Some of you may recall that I had a very qualified carb guru give my ZS carbs the once over trying to resolve poor idling and sticking needle valve issues. "The three darlings", as I liked to call them, seemed much better after the do over, but that lasted less than a year when the needle valve issue once again raised it's ugly head.
The "three ZS darlings"
ZS needle valve...brass color with plunger in the middle and a hole on either side
Late summer 2018, I had to turn back home on the way to 2 different car shows because of stuck needle valves...wife Rhoda, being the ever sensible one, asked me, "Isn't there a more modern thingie available to replace the ZS thingies" ?
Well of course that got me thinking and I remembered hearing about Mikuni carbs. A Google search turned up John Parker's company, "Vintage Performance Development" http://www.v-performance.com/products/air_fuel.html.
A review of the excellent web site convinced me that three Mikuni HSR 42 carbs might be the answer to my carburetor issues, which had been going on since 2014.
I exchanged emails with the owner John Parker who answered all my questions, so last fall I went ahead and ordered all the parts John recommended.
I order the optional tuning kit (recommended) that provides additional main, pilot, and needle jets allowing John to customize the Mikunis based on the performance modifications on my engine. This option not only provided a good starting point for tuning, but allows for any future changes.
I was able to reuse the "Goodparts" triple manifold from the ZS setup.
The Mikunis are quite easy to install via rubber boots and clamps.
I cut the provided steel rod and used the provided couplings to link the three Mikunis.
I needed to provide the fuel line, "T" connectors, and shut off valve (optional) to plumb in the fuel connections. The cable running from the choke hardware to the fuel line clamp is to stabilize the fuel line ( my rube Goldberg setup ). :-)
I bolted an extension to the original Ratco bracket to move the throttle cable out and more in line with the throttle arm.
The final piece of the puzzle is the hardware kit John provided for the chokes a.k.a. "starter plungers". The chokes face the front of the car, so a special bracket is needed to be mounted on the front carb.
Rear view showing the starter plunger cables...note the main choke cable on top of bracket
John's kit provides 3 different length cables (one for each carb) to accommodate the different distances between carbs.
Finally, I needed a locking choke cable to replace the ZS cable. It turns out the MGB choke cable was the perfect answer...right length and it locks on. I did need to turn to ebay to procure the MGB cable.
Plungers locked "on"
Final setup...this conversion is not what I would call "plug and play", but it is very well thought out, and the average car guy (or gal) can do the work themselves.
I only have driven Miss Tillie about 100 miles since finishing the Mikuni conversion, but so far it seems that I'm on the right path. The idle is definitely better, and the power is strong all through
the rev range.
More Mikuni updates to come.
Happy Summer Motoring !!