Struggling to get past 45 mph

[OllieRust]

Bike Model = : Aquila GV 125 2004

Hi everyone,

Looking for some advice with my bike as I’m running out of ideas.

The bike has been running badly and seems to be running lean/poorly under throttle. Symptoms are:

• Bogging/ feeling like a rev limiter at 7000rpm
• Poor running especially under load struggle to get past 45mph
• sometimes going through rpm it’s sticking at certain points
• Occasionally feels like it wants to die
• Bike has an aftermarket exhaust fitted
• One spark plug was heavily black/carbon fouled while the other looked more normal

So far I’ve done the following:

• Removed and fully cleaned both carbs they looked alright!
• Removed main jets and pilot jets
• Sprayed carb cleaner through all passages and holes
• Checked the diaphragms and slides
• Cleaned emulsion tube area/passages
• Inspected airbox boots/connections hard to tell
• Fitted fresh oil
• Bought new NGK plugs (currently sorting plug cap compatibility)

The stock main jets are 82.5 and I was considering going to 90s because of the aftermarket exhaust, but I’m unsure if that’s masking another issue like:

• vacuum leak
• weak spark
• carb sync issue
• diaphragm issue

The carbs are an absolute nightmare to remove/refit on this bike so I’m trying to avoid repeatedly tearing it apart unnecessarily.

Based on these symptoms and what I’ve checked already, what would you guys look at next

Any advice appreciated

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