Honda MTX 125 rev limitations

[chloeejones12...]

Hello,
I have a French model MTX 125 with the atac system installed.
When out Riding the bike it will ride perfectly then will suddenly start limiting revs, before the power comes and goes making the bike jerk then it completely dies. Once the bike has been turned off and back on it rides perfectly again.
Recently this intermittent problem has been getting worse and is happening more often as well as being more stubborn to restart. The bike especially doesn't like being under load or going up hills and has been known to limit revs/ power in gear 1 right up to gear 5.
I have cleaned the atac valve.
The head was inspected 80 miles earlier.
Checked the spark to earth.
And the carb has been cleaned regularly, I might take this out today just to be sure.
I would really appreciate any help, diagnosing the bikes problem has been really hard with the problem being intermittent.
Cheers chloe

[-]

Sounds like fuel starvation. What's the flow like if you pull the fuel hose off the carb? Sometimes there's an inner filter in the tank petcock which can almost melt over time with modern fuels.

Is there a vent in the filler cap, is it clear?
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