38 replies to this topic

[ljv8]

Hey guy's,

 

I'm running triple HS6 SU's on my 202 in the LC GTR.  The bugger is hard to start when she hasn't been started for a couple of weeks.  It takes a hell of a lot of cranks to finally get her to fire.  Once it's up and running and there is fuel in the system no issues starting it over the next few days.  Couple of cranks and it's alive!  It's only when it sits for a while and I'm guessing the fuel bowls / lines dry out.  I'm running a mechanical fuel pump, so it takes a while for the fuel to get there.  I know an electric fuel pump would probably help, but don't want to do that.

 

I found a few posts on this forum and others sites that SU's really need the choke connected to make starting them easier when they haven't been started in a while.  I never bothered connecting my choke thinking I wouldn't need it.

 

My question is has anyone setup the chokes on triple SU's and if so is it sufficient to just connect one of the carbs up to the choke cable, or do they really need all three connected like the XU-1 choke setup on the Strommies to get it to cold start easier?

 

As per the pic below Skinner Union make it easy for us to connect the choke.  There is a little brass tube stopper for the cable outer to rest in (red arrow), and the choke lever is ready to accept the cable (green arrow).

 

 Choke 01.png   425.08K   6 downloads

 

This pic I found on the web shows the choke cable setup on a little Brit four pot.  This setup however has a cross rod between the carbs that actuates both chokes from a single cable. 

 

 Choke 02.jpeg   35.41K   6 downloads

 

I'm guessing if I buy the XU-1 triple choke cable and block setup, I will mostly likely be able to adapt it to the SU's.  Has anyone else done it?

 

 Rares XU1 Choke.png   64.1K   5 downloads

 

I guess I could try connecting up a choke cable I have to a single carb and see if it works, but I'm keen to see what others have done and what works for you.

 

If anyone has any experiences or pic's to share of their SU choke setup, or tips on cold starting SU's it would be greatly appreciated. 

[warrenm]

I had an XU1 style cable attached to my HS6 & later HS8 carbs, I don't bother with the HD8, as I run Methanol. If the carbs are tuned correctly(not rich at idle), you should need a choke arrangement too start when cold.

[rodomo]

I used to pull down the jet on the middle carb and hold it there with a clothes peg

[hanra]

I never had a choke on my Twin HS2's on my little red cute car. And it was the same... very had to start. Finally got around to fitting the choke mech, which has a rod interconnecting the two carbs etc and engages a fast idle as well as lowering the jet to enrichen. 

 

Made a huge difference. Never an issue when I start it once a year now. 

[ljv8]

Thanks for the responses guys much appreciated.  It looks like I'm on the right path in thinking I need to fit up a choke (or peg in the short term ).  Good to know you got the XU-1 arrangement working with your previous HS6's Warren, I will go down that route too. 

 

When using the choke with the SU's I'm guessing there is no need to pump the accelerator pedal, its feet off and crank?

[hanra]

Yep. Just pull the choke and crank. If the fast idle cam is set correctly there is no need to touch the pedal. 

[ljv8]

Ok excellent thanks Brad.

[warrenm]

Thanks for the responses guys much appreciated.  It looks like I'm on the right path in thinking I need to fit up a choke (or peg in the short term ).  Good to know you got the XU-1 arrangement working with your previous HS6's Warren, I will go down that route too. 

 

When using the choke with the SU's I'm guessing there is no need to pump the accelerator pedal, its feet off and crank?

It's of no use to pump the pedal of an engine fitted with SU carbs, as they don't have an accelerator pump.

[Hot mustard]

Mate have you tried a few squirts of Start you bastard into front carby.
It gets the engine to fire and stuck up the petrol.
It has worked for me when I have had the same problem.

[hanra]

Might best to just solve the problem instead of using a band aid solution. 

[Hot mustard]

Maybe but I have a standard set up xu1 with working original choke set up which all operates properly and it still takes heaps of cranking if it's been sitting for a few weeks. A squirt of Start you bastard gets it going quickly and then it's fine thereafter until left for a long time again.

[ljv8]

Thanks Warren, that explains why it seems to make no difference in getting it to fire quicker, when pumping the pedal madly!

 

Thanks David, yeah I brought some Aerostart that I used when I first fired up the engine to run the cam in.  I did use it last time I started it to help get it going.  It is a pain to have to pull the air-filters off every time I want to start after the bastard has been sitting for a week or so though . 

 

I will buy and hookup the choke cables, which sounds like it will resolve my problem. 

[Hot mustard]

Hopefully it will work well for you.

Unfortunately, mine needs a ship load of cranking, even with the choke on, after sitting for a long time. Taking off the airfilter is pain but what I did was make a 1/8 hole in the airfilter of no.1 carb and just poke the straw of the Aerostart in. A few quick sqirts and off she goes.

[ljv8]

Ha clever David thanks, good idea.  I will see how it goes just with the choke.  Thanks for sharing your experiences.

[Hot mustard]

No problem.
Hope all goes well with getting it sorted.

[ljv8]

I just wanted to book end this post that I started and report back that I had complete success, and share my learnings along the way.

After setting up the chokes correctly the car started to cough into life in about 3 seconds. That is after not being started for nearly two months. I just couldn't believe it, I didn't think it would work this well. In the past without a choke connected if it had not been started for about two or more weeks, it would take a forever to get it started. Crank for ten seconds, give it a rest, crank another ten seconds give it a rest. A few more squirts of Aerostart and lots of cranks with the little battery tired and nearly dead it would finally start.

To say I was happy with this fix is an understatement. It took a bit of trial and error to get there though. I purchased the Rare Spares XU1 choke linkage kit. https://www.rarespar...rt-cables-clips

Now if you look at the first photo in my original post you will see there was a screw and nut in the choke lever arm. What I did was drill a hole in the screw to feed the choke wire through, and tighten the nut. I did this for all three and connected the choke cable. The choke cable was really stiff to activate and the choke arms barely moved. I'm thinking all this mechanical leverage needed for three cables to open all these chokes might be an issue when it was designed for XU1 Strombergs. I backed off the adjusting nuts that activate the throttle mechanism on fast idle thinking maybe the return springs are making it stiff, but still no good. It didn't look right to me so I disconnected everything and just connected the choke cable on it's own to one of the carbs, but same problem.

Looking into it I found this video useful that explained the operation of the choke mechanism on SU's quite handy, watch from about the 1 min mark if interested.
https://youtu.be/T4kzFiy-v-c

Moving my choke levers by hand it was transitioning from fast idle to enriching, where the choke opens the jets in the last stage as explained in the video. Once the cable was connected it was being severely restricted. So I went and dug out the carbs I have lying around the shed to have a look at the choke mechanisms. I have a single barrel downdraft Stromberg from a stock 202, and a Holley 350. Both had a choke cable stop that pivoted. I realised straight away looking at these pivoting cable stops that is why my choke cable was binding, being solidly mounted wasn't allowing the cable to move in it's full arc. The cable stops on those carbs won't fit the SU's unfortunately.

So how do I find a pivoting cable stop for a SU HS6? Turns out no one makes them. There was a pivoting cable stop for the Jag HS8, however it was used to activate a slightly different mechanism. While it may have worked, finding one was near impossible and the only reseller that had them was based in the UK. Searching pivoting choke cable stop I found a hot rod shop in the US sells one that might work, but I'm impatient and can't wait weeks and weeks for delivery.  I also found a US aftermarket boat steering manufacturer Ultraflex sold a choke cable stop. The part is called “Ultraflex L13 - 30335G Stop collar. Fits B14 cables”. That didn't mean much but it looked like it might fit. The drilled hole in the choke lever is 5mm. The Ultraflex stop collar shaft diameter is 6.3mm. I thought with a bit of modification / filing I can make it work. A local online search reveals there are a few online boat parts resellers that stock them in AU and are readily available at about $15 bucks each.

 Choke cable stop 00.JPG   27.89K   5 downloads

There wasn't a lot of meat on the choke arm, so I ended up filing down the stop collar shafts to 5mm and they fit perfectly and swivel nicely. They are still plenty strong, and being brass were easy enough to carefully file down in a vice and checking until I got to 5mm with a vernier along the way.  See below filed and un-filed example. 

 Choke cable stop 01.JPG   29.8K   6 downloads

They fit really well, I just added a thin 5mm washer before the split pin, and they are able to pivot easily and don't wobble. For a test hooked up the choke cable directly to one carb and it worked perfectly. The choke was easy to pull all the way out, and it would transition from fast idle all the way to open jet and enriching where you can see the jet lowering and the brass shaft as per the video. Happy days!

 

 Choke cable stop 02.JPG   56.85K   8 downloads

Connected up all three and it worked perfectly. All had full activation, and as mentioned after sitting for two months un-started she fired into life almost instantly. In the end it wasn't an expensive fix and well worth it to alleviate a horrible starting experience.

 Choke cable stop 03.JPG   89.6K   9 downloads

If you have SU's and no choke cable and it's hard to start, it's a worth setting up the chokes.  If you have a choke cable fitted to your SU's and it's still hard to start, check that the cable is getting to the enriching stage. If you haven't got pivoting cable stops, the first step is to "get some!". Thanks all who helped steer me in the right direction, and hope this post helps someone in the future with the same frustration and a shorter path to a solution.

[klevliend]

Thanks for taking the time to post the conclusion and results! It drive me nuts when a thread finishes and I don't know if the idea worked or not.
I have SU's waiting to go on and at some point in the future will be referring back to this, cheers!

[claysummers]

Updating this old thread on HS6 choke mechanisms, as I found the correct cable end pivots on ebay at $9 each.
https://www.ebay.com...emis&media=COPY
They arrived today and fit perfectly.

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[ljv8]

Thanks for sharing Clay, and updating my thread. 

[claysummers]

Your info is very helpful steve. I'm off to rares in a minute to lash out on the XU-1 choke setup.

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[claysummers]

Lot of coin for a few machine screws, bits of plate and some push-bike brake cables.
Can't see myself being able to use these clips as they appear specific to the Zenith Srrombergs.

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[claysummers]

These are the do-dads I am using.
Could possibly do with a flat washer between the cable and lever.

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[Bruiser]

Geez, they know how to charge for things these days, don’t they?
Nifty looking doodads too
I am curious as to how hard it is to pull up 3 chokes at once
Mine is a two handed both feet on the dash effort to pull up just the one

[claysummers]

Thanks for correcting me on the spelling. Yer I’m wondering. Soon find out.


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[claysummers]

Not ideal. I made up a grip and getting enrichment. Feels like about 70 Newtons required currently. My dash should withstand that. Just need to refine things. Maybe I need an XU-1 primary cable $$$

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