Misc: Carburettors Noches

[moto8500]

or rather notches. In a recent post I asked for assistance with a Shadow engine which would not start until it burst into life after 10/15 minutes of cranking. The very helpful replies directed me towards the engine flooding and running rich fouling up the plugs. In my quest to get this sorted I begun to tackle the source of the problem the 276 and 289 Amal carbs. First off were the floats as both carbs would flood and leak. The right hand carb as you sit looking down had the float needle on the top notch and as the float was at it's highest setting it would rest on the bottom of the trickler when full of fuel thereby not allowing the needle to seat properly in it's jet and cut off the fuel. On the left side all looked OK and I note the needle cannot be pulled out as it seems to be connected to something which cuts off the fuel when the float goes up.

One thing of note was the float on the right side sat higher in the chamber when full of fuel than the left side but the trickler on the right side had a longer stub than the left. I put the needle on the lower notch on the right side so it would not touch the trickler end, however it sits very close to it. I am wondering whether the tricklers should be swopped over as the longer one sits very close to the float while the other has much more of a gap. Common sense would say swop but before doing so I thought I would put it out there as Amal fitted them in this way.

 

[bmetcalf]

See Thread 'Rear 289 Float Bowl Top' https://www.vincentownersclub.co.uk/threads/rear-289-float-bowl-top.15548/

If you search the forum for "tickler", be sure to spell it that way.

 

[Speedtwin]

If the fuel level is to high in the float bowl.
Setting up the carbs there are some basic steps that will help.

Tickler you may have to shorten the pin so it is not in contact with the float when float is at max height.
They are a set length which needs to be altered sometimes.
First of all set bowl/carb positions before getting the file out.

Carbs:
Carbs are surgically clean and functional.
I clean mine very year due to E fuels.
Things to check.
Have you the slim paper washer, bottom of the jet block installed and the block tight?
Tip make sure this gasket is not fouling the pilot hole.

Setting fuel level:
There is a small plug screw on the arm from the float bowl you can remove the screw and fit a bit of clear pipe run this up alongside the float bowl to reveal your true fuel level.
Adjust the floats as needed might need to file some grooves in pin.
Fuel level should be set just below the air mixture screw.

Leveling carbs:
I spend a bit of time getting the carb positions correct before going on to tune.
Check your carb/bowl is level, move on inlet stub as needed.
Move float bowl forward or back to suit.

Floats:
Floats the replacement white plastic boys are more buoyant I find than the old school copper ones, thus fuel level height can be to high with the new ones, I had to file new grooves to fix this.

Tuning carb once all the other stuff is right.
I start off the carb tune once the fuel level and carb set is sorted at 1 and a half turns out on air screw and tick over fast.
Once tuned return to normal tick over and tune again
My twins like to run rich and start easy.
Sorted.






Al

 

[greg brillus]

Most bikes run rich.......a bike that starts and runs quite well and even idles from near cold is basically rich.......this is not a bad thing, but it can and will fowl plugs and wash the bores a bit as well........if this is the case, it is worth while to actually lean off the carb, even if this just means winding out the pilot screws a little.........if the engine spits back a little from cold, this is actually a good thing as that issue will go away as the engine warms up........it can be a fine line between running rich and leaning them to run more clean.......Constant bad spitting back is too lean, and a smaller cut away will fix that.......however going from a 4 slide to a 3 will be too big a jump and the engine will run too rich.......On shadow carb's a #4 slide with around 20 to 30 thou machined off the base of the slide will fix this condition.......any more and it will run too rich.......they can be quite sensitive, but once you make these changes, the bikes run so much better for it........Cheers.

 

[moto8500]

Thank you all especially Speedtwin and Greg for the time you spent in your very helpful responses and bmetcalf for pointing out the differences in a tickler and trickler.

The floats are white plastic and obviously sit too high in the chamber so I will look into getting another notch cut in the needle.

One final question - if I were to take the carbs off their inlet manifolds while the tank and seat remain in situ are the cables long enough to enable me to unscrew the tops to get access to the throttle slide/choke?

 

[Speedtwin]

Take the seat and tank off ten minute job and every time you do it it gets easier.
No cables are not long enough and yes they are a pain in the arse.

Here are your seat off, tank off,tops af, tips for today.
Remove the nuts and shaft from the front seat mount.
Put a wee towel over the back guard.
Remove the rear bolts by two on the seat.
Put seat in the corner.

Undo the two rear tank bolts remove note the way the rubbers go for re fitting.
Look under the tank by the fuel taps you should see on each side a nut which holds the rear tank brace remove the nuts shaft and spacer bar.
Undo the two fuel pipe feeds.
Go to the front of the bike.
Get your masking tape out.
Remove the oil filler cap and tape around the neck.
The neck of the filler not your neck or you are a vicar,,

Tape over the head stock and damper knob on or near the bars.
This for a reason it will become apparent when you are bashing the tank off them on your first removal.
I recommend the following words be used during the operation, fek,bugger and bastard.
Nah kidding it is an easy one and one you need to master grasshopper.

Undo the two front tank mount bolts and remove them.
When removing the tank I wiggle forward then back reach in, reach round and pop out the front tank rubbers to give clearance for a smooth extraction of the tank.

All done refitting is the reverse.

Tips for when tank is off.
Note route of throttle and choke cables, make it better,note route of clutch and dec compressor cable for when you trap them putting the tank back on.
You can use the aforementioned swear words at this stage also.
I like the clutch and de con inside the front tank mount.
Throttle near side through the top front engine mount or around the head stock.
Throttle choke off side inside front tank mount straight back to carb lovely job.

Unless you are a gynecologist this is the easiest way to get at the carbs and sort them out.
It is all, discovery and training skills that will make ownership fun and expand your vocabulary to include many anglo saxon phrases and terms.
Al

 

[Simon Dinsdale]

I would disagree with Speedtwin. I have 3 twins and on all 3 I can pull the front and rear carbs off their inlet manifolds and if control cables are standard length then they are long enough for the carb to drop down clear of the tank and so you can then unscrew the carb tops and withdraw the slide and needle. I've done this on the road side when setting the carbs up where I have wanted to raise or lower the needle in the carb which required taking the slide out the body and in less than 5 minutes had the carb back on and the bike running again. So no need to remove the tank and seat.

Simon

 

[Speedtwin]

I stand corrected yes you can pull the carbs off, I find it easier to remove the tank and seat when in the workshop.

 

[moto8500]

Thank you Speedtwin for the time you took in your reply and Simon for his clarification.
There will come a time I have to take the tank and seat off so I will file Speedtwin's response for later reference.