Drla

[a14blue]

I've have a pair of Drla 36's they been set up with

28 venturis
118 mains
55 idles
9164.2 emulsion
35 pump
180 airs

As euro carb recommend for 1.6 I have also CB manifolds & throttle bar.
But I can not set it up without an air leak under load I've taking it apart 3/4 times and can not seem to find out where?

 

[Trikky2]

Sorry, I don't understand what you mean by an air leak under load. Can you explain a bit more?

 

[a14blue]

It screeches and loses power under load, like when I'm going uphill or quick full throttle

 

[Trikky2]

That doesent sound like an air leak.

If you have an air leak between the carb and the engine it will affect the power when there is vacuum in the inlet system, such as when ticking over or cruising on light throttle, plus you would likely experience back firing on the overrun.

The problem you describe sounds more like its "bogging down" when you open the throttle quickly. This can also be described as a "flat spot" (all be it a large one in your case).

Assuming no other changes were made to the engine when you fitted the carbs, its likely caused by incorrect fuelling under sudden load. The first thing to check is that the accelerator jets are pumping fuel into the throat of the carb when you operate the throttle. You can see this by looking down each carb and operating the throttle, without the engine running.

None or very little will cause bogging though if there way too much it can also cause bogging - but then it would be accompanied by a bit of black smoke from the exhaust when revving the engine.

Have you adjusted the mixture screws for fastest tick over as per the manual?

 

[jonboylaw]

As above, check for accelerator pump diaphragm splits and if all that is ok, look at the fuel pump to ensure it is providing enough fuel.

Not sure what you mean by screeches, that could be the fan belt slipping.



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[a14blue]

Thanks for the replies, I will check the diaphragms! Also I have a VW Brazilian mechanical fuel pump , I have read that it should be okay ,but is it? I think I'll have to buy the dellorto book as I've been looking at YouTube and trying to set them up and there was not enough information me thinks. Also I don't have any trumpets on my carbs , I can't see that they can do that much? But what do I know. Cheers though because I have been pulling my hair out over it.

 

[StuF]

According to this thread your main jets may be a little small

http://ssvc.org.uk/phpbb/viewtopic.php?f=6&t=96290" onclick="window.open(this.href);return false;

He posts that he is running the following

180 air correction,
135 main
33 accelerator pump
52 idle jets

Maybe try a larger main and keep your others as they are?

 

[jonboylaw]

135 mains for a 1600 will be too big. I run 130s on a 1955cc engine, using 30 chokes and 60 idles.

The trumpets will help a little with torque but not cause the problem you have.


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[a14blue]

I've checked the diaphragms and they're in very good condition. Are there any other things I'm missing as I set up?
So far I've been disconnecting the linkage , then using my snail gauge to balance the carbs on the throttle linkage, then reconnecting the linkage, adjusting the mixture screws in until the engine begins to cut out , then I adjust it half a turn out. What I am finding is I struggle to find the point where the engine does cut out

 

[Dave.P]

Buy the dellorto book by Tomlinson, its a must with drla's . It has all the answers !
Your jetting seems ok, maybe try bigger idles like 60,does it pop under load? mains are venturi size x 4-4.3 (4.1 i found works best), have you set your timing ?
You need to run a fuel pressure regulator set to 3.5 or you will have probs with a std fuel pump, do you have one on?
The screeching, is it like a chirping only under load ? Think I know what that is and how to fix it, mine used to chirp too , doesn't affect performance though ,just annoying

 

[a14blue]

I'm going to pickup a book tomorrow, the noise sounds like the alternater belt slipping and I do loose power?

 

[Dave.P]

Take off your fan belt, floor it for a really short drive ,like 50 yds max to see if noise is still there with no belt. Put belt back on. That's what I did.
There is a part of some drla's that ,if not plugged, will cause a screeching/ chirping under load.

 

[a14blue]

Thanks Done that it definitely not the belt

 

[Dave.P]

Ok, this took me about 3 years to find out how to fix..
You could google drla whistle stoppers
Or check these threads as I just did it :mrgreen:
http://www.shoptalkforums.com/viewtopic.php?t=125776" onclick="window.open(this.href);return false;
http://vwparts.aircooled.net/Dellorto-DRLA-Anti-Whistle-Base-Gaskets-PAIR-p/dellorto-whistle-gasket.htm" onclick="window.open(this.href);return false;

Yes it's as simple as filling those two holes in your carbs throats, which I did with chemical metal or something similar after drilling holes inside the holes for a key, or fit the gaskets with the little rubber nipples attached .
Job done !
That and the dell book should see you right

 

[a14blue]

Thanks for everyone's advice! It conspires that the left hand carb must have had a blockage so after a strip down clean and blast out with air , I got everything working . I also adjusted the floats. So after many weeks with him off the road and many hours bent over the engine and some black thoughts? The dellorto superformance book is worth it's weight in gold.
Still got the whistle but I will live with that for the time being as I'm enjoying using him again. Thanks again everyone

 

[TeamBrian]

My right hand side carb whistles.....must ead the links :roll: