kx100 missing at top end

[waggie16]

my son has a 97 kx100 which blew a head gasket so i replaced it and threw in some new rings aswell while the head was off but when riding now at full throttle in top gear it starts to missfire and sounds like it wants to cut out,what could be causing this is it a minor detail such as filter plug etc or does it need a rebore and new piston as this only happens in top gear.the plug is a br9eix

[radio592]

that happens to mine when im low on gas. put fresh stuff in and try

[FPMXer]

A dirty airfilter will cause your symptoms.

[waggie16]

come to think the filter hasent been cleaned in a while if thats all it is then happy days thanks.

[FPMXer]

?

[ToddOwnz]

is that what it was?? (<--haha, stupid banana)

[waggie16]

havent tried it with clean filter yet as forks are going in for a service hope thats all is,carnt really think what else it can be the bike goes like hell and will stay with my 02 yz125 on short tracks no problem.?

[yz boy]

did you break it in right