Monobloc troubles

[irsooty]

Hi all,
I'm running out of ideas so though I'd pick your brains.

So took the old girl to her mot the other day and got a few yards and she stopped, wouldn't fire up again so pushed it 2 miles. Fired up briefly for the nice mot man and stopped, passed her mot and I pushed her home again!
she always started easily but no tickover and very rich!
Ordered every new internal part for the carb, re checked timing and valves.
With new jets, I could set a nice tickover but fuel/air screw had to be almost fully out!
New throttle slide kept jamming so old one in, needle set one notch lower. Out for a test, got a couple of mile and starts to splutter, waggling the throttle got a few more splutters the dies. Refuses to start plug is a bit sooty, another walk home!😒.
Changed to old float and needle (thought needle might be sticking?), checked float fuel level which was correct! Another test and got a mile or so and same thing happens! Carb off again and where the pilot jet seats appears to be damaged (old jet was wound hard in) would this be enough to cause my problems? Called Amal and the won't sell a carb body and jet block separately and want £170.
My jet block is tight to remove, I think it has been hammered out before and one of the bits that hold the choke slide in place is missing! Any ideas of what to to next would be great fully received!
I'm getting sick of pushing her around!
Thank you in advance,
Iain.

[Rob Harknett]

You mentioned plug a bit sooty, did you clean it? Have you tried a new plug. If you answered yes & no. Do try a new plug. Plugs cannot be cleaned these days as the central electrodes are no longer glazed. A cleaned plug will soon contaminate.

[irsooty]

Hello, thanks for the reply!
I put a new plug in a couple of days ago, it had run in the shed 15 minutes or so prior to latest run out.
I tried clean the plug once it had stopped but wouldn't start, previous time I went for a run I cleaned the plug at the roadside and it started straight away but only went yards before conking out again?

[Ozmadman]

Send your carb here, the guy is a genius and will rebuild it and do any machining it needs approx £70 but it will come back better than a new Amal and my model 8 now ticks over as evenly as a swiss watch

Martin Bratby, on 01543 572583, or mobile 0777 2169524

Martin Bratby
1 Coachhouse Works
Limepit Lane
Huntington
Cannock
South Staffs
WS12 4PA

[dave16mct]

+1 for Martyn Bratby.
But the usual reasons for extreme richness include: Blocked pilot jet or passageways, severe wear between slide and body, slide needle too short (you don't say what the bike or carb or year etc) washer missing or broken from under the jet block, sticking float needle assembly. Wrong assembly including a washer under the float needle body (only on an old monobloc), you may have the choke on (the opposite way to modern bikes) so pull to put off. It'd be much easier if you gave details of the bike etc.
Dave.

[irsooty]

Just been on the phone to Martin, he told me to colour the end of the pilot jet and see if it was seating properly (which it wasn't!). It means the carb body has had it but he has a reconditioned one on the shelf so posting mine off to him in a bit to look at!
At least I will know the carb is sorted so if problem persists I need to look elsewhere!
Thanks Paul!

Iain

[irsooty]

+1 for Martyn Bratby.
But the usual reasons for extreme richness include: Blocked pilot jet or passageways, severe wear between slide and body, slide needle too short (you don't say what the bike or carb or year etc) washer missing or broken from under the jet block, sticking float needle assembly. Wrong assembly including a washer under the float needle body (only on an old monobloc), you may have the choke on (the opposite way to modern bikes) so pull to put off. It'd be much easier if you gave details of the bike etc.
Dave.

Sorry, looking back I was a bit vague!

1961 AJS model 8,
Carb 389 / 42
Jets as manual recommends.

[Colin F]

Although you do have carb problems the running and then cutting out and then being able to restart once it has cooled down could be due to your condenser breaking down. Have you checked it, when was it last changed? I had one fail just before Christmas, it had only been on the bike 20 years!

[MikeM.]

The pilot jet mixture on my Model 31 has suddenly gone very rich and I am having to screw the airscrew out at least twice the normal setting until I get time to take the carb off to deal with it, the last time this happened I had gone through a swarm of tiny black flies riding up the Puy de Dome in France, one of the little blighters had gone into the pilot air feed hole!!!

[irsooty]

Although you do have carb problems the running and then cutting out and then being able to restart once it has cooled down could be due to your condenser breaking down. Have you checked it, when was it last changed? I had one fail just before Christmas, it had only been on the bike 20 years!

How would I go about checking the condenser?
I presume it has never been changed?