I give up! - advice on who can help - oil everywhere post rebuild

Yes it could.

If they’re genuine newish Weber carbs they’ll have ‘Made in Spain’ stamped on them or ‘Made in Italy’ if they’re quite a few years old. And the vents and jet sizes should be stamped on each part.

10 to 11mm float height should be okay (the float spindle can’t come out once the carb is assembled). 28 vents will work but IMO 26 would be better on a small capacity bus engine, but it really depends on what you want the engine to do. Smaller helps the low end, bigger for top end bhp, too big and tuning is more difficult, too small and top end power is restricted.

F11 emulsion tube is as supplied with new 40 IDF’s. Did you pull the main jet out of the tube? The size should be stamped on one of the flats. This will help identify the parts http://www.914world.com/bbs2/lofiversion/index.php?t101860.html

It sounds like you haven’t fully disassembled the carbs and I hope you’re not assuming it is clean without checking every part. This is what you need to do: https://mirrors.disavowed.jp/www.carburetorclinic.com/setup.htm

Now you have found a problem with the float needle valve you’ll understand why we kept banging on about checking the carbs before you had them tuned – what did the RR guy actually do by the way?

 

Hi guys, so both needle valves and float height were done. The float bowl was clean but i cleaned it anyway. I blew out the jets - all looked clear and good. I checked the accel pump - ok on squirts.
Remember also these carbs were on the van originally working fine. They went back on the van post version 1 rebuild and it ran even with a holed piston.
Taking them off was to be sure on the float height. The float height was ok, but the needle was not sealing, which i found through blowing in the intake with tge float set to shut that is now sorted, but my running rough is not. It seems to stumble and judder as if its trying to go but something is off. I have no reason to question the jetting as its close to the original jetting except up a main size from the tuning and it ran good at the tuning until a patch when it was hot and it was thought it was vapour locking, after which i re routed the fuel pipes - the engine has only gone up 41cc. I swapped out the dizzy today- no change. I am in a quandary doubting everything, but reckon k should swap the coil in case its heat failing as it seems worse when its been running a while.

 

The thing you show is an emulsion tube, code F11.

The float spindle is held in place by the profile of the float chamber. You want to be able to get it out ..




I would cough up the cash and go to Eurocarb and get a set of likely jets - I have a box in my bus with a good selection of Weber Progressive jets...

For my carburettor - the long thin ones are idle jets, the short "screws" are main jets, the cylindrical threaded ones are air corrector jets. All of these have their internal "diameter" in 0.01mm units stamped on them.

Over on the right are the better fuel metering valves my carburettor has used - sometimes I changed them with very little wear and have polished the needle .. so I keep them there for the day I have a problem.

I would recommend buying a copy of Tomlinsons Weber Carburettor book.


I wouldnt mess with drilling them out as when you want to go back to the old size, you dont have them any more, and what is more the stamping on the jet no longer matches the actual size.
I would get the other needle valve from Eurocarb too.

And think about getting a PLX or Innovate AFR gauge and never darken the door of a rolling road tuner again, as they only tune for a "drag racer" scenario in which the bus is running at WOT against the inertia of the rollers. Strangely few of our buses ever actually spend any real time sitting on top of rollers.

 

And get a new needle valve, please, to me, it sounds like that has been sticking and causing a problem.

 

There's an advantage to the progressive at last! We have to buy 4 of everything.

 

One thing about having one of the PLX devices AFR gauges which update 10 times a seconds is you can watch it "flickering" if one cylinder isnt firing - it goes leaner when fuel doesnt burn, as the oxygen concentration remains at 21%. So when its rough, and a spark plug lead is lying on the tinware, it shows at idle. That is with the sensor in the 4 to 1 collector in the exhaust.

 

f11's are ok
This is the layman setup for Weber carbs
#30 to 35 idles a start
Now you need an air/fuel ratio meter that works on wide band oxy sensors with a connection into your exhaust.
run the engine
Step 1
take the main jet tree out (that's main jet, emulsion tube and air correction jet)
adjust the idle mixture's and adjust them again (13 to 1 is good)
drive the vehicle (alot) with a tacho and work out what rpm the whole thing dies (leans out) while in the range this is your idle jet mixture and should sit around 12.9 to 13.2 af ratio up to lean out (adjust the idle jets to be in this area). This will be around 2500rpm
You'll see it as a total lean out on your afr meter (and you won't be able to go any faster)
step 2
Put your tree back in with an overly rich mainjet and go driving.
At what point do you become overly rich. If beyond your lean out on the idle jets, reduce your air correction jets (20 at a time)
If rich before your idle lean out, increase your air correction jets (20 at a time)
step 3
Now pick a main jet (115) and drive flat out under load up a long hill or a freeway full throttle
Aft should be 12.9 to 13.4 (change main jet to suit)remembering we need a slightly richer mixture on a Hot running air cooled engine

This is the basics before you ever get a dyno tune

 

My bus is a 2ltr with a c25 Scat cam
duel 44 webers
flat top pistons and 8.5 to 1 comp
We sit on 120km/h (what ever it is in pomy speak) when ever we are on the freeway (raises eyebrows sometimes)
engines done 2500o km since I rebuilt it and going strong.
I'm building a monster atm.

 

How big is the monster?
120km/h is about 74.5 mph

 

not sure yet
I've got 3 sets of cases
2 to build up (STD ) and sell
1 monster for me
Problem is if I want to use the Nickies from LN engineering I may have to weld an re drill the head studs
don't want to do that. My have to go for a longer stroke
Also putting a Subaru 5 speed gear box on it (modified a few)

 

Good post.

In the UK with small idles like that we would not be able start up in the winter. We tend towards 52-57.

I would say shut your eyes to the meter setting best idle though I'd agree that's most likely about where it will end up.

You can be a lot leaner than this with an SVDA distributor. You can go leaner and leaner until it won't drive, then back up one - good for mpg, noticeable in a Beetle... but it's a bit pointless in a bread loaf and as above, in the UK will make it harder and harder to start from cold. Mine's 2.4L, whatever size idles, with the main stacks out I've never got over 35mph. In fourth no chance of getting anywhere near 2,500rpm - maybe in a Beetle?

 

I can’t justify the cost of Nickies and went for a longer stroke and Biral cylinders. And a .82 4th gear in a 6-rib. It has enough torque to bridge the gap in the gears and climb the hills where I live and most of the roads I use have an 80km/hr limit.
80mm crank
96mm flat tops, Biral cylinders
Scat C25
9.0:1 CR
Dual 40 IDFs

 

The engine seized and the rebuild broke a piston. I wouldn’t call that working fine.

 

So....the vans back in the land of the living. Running like a dream again. It turned out that i must have had a duff plug lead which was causing cross firing on cyls 1 and 2. Very weird as it only happened on lower rev range and cleared once at higher revs. Feel a bit silly as i missed it, but guess i was fixated on it being the carbs after the tune up. Anyhow all is well, smooth accel, and super responsive and loads of power which is chalk and cheese from how the old engine was since i owned the bus. Cruises at 60 with barely any throttle and no struggles on inclines. I am happy again.

 

How did you diagnose the duff wire? I ask because I keep getting sparked on my forearm as I reach over to the linkage. Not sure if that's normal for a plug lead but given what you've said and my lack of power I wonder if it's related?

 

No, not normal, means either a broken ignition lead or partially fallen off spark plug lead, cracked insulator or hole in the rubber of the leads. Shouldnt do this, also if the plug is in circuit, there should be only enough voltage to jump 0.6mm as thats the gap of the plug.

I would guess your bus is actually only running on 3 cylinders. Go round the engine, pick up the spark plug lead lying on the tinware, put it back and feel sheepish. (my 1641 will do nearly 50mph on the flat with a missing spark plug lead, and careful nursing. People with bigger engines may not even find difficulty reaching 70mph .. )

Similarly, cross-firing means there is a massive gap somewhere in the ignition leads downstream, or the distributor cap is really filthy.

Or you have points that have not been gapped properly before setting the timing, leading to the firing point of the points (when they open) being many degrees away from when the rotor arm points at the spark plug lead inside the distributor..

 

Timing and points were not an issue on mine. I think the leads had awful insulation. They were a cheap set which i regret buying trying to save a few quid thinking they were a deal and were close to one another i guess. I'd even changed the dist from one with an ignitor to one with points thinking it was that and it did the same thing.

 

Weirdly it also cleared the higher up the rev range you went.

 

Easy option is to look into the noisy cupboard when it's dark and see if there's any sparky-arciness going on ....
If there's problems further behind the tinware you may not see any arcing, just bite the bullet and buy a decent set of leads

Sent from my SM-G960F using Tapatalk

 

Often the case with a weak spark.