Yamaha YBR 125cc Missing/ Bogging from 6.5 to 8 RPM

[Plover]

My YBR has started missing after i got its oil changed and filter cleaned, just after this.
It has done 15k and never faced any issue.

But just a short trip to mechanic and this happened. I am feeling very said.

First i though it must be because of chocked filter so i run it without filter but nothing gain. I replaced filter still same issue. I've cleaned carb thrice. Cleaned fuel filter aswell. Changed spark plug.

It has a cv carb.

if i accelerate in 3 gear the missing is very less and not much noticeable so it can pull the rpm upto 10k
but in 4th gear it struggles to pull the rpm and the booging or missing is more evident.
in 5th gear the missing starts from 6k rpm, it boogs and produce less power. so it can't pull beyond 6k or 7k.
on downhill it pulls to normal 9k rpm in 5th gear giving max speed on speedometer as usual.

Spark plug color is good tan like before. plz help. plz help.

[stinkwheel]

Who did the oil change, did they fill it to the correct level?

One thing I've seen after a service is someone trap a wire under a cover or piece of bodywork which can cause intermittant electrical issues.

Some of what you are describing sounds like it might be fuel starvation. Is there good flow out of the tap? Try riding it with the fuel cap loose in case there is a blocked tank breather.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[WD Forte]

CV Carb?
If its a carbed YBR then it must be pre 2007 ish
Also, Fowlers fiche shows them to come with bog standard slide carb
not CV carbs. This suggests owner 'improvements' ?

If you do have a CV carb, the symptoms suggest a dodgy diaphragm perhaps

My old 250 had a stiff one.
____________________
bikers smell of wee