Hard Start (again)

Lineslinger · May 30, 2023

MichaelB said:
Do you close the fuel tap, or leave it open?

My method is to close the fuel tap immediately after I switch the engine off.
I open the tap immediately before I turn the ignition key to on position prior to starting.

jbruney · May 30, 2023

Lineslinger said:
My method is to close the fuel tap immediately after I switch the engine off.
I open the tap immediately before I turn the ignition key to on position prior to starting.

Sounds the same as my drill.

ludwig · May 31, 2023

Check your float level.
It could be too low.

cash · Jun 5, 2023

I run twin Mk2 Amals and as I've aged, lost weight and weakened the bike can be hard to start cold. The spark is strong, the plugs are dry, it's on full choke and the floats are levels are bang on. I've found that if I turn both air screws in by 1/4 to 1/2 turn, choke still on the bugger fires up first kick. I now after setting the idle mixture correctly turn the air screws in an extra 1/8 turn. I now find the old girl takes at the most four kicks to fire her up. Tick over slowed a little but otherwise has not been effected.
Is it my slow kick not creating enough vacuum to draw the fuel through the choke and primary jets?

kommando · Jun 5, 2023

cash said:
Is it my slow kick not creating enough vacuum to draw the fuel through the choke and primary jets?

Its even worse on singles, my fix on my B44 is extended throttle stop screws and the fitting of a choke. The choke does not help much except on hot starts but the extended throttle stop screwed in 1 to 1 1/2 turns does. Then as the bike warms up after 1/2 mile I unscrew the throttle stop, with the stop extended a gloved hand does it easily, on a twin it makes it more difficult as they need to be balanced but some guide marks would help.

concours · Jun 5, 2023

cash said:
I run twin Mk2 Amals and as I've aged, lost weight and weakened the bike can be hard to start cold. The spark is strong, the plugs are dry, it's on full choke and the floats are levels are bang on. I've found that if I turn both air screws in by 1/4 to 1/2 turn, choke still on the bugger fires up first kick. I now after setting the idle mixture correctly turn the air screws in an extra 1/8 turn. I now find the old girl takes at the most four kicks to fire her up. Tick over slowed a little but otherwise has not been effected.
Is it my slow kick not creating enough vacuum to draw the fuel through the choke and primary jets?

Enricheners.

Mart UK · Jun 5, 2023

concours said:
Enricheners.

Not at what they cost. More like 'impoverishers'.

marshg246 · Jun 5, 2023

cash said:
I run twin Mk2 Amals and as I've aged, lost weight and weakened the bike can be hard to start cold. The spark is strong, the plugs are dry, it's on full choke and the floats are levels are bang on. I've found that if I turn both air screws in by 1/4 to 1/2 turn, choke still on the bugger fires up first kick. I now after setting the idle mixture correctly turn the air screws in an extra 1/8 turn. I now find the old girl takes at the most four kicks to fire her up. Tick over slowed a little but otherwise has not been effected.
Is it my slow kick not creating enough vacuum to draw the fuel through the choke and primary jets?

Sounds like your enrichers are not fully doing their job (rubber tips not sealing). Turning the air screws in compensates somewhat. You probably need new cold start plungers (Amal part 2622/079).

Desmopower · Jun 5, 2023

Do you have the correct phenolic spacers fitted ? https://amalcarb.co.uk/mk-i-concentric-series/900-series/gaskets/spacers/phenolic-spacer-32mm.html

cash · Jun 6, 2023

marshg246 said:
Sounds like your enrichers are not fully doing their job (rubber tips not sealing). Turning the air screws in compensates somewhat. You probably need new cold start plungers (Amal part 2622/079).

The plungers and seats are in good condition and are sealing. If they were leaking it wouldn't matter on cold starting as they will be half or fully open.

cash · Jun 6, 2023

Desmopower said:
Do you have the correct phenolic spacers fitted ? https://amalcarb.co.uk/mk-i-concentric-series/900-series/gaskets/spacers/phenolic-spacer-32mm.html

Don't need them Mk2 are mounted on rubber tubes. The phenolic spacers stop engine heat boiling the float bowls dry.
What I forgot the mention was when I get my Grandson to pop, a fit young man, round it fires easily for him.
Any how, it's firing up for me now with ease and turning in the air screw a tad and if required turned back once running might help other old beggars like me.
And the bike is running really well too.
Happy days and the sun is shining a rare thing here on the NW coast of England.

marshg246 · Jun 6, 2023

cash said:
The plungers and seats are in good condition and are sealing. If they were leaking it wouldn't matter on cold starting as they will be half or fully open.

You lost me. They are not chokes - they are enrichers that enrich by the rubber at the tip of the plunger blocking the hole at the bottom.

cash · Jun 7, 2023

marshg246 said:
You lost me. They are not chokes - they are enrichers that enrich by the rubber at the tip of the plunger blocking the hole at the bottom.

Indeed they are not chokes . I know exactly what they are its just a habit I and I'm sure others have to name the cold start system on a carburetted petrol motor.
All vacuum cleaners in the UK are often called Hoovers when clearly most are not.

Sorry for the confusion.

KiwiShane · Jun 7, 2023

cash said:
Indeed they are not chokes . I know exactly what they are its just a habit I and I'm sure others have to name the cold start system on a carburetted petrol motor.
All vacuum cleaners in the UK are often called Hoovers when clearly most are not.
Sorry for the confusion.

Your not alone ....

cash · Jun 9, 2023

KiwiShane said:
Your not alone ....

I pleased to say she's still starting well with very little effort from me.

KiwiShane · Jun 9, 2023

cash said:
I pleased to say she's still starting well with very little effort from me.

Your not alone ...meaning...Hoovers ...vacuum cleaners...and another example
Tappets.... lifters ....cam followers

I understood what you meant...enriches chokes...I ran MkIIs on Commando's for years...and i still call them chokes...pleased she's starting well for you mate...

baz · Jun 9, 2023

cash said:
Indeed they are not chokes . I know exactly what they are its just a habit I and I'm sure others have to name the cold start system on a carburetted petrol motor.
All vacuum cleaners in the UK are often called Hoovers when clearly most are not.
Sorry for the confusion.

Don't worry about it
It took me 50 years to figure out what "sticky back plastic" was

daveforty · Jun 9, 2023

I have Premier concentrics on my bike, and took the choke slides out to put blanking screws in the top of the carbs.

(having once had a breakdown when one section of a choke cable broke and the spring closed the choke slide and made for a very rough running engine)

I often find that from a cold start the carbs need 're-tickling' as soon as the engine starts, otherwise it will cut out after running for a few seconds. A bit of quick handiwork required while sitting on the bike and holding the throttle and tickling the carbs. But fine once the engine has warmed up a little.