Weber falls flat at 1800

[JohnnyC]

you can spray carb cleaner round the weber to see if there are any cracks ...doughtful...but...ya never know....if the idle increases thats were the crack is located.

Question
what were the jet sizes?

 

[ludwig]

Johnny c
Did that first thing last week before doing a manifold pressure check and nodda on the rpm jump from spraying the entire manifold and carb. Went to 155/180 on the jets as recemmended and it does not change a thing. Orginally were 145/180 Still thinking a cracked carb somewhere.

 

[JohnnyC]

question 1:
how far out are your 2 idle adjustment screws?

question 2:
have you check to see if you are getting advance from the dissy?

question 3:
what is the timming set at?

question 4:
are you getting full throttle?

 

[ludwig]

#1 3/4 to 1 turn seems to be good for the mix

#2 dissy advances looking from front to rear counter clockwise

#3 timing set on the ball or advanced {clockwise} does not matter

#4 this is the problem. At idle ok as we run the rpms up past 1500 it stalls or sluffs off. Looking from the top of the weber in there is fuel comming out at low rpms but no fuel { { the cutting off part} seems that the carb runs out of fuel. We do not see any fuel coming from the top sprayer. The carb has been cleaned and recleaned .

 

[JohnnyC]

5 have you adjusted the float?

6 do you have a plastic float? or brass?

7 you replaced the float needle valve correct from the kit? and positioned the holding bar on the float...the float should move the valve up and down
#14 in diagram: http://webernorthamerica.com/pdffiles/38_DGASES.pdf

8 when the truck runs up and starts cutting out ...try to keep it going for alil while longer then shut the rig down including the Fuel pump...remove the top plate of the weber and see how much is in the bowl.

 

[ludwig]

#5 Adusted the float to specs. .236 or something, cant remember the exact lower # and the travel to .551
#6 Brass
#7 That is correct on the needle. But thanks for thinkin
#8 Had this thing apart 20x always the same level in the bowl, just above the top port holes that are above the main jets,
What should be left in the bowl?

 

[71cruiser71]

i just had this same problem with mine no more than 2 days ago...

1 set timing to specs
2 adjust valves when hot
3 adjust your screws to the best as it can get
4 drive it around... its gotta be under load to get it right
4&5 adjust timing to where your motor likes it
4&6 finish by adjust the screws again

i did this and fixed mine right up. its so frusterating but it takes time. really hope this will fix your problem

 

[JohnnyC]

when measuring float it should be 44.5mm drop when you measure from gasket to bottom of float when held horizontally.

is that were the float is set?

sorry cant convert your numbers quick

 

[ludwig]

yes that seems to be the right number and it is set. how much fuel should be left in the bowl JohnnyC

 

[JohnnyC]

it should be about half full...i dont have my speck book but from what i remember about 28-38mm measuring from top of carb.

 

[ludwig]

Johnny C
Thanks for the time today. Im going to check the fuel level tommorrow, if the float is set right and the fuel is lower than 28-38mm, whats up with the low fuel level.

 

[Pin_Head]

So it is not a fuel tank/pump problem. Keep going up in main jet size and see if the problem goes away.

If you have a points type distributor, it also might be an ignition problem with the points gap too large. The would cause high RPM related misfiring, but it wouldn't buck and spit back through the carb, like a lean condition does.

 

[ludwig]

Pinhead
Tried joining up to a 160 main and the same response. the dwell is at 38 and the points, are new in a new dissy are gaped at a tight 17. Starting to think its a crack in the interior and is terminal?

 

[JohnnyC]

i just noticed your other thread...a cracked e-tube...thats quite strange.

did this weber run good at one time...or has it always been an issue?

did you pick it up used? 10 years ago

wondering if somebody has one around you used to slap on and see if the problem goes away

 

[JohnnyC]

my bad ...the measurement i gave you is aprox 38mm from the bottom of the foat bowl.

but...that e-tube is odd...where did you get that weber?

also ' 213_dan ' in tx has an almost new weber38 for sale for 200-250 obo ? something like that

 

[ludwig]

JohhnyC
This weber was bought new buy me some 25yrs ago and the 40 ran great for 10years with the carb. Never had to touch anything short of a small idle adj every now and again. Then one day bamm!!!! Now power and backing up thru the carb. Thats when I found the cracked E-tube on the header side. AS my hunch that its cracked somewhere in the middle of a channel or where will never find it.

 

[JohnnyC]

I have never seen anything like that before...you may be correct.

maybe some water was in there when you stored it and if froze ? just a thought

this was just posted for 100:
https://forum.ih8mud.com/sale-parts/262428-weber-carb-74-fl.html

 

[ludwig]

The problem happened on the Outer Banks of NC in warm weather but that was a good idea on the the h2o. I found a new carb for a decient $ so will see come next week if this is the solution to a nagging problem. Thanks to evreryone and will keep yall informed of the progress. At least we know the valve train is good as well as the fuel delivery asnd dissy ECT....

 

[Pin_Head]

If the larger main jets did nothing, I would look at the fuel path from the main jets to the nozzles. Maybe the nozzles are clogged?

 

[ludwig]

reopen and update on this weber

Just a quick update on this weber issue I had a few weeks ago. First of all thanks for all the great advice, we were reaching there a time or two.
We finally ordered a new weber and it cranked the first turn of the key and ran like the old one used to. Some minor jetting and we think we have a running 40 again. Still waiting to tag it and get legal. All we can come up with is that when the emullision tube cracked 10yrs ago that the inside of the body cracked as well. That was a lost two weeks of carb rebuild, but we are now up on all the ins and outs of the weber. Now lets attack some 33 year old rust!