Rebuilding a 34 DATR 2/250

[droptop]

I rebuilt the carb on my '78 spider without any difficulty and what I found most interesting was while I was speaking to someone in Webcon in the UK regarding increasing the primary choke jet sizes to compensate for my K&N pancake filter, he advised me to go up TWO sizes at least due to modern petrol being diluted with ethanol which burns at a lower temperature and can ruin the car's power.
He also mentioned taht I should go up one size on the '79 with standard air filter.
I've refitted the carb on the '78 and it works a treat after some retuning of the idle air/fuel mixture screw and I rebuilt a spare 34 DATR I had with the intention of fitting it on the '79 and it was fortunate i did.
When I went to swap them over and convert the "new" carb to the manual choke on the car, I discovered that someone in their wisdom had fitted a 30/32 DMTR 90/350 on a 2.0 engine and a quick internet search determined that this carb was for the 1.3 strada and Delta.
I'd never driven the '79 on the road, but bought it as a project which I'm currently ressurecting and plan to be driving in the next couple of weeks.
the previous owner advised me he had a lot of running issues with it, one of which turned out to be an active immobiliser he was unaware of and I recon the wrong carb didn't make for decent progress when the car would run.
I just thought I'd mention the rejetting thing in case it helps anyone who feels that their Beta seems lackluster for no apparent reason

[smithymc]

Fascinating. I must admit I was wondering in my ignorance about doing something similar, as I have the k & n element in the standard housing and a custom exhaust. I can't say mine seems lacklustre as I don't have anything to compare it to and I am spoilt by daily transport.

So are the recommended sizes linked to part numbers we could order?

Mark

[mangocrazy]

This advice to go up a jet size or two sounds wise to me. It's not just the ethanol that causes problems (and that can cause plenty), it's also the fact that modern petrol has changed significantly since our carbed cars were current. Petrol is now a real cocktail of additives and chemicals, and not the relatively uncomplicated stuff we used to fill up with.

[Neil-yaj396]

My car would definitely benefit from larger slow running jets, as it is often lumpy until the second throttle opens, after which everything is fine. Any suggestions on sizes and where to source new jets?

[droptop]

I got my jets from a Dublin-based classic car specialist reccomended to me by Webcon in the UK who don't sell directly to the public, but through authorised dealers here and in the UK.
They were extremely helpful and easy to talk to.
However, I'm now experiencing difficulties with low idle over-fuelling!
I had stripped the carbs from both spiders fully and cleaned them thoroughly with thinners and a brush followed by a water-based degreaser then a rinse in water followed by blowing all chambers and passages out with an airgun.
Starting from cold is so much easier now, aceleration is even better than ever and for a single carb, I have to say it was never shoddy, but after driving for any length in traffic, idle gets lumpy and the plugs start to foul.
All gaskets, seals and "o" rings have been renewed, float level set, points and condenser replaced, timing set and a new aftermarket coil fitted.
Spark is massive with no chance of it being extinguished and I'm using NGK BP6ES plugs.
I've reverted to the original jets with no change in the fouling of the plugs but I fear the mistake I made may have been the removal of what I imagine is the idle air mixture screw at the base of the carb near the cut-off solenoid, without first counting the number of turns
Without access to a gas meter, is there a way to set the mixture or do I need to get one?
The other thing is that hot starting is still no different than ever, in that it has always required more cranking than I'm happy with and a little feathering of the throttle pedal which then causes it to fire at highish revs.
Unlike my '79 car which has OE electronic ignition and starts flawlessly every time.
Having said that, the '79 car has had its' carb rebuilt in similar fashion and I'm still working on it so it has never been driven so I anticipate similar trouble on low idle
I'm open to all sujjestions

[peteracs]

Hi

A quick thought on the idle issue, I assume you still have the return line and mech pump etc, is it possible that the return line is not blocked, but has a partial blockage, so when you are not using much fuel it is causing an issue?

The warm start could that be a heat evaporation issue?  You could also try changing the coil/leads etc and/or one of the electronic ignition units fed from the standard points.

Peter

[droptop]

I'll check the return line Peter as the ignition system is all new components and you could weld with the spark!
Also, would incorrect float level lead to this idle problem?
I always used to set floats as close as possible to paralell to the upper face of the carb with needle fitted and upper body held upside down but I noticed before ever dismantling the carb that the float was inclined with the free end, i.e. the end away from the needle/pivot point, closer to the carb body so i corrected this with the new needle which in my mind would mean somewhat less fuel in the bowl before the needle closes the inlet.
My biggest concern is washing the tops of the cylinders with excess petrol and causing premature wear

[capriblu]

Regarding the idle mixture screw then my "basic" process is as follows -

With engine warm and idling evenly turn mixture screw in (clockwise) very slowly until you just meet point at which you can hear engine revs start to drop and struggle to idle. In my experience this happens quite markedly so need to repeat very slowly once or twice to find point.  Then simply back out mixture screw one full turn and a smidge.

Regarding hot starts -

Fuel evaporation in lines and initial lumpiness  / hard start after leaving stationary with engine warm was always a bit of an issue with these motors.  Find situation is more pronounced now than 25+ years ago when I was driving various betas every day.  Increasingly have found my 2 litre car takes quite a few turns to start after being left for a day or so. Initially had concerns that fuel was being lost from float chambers.  Having researched subject seems to be an increasing problem with older (carburetted /  low fuel system pressure) vehicles as latest pump fuel cocktails seem, even at relatively low temperatures, to be far more prevalent to evaporate than good old "4 star of old".  A few years ago was twice left stranded in stationary traffic in warm weather - start of vaporisation in lines.  Standard mechanical pump can struggle a bit to clear.  As a back-up I have fitted a simple priming bulb before the fuel pump - has helped out a couple of times.  A decent electrical pump would probably solve these issues.   

[droptop]

Regarding the idle mixture screw then my "basic" process is as follows -

With engine warm and idling evenly turn mixture screw in (clockwise) very slowly until you just meet point at which you can hear engine revs start to drop and struggle to idle. In my experience this happens quite markedly so need to repeat very slowly once or twice to find point.  Then simply back out mixture screw one full turn and a smidge.

Regarding hot starts -

Fuel evaporation in lines and initial lumpiness  / hard start after leaving stationary with engine warm was always a bit of an issue with these motors.  Find situation is more pronounced now than 25+ years ago when I was driving various betas every day.  Increasingly have found my 2 litre car takes quite a few turns to start after being left for a day or so. Initially had concerns that fuel was being lost from float chambers.  Having researched subject seems to be an increasing problem with older (carburetted /  low fuel system pressure) vehicles as latest pump fuel cocktails seem, even at relatively low temperatures, to be far more prevalent to evaporate than good old "4 star of old".  A few years ago was twice left stranded in stationary traffic in warm weather - start of vaporisation in lines.  Standard mechanical pump can struggle a bit to clear.  As a back-up I have fitted a simple priming bulb before the fuel pump - has helped out a couple of times.  A decent electrical pump would probably solve these issues. 
  

Appreciate all the advice.
All I need now is a dry day to bring the car outdoors and get the mixture sorted
I'm used to tuning two stroke carbs but "real" carbs are still something of a mistery to me despite growing up with them and not owning a fuel injected car until the mid-90's
It's actually reassuring to read about your problems with evaporation as I had visions of the fuel being somehow syphoned back to the tank via the return line while the car was parked.
In fairness to Lancia, they did a great job with the routing of the fuel lines when compared to carburetted Fords where my early Fiesta had the fuel line coming up between the manifold and the block, with no return line, just an overflow a la domestic water tank, which came down at the back of the block and allowed excess fuel to spill out beside the exhaust. (And the little 950 cc engind struggled to make 20 MPG I wonder why?)

[peteracs]

Hi

They are still pretty near to the exhaust manifold and heat soak when stood still could cause issues, you could try lagging the exhaust manifold to try to cut down on the heat and would help protect the steering rack rubbers as well.

Peter

[droptop]

Hi

They are still pretty near to the exhaust manifold and heat soak when stood still could cause issues, you could try lagging the exhaust manifold to try to cut down on the heat and would help protect the steering rack rubbers as well.

Peter

Luckily the rubber bellows is falling apart on mine so I don't ahve to worry about it any more
Perhaps it would be easier to shield the fuel lines than wrap the manifold?
After the struggles I had with mine earlier this year, I never want to see it again but something needs to be done as the starter comes under excessive strain from the extra cranking

[capriblu]

The lines also run close to the transverse exhaust box at the rear of the car.  A good electric pump running for a few seconds before cranking or (as I have) a simple manual priming bulb/pump should solve the issues.

[Gromit]

This is an old thread but I thought I would add my two bobs worth and back up capriblu`s suggestion re a priming pump. We have just fitted an electric pump for priming duties to my father`s 79 Beta Coupe (with the standard mechanical fuel pump). The car is used infrequently and required extended cranking to get fresh fuel to the carburettor. Dad was worried about excessive wear on the flywheel ring gear etc and we finally had an electric pump fitted and powered via the ignition circuit. The new priming pump works a treat - with 30 seconds of priming and then start the cranking time is down from 10 seconds+ to 1 second.

The electric pump (a cheap Fuelmiser FPE-109 branded Chinese made one purchased at the local Repco auto retail chain) was mounted above the rear cross member with a manual on-off switch mounted on the console. I am not sure about the durability of this particular electric pump but for the amount of work it will do it is probably irrelevant. Highly recommended and a great back up option if the mechanical pump gives any problems or there is a fuel line vapour lock etc from heat soak in hot weather! Capriblu`s manual priming bulb arrangement before the mechanical pump is a clever and lower cost alternative option.

[capriblu]

I think 10 seconds after a period of not being run is about right  - my car was regularly taking quite a bit longer.   I always like the car to crank for a few turns before firing as this ensures a bit of oil circulation.  My procedure for starting the car after an extended period (couple of weeks+) of being stood is to crank for a few turns, prime and then re-crank.  Nothing worse than priming firing straight away and being greeted with a nasty bottom end rattle for split second.