One more SU HS6 question

[tdskip]

Hi guys. Back from work travel and pulling off a successful birthday part for our 3 year old, so back to the car stuff.

On reassembly, how should the jet height be set? Should it be flush with the carb body?

 

[DNK]

Tom , I'm not buying the title of this at all :laugh:

 

[tdskip]

Now Don, I didn't say;

"One <span style="text-decoration: underline">Last</span> SU HS6 Question"

or

"One <span style="text-decoration: underline">Final</span> SU HS6 Question"


LOL

 

[DNK]

Wait a minute. Did you change that title??? :confuse: :confuse:

 

[tdskip]

Nope....been drinking already? LOL.

 

[poolboy]

Tom, you know I haven't fooled with SU's much lately but I do have some links I'd like to pass along.
https://www.teglerizer.com/sucarbs/index.html
https://sw-em.com/su_carbs.htm
https://www.zparts.com/zptech/articles/mal_land/ml_sucarb2/images4/SUcarb_111601d.htm
https://www.jcna.com/library/tech/tech0006.html

 

[tdskip]

Thanks Ken.

I need to be more specific with my question too.

1) What I am really asking if if this assembly should be flush? This is the adjusting nit <span style="text-decoration: underline">without</span> the jet/tube that the fuel comes up through.

OR

2) Is the jet tube as it sticks up through the assembly above my reference point for height adjustment? That is to say, that the thin inner tube on the jet unit what needs to be adjusted for height.

I am thinking #2. Yes/no?

I feel a write up with pictures coming up here....

 

[poolboy]

Tom, I'm not sure if this is what you mean but it's the distance between those 2 hex heads on either side of the spring that indicates the jet height and that's where you make your adjustment.
I

 

[tdskip]

Hi Ken - thanks for the note.

Yep, I'm with you on that. What I'm doing a bad job of asking is what should the relative height of the jet in the bridge be? AND, if the initial setting of the height is done with the nut/spring assembly w/out the jet or are all the initial settings based on the jet inserted.

Is that clearer?

 

[poolboy]

Yeah dat's mo clear.
Here's my thinking on those inital settings, especially on something so precise like you find on carbs.
If an adjustment screw has say 6 threads, you'll usually be pretty close mid way, 3 threads.
I try to think like a designer with an eye on the bottom line might. He wants a precision adjustment screw. He wants a full range of adjustment, but he doesn't want to pay the manufacturer for unneeded length (things add up); so he buys one just long enough to cover the obvious range of normal adjustments. So I figure mid way is just about the ideal starting point. Works alot.

 

[tdskip]

Thanks Ken - had ever really thought about why the adjustments are like that on our cars but that makes a lot of sense.

 

[DrEntropy]

ummm.... the outer sleeve (bushing, bearing, guide) should be tightened with the jet in the fully flush position (business end flush with the top of the sleeve), and the needle/piston/chamber assembled. This allows jet "centering" as the top nut (the one securing the sleeve in the body) is tightened. The piston assembly should rise and fall easily, a "thunk" heard when it is dropped to "zero" position. Once this is achieved, with the jet top flush with the 'bridge', lower the jet by 12 'flats' on the lower (sprung) nut. That should be a very close setting from which to begin tuning it.

 

[tdskip]

Hi Doc - nice to find out how you got your nickname BTW (from one of the other posts)!

Yeah, I'm with you now. I sat and stared at it for a while last night and it started to make sense.... (slow night here....LOL)

Thanks Doc, that explanation helps nail it!

 

[DrEntropy]

That was th' "sanitized" version of th' tale... :smirk:

If you can find one, the "kit" for setting up SU's with the li'l wires 'n tubes is a good thing to get... the only REAL tool in there is the "anvil" used to center the jet sleeve. The rest is kinda TinkerToy stuff. PITA to use.

 

[tdskip]

I've never seen that kit Doc - what does it look like? Almost sounds like you knock the jet into center???

 

[DrEntropy]

The "anvil" is put in the piston in place of the needle and has a bit of it stickin' down where the needle would normally be, it has the diameter of the sleeve it fits into. You assemble the carb as normal, then snug the sleeve nut with the anvil used as a "centering" device... works a treat.

 

[TR3driver]

works a treat.

I have a different opinion, based on my experiences with H6 carbs ... the anvil allows all the clearances to stack up on one side with the result that the needle rubs on the side of the jet at idle. This leads to worn needles and jets.

Although it does take longer, I can do a better job of centering without the little anvil.

But I do like the synchronization tool in the kit. Easy to use, accurate, and it can check synchronization while the linkage is under throttle tension, which is very difficult to do with a Unisyn type tool.

 

[tdskip]

Hi Randall - how do you like to center the neddle? Take me to school here...

 

[KVH]

Here are my questions, comments:

How is it that the HS6s don't leak? They have no fiber washers or fiber gaskets, and no cork gaskets?

That spring mechanism that screws into the side of the jet to keep it snug up in the jet bearing--doesn't it always stick after using the choke? Mine is always hanging down about 1/8 inch.

I always thought that the jet bridge and bearing should be level with each other, and that the fuel was totally shut off with the jet in its highest position and with the adjusting nut all the way up. Then, you start 12 flats down and adjust from there.

Randall, why is that little tool in the kit (expensive for aluminum) better than a Unisyn tool?

Isn't that little centering tool indispensible on the HS6s? I lost mine and had a real time getting that piston to drop freely.

Thanks.

 

[TR3driver]

Hi Randall - how do you like to center the neddle? Take me to school here...

Turn the mixture nut full lean (or remove it entirely), so the jet is higher than it will ever be in normal operation. Tighten the big nut that locks the jet housing until the housing will just barely move when rapped (I use a brass drift as I don't have a hammer small enough to fit into the space) and then tap the housing around until the piston & needle falls freely (listen for the click when it lands). Then finish tightening the big nut and check that it still lands with a click. Usually takes me two or three tries to get it just right.