Weber Throttle Issue

[Roady]

The latest issue everyone, I have been mucking around with pretty much every component on the webers over the last 2 months, learning and getting them sorted on this engine as a baseline ready for the new engine when I can build it. (Triple Weber set up - all connected to each other, not with an individual rod to each carby).

 

Today while driving, everything was fine and normal until I came to rest at the lights and it was now idling at 2500rpm. Normally when this kind of thing happens I go back and look at what I last touched because guaranteed it's something I've done.

 

Yesterday and today I had mucked around with the bleed air screws and the dizzy timing. Now with that said up until this point, it had all been driving just fine with no issues then this high idle appeared. Upon further investigation I found that it is throttle related. If I rev the engine, then let it return to idle it does so slowly (because the throttle is remaining partially open). If I open the bonnet I can manually restore the correct idle by pulling on the lever.

 

All three carbs are interconnected and I have never had this issue before. My latest plan to trouble shoot, will be to disconnect the carbs making them individual again and test each one. I think perhaps I have broken a return spring in one of them.

 

That said I also have a secondary return spring as part of the set up and it obviously hasn't been enough to close the throttle on the carbs.

 

All ideas welcome before I begin the witch hunt.

 

Cheers

[C.A.R.]

Hold on...
You only have ONE throttle arm activating the THREE carbs?

There is your problem.

Convert it to run on three drop arms - one to open EACH carburetor. 
You could well have twisted the throttle shaft on the carburetor that the primary drop arm is attached to, casing the engine to idle high.

 

[Roady]

Sorry to clarify, I have used Weber parts to connect them all. From the research I did, it looked to be a good way of keeping them all synchronised using these connectors, as it doesn't allow movement which sometimes can occur with the 3 individual rods, and to date they have never gone out of sync in the 6 years I have run them on road and track. I totally get what you are saying, and it's still a possibility but I just thought it would have happened sooner if it were going to happen.

 

I have run it for years with no issue, I just found it strange that all of a sudden it's changed. After some sleep I don't think it would be the throttle return spring because all the other springs would return it to idle. The only other time I recall something similar was when I had SU's and after I came off the track and got some dirt in the mechanism - WD-40 fixed it.

[PeterAllen]

It isn't something simple like dirt on the butterfly?

 

Have you given them a spray with 'throttle body cleaner'?

 

Pleased to hear you've had no trouble in 6 years as I plan to run a similar carby on a 202 in the Bolwell.

Edited March 16, 2017 by PeterAllen

[Roady]

Hey Pete,

Only thing I can suggest if you haven't already bought some, is don't buy Weber DCOE 152's... find 152G's etc. all to do with the Progression Hole which I can tell you all about later if interested.

 

Thanks for the tip and I'll check it out as well

[AndBir]

Hey Pete,

Only thing I can suggest if you haven't already bought some, is don't buy Weber DCOE 152's... find 152G's etc. all to do with the Progression Hole which I can tell you all about later if interested.

 

Thanks for the tip and I'll check it out as well

 

A good explanation can also be found here : http://www.weberperformance.com.au/product_info.php?cPath=1_9&products_id=1

[dat2kman]

You may find the moustrap coil springs at each end of throttle shaft, captive inside the carb bodies, are fouling/sticking, and, that you have overtightened the throttle shaft locknuts, that are only done up to a bees dick above finger tight, before you fold their lock tabbs over them.

And, yes, fit ta external return spring at each carb, as a ex CAMS Tech inspector, we learnt never to rely on those hidden mousetrap coil springs, as they do stick, ofetn at partial throttle, hence the requirement for minimum of two external springs.

[Cozza]

Can you post a couple pics of your throttle shaft setup please.

 

Jason. Are you suggesting 2 external springs per carb or 2 springs total?

[dat2kman]

CAMS only require two external springs,

I'd suggest one spring per carb, just incase any linkage rod, screw, balance link bracket etc, was to come undone, break, fall off.

 

Few years back, we had a death in motorsport, at Lakeside raceway, car was heard at full rpm, front wheels locked up, off track, onto grass, accelerated into a armco barrier. Throttle was found in wide open position, ne external springs, bits dislodged and broken around the Webers, before during or after, who knows?

It was at a Sprints day, with no scrutineering conducted.

[Roady]

Hi Cozza, did you want me to post a pic or were you asking the other Jason?

[Roady]

Thanks for all the advice and ideas. Looks like part of the throttle rod mechanism needed some lubrication. WD-40 to the rescue and everything now back to normal.

 

Cheers

[Cozza]

Glad to hear it's sorted Roady but if you could post some pics would be good.

Cheers

[Roady]

Hey Cozza - this pretty much shows the set up. There is also a throttle return spring (external) attached to the middle carby which it doesn't look like I got a proper photo of, but it is there. As others have mentioned, well worth putting an external spring on each carby.

 

Let me know if you want any other views but I think that will clarify it.

 

Cheers

Edited March 19, 2017 by Roady

[luvemfast]

I just don't understand what the advantage of this is over individual link arms

[Roady]

Not sure if there is an advantage - just a different set up.

 

I have never run the triple arms, but the advice I was given originally was that over time and due to vibration the arms can get themselves out of sync. As I said I have never used an arm for each carby, so what I was told may never actually happen, but I know the results from this set up and I've never had a drama needing to re-sync the 3 of them. From the day I first installed them until now all throttle plates still line up perfectly when viewing them through the Progression holes... at the end of the day it may just be an alternative means of connecting the carbs.

[Cozza]

Yep, just another way to skin a cat!

Personally, I'm not a big fan of driving 1 throttle shaft via another one but it sounds like it works either way.

Thanks for uploading the pics.

[dat2kman]

Linking two or three carbs together like that, is fairly common, the linkage arms between each carb is very finely adjustable, via the threaded adjuster.

Only downside is, if carbs manage to move/dislodge, on the mounts, this is very small movement, and gets taken up in the screw adjuster.

 

The downside of the long rod, with three clamped on crank arms, and their drop link to each carb, is that,

1, the clamped on arms can shift on a round rod ( hexagonal rod with matching arms dont shift!)

2. The screw threaded drop links ( balls at each end) can also come undone ( their adjusters between the balls)

3. The balls have a small amount of slop/freeplay, in each one ( 6 lots of fine freeplay)

 

The method employed in the pics of Roady's car, is the preffered method, might not be "blingy" enough, but its a better method.