Carburettor Help

[ZedHead]

Hi Arctic fox
based upon the pictures I would say it's the third carb and it's a Mikuni VM28SS. The black rubber shouldn't be on the copper tube. The copper tube is connected by a rubber hose to the vacuum fuel tap.
You have to look for a number embossed in the carb slide. If you found that number you can identify the type of bike it was on originally. My guess: a Z1000ST or Z1000MK2, the carbs are very similar, only the main jets are different.
Good luck
Philippe

Makes sense for these to be 1979/8 carbs which went back to Air screws instead of the under bowl pilot screws

I agree the rubber plug should not be there, although I think the nozzle are breather vents. Does the fuel tap vacuum pipe not come off one of the vaccum gauge take offs?

Is there a cross reference somewhere for the slide numbers?

[Philippe]

Hi guys

@ arctic fox: sorry I can't help you with the jetting. As I wrote: I allways mount them to standard specs and have no experience in adapting those. I'm sure there are some guys on the forum who can help you out.

@ zedhead: in the case of VM28SS carbs the fuel tap vacuum pipe doesn't come from the rubber intake nozzle. It comes from the nozzle of the third carb. Take a look at that carb: the nozzle exits in the bore towards the intake rubber . When the engine is running the suction creates a vacuum, opening the diafraghm in the fuel tap allowing fuel to run to the carbs.
I don't know if there's a cross reference for the slide numbers, I try to determine what carbs I have and then check the details in the technical workshop manuals in order to be sure.
GrtZ
Philippe

[ZedHead]

@ zedhead: in the case of VM28SS carbs the fuel tap vacuum pipe doesn't come from the rubber intake nozzle. It comes from the nozzle of the third carb. Take a look at that carb: the nozzle exits in the bore towards the intake rubber . When the engine is running the suction creates a vacuum, opening the diafraghm in the fuel tap allowing fuel to run to the carbs.
I don't know if there's a cross reference for the slide numbers, I try to determine what carbs I have and then check the details in the technical workshop manuals in order to be sure.

Thanks Phillipe,
It is hard to tell where the nozzle exits from the picture. There appears to be galleries going to the bowl breather?

I have figured the throttle valve numbers are just the cut off height. Which is shown in the parts manuals to assist in identification.

I am pretty convinved that Neils carbs are non-US MKII

[Philippe]

Hi Zeadhead
the only difference between MK2 and ST carbs is the size of the main jet. MK2 has a 105 main jet, the ST has a 110 main jet. You can mount the same carbs on both of the bikes, 0,05 mm doesn't make a big difference.
GrtZ
Philippe

[ZedHead]

Hi Zeadhead
the only difference between MK2 and ST carbs is the size of the main jet. MK2 has a 105 main jet, the ST has a 110 main jet. You can mount the same carbs on both of the bikes, 0,05 mm doesn't make a big difference.
GrtZ
Philippe

Thanks for sharing your expert information on this. Just one addition from me. Mikuni jet numbers are the flow rate in cc's per minute when poured from a height of 50cm's. The attached gives details one persons research on the numbers.

[Arctic Fox]

Inspected the carbs, those nozzles go to the top of the fuel bowls, so are indeed breathers.

[Philippe]

Hi Zedhead
thank you for the explanation! JC I didn't know that!!! I assumed it was the diameter in hundreds of mm that was stamped on the main jet. Now I know how little I know. Thanks again Sir.
GrtZ
Philippe