Sorry, I misnamed this topic. I will be installing a 40 mm CV carb on my Softail Heritage. It will be replacing an HSR 42 Mikuni. My question is....will the spigot on my CV carb fit directly to the intake manifold, or will I have to replace the manifold altogether, or perhaps find some kind of adopter? I don't know yet if the spigots on the Mikuni and the CV are different sizes. Thx

 

If they kept the original intake manifold with the slip on connection when installing the HSR42, then it should like the factory setup. If they used a Mikuni manifold, that have bolt flanges and require an adapter. And depending on the age of the HSR42 (older ones used different cables), you may need new throttle cables too.

So have a good look at the existing manifold and try to identify it, or take some pictures and post here.

Anything wrong with the Mikuni? They are good carbs once dialed in and typically do not require much maintenance after that.

Paul

 

One reason for getting rid of the Mikuni was all the clacking. I just heard it with a stethoscope, without the air cleaner, and it sounds like a Detroit diesel. The noise is clearly coming from the carb. I don't want to start an argument about that at this stage of the game. I am way passed that. I have the new CV carb and will be taking off the old one today. I will find out today if the existing manifold accepts the CV carb.

 

I get it. The clacking noise is from the slide (and it is annoying), which is vacuum operated. On a vtwin they are noisy as all get out because of the pulses or the two cylinders, so I understand. I'm running one and have threatened to replace it several times because of that, but it's only at idle and the bikes runs well with it.

Also, the choke cable is different for the Mikuni. They look the same and will fit, but they don't work correctly at least moving it from the CV to the Mikuni, it will cause a rich condition because the en-richener plunger won't seat properly. So unless the original choke cable assembly from the original CV cab was reused on it, you will need to get the correct replacement. The Mikuni choke cable can be identified by the brass tip at the center of the pull **** (see the image below), and that the cable will not stay in the chocked position, it will automatically return to the open position.

Generic image of the Mikuni manifold below and an OEM EVO manifold too.

Paul






OEM Evo manifold with no flanges

Mikuni manifold with flanges

Paul

 

The spigot a on the CV40 and HSR42 are the same size.

 

Max Headflow, I have the CV carburetor and the Mikuni carb here, side by side, and even with the naked eye, I can tell that the Mikuni spigot is larger. I tried inserting the CV carb in the manifold, using the old rubber boot, and the carb fits way too loose. I doubt that they would sell a rubber boot to make the carb spigot fit any better, but I don't know. It appears that the original owner of my bike used all Mikuni parts. I will now have to find a new choke cable(pgreer was correct about the choke cable) and new CV manifold.

 

Are you sure the Mik is a HSR42 or is it a HSR45? What are the diameter of the spigots?

There is the size of the carb spigots. Carb Mount. The HSR42 is only 0.005" larger than the CV40.

 

Yes, I confirmed with my mechanic, who had the carb off about four weeks ago, that it is an HSR 42. Even with only 0.005" difference in spigot sizes, the spigot in the CV carb fits too loose in the manifold, unless I can find a beefier rubber boot that will make up for the difference of 0.005"

 

If you have the manifold and rubber adapter in the pick above, isn't there a hose clamp? The HSR42 was designed to be able to plug right into the stock manifold. About all you had to do was replace the seal if going back to a CV40 over the HSR42.

 

I have to correct myself. My wife was able to get a photo of the manifold. Surprisingly, it is a Screaming Eagle, HD part no. 29637-99. It did not have a hose clamp. The spigot from the Mikuni was simply pushed in. The CV carb should have fit the same way. I just don't understand why the spigot of the CV carb, which is a 40 mm, fits so loosely in the existing manifold seal. As you all have said, it should have been a direct and snug fit. Tomorrow I will be going to a motorcycle shop to see if they have a seal that will allow the CV carb to fits snugly. Thank you all for your assistance.