Hif 38 carb question

[andrew.searston]

Hi everyone
Just got my rebuild engine running has 1275 head, fitted a hif 38 carb, its runs a bit rough and doesnt pull under load, i have set ignition timing with proper light, so its down to carb now. Is there a basic setting to start from like turn mixture screw in all the way, back it out so many turns?

[palacebear]

The rule of thumb with a 'standard' Minor carb is to wind the jet adjusting nut fully up (or in) then back 12 flats (3 full turns) of the nut. That should get the mixture in the ball-park although fine tuning may be needed. I assume the Hif38 isn't much different. If I'm wrong, I expect someone will be along shortly with the right answer

[andrew.searston]

Thanks for the reply ive heard about the 3 turns, but not sure for the hif38, need to get it somewhere rough so i can drive it 20 miles to a garage for fine tuning on dyno

[liammonty]

Have you blanked off the necessary vacuum ports? If not, the ingress of air would make it run very badly. There is a picture of a HIF38 somewhere on here with all the ports labelled - perhaps do a search.

I haven't adjusted mine for a while as it's set up nicely, but IIRC, turning the mixture screw in richens the mixture (counter intuitive, as on most other carbs - Webers etc - it's the other way round). I'm not aware of a 'generic' setting to get them running - you ought to be able to get it in the ball park by setting the mixture for the highest revs and then leaning it off a quarter of a turn or so. If that doesn't work,Ii suspect wither the needle is way out (do you know what you've got in there?) or you have got air getting in somewhere, as above.

[silloyd]

The diagram here shows where the idle screw is and what the various connectors are (the rest of that thread is also worth a read).

Also, this thread includes a link to a useful document and my post from that document covering where to start with the needle height.

[Declan_Burns]

Andrew,
I have the same set-up-1098cc/940 head and HIF 38.
As far as I can recall the mixture screw on mine is almost fully in (rich). I can't check it at the moment as I am not mobile.
Regards
Declan

[Monty-4]

Wrong needle? Might need a leaner one.

I had these problems with a HIF38:

1. Fuel bowl gasket leak. Drips fuel at idle, sucks in air under load.
2. Choke/starter spindle seal can wear out and skew the mixture (way to rich and will feel like mixture adjustment screw does nothing).
3. Wrong connectors blanked off or leaky.

I've gone back to HS carbs!