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Adivce on how to center jets of SU HD6 carbs

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fishyboy

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Hi All,
I have been a owner of a BT7 for the last 24 years. I am based in the UK and this is my first post.
This weekend I decided to rebuild the twin SU HD6's. The rebuild was fairly straight forward (apart from trying to remove the lower rear manifold bolt on the rear carb - how do you do it?).

I have two questions:-

Firstly, what is the best way to center the jet. I have followed the SU/Haynes manual but perhaps someone out there has a better solution. It seems more difficult than on the HS6's.

Secondly, how does the diaphragm type jet work? I have HS carbs on another car and see how the jet works, but I just cant work out what role the diaphragm plays on the HD6's.

Many thanks

Phil
 
fishyboy said:
Hi All,
I have been a owner of a BT7 for the last 24 years. I am based in the UK and this is my first post.
This weekend I decided to rebuild the twin SU HD6's. The rebuild was fairly straight forward (apart from trying to remove the lower rear manifold bolt on the rear carb - how do you do it?).

I have two questions:-

Firstly, what is the best way to center the jet. I have followed the SU/Haynes manual but perhaps someone out there has a better solution. It seems more difficult than on the HS6's.

Secondly, how does the diaphragm type jet work? I have HS carbs on another car and see how the jet works, but I just cant work out what role the diaphragm plays on the HD6's.

Many thanks

Phil
Click to expand...

The diaphragm separates the fuel circuit on the float-bowl side of the carb from the venturi area; the fuel can only get in through the jet in the middle of the diaphragm.
Moss sells a jet-centering tool: see item 386-500; there's info (possibly a video) describing its use.
 
Hi Steve,
Just looked at the Moss tool, which looks like its for centering on the HS type carbs. Not to sure it would work with the D type, but I shall investigate.
Thanks
Phil
 
fishyboy said:
Hi All,
I have been a owner of a BT7 for the last 24 years. I am based in the UK and this is my first post.
This weekend I decided to rebuild the twin SU HD6's. The rebuild was fairly straight forward (apart from trying to remove the lower rear manifold bolt on the rear carb - how do you do it?).

I have two questions:-

Firstly, what is the best way to center the jet. I have followed the SU/Haynes manual but perhaps someone out there has a better solution. It seems more difficult than on the HS6's.

Secondly, how does the diaphragm type jet work? I have HS carbs on another car and see how the jet works, but I just cant work out what role the diaphragm plays on the HD6's.

Many thanks

Phil
Click to expand...

Q 0: I reach my hand under the front carb and can just reach the back nut (should be a nut on a stud, not a bolt).

Q 1: I believe the centering tool works on all carbs (it substitutes for a needle). At least, it worked on my HD8s.

Q 2: Already answered.
 
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