KX100 goes hard then bogs down after 5 minutes?

[Orville]

Hi all,
My KX100 goes really hard after start up and for about 5 - 7 minutes, then (when its warm) goes off the boil - will not get back on song and bogs down like its running out of fuel. All I can do limp back to base. What is going on? I changed the plug - it made no difference - same fault. At first i thought it may be an air lock in the fuel dilery - maybe the tank was not vented to atmosphere - so I ran it with the cap off - still no go - wait for it to cool down - whammo - flying superbly - again soon as its warm - bog down time?

[Motorrad]

have you checked the water pump?    perhapse a broken bolt....

[Orville]

Ok, so it might be overheating? Thanks shall check that out.

[Motorrad]

Ok, so it might be overheating? Thanks shall check that out.

very possible....

[Ims Roll]

could be a bad head gasket? head seals when cold then as soon as in heats up starts leaking?