5 replies to this topic

[MiniMax1984]

Hi Everyone,

 

i am close to finishing my enginebuild and need advice with jetting the carbs. Specs:
 

- Twin HS2 carbs with K&N filter, Carbs were vizarded (modified piston, cut butterfly)

- ported and matched intake manifold

- LCB and bigger RC40

 

- ported head with 36 inlet / 29 outlet

- 1275 A+ with +0.20 dished pistons, 10.5:1 CR

- KMD 266, timed 3° in advance

- 1.5 highliftrocker

- full breather setup with catchcan

- mechanical dizzy, modified for the cam

 

For the Setup i do have an AEM Air/Fuel Ratio Gauge with lambda

 

The Carbs are new and came with a "AAZ" needle it seems.

Any of you have an idea what range the needle should be in? Or even better does someone run a similar setup?

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Edited by MiniMax1984, 12 April 2021 - 02:41 PM.

[richmondclassicsnorthwales]

Run with them needles and see where you get to

 

Cooper conversion HS4 twins run with AAK AND MME

[MiniMax1984]

Run with them needles and see where you get to

 

Cooper conversion HS4 twins run with AAK AND MME

 

My Bad, had HS4 written in the post, i run twin HS2. corrected the post.

[MiniMax1984]

I understand that the twin HS2 on 1275 Cooper S run between AH2 (Rich) and EB (Lean) needles, correct?. According to this comparisoon the AAZ might indeed be a good start.
 

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[timmy850]

The spring and the damper oil will also make a difference to tuning.

I’d just go for a drive and see how it goes if you have the afr gauge.

As some have mentioned before, “Vizarding” carbs can make them a bit strange on the road as you have changed the airflow balance from the stock carb

[MiniMax1984]

The spring and the damper oil will also make a difference to tuning.

I’d just go for a drive and see how it goes if you have the afr gauge.

As some have mentioned before, “Vizarding” carbs can make them a bit strange on the road as you have changed the airflow balance from the stock carb

 

Yeah but i wanted to try by myself. New pistons are quickly installed. And i might have to switch to bigger carb(s) anyway, we'll see!