Power loss after 4000 rpm

[cpazambrana]

Hi to all. I have a 1980 XS400G with brand new Mikuni VM34 carbs. The bike idles perfect at q200 rpm and runs fine but won't get past 4000 rpm when running. After that she is not responding and she keeps running but losses throttle response after 4000 rpm. As I mentioned the carbs are brand new and original but I left the stock jets that comes with the carbs which are 260 main and 35 pilot. I adjusted the air/fuel screw to the T and bench-sync the carbs. Will I need to go to the bike original carbs pilot jet size of 42.5? Any help will be greatly appreciated.

 

[xschris]

You got the mikesxs ones right? Those are not good from the start. Really anything other than a stock setup ( intake and air filters) is plug and play. There have been a few people to try this setup and most had lots of issues and took lots of adjusting to make sort of usable. Search mikesxs carbs for the threads on this.

As for real mikuni vm carbs most people say the 28-30mm ones work better for our size bikes. I think there are a few threads on these also.

 

[cpazambrana]

Thanks. I don't have the mikes. I had her with a single carb but then changed it to two carbs. Mike xs carbs are the ones that you get in Amazon at $30 each. I got the original Mikuni VM30-83 which are the ones that I used on a kawasaki kz that I had and they worked great with her.