Hi All, Well, after spending about 3 years reading up, tinkering and generally working out how K-jet fuel injection works I have gone and bought myself a car with good old fashioned twin carbs - back to square one! Bascially it's a Mk1 1500cc with twin Dellorto 40's on it. I can get it running ok from cold but only by putting my hands over the trumpets (is that what they're called) to restrict the air a bit and act like a choke. There is no manual or auto choke fitted so cold running is a bit rough, and pretty rich by the smell of it. This is a pic of the carbs: Am I right in thinking if I make a little linkage to connect up the two spring loaded levers in the top middle of each carb to each other, and then hook that up to a cable I will have a manual choke mechanism? I have worked out how to lower the idle speed so far and it runs good when warm but my knowledge of carbs is pretty basic. Anyone got any tips or good links for info? Much appreciated. Incidentally, the noise they make is far better than K-jet!
Get it set up on a rolling road, I don't use a choke just two pumps of the throttle and away it goes.
Not much choice with the fuel line, that linkage totaly buggers up any chance of linking the carb fuel unions the normal way. Ive got the same setup on my mk1 and am currently looking for new unions to overcome this.
generally people try not to use the cold start system on carbs like that. Dellortos aren't prone to the dramatic failure that webers are, but a well set up set of carbs will just need a couple of pumps, crank the engine, and she'll fire - then for a minute you may need to hold it on the throttle and it should be fine.
The little linkages are indeed the choke mechanisms. I think it just adds a little extra fuel, certainly can't do any harm to put a cable on them and see if it helps. SteveD is right though, a check up on a rolling road is no bad idea, and be prepared to have it done once a year or so. Unlike more 'normal' carbs the paired twin chokes do wander off song. I'm back on a carb - nothing so exotic mind - and still getting used to erratic cold running, carb icing and the like. Oh yes and be prepared for the car to be a complete b*tch in traffic on hot days Barkstar
Stu if you want to take it to a rolling road to egt it set up try, WGT Auto developments in Northwhich.
Jamie - It may well have been set up there already as I bought it from a lad in Northwich and he said it was set up locally! I would like to connect up the cold start mechanism if possible, seems a waste not too since it's there and it may help start the car one day. Noted about pumping the throttle a few times before starting, all new to me this carb stuff! I do have the original (Solex?) carb and manifold etc with the car but I want to get it running reliably on the 40's if possible, I expect they give far more power and a better noise! I will see how I get on and report back, only had the car running briefly so far as there are a few other issues to sort out before running it for an extended period. Smells pretty rich at the moment to me but again that may be my inexperience of carbs.
Ive got a haynes manual on carbs, I will dig it out and email you the pages if you want dude, Ive a lovely set of 45's that are going on the Jetta in the spring, so I will be in the same boat as you mate.
Chees Steph - that would be very handy. I had a look at a Haynes book my Dad has on carbs but it only covers Pierburg, Solex and a few others, nothing quite like these ones. How come you are going to carbs on the Jetta? Do you just fancy the noise or do they give more power/torque?
The learning experience I think , I was wanting a change from the KJet ive had my moments some as low as 81hp, , Ive been after 45's for a couple of year and was originally let down with the carbs, so I started getting the megasquirt and turbo stuff, then i was offered the carbs as well so I bought them too , I can sell them on if I dont like them any way.
Nope, just ideally not kinked like that. As above, I see now that it's necessary because of the slightly flawed design of that particular throttle linkage. It's not a major problem.
Twin choke sidedraughts have an accelerator pump. It is a bit crude but if you put your foot down quickly it squirts neat fuel into the choke. It helps overcome a flaw in big carbs. On a big bore carb at low engine speeds the mixture is moving slowly - comparitively - and if you then apply the lead boot it will bog down, a squirt of neat fuel helps stop this. So on cold start pumping the accelerator will shove a bit more petrol in to help fire it up. Barkstar
Stu the guys at WGT are pretty handy, they used to tune a fair few RS turbos and XR3isso are pretty handy with Kjet as well, although they offically specialise in RX7s.
Sounds good Jamie - I wonder if they could set up my Mk2 16v with the Audi 6A engine in on the rolling road if they know k-jet? Nice and local, don't want to go all the way to Stealth again if I can help it but don't want to let anyone mess with it if I'm not sure about them as it runs good already with my DIY setup. Barkstar - thanks for the info - makes sense!
It would be worth giveing them a call, like I say they used to get through a fair few RS turbos and XR3is and they do know there stuff. They have got a rolling road so its got to worth a try.
all you need to do is turn the fuel banjo round, so that it faces the other carb, and connect them accordingly
That seems like a nice simple solution, I should have thought of that! Only thing might be whether the pipe then fouls the throttle linkage? I will have a look and see. Cheers
