike 'til warm, then lean the bike WAY over both ways with the engine running.

The shop manual indicated to do this procedure, but I blew it off and as a result, had trapped air in the engine somewhere. Apparently, leaning the bike over allows the air to escape back into the overflow bottle.

I've run the engine to 3 bars a few times since 'burping' it and it hasn't overflowed yet.

It worked for me, anyway...

Good luck.
Not sure how the next turkey is going to taste flavored with old motor oil. :mrgreen:

Not to mention the popcorn...
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