40 dells and the shakes

[njv]

hello.
made it here from stf seems a bit more relaxed here !!!

heres my question i have a shaking engine at aaround 1600-1800rpm.

now is this when the engine is going from the idle circuit into the mains ?

its super everywhere else so i dont think its my engine out of balance !

could it be a linkage thing its a weber linkage on dells 40 these came of an alfa .

ive just left the chokes as they are with no cables fitted in the off position is this ok ?

many thanks in advance.

[kdanie]

Welcome to the GL. Lots of the same people here as on the STF but it is definately more relaxed and open minded.
What vents and jets are you running? I have seen the choke mechanism blocked off with a plate and left alone so either should work, just be sure the lever can't move if you leave it on. It does sound like a transition problem to me but I'm not an expert.
ken

[njv]

hello
well at the moment its running 30 vents way to small ive a set im looking at right now that are getting bored out to 34 or 35 mm im not going any bigger as i dont want to lose to much torque i think 38 mm would be the limit in 40s anyway.

heres my engine spec .
76 stroke 94mm bore web 163 full base circle cam 2ltr rods bushed for 22mm mahle forged pistons super short inlet manifolds by oliver knuf heads at the moment 40 in 34 ex sqr port la performaance j tubes standard 2ltr back box with all the ports opened up to 40mm (theres plenty they to grind away at the openings . cro moly push rods .

40 dells with 135 main 55 idle 180 air 35 pump. the idle screws are only 1 1/2 turns out at the minute i supose this will change when i put the larger venturies in.

future plans are 44 inlet 38 ex sqr port heads possibly getting a set of 94 barrels ive got taken out to 96 mm .

its like fast as it is real fast im well cuffed with it .

ive a feeling its a proggresion thing and the fact that the idle screws are only 1 1/2 turns out is sort of chokeing it .

any thoughts most welcome.

o and im still looking for a 411/12 plastic air intake housing .

[kdanie]

I would guess that the 30mm vents are whats choking it off. If the idle screws are adjusted for the best idle mixture quality I would not screw them out more to cover the problem. You might try going up a size on the idle jets and see if that helps. Be sure you don't have a plugged progression hole or something simple like that.
good luck
ken

[njv]

hi
im thinking that i will get my 35 mm venturies installed thus makeing me wind my idle screws out a bit more put in fresh clean plugs and see my mixture is ok then see if this shake disapeares .

i do know im gonna take my time and each adjustment will be noted and reversable should it be required , at the moment my plugs are still showing that im a little rich with only 1 1/2 turns out i think my jets are ok and the bigger vents will resolve this situation. hopefully.

i will see how it goes.

[njv]

hello.
fitted 35 venturies today while the carbs where in bits i checked the float levels yess i broke my own golden rule the floats acording to the cb dell superformance book where way out!!!

so of course ive adjusted as per at 5mm with the carb top turned upside down and 13 mm with the floats dangling in the wind(and a very cold wind here in germany today too).

before my adjustment it was set more like 2mm-20mm.

well at about 60 kph it falls flat on its nose just sort of runs out of fuel not good im not happy. and i ran out of daylight to8-( .

tommoro i will strip dem both again and put the floats back where they were !

at least this way i will know how i stand with my new 35mm venturies .

thing is it seemed better to drive today not so neck jerking on accelaration it was actually a bit difficult to controll at low speed with the 30mm venturies fitted these where obviously to small for my engine anyway.

im putting another post on with reference to dell float settings see what sort of replys i get .

report what happens tommoro.

[njv]

hello all.

well striped my carbs again and reset the floats again sadly when i drove it it fell flat on its face still 8-(

soooo i decided to try a different aproach i found the original alfa 115 main jets out took myself a 1.5mm drill and well you can guess the rest .

it is driving a hell of a lot better in fact its frightning 8-)

my head temps are down 50 o F and this is good news .

ive done a big jump here from a 135 main to a drilled 150 (bigger id imagine by default ) i now want to try a 140 / 145 for the perfect setting.

as much as i didnt like drilling out jets doing it and fitting a bigger main has saved me a lot of pain.

here is how they have ended up.

40 dells (ex alfa)
35mm vent (custom bored by local tame engineer type)
150 main (drilled sadly by my own wavy hand)
180 air (as per usuall)
55 idle (out 1 1/2 turns running 900rpm)
5mm- 17mm float
35 pump (still on alfa setting needs checking)
cold start wired shut
on 21/2 in tall manifolds
fuel pressure (lazy man still not checked left to right carb flow!!!)


and does it rev o yea need ther weather to get better so i can get onto the autobahn and open it up a bit

the locals really dont expect to be overtaken by an old typ 3 with english number plates on it but i cant help myself and it just seemed to happen loads today.

well worth a conversion to a typ 4 engine.

my gearbox is going to die i think!!!

[Farmer]

Hi Neal
35 mm venturies require about 140 - 145 mains. In few cases up to 150.
I would say go back to the factory settings with the float bowl. then you are more secure at higher rpms. And of course check your fuel pressure.

The uneven running at 16-1800 rpms is most likely an error in your linkage. My bet is that it does not open equally as that rpm range is not where the transission area normally is.

As for the idle, try and screw the air bypass screws out by ½ - 1 turn. That will allow more air to go through the system hence leaving you the option of getting your idle screws furthewr out
Another thing. you write that your idle is now 900 rpm. Is that with the throttle completely closed ??? It sounds a little off to me.

The "drop on its nose" at 60 mph. could be a mix between a lean idle and pump jets being on the small side for the engine size. I´m pretty sure that 55 idles will create a lean setting on that size engine, so I would try and go up to 58 or even 60 and work my way from there.
If you need jets you can contact me, I can help you out with that.

Merry Christmas.

Torben.

[njv]

hello
well zou bet its my linkage it turned out that the aluminium arms that come of the hex bar were not level with each other !!

obviously no amount of adjustment on the drop links is going to get me there in this case .

having adjusted them in my vice its a lot better than it was but still a very slight mismatch at 1750rpm i think more fine tuning will eventually iron this out.

its the way that the drop arms are splined onto the hex bar that has arose these problems .

its at times like this i cant help thinking a bellcrank push pull linkage would be a lot easier to set up because this is on a type 3 i dont know if that would work mind as the manifolds are so short the throttle shafts are well below the level of the tin!

if i did this the arms that go on the throttle shaft would have to be verticle.

i need a set of 145 mains to try or possibly 147s and would also as you suggest like to try a slightly bigger idle i feel a 57 would be worth a go.

one of the air bypass screws (cylinder 4) is stuck and the slot for the screwdriver has been chewed up not funny, all 4 measure the same air intake with my sync meter and i dont think it would be right to screw 3 of them 1/2 a turn and leave the one that is stuck in there but i definenately can see how this would help just cant do it.

plugs after its been idleing for 5 minutes are quite fouled up one thing i think could help here is a new set of mixture screws as the tips on these dont seem as good and sharp as they could be im sure this would help a lot with idle adjustment too.

floats are at 6mm i could try 5mm to richen it up a bit at the top end when i go down a size on the main factory was 5-6mm low being lean high being richer .

still havent checked my fuel pressure i need to get a sensitive pressure gauge (here in europe ) 1-10 psi in 1/4 or less of a pound incre3ments my gauge is up to 50 psi and not sensitive to these low pressures .

im close and i know it i can feel the power need to drop oil change filter set tappets with all this milage doing testing8-)

[yetibone]

Hi Neil
Sounds like you are getting close. I Got the carbs we are using
on my girlfriends GL off Ebay. I think they came from a Fiat or Alfa
or something, but they are Dellorto DRLA40S's and I eventually did get to about the same jetting on our 1835 T1 that you have on your bigger engine. 180 air correctors, #2 emulsion tubes, 150 mains, 060 idles, screws our 3/4 turn, 32mm vents.
Trial and error is really the only way to get it right, but I hope this post might be usefull as a reference.

Yetibone


P.S.
Check and make sure that those little washers, and O-rings are on the ends of the mixture screws. If not, there is a chance aitr can be sucked in past the threads, and cause a lean misfire right off idle.

[njv]

hello
well the carbs are rebuilt all the o rings and such like are new im about to place an order with the dellorto dudes in the uk for a set of new idle screws some 145 and 155 mains and a set of pumps in a 28 flavour now that i have solved a little idle problem i had ill be on it again proper.

these are 40 drlas too ive had the original tiny set of venturies bored out to 35 mm.

be good.

[yetibone]

....SOOOO Much better than Weber IDF's! It's a shame they're not manufactured any more.


yeti.

[njv]

hi
well i guess im spoilt ive never had webers ! so nothing to compare too.

you say you had 60 idles out 3/4 turn on an 1835 .

well mines 2110 and im on 55s out 1 1/4 turns still got a bit of the shakes at 1750 rpm could this be a progression problem?

odd thing as well is its very difficult to hold at this rpm it either whants to go up two 2000 rpm or down to about 1400 ..

many thanks for reading take care.

[yetibone]

Sounds like It's running lean if it won't hold a steady 1750 rpm. I've used 40 DRLA's on a 2180 before with 36mm vents, 160 mains, #2 emulsion tubes, 180 air correction jets, and 35 pump jets. The 40's were really too small for a 2180, but I never had a problem with drivability, unless one of the pilot jets stopped up.

Which....By the way.....
Sorry I never thought of this in a previous post, but a stopped up Idle jet will cause a serious shake at part throttle, and idle. Usually it goes away at 1/3 throttle and beyond. check each idle jet, jet holder, and idle circuit passage (the hole that it screws into) for a piece of dirt. Hummbug's got stopped up about twice a month, and my old sandrail (with the 2180) got it's jets pulled about once a week!

An electric guitar string makes a great jet cleaner. Use G, B, or high E as they are the ones that do not have nickel wire wound around them. They are about 016 012 and 009 guage, I think.
y-bone

[njv]

hello
yeti , that engine sounds quite close to mine 36 vents in dell 40s must have been the limit

ive ordered a set of 145 mains and a set of 155 s too also a set of small 25 mm stacks a new set of idle screws (all them gallons of fuel over the years have taken there toll)

im gonna fit the 155s first and test then the stacks .

i too have a seat of the pants feeling that my 163 cam and only 40 in 34 ex valves means this motor is quite greedy allready down low in the rev range and the proggresion drillings arnt quite keeping up .

thing is im also sure that the mains at the minute drilled out by my own fair hand are going to actually somewhere in the region of 152s the bit measured 1.48 mm but i dont posses any jet size gauges to check . must buy a set.

this plugged idle business is not funny another reason i will be looking at the dell update kit in the future sometime .

pokeing things with guitar strings is a bit of a no no really especially if it was a heacy set of strings and the hign e was a 12 i just sold my electric only got jumbo 12 strings hangin round now~~

its still ok at the moment and a big grin to drive but its allways good to just drill the last drop of juoce out of the apple.

many thanks.