BS38 carbs without Mikuni marking on top of carbs

[hamma]

Do all Mikuni BS38 carbs have a stamp with the name on the top of them? I picked up a set of what appears to be a 1978-79 set of BS38 carbs for my 1977 xs650 but not sure they are genuine Mikuni. They are blank on the tops - no markings at all. Any ideas as to what that means? Thanks

 

[jetmechmarty]

Pictures. Please attach pictures.

 

[hamma]

Here are my pics. Another thing about these carbs are that the brass tube that should be pressed into the inside of the float bowl is missing - on both carbs. Not sure what the tube is though.

 

[gggGary]

Those are the correct 78-79 carbs, 78-79 do not have external float bowl vents or overflows (the brass tubes) float bowl vents are the small holes in the intake bell. This improved how they worked. The lettering on the cap was raised, someone filed, sanded it off.

 

[hamma]

Ok Thanks for the reply. I guess I should be able to rebuild these to original specs. Do i need to change jets (main and/or needle) if all I'm doing is adding pod filters?

 

[gggGary]

Start with stock jetting I've had several running well on that.

 

[hamma]

Will do Thanks again

 

[nj1639]

That's a good year for those 38's.
Mine come off the enrichener 15 to 30 seconds after startup, pulls strong.

 

[5twins]

Yes, the last set of BS38s, and what many of us consider the best. They are the most refined. They have spring-loaded needles which gives smoother low and midrange performance. You look to be missing the angle bracket that goes between the carbs across the lower front .....

Easy enough to make one if you can't find one somewhere. I can provide you with the hole spacing measurements if you need them.

 

[hamma]

Thanks guys with your input. I have another question. It doesn't appear the mixture screw ever had a spring, only the o-ring. I have to believe that is how it is suppose to be because there really isn't enough room for a spring having the stepped type screw and as short as it is from the point to the threads. Is this correct?

 

[Jim]

I'm not aware of any carb's mix screw not having a spring. The spring tensions it.... kinda like a lock washers so it doesn't turn from vibrations after it's set.

 

[5twins]

No, there should be a little spring on it. It holds the screw where you set it. Don't know where to get one though. You can't buy them new anymore. Scrounging one may be your only option. Check the hole the screw came out of, often the spring stays stuck inside.