New to the XS400 Community

[Nelso]

Recently, I bought a 78' Yamaha XS400 2E motorcycle with only 10,000 miles on it. However, it appears to be firing from only one cylinder. I conducted compression tests and verified that both plugs are receiving sparks. This leads me to believe that the carburetor might be the issue. Additionally, the fact that it requires constant throttle to start further indicates a problem with the carburetor. Can you confirm if my assumption is correct?
If that is the cause, would it be better to order the 32mm replacement carbs from MikesXS or just send these 34mm Mikuni carbs off to be ultrasonically cleaned, and rebuilt? I'm thinking of performance and cost. Thanks for any feed back or help you can offer!

-Nelso

 

[tstidham]

I would clean and rebuild the 34's and not have to change a bunch of stuff to get the mikes kit to fit. Once cleaned and adjusted, the 34's work great. Mine are working great at the moment and I have no complaints.

 

[Nelso]

I appreciate the feedback. Do you think it is a fuel delivery issue I am facing?

 

[tstidham]

Probably dirty idle circuits and jets.

 

[Nelso]

I'm not entirely certain about the size, but it appears that my bike is equipped with Mikuni Carbs. However, according to my research, the standard carbs for this bike model should be CV34mm Keihin Carbs. Can someone confirm if this information is accurate?

 

[tstidham]

They should be mikuni bs34's.