1964 G15 monoblock carbs

pierodn said:
Well thank you.
A question, please.
Why a chopped carb and not another full ?
Piero
Click to expand...

A mirror image full carb would be ideal. There were some made, but they are rare.

The are two problems with the chopped carb ..... 1) the pilot adjustment screw is nearly unreachable on the left carb, and 2) feeding two carbs from one needle and seat will fuel starve a hot 650 engine, and a warm 750 engine.

I use a needle and seat having a 0.200 inch dia orifice, the typical 0.125 inch dia will starve the engine at high revs.

Slick
 
texasSlick said:
A mirror image full carb would be ideal. There were some made, but they are rare.

The are two problems with the chopped carb ..... 1) the pilot adjustment screw is nearly unreachable on the left carb, and 2) feeding two carbs from one needle and seat will fuel starve a hot 650 engine, and a warm 750 engine.

I use a needle and seat having a 0.200 inch dia orifice, the typical 0.125 inch dia will starve the engine at high revs.

Slick
Click to expand...
I think the "mirror image" carbs are referred to as "handed." There was a transitional period of, I think, a year or two, during which the twin carb featherbed bikes used handed monoblocs before going to concentrics which were then in use when the Commando went into production. Burlen has reintroduced the chopped monoblocs but not the handed ones. Personally, I'm not a racer and I find the monoblocs much easier to work on and live with than concentrics even though dialing in the left carb on a twin carb setup with a chopped monobloc is a witch.
 
Bodger said:
I think the "mirror image" carbs are referred to as "handed." There was a transitional period of, I think, a year or two, during which the twin carb featherbed bikes used handed monoblocs before going to concentrics
Click to expand...

Bodger, do you know how/if the monobloc fuel supply worked in this setup? Via balance tube, metered by one carb float like the chopped setup, or was each fed separately with its own float?
 
AgentX said:
Bodger, do you know how/if the monobloc fuel supply worked in this setup? Via balance tube, metered by one carb float like the chopped setup, or was each fed separately with its own float?
Click to expand...
Each carb had its own fuel banjo. I think the right hand was a 689. See picture below. Now the question is, what are the fuel connections on the float covers for? I have seen them but dont know their purpose. To measure float height?
 

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texasSlick said:
A mirror image full carb would be ideal. There were some made, but they are rare.

The are two problems with the chopped carb ..... 1) the pilot adjustment screw is nearly unreachable on the left carb, and 2) feeding two carbs from one needle and seat will fuel starve a hot 650 engine, and a warm 750 engine.

I use a needle and seat having a 0.200 inch dia orifice, the typical 0.125 inch dia will starve the engine at high revs.

Slick
Click to expand...
Hi Slickk, thank you.
You “use a needle and seat having a 0.200 inch dia orifice”.
Sorry, i dont understand what is the needle (is the jet needle .106 or the viton?) and what you mean for seat (the chamber where the viton works?)
Who supply 0,200 inch needle and seat?.
Thank you.
Piero
 
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Another question about the fuel line from the two tank petckoks.
Better to use a single n. 6 banjo with a T piece to tank or go directly from tank to carb with a double banjo?
Thank you.
Piero
 
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pierodn said:
Hi Slickk, thank you.
You “use a needle and seat having a 0.200 inch dia orifice”.
Sorry, i dont understand what is the needle (is the jet needle .106 or the viton?) and what you mean for seat (the chamber where the viton works?)
Who supply 0,200 inch needle and seat?.
Thank you.
Piero
Click to expand...

Piero:

I see AgentX has jumped in here while i was typing. Thanks for the picture AgentX.

My needle and seat was made by a small business that no longer exists, called Webco, or Webbco.

Amal, now Burlen, makes a fuel needle for alcohol, that is about 0.188 dia, but they do not make the seat. I talked with a Burlen technician about this, and he suggested drilling out a standard seat. This is an operation that must be done by a skilled machinist, otherwise the needle and seat will leak.

I ordered a needle and seat from Burlen and received one with a 0.100 inch orifice. I, too, could not find any orifice info on their site, hence I made a call to their tech support.

I will search their site to see if I can get a part number for the alcohol needle, then edit this post. I have the purchase records at my office, thus it may be a few days before I can update.

Slick

Update: I have searched Amal website and do not find the alcohol needle listed alone, but it is included in a kit, see ....
http://amalcarb.co.uk/mk1-900-series-alcohol-repair-kit.html

The needle is that fat thing just under the bowl gasket.

I will search my purchase records to see if I can get a part number on the alcohol needle. Will take a few days.
 
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Hi D
texasSlick said:
Piero:

I see AgentX has jumped in here while i was typing. Thanks for the picture AgentX.

My needle and seat was made by a small business that no longer exists, called Webco, or Webbco.

Amal, now Burlen, makes a fuel needle for alcohol, that is about 0.188 dia, but they do not make the seat. I talked with a Burlen technician about this, and he suggested drilling out a standard seat. This is an operation that must be done by a skilled machinist, otherwise the needle and seat will leak.

Slick
Click to expand...
lick.
I boughtt this from Andoverthe one in aluminium:
https://andover-norton.co.uk/en/shop-details/17479/float-needle-viton-tip-622-197-622-068-99-0511-

Please, about fuel line what do you sugest is better?

Thank you.
Piero
 
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pierodn said:
Another question about the fuel line from the two tank petckoks.
Better to use a single n. 6 banjo with a T piece to tank or go directly from tank to carb with a double banjo?
Thank you.
Piero
Click to expand...

Either way is more than adequate fuel supply to the left carb needle and seat.

I would do which ever way is better appearance.

Slick
 
Bodger said:
Each carb had its own fuel banjo. I think the right hand was a 689. See picture below. Now the question is, what are the fuel connections on the float covers for? I have seen them but dont know their purpose. To measure float height?
Click to expand...

Each carb with its own banjo, needle and seat, is a must to get adequate fuel supply to feed a hungry 750 engine, using the typical 0.125 dia orifices.

I have never seen the tubes on the covers. They seem to come off at the bowl centerline, which is the recommended fuel height, thus they could be used to measure fuel level. The same function could be gained by drilled and tapped holes at the centerline in the covers. Adjust floats until fuel just dribbles out, then plug.

Using a chopped carb off one needle and seat, automatically gives exact fuel level in each carb. Having dual floats, will require setting each float level independently to get the same fuel height.

Slick

Edit: Right or wrong, I have decided those tubes on the covers are fuel level balance tubes.
 
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twxasSlick said:
I talked with a Burlen technician about this, and he suggested drilling out a standard seat. This is an operation that must be done by a skilled machinist, otherwise the needle and seat will leak.
Click to expand...

A nit having a go with a drill can be successful at enlarging the hole in the needle seat.
 

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