Coolant flush and refill technique.

[CYCLE_MONKEY]

I just flushed and refilled my cooling system the other day and thought I'd share this:

When I first moved here to Boulder Colorado (about 5,400 ft above sea level) from Cleveland (about 200ft) I noticed when I would ride in the mountains (about 9,000ft), my bike would spew coolant out the overflow tube from the catch tank. There was one time where it was actually bubbling in the catch tank like a waterpipe(!!) and it was prone to running hot. Well since the coolant was dumping in front of the rear tire, it was a major concern. What I figured was happening was that the cooling system wasn't properly filled in Cleveland and there was an air bubble in there from that lower elevation that was expanding at our upper elevations. So, what I did was uncap the radiator while on the sidestand and let it run until it got hot, while adding coolant to it. I saw several big bubbles come to the surface while doing this, and when the coolant expanded until it was at the top of the filler neck, I capped it, and topped off the catch tank.

So, when I did a flush and refill recently, I basically did the same thing. I emptied out as much of the coolant as possible (there was still a little left below the radiator return hose-neither are located at the bottom for whatever reason), and then started the bike and kept pouring fresh distilled water into it while running until it came out as clear as possible. Then I reattached the return hose, poured enough pure antifreeze in to dilute the water 50/50, then ran the bike on the sidestand while pouring fresh 50/50 mix into it. As before, I saw several big bubbles come to the surface, and kept filling it while running until the coolant came up to the top of the neck again and put the cap on and topped the catch tank off. I let it cool overnight and the system pulled a lot of coolant out of the tank, so I checked the radiator (totally full), and then topped the tank off again. I've taken it back up in the mtn's twice now to 9,000ft and haven't lost a drop, so I feel confident that I've gotten all the bubbles out.

Happy wrenching!

[frank2]

Frank, on my K-5 there is a bleed screw on the thermostat. This is to be opened when the bike is running. Thus releasing all the air. Does the K-1 have a bleed screw?

[CYCLE_MONKEY]

Frank, on my K-5 there is a bleed screw on the thermostat. This is to be opened when the bike is running. Thus releasing all the air. Does the K-1 have a bleed screw?

Good question. I'll look in the manual and let ya know. Thanks!

[OUTLAWD]

my K3 does.

another tip I learned was to fill it up cold, cap it, then lean the bike over on both sides (if you can hold your bike up without dropping it). this will make the air pockets rise to the highest point (cap) if they are stuck at all.

[CYCLE_MONKEY]

So far all seems well, I've gone to elevation twice now without a drop of leakage, so I think running it with the cap off got the bubbles out by flowing the coolant, as I saw a couple major bubbles come out, but I'll check the manual about the thermostat.