Twin Hitachi HJE38W flat-top S.U carburettors

[Josh]

Ive Thrown a pair of GX S.Us on my car and some of us datsun chaps are trying to tune them but Id like to drain the oil and re-fill with some 3-1 i have, Giving a fresh start point for tuning. Does anyone know how much oil to put back in? Is there a level gauge of some sort?

Im presuming I just put plunger in, remove and wipe off oil until i run out of wipe material, yeah?

[DAT620]

I have no experiance with hitachi SU's but I know with British SU's you stick your finger up the throat of the carb and push the piston up the whole way fill to the top then let the piston go. For a greater range of fluids for tuning I use motorcycle fork oil, it comes in numbered weights 1-10.

[classicdat]

On the damper shaft you should find some groves cut, this is like the markings on a dip stick, with piston right down, add oil, fit damper and check. I bought penrite oil for mine from super cheap, just make sure you get the internal dash pot one and you can't go wrong.
Oil weight is really important.
Flick me a PM if you have any probs, through trial and error and a few strips and rebuilds I have mine running well now, no expert but am always learning. I found colour tune plugs made getting the mixture right really easy.

[pl510]

I had an idea SU's were supposed to use SAE 20 which is about ISO 68?

[Bartman]

If you get stuck josh, a mate of mines dad is pretty handy with SU's. I dunno what he'd charge, but he made mine run perfectly. The car went from being a jerky pig, to being a wee sweety.

[dattoboy]

I have a HIF SU infront of a turbo in my 1200 and i have just used the 3-1 oil you have used josh, the mini man from swift automotive just told me to fill it right up and the excess oil will just sit on top of the dampener. I just moved the float up a few times to get the dampener to bypass the extra oil

[Josh]

Yep went with the 3-in-1, man its watery!

Its being a real slag now(Unrelated to oil,just poorly tuned by myself), idle keeps creeping up to 3-4k after adjustment and short drive. Im heading to the shed now to pull them apart and check the adjusters,springs and everything.

[classicdat]

When I was running the lumpy as cam and poor oil level in mine the pistons would bobble up and down effecting the idle speed, so oil can effect the idle speed to some extend I would think.

[nick_m]

he's out tinkering for the last couple of hours, I think he's sorted out a few of the issues. I'll leave him to update.
the 3 in 1 oil is damn watery though I thought they took 20w too

[Josh]

I got high as hell and a headache. Not alot more achieved.
Found that the underside chokes were sticking, turns out the poor design means they bind if the hoseclamp moves. I did manage to stop the idle creep..for now..then fixed the over-run but experienced popping n farting under load. Gave up for the day, more for the neighbourhoods sakes!


THIS http://datsun1200.com/modules/myalbum/p ... ?lid=20177 is a link to MANY pictures of a chaps carbs pulled down,some handy info with pictures...so much to take in though