Mikuni Adapters

998cc

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Several months back, I ordered a set of Mikuni VM carb adapters from VOC Spares. Internally, the adapters were only partially machined and were left as cast for about 35% of the interior. This left ledges and excess material that had to be removed. Well, okay, not too much involved there.

The issue that came up during fitting yesterday is that the front carb is fouled by the rear head to the point the carb cannot be installed; the interference is about a quarter inch. The designer must have measured for adequate clearance prior to having these items cast.

Since my front head is a very early component which lacks the vertical ribs that were cast into the later heads, I am wondering if the intake port was moved in the later casting? Anyone have any similar experience?

~998cc
 
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Several months back, I ordered a set of Mikuni VM carb adapters from VOC Spares. Internally, the adapters were only partially machined and were left as cast for about 35% of the interior. This left ledges and excess material that had to be removed. Well, okay, not too much involved there.

The issue that came up during fitting yesterday is that the front carb is fouled by the rear head to the point the carb cannot be installed; the interference is about a quarter inch. The designer must have measured for adequate clearance prior to having these items cast.

Since my front head is a very early component which lacks the vertical ribs that were cast into the later heads, I am wondering if the intake port was moved in the later casting? Anyone have any similar experience?

~998cc
I have a question, wasn't the early v twins built at a different angle to the later twins?
Early ones were 47.5 later ones were 50 degrees.
 
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Fast Eddie

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Several months back, I ordered a set of Mikuni VM carb adapters from VOC Spares. Internally, the adapters were only partially machined and were left as cast for about 35% of the interior. This left ledges and excess material that had to be removed. Well, okay, not too much involved there.

The issue that came up during fitting yesterday is that the front carb is fouled by the rear head to the point the carb cannot be installed; the interference is about a quarter inch. The designer must have measured for adequate clearance prior to having these items cast.

Since my front head is a very early component which lacks the vertical ribs that were cast into the later heads, I am wondering if the intake port was moved in the later casting? Anyone have any similar experience?

~998cc

I’m not sure what kind of manifolds you have there, but if they are the male stub type that take a female-female rubber, these angled ones for Triumph TSS may get you out of a pickle...
https://www.ebay.co.uk/p/1623916561
 

998cc

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I have a question, wasn't the early v twins built at a different angle to the later twins?
Early ones were 47.5 later ones were 50 degrees.

Thanks Bernhard. I should have clarified that the front head is from an early Series B post-war engine. (Ref KTB, 1977)


Yes, the pre-war Series A V-twins are 47.5 degrees.

Regards,
Russ
~998cc
 

998cc

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I’m not sure what kind of manifolds you have there, but if they are the male stub type that take a female-female rubber, these angled ones for Triumph TSS may get you out of a pickle...
https://www.ebay.co.uk/p/1623916561

Thank you Nigel. I have a set of those angled rubber adapters "somewhere" in the garage. :confused:

Here is a screenshot from VOCS:

VOC-Mikuni.PNG


I took a much closer measurement this morning. The carb bowl needs to move 3/8" to allow for a little running clearance. I should post this in the VOC forums as well. Never posted there as of yet.

Russ
~998cc
 

998cc

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Heard back from VOC Spares this morning. Other owners have experienced problems with the adapters as well. :confused:
 

Fast Eddie

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Well at least they’re honest!

Did they offer anything by way of a solution ??
 

998cc

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Yes.
They got back to me and said others have either:
1. Angled the flange and used washers to accommodate the nut.
2. Extended the "rubber mount".

I tried a combination and angled the adapter flange about 1/8" and made up a steel tube to tie two rubber connectors together. Clearance to the rear head and petrol tank was lacking, so I have gone back to an adapter I made in the early 80's. The carb fits fine, though the adapter is a bit rough on the outside.

Hoping to have it up and running shortly. :)

(edited)
 
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