Do I have a cooling problem?

[razorboy]

When I start my CR250, it fires first kick and idles pretty good.

I run the bike up and down my lane a few times and it starts to make surging type sound.
it sounds like boing--ding-ding-dign-boing-ding-ding.
The boing being the strange sound and the ding being the typical 2-stroke sound. I can also hear what sounds like detonation when I get off the throttle and coast.
When I am on the throttle, the bike seems to run pretty decent.
After I stop for a few seconds (maybe 10sec.) the boing sound goes away and the normal bing bing sound comes back.
It all seems funny I know but it is the only way I know how to describe the way it sounds?
Could this be caused by a faulty cooling system? Is it possible that my water pump is failing and not cooling the head properly?
whaddaya think?

B2

 

[NacNac250F]

When you say the boing sound, do you mean that it is bogging? You won't really hear the bike detonate unless your really hard on the gas in which case it sounds like the chain is repeatedly slapping. It's hard to understand what you mean by the way you described it. Are you warming the bike up before you ride up and down your lane? A two-stroke will run bad and could even mess up the motor if you dont warm it up before you ride.

 

[razorboy]

No,
I mean a lump in the sound of the idle....
The best way to describe it is almost like a surge every couple of seconds?
The bike was plenty warm. It actually doesn't do it when the bike is cold. It only starts after I run the bike harder. After I let it idle for a few seconds, the boing sound goes away?

Very Strange?
BB

 

[mojonito]

air leak somewhere near the reeds could be responsible. when hot, it sucks in air and surges.