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Had a Eureka! moment... or was it a D'oh! moment... [SOLVED]

David Jenkins - 12/10/20 at 08:09 AM

A while ago I put my Weber 32/36 DGV carb on my Locost - I had it tuned on a rolling road, it worked well, but it was a total PITA to start from cold. Here's the original thread on this subject:

https://www.locostbuilders.co.uk/viewthread.php?tid=205783

I got so fed up that I reverted to the bike carbs for a while.

Over the past few weeks I decided to re-fit the Weber and try again (for a multitude of reasons) but with the same result. So I did some Google research - which I should have done ages ago. These carbs seem to be very popular with people who tinker with old Volkswagens, Volvos, etc., especially in the US of A. Many of them report the same struggles when starting on choke. Buried in amongst all the owners' forums I found a brief post written by someone who seemed to know what he was talking about.

The issue is that Weber auto chokes have a fast idle adjustment screw, but the manual chokes don't. Weber expect owners to adjust fast idle by bending a linkage, which is made of wire of about 3mm diameter. Trying to bend this in situ is liable to wreck other parts of the mechanism. The American bloke simply fitted a sleeve over a pin that rides on the choke pull cam - this takes up most of the slack in the linkage (leaving a little bit of clearance).

Over the weekend I tried it out - spent 10 minutes turning a small sleeve on my lathe, fitted it, and now I have fast idle on cold start!

While I'm chuffed that the problem is fixed, I'm a bit annoyed that I hadn't spotted ages ago that the throttle linkage was hardly moving when the choke was pulled out... D'Oh!

Now, a question: can anyone suggest an adhesive I could use to fix this sleeve in place on the pin? It's a stainless steel sleeve on a steel pin. I have some Loctite 601 that I could use, but I'd never be able to get the sleeve off again if I wanted to make some adjustments. I'd like something that would keep the sleeve in place, but would allow it to be pulled off if necessary. It would have to be resistant to petrol fumes and heat, so Bostik might be pushing my luck!

[Edited on 12/10/20 by David Jenkins]

David Jenkins - 12/10/20 at 08:37 AM

A few pictures (pin highlighted) - the chunky wire on the left of the pin is the one that's meant to be bent.

[Edited on 12/10/20 by David Jenkins]

steve m - 12/10/20 at 08:56 AM

Good one David

When i ran the twin 40's on my 7, it didnt have any chokes, so from, cold, just pumped the throttle 3 times, and it would start,
was a bit lumpy for a couple of mins, but was ok after that

steve

roadrunner - 12/10/20 at 09:30 AM

Nice job.
Can you not drill and tap it out for a grub screw.

roadrunner - 12/10/20 at 09:35 AM

Or drill and tap the pin itself for a washer headed bolt.

HowardB - 12/10/20 at 09:43 AM

quote:

Now, a question: can anyone suggest an adhesive I could use to fix this sleeve in place on the pin? It's a stainless steel sleeve on a steel pin. I have some Loctite 601 that I could use, but I'd never be able to get the sleeve off again if I wanted to make some adjustments. I'd like something that would keep the sleeve in place, but would allow it to be pulled off if necessary. It would have to be resistant to petrol fumes and heat, so Bostik might be pushing my luck!

Loctite is ok, you can always remove with some heat,... small blow torch

David Jenkins - 12/10/20 at 09:45 AM

quote:
Originally posted by roadrunner
Nice job.
Can you not drill and tap it out for a grub screw.

It is an option, but the wall of the sleeve is very thin. I'm not sure how many threads I could get in the thickness.

I'd rather not modify the linkage itself, but I do see what you're suggesting... my worry is that there's a fair chance of making an expensive mistake! Also a bit fiddly to do it in situ, and I don't want to take the carb off again if I can avoid it.

David Jenkins - 12/10/20 at 11:16 AM

quote:
Originally posted by HowardB

Loctite is ok, you can always remove with some heat,... small blow torch

The thought did occur to me! The potential for disaster is high...

David Jenkins - 12/10/20 at 11:19 AM

quote:
Originally posted by roadrunner
Or drill and tap the pin itself for a washer headed bolt.

This solution is niggling at my subconscious - it would be the perfect way to do it, but I'm not sure whether it's too ambitious...

Damn, now I've got to go and investigate!

coyoteboy - 12/10/20 at 11:44 AM

Totally, drill and tap the pin for a SHCS with the right OD to hold your sleeve on. Looks like an M3 or M4 might do it? Then you have bolt on bolt off adjustments.

rusty nuts - 12/10/20 at 12:08 PM

Convert to EFI , all your cold running problems etc cured in one go, carbs are so last century. Jacking aside drilling and tapping and perhaps a cam shaped sleeve for a bit of adjustment ?

gremlin1234 - 12/10/20 at 12:33 PM

another way to do it...
drill a small hole though the sleeve, and peg, then use a small 'R' clip to hold it in place

gremlin1234 - 12/10/20 at 02:07 PM

or narrow your sleeve, and file a grove into the end of the peg, and hold the sleeve in place with a circlip

David Jenkins - 12/10/20 at 02:12 PM

Done!

The peg now has an M3 threaded hole in it...

Usual thanks to everyone who contributed - your comments did make me think about the problem, even though I only followed one suggestion...

And Mel - this change over to the Weber DGV has cost me about Ł2 for a new inlet manifold gasket, Ł2.50 for a pipe connector, Ł1 for some o-rings, and a bit of postage for the old oil catch tank that someone kindly donated. The rest came from stuff lying on my shelves. I think EFI would have cost me quite a bit more...

Mr Whippy - 12/10/20 at 02:15 PM

quote:
Originally posted by rusty nuts
Convert to EFI , all your cold running problems etc cured in one go, carbs are so last century. Jacking aside drilling and tapping and perhaps a cam shaped sleeve for a bit of adjustment ?

Converting a carb car to EFI is not a minor task unless you manage to get hold of a complete OEM system in good condition but that's unlikely to be cheap either. Most carbs once set up correctly are very reliable and cheap to overhaul and for all the use these cars really see the actual fuel savings from running injection are irrelevant.

I like the carb on mine, it's basic, simple, fixable, I have a manual choke to play with and the roaring intake noise is great

David Jenkins - 12/10/20 at 02:19 PM

The intake roar is one of the reasons why I changed back from bike carbs - on hard acceleration the roar was 2 or 3 times noisier than the exhaust (and that's not quiet)!

It's fun the first few times, then it gets wearing...

(And Mel was only teasing me - his car has a very nice EFI system, and he's always suggesting that I change over... )

[Edited on 12/10/20 by David Jenkins]

rusty nuts - 12/10/20 at 03:03 PM

quote:
Originally posted by Mr Whippy

quote:
Originally posted by rusty nuts
Convert to EFI , all your cold running problems etc cured in one go, carbs are so last century. Jacking aside drilling and tapping and perhaps a cam shaped sleeve for a bit of adjustment ?

Converting a carb car to EFI is not a minor task unless you manage to get hold of a complete OEM system in good condition but that's unlikely to be cheap either. Most carbs once set up correctly are very reliable and cheap to overhaul and for all the use these cars really see the actual fuel savings from running injection are irrelevant.

I like the carb on mine, it's basic, simple, fixable, I have a manual choke to play with and the roaring intake noise is great

.

Converting to a properly set up EFI gives loads of benefits , nowhere as difficult as it would seem . Would I go back to carbs NO.

nick205 - 12/10/20 at 03:58 PM

I used a Weber 32/26 DGV on my Pinto in my MK Indy and fitted a manual choke. Started cold OK with the choke and never had any problems with it overall.

Sounds like what you describe may help others if they're having the same issue you were though. Maybe you could make a little kit for others to fit to their carb?

snapper - 12/10/20 at 05:31 PM

Another option is a slightly shorter sleeve and use a circlip to hold it on

David Jenkins - 12/10/20 at 06:23 PM

quote:
Originally posted by nick205
Sounds like what you describe may help others if they're having the same issue you were though. Maybe you could make a little kit for others to fit to their carb?

I'm not up to making parts for others... though I have put details about the fix on my website now.

nick205 - 13/10/20 at 09:10 AM

quote:
Originally posted by David Jenkins

quote:
Originally posted by nick205
Sounds like what you describe may help others if they're having the same issue you were though. Maybe you could make a little kit for others to fit to their carb?

I'm not up to making parts for others... though I have put details about the fix on my website now.

Fair do's - the info is shared and available for others to make use of. Making things for others can often invite "support" quesions when they need help (sometimes best avoided).