Curlew carby issue .... I think ...

[Arbian]

I managed to get my hands on a Curlew a while back but due to one thing or another only just got round to trying it out. Recoil only engaged intermittently and not keen to start or keep going and fuel tap leaking badly. Replaced cork on tap and took off the recoil housing and found the flywheel nut finger loose! Torqued that up and put housing back on, tried again. Motor started but wouldn't come down to an idle even with throttle cable adjusted till loose. Carb bowl was continually flooding so took off carb and removed float / needle and cleaned with carb cleaner. Put back together and tried again. Bowl no longer seems to be overfilling and adjusting the carb slide stop screw got revs down but the motor wont idle and conks out. Could it be a blockage in the pilot jet? The carbs condition looks generally good with no obvious corrosion ........... any help greatly appreciated. Cheers

[Charles uk]

Depending on exactly which model & year of Curlew it's Amal 418 carb will slightly vary in model number,

418 1 ,2, 10 or 11

Most will have 2 adjuster screws on the side, the highest is the tickover adjuster (furthest from cylinder) which raises & lowers the throttle slide & the lowest (closest to the cylinder) the pilot adjuster which varies the air mix in the emulsion tube.

With the engine fully warm from running for a few minutes in your test tank.
Stop motor.
Close the pilot adjuster completely & open one full turn.
Undo tickover adjuster screw 4 or 5 turns.
Set throttle to fully closed (lever or twist grip) & adjust cable adjuster so it takes a small movement before throttle slide starts to move.
Restart motor, to a fast tickover only by using throttle (lever or twist) screw in throttle adjuster screw until tickover speed rises, now close throttle (lever or twist) all the way, & screw in throttle adjuster until you get a tickover just faster than the point where the cooling water flow stops.
Now fiddle with the pilot adjuster to find the best revs, reset throttle adjuster to perfect tick over, try the pilot adjuster fiddle again to ensure you got it right the first time.
Hey Presto you should be there!

I was taught this 15 years ago in Bermuda by Dean Borman, thanks Dino it was a valuable lesson!

[Arbian]

Ok, I have now tried that Charles. Struggled a bit with the fast tickover without it dying then got it sussed and managed to follow the procedure till I got a sensible tickover. I couldn't really notice too well what the adjustment of the pilot was doing but ended up about a further half turn out so circa 1.5 turns out. That seemed ok but she conked when put into gear. Had another go and after giving it some throttle, the next thing the revs would not come down after closing the throttle. There seems to be a real rev lag when turning the throttle also, like it is struggling then picks up. Any clues?

[Charles uk]

Remove the float bowl the jet is that hex in the middle, you'll see a number stamped in the middle of one of the flats, what is it?
Is the needle valve hooked into the groove on the float?

Remove the throttle slide, what's the number on the bottom? & which groove is needle circlip in?

We will never know how good the last carb rebuilder was!

[Hugz]

I had a bit of fun with my Curlew a while back. Rather relevant.

https://www.youtube.com/watch?v=QL1yVMm2Jdo

[Collector Inspector]

I had a bit of fun with my Curlew a while back. Rather relevant.

https://www.youtube.com/watch?v=QL1yVMm2Jdo

I find myself replaying the spark plug touch over and over again



BnC

[Arbian]

Thanks Hugz ..... that video has sent me into a deep depression! Mine wont come remotely near those level of revs without dying. I am going to check the Jet and needle setting that Charles noted today but pretty sure the main jet is a 100 and that the needle circlip was set in mid notch (both standard I think) could it just be shite in the fuel system blocking the jets? In the meantime I will watch Hugs' video again and dream ....

[Hugz]

Have to say I pulled the carby down and flushed with compressed air and with a visual all jets seemed perfect but it didn't idles quite as well as it does now. I then pulled the carb down again and used carb cleaner in a spray can with the very thin red tube and cleaned every orifice to get low tick over. Plug/head gasket and head was replaced.

viewtopic.php?f=2&t=3142&hilit=Aussie+curlew

[Arbian]

Charles, Just checked carb and shut off needle sitting fine in slot and main jet is a 100 but needle clip was in top not middle slot (should I move to middle?). Hugz, thanks for the info. I had cleaned the inlet where shut off needle sits but will now give all a good clean. Where should airline be blasted? Cheers Ian.

[Charles uk]

Airline everywhere.
Needle clip in middle slot, for now.
Is yours a black rubber fuel pipe?
Does it have a fuel pump?
What's the number on the bottom of the throttle slide, near where the needle sticks out?

That's the right jet!

Remove the grey plastic fuel pipe banjo fitting is that filter clear?
This carb really needs 30 minutes in an ultra sonic cleaner in soapy water.
Is there easy passage for fuel through the fuel pipe?

You will get a tickover as low as Hugz's, Only if your flywheel has the cast iron additional weight fitted to the top.

[Arbian]

Ok, rubber fuel pipe. Number on bottom of slide is 3. Fuel filter behind banjo pretty clean but not in great shape. No fuel pump. No cast iron weight just the plain ring steel one, engine is a 1988 .... oddly with a QB prefix rather than CS??? Carb clean will need to wait for weekend. Cheers for help. Ian

[Charles uk]

Replace the rubber fuel pipe with a good quality see through one, not a cheap one that will go hard when it sees petrol, you will have to grind of the clips on the rubber one.
Some rubbers will perish & expand in fuels that contains alcohol, most UK fuels contain 5% + of alcohol this didn't happen in 88.

The steel ring is cast iron.

[Arbian]

I have an August 1991 spares supplement which says that during 1990 (date not supplied!?) the aux flywheels were changed from steel to cast iron and that hereafter a counter balance weight was no longer used in the flywheel.

[Arbian]

Well that's the carby cleaned throughout with carb cleaner then blown out with airline. Put it all back together with new fuel line, filter gauze on banjo and filter on fuel line. Fired it up and ..... absolutely no bleedin difference! Still wont settle to a suitably slow idle without cutting out and sometimes also revs stick high when throttle blipped or rise on their own. Anyone got any other suggestions?

[headdownarseup]

Possibly time for major strip down of the powerhead. You never can tell what lies inside. It might be ok, but then again you wont know for sure until its been apart for a thorough ispection.
Sleeves up and get stuck in.


Jon