Coolant draining from hose under WR426?

I have an '02 WR426. The bike has been sitting for almost 2 years. I drained the gas, changed the oil and did the usual service. After considerable effort, I finally got it to start. It was backfiring a little, but seemed to run better as it warmed up. After running it for 10-15 minutes (mainly at idle and low speed) coolant started running out of the drain hose underneath the bike. As soon as I noticed it I immediately shut the bike off. What does this mean?

i'm assuming your bike doesn't have coolant overflow bottle?? if it doesn't and you had coolant spilling out its okay. coolant expands as it warms.

It does have a coolant overflow reservoir under the rear fender. It wasn't just a leak, a good constant flow of coolant was spilling out.

Was the coolant hot ? like boiling over hot ?

How full was your catch tank ?

Yes, the coolant was hot, like the bike was overheating. The catch tank was at its normal level. After it cooled it appeared to be a little lower than usual due to what spilled out.

Well that rules out the easy fix I was thinking.

When you say 10-15min at idle to slow speed. Did you go fast at all ?

If you go less than 8 mph your cooling system doesn't work and it is possible to overheat in that time.

Backfiring could also mean lean which would make it run hotter. Look for an air leak/ stuck hot start.

Most of the 10-15 minutes was under 8 mph, so I guess it just started to overheat. Is it normal for coolant to rush out of the drain hose when the bike overheats? I was thinking of flushing the coolant since the bike has been sitting for so long. I'm not sure how often that needs to be done.

Definately change your coolant. Should do it every one to two yrs anyways. I'm not sure on the older wrs but it is usually the bottom bolt on the water pump cover to drain. Your coolant should go to your catch tank though so this means a line must be pinched/ plugged somewhere in your system from the rad to catch tank/ overflow.

Is your bike still backfiring ? Check your plug to see if you're lean. Even if you only speed up a couple times above 8mph it should be enough to not overheat.

It still backfires a little. I assume that means I need to re-jet the carb?

If the bikes been sitting for 2yrs but ran fine before just clean the carb mainly the pilot and main jet, and clean the hot start plunger.

Look for any air leaks on carb boot.

Check your spark plug. If you have a really lean running problem it will be obvious with the white plug tip.

Change your radiator cap also!

sounds like you overheated it because you ran it at low speed for to long .

drive faster and buy some fancy coolant .

+1 on the partially plugged pilot jet.

Change your radiator cap also!

Whats a good replacement cap?

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