Difficult start and hunting idle?

[JW240]

As the title suggests, the engine has been rebuilt and a pair of brand new HS6 carbs with SM needles installed.
Its really hard to start, to the point where if i didn't know it actually ran i would probably give up. Choke doesn't seam to help this. Once running its ok, hot starts without hesitation but the idle hunts, fluctuates from 800 to 1000.
Personally i thought it might be a vacuum leak? i have tried spraying possible areas with brake cleaner to see if the engine idles up however this is tricky as the engine idle fluctuates every couple of seconds, like a heartbeat.
Im not a massive carb guy, hence going with brand new, just wondering if anyone might know?

 

[toopy]

Choke - Have you checked the mechanism is working/moving correctly.

Hunting idle - Assuming there are no vacuum leaks or inlet gasket leaks, it sounds like the carbs are not balanced properly.

 

[jonbills]

does it have a mechanical fuel pump?

 

[MCBladeRun]

Farmer has HS6's running on his. Hopefully he'll see your post and respond accordingly.

Bowl floats set up correctly?
Have you balanced the carbs?

 

[SacCyclone]

Plug up power brake booster to see if it has a internal vacuum leak.
New carbs should be fine but check to make sure the main jets at the bottom of the carbs are in the fully up position, push up with your fingers at the base of the carbs.

 

[Farmer42]

Farmer has HS6's running on his. Hopefully he'll see your post and respond accordingly.

Bowl floats set up correctly?
Have you balanced the carbs?

As Martin (MCBladeRun) has said, I have HS6 carbs on mine. As he also said, you may need to take off the top of the float chamber and set the float levels by bending the tang to the correct measurement. It really does make a difference. Also, another thing to consider is the fuel. As I have found, it will not run on the E5 s**t with HS6 carbs. You have to put Super unleaded in it or a fuel octane additive. I use the Esso Synergy in mine as it is Ethanol free.

With balancing, a general rule of thumb is to wind the mixture adjuster right in and then back out around 2 1/2 turns on each carb.

Where are you based? If anywhere near Bristol I am happy to take a look. I managed to get Martin's to run although his are Hitachis. Send me a pic of the carbs and I may be able to see any potential air leaks as there are a few places that need to be blocked off that are different from the Datsun carbs.