XJ650 4k0 1980 carbs issues need your help

Hello dear XJ Enthusiasts,
I have for quite a while a Yamaha XJ650 4k0 1980 - europe version and we finally out it back together, but now I am encountering this issue: After getting warm, if I go over 3000 RPM or more - it hangs in there no matter what. I have to kill the engine. Not good.
Clutch not doing anything, throttle cable looks fine with normal play and a good return spring. Now comes the perpetrators.
The carburetors were cleaned and put together in a motorcycle service. The carbs are sync.
I am open to suggestions - we want to reopen the carbs and recheck and reclean everything. We used the parts that came with the motorcycle - nothing new on the carbs except bottom cups seals.
Please give a Romanian a hand in need.

Best Regards,
Roland
Yamaha XJ650 4k0 1980
Yamaha FJR1300 2002
Yamaha Tenere 700 2019

 

Strip, clean and synch them yourself, taking care with every step.

 

Can you please pinpoint me to the thread or discussion link for this procedure on this forum? Thank you in advance

 

Church of Clean

 

https://www.xj4ever.com/hitachi throttle shaft seals.pdf

Where are the idle mixture screws set? Normally after a rebuild they are set at 2.5 turns out from a soft seat if they are the fine thread version, yours may be coarse thread being older so not sure what that initial setting is. Either way, you might try turning them CCW another turn to richen the mixture to see if that helps.

You can also try pushing the linkage closed just to be sure it is not hanging slightly, which sometimes occurs after a rebuild if not assembled correctly