Float heights on 40 DRLA 's

Busboy75 · Post by **Busboy75** » Tue Jan 09, 2007 6:45 am

Just bought a set of second hand 40 DRLA 's for my 2ltr type 4 thats in my bay. the tabs for the floats are different on each carb. does anyone know the correct height settings for these?

cheers Arran

ecdez · Post by **ecdez** » Tue Jan 09, 2007 9:56 am

The dellorto book says about 1/4" from the bottom side of the top casting to the top of the float.

I'll have to double check that, it's been a while since I did mine.

scousebob · Post by **scousebob** » Tue Jan 09, 2007 12:13 pm

According to the Dell tech book I just happen to have in front of me it states -

the closed float level should be 5-6mm (0.1969" - 0.2364")(SORRY IM A LIMEY, WE USE the metric system like everyone else in the world).

the dropped float level is 12 - 13mm (0.4728" - 0.5122")

You just need to be carfull with the small brackets.
If it all looks a bit worn you should replace.

Good luck
bob

Busboy75 · Post by **Busboy75** » Wed Jan 10, 2007 3:42 am

thanks a lot for the help

i'll set em up tonight

RonW · Post by **RonW** » Sun Jan 14, 2007 8:08 am

just to add to this thread, here is a picture for reference. which in this orientation, measurement "B" should be 5-6mm and bend tab "C" to get that. then orient top plate horizontally and let the float drop down and that measurement to the apex of the float should be 12-13mm. The adjustment for the horizontal position is on the tab opposite to the shut off valve "A"

FidoDido · Post by **FidoDido** » Mon Jan 15, 2007 2:26 am

Dumb Q...

does the 5-6mm include the gasket thickness?

I set mine to 6mm from the gasket, and am now having to go up a jet size on the idle jet - just wondered if the float height could do that? Would changing the float height by 1mm effect mixture that much?

dstar5000 · Post by **dstar5000** » Mon Jan 15, 2007 3:17 am

YEP! The measurement is from the plate, without a gasket.

Don

FidoDido · Post by **FidoDido** » Mon Jan 15, 2007 5:48 am

looks like I'm pulling them apart again then!

FidoDido · Post by **FidoDido** » Thu Jan 18, 2007 5:51 am

dstar... Many thanks !

turns out my floats were 7mm from the carb top itself. Now adjusted to 5mm, and the hesitation has almost dissappeared! Massive difference in 2mm of float height - would never have thought it!

Now need to do a little fine tuning to eradicate that final 5% hesitation (now around 1800-2000 rpm. Slight main jet increase is what I'll try next (122 to 125). Hesitation almost dissappears when the engine is hot, so thinking must be something to do with main jet, cold air etc

dstar5000 · Post by **dstar5000** » Sun Jan 28, 2007 10:21 am

You are right, the cold air increases the required fuel in that
*bad spot* that we all have had to deal with.

The symptoms dictate that you need to the tighten the accel pump
lever a couple turns.

That will increase the fuel so that the hesitation should disappear, but
if it causes sit to smell of raw fuel, back off on the turns.

Don't want to burn more petrol than needed to overcome the hesitation.

You might even increase the timing to 8-10, which is just a little over
the 7.5 that you are probably running.

Don

Plastermaster · Post by **Plastermaster** » Sat Feb 10, 2007 2:16 pm

Very important is that as the pic shows the carb plate is in the vertical position. That is the correct way to measure it. The Dell book shows a horizontal position. That makes a BIG difference in the working fuel level. Set it vertical and then turn it horizontal and the the setting goes to about .5mm.

Also I was reading some carb info I got off a motorcycle site, just a small difference in float level can make a big difference in mixture if it causes the fuel to fall below a hole in on the E-tubes. I aways thought that the air bubbled in the fuel throughout the length of the tube, but the way this site explains it is that if fuel is covering the hole on the E-tube, air will not come out of that submerged hole. What happens is that as fuel is sucked off the top of the jet well it only mixes with the open holes ABOVE the fuel level. That is why float hight can make such a difference at transition at steady throttle but give it the pedal and the difference is not as noticeable.

Now I will start a new thread with my own carb problems...again.

Ron

FidoDido · Post by **FidoDido** » Mon Feb 12, 2007 1:56 pm

Dstar - tried the 10* tming - helped with idle (had to turn the idle stops back a little) - I have an automatic, and it usually drops around 200 rpm when put into drive with the brake on - dropped slightly less with the 10* idle (prob 150-170 - my guage isnt that accurate, but it crawled quicker! I set my idle to 850 in neutral).

However, at cruise (3500-4000 rpm for me), head temps were up by 30* or so (timing is 31* BTDC with a 10* idle). So its back to the 28* max advance, which is 7* at idle...

60 idle jets are next, although I'm wondering if changing tubes would be better? I have 9164.3 tubes right now - according to the CB book these are "intermediate". They have alot of holes - all the way up. Now I'm not so clever about tubes and how it all works, but seems to me that more holes = more air, therefore potentially leaner mixture? Am I way out? Where can I read / learn more about how these things work?

Plaster.. interesting. I bought the carbs off Gabrielle (Ebay ALFA1750), and pretty much just stuck them on a year or two ago - they ran so well, I didnt take them off and do any fine-checking (I put them on to get my ass on a family holiday and time was tight - I got lucky!!). Anyway, I checked the float height this winter as there was always a slight smell of gas after the engine ran, and having replaced all fuel and breather lines, I came to suspect carbs (Dellorto drip??!!!! ) - the gasket between the manifold and head on 1/2 was gum - sure sign that fuel is dripping.... On inspection, the floats were at around 0.5mm closed (horizontal) and around 8mm open (slightly off vertical). So I reset to 6mm from gasket (vertical - turns out this was too much), now I did 5mm from the metal of the carb (horizontal - although seemed to be same vertical)....

I'm confused, but I'll figure this out eventually... fun taking it all apart and getting it right. great too that at 28* timing my head temps are the lowest they have ever been (330* running steady 3800rpm in a bus with an auto tranny!!! bring it on!)...

Plastermaster · Post by **Plastermaster** » Mon Feb 12, 2007 4:48 pm

The difference between Horz and vert is that in the vertical position the float comes to a stop when the tab starts to close the needle. In the horizontal position the needle is closed the whole way. It sound like you raised the float level by about 2mm. The additional fuel in the bowl could exasterbate (

) the drip. Since they ran good when you got them, I would put the floats back where they were, or make smaller changes. If you got the same measurement vertical as horizontal, you have to be more careful and make sure its not hanging up or something.

Ron

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Float heights on 40 DRLA 's

Float heights on 40 DRLA 's

Float level