[paul.w]

Got it, I think!
You were right klaudius - but not for the obvious reason.  I had already noticed the top of the float bowl wasn't original, not really a surprise - I've had them unscrew themselves and drop off in the past - but...
The tickler on the replacement top was just slightly longer than it should have been.  The result was that it didn't quite let the needle seat on its bed.  In normal use it wasn't obvious. I'd flood it to start it - so petrol coming out of top anyway - then when it ran it was drawing enough petrol that it wasn't obvious.  On the road though with the float bouncing up and down it was letting more petrol through so it was getting much too rich.  File a mm or two off the end of the brass tickler and things are much better.
Another test run just to confirm it when the weather improves slightly, then its on to the next question - there will be a post about that shortly!
Thanks for the help.

[phutton]

Have you got a good spark?

P.

[klaudius]

Hello
The cam and its drive is marked on the control side. If the cams are the correct 30 / 60-60 / 30 (should be checked) there is not much that can go wrong. For me it was the carburetor. At that time it was an M9 1933. Were exactly the same symptoms as described by you. Greetings Claudius

[paul.w]

Sorry, I don't quite understand what you are saying - remove the carb and then check the fuel level without the carb.  I think something might be lost in translation. Added thought..... are you saying take carb off, attach fuel line and see where the level sits in the jet??

I don't see how the level can be adjusted. The float needle has only two positions (it is a new float and needle from Burlen with grooves for the securing clip).  In one position it never closes so petrol just pours out, in the other it works as intended and shuts off the fuel. I'm more used to an SU where the level is adjustable by altering the brass lever that shuts off the valve, an AMAL doesn't have that adjustment available.

I think the level is OK though because if i have the bike running on tickover and lean the bike over to the left on its stand (effectively lowering the fuel level relative to the jet) then it falters and doesn't tick over so well, suggesting to me that it is going lean.

I've just taken the tank off so I can clearly see the valves opening/closing and as far as I can tell by eye they appear to "rock" at TDC - but I'm not sure I can tell accurately enough.  There does seem to be a fair bit of overlap (ie., inlet opening before exhaust is fully shut) but I don't know if this is normal.  Does anyone know what the valve timing looks like and whether there should be overlap?

[klaudius]

I've had such mistakes too. Check your fuel level. To do this, you have to remove the carburetor and check the gasoline level without the carburetor. Simulate fuel supply as in the original. The float needle must overflow the lower carburetor shell 2 mm. Try more often. It has to close 20 times at 20 attempts. The  red line shows the fuel level and is crucial.Claudius

[paul.w]

The problems not gone away - but I delayed posting until I had something more to say.....
So!  I've now tried it with 150, 170 and 190 jets (the 170 was fitted originally).  The plug colour looks OK (I tried a plug chop from flat out - it did soot the plug when I briefly tried a 230 jet, 'cos I had one, but it ran like a dog then as well) so I don't think the jet is too far out.  It has (according to the book and Burlens) the correct needle jet and slide and the needle is currently in position 3.  The timing is spot on (fully advanced it is inclined to bite back on the kick start, 1/3 retarded it doesn't) and the points gap is correct.

It still dies completely when the throttle is opened sharply - but there is an additional symptom I've established. It still does it on the road, but I don't need to be riding it to get it to do this.  On the stand it ticks over happily (-ish, I think the slow running mixture and needle position might need adjusting) but it I open the throttle sharply it just dies.  Close the throttle and it picks up again and then open the throttle slowly and it is fine.  One final thing, if I try this with the 190 jet in it (ie., running rich) it actually spits back a sheet of flame out of the carb inlet (this caused great consternation when it ignited the excess petrol on the frame from when I'd tickled it).

Additionally, The valve springs look OK (I did wonder if one might be broken).  It has lots of compression (I can stand on the kickstart so it not a damaged valve), valve clearances are according to the book.

I'm completely at a loss.  The only thing I can think of that I've not checked is valve  timing.  Could the symptoms I've described be caused by incorrect valve timing?  Help!  Its a lovely bike and great to ride (up to 50mph) but there is  something wrong and I'm out of ideas.  Anyone have any suggestions?

[phutton]

Carb settings for 1931 are as follows:

Model: Amal 29-001, 1 3/32" choke dia (289-001 is "modern" equivalent)
Main jet: 160
Slide: 29/4
Needle posn: 3

You may also have a magneto problem! Try checking the condition and setting of the points (0.012")

P.

[klaudius]

Hello.
Do both slides open completely?
Is the fuel level correct? Checked in the expanded state?
Are the carburetor cables free and without kinks?
Carburetor slide without much play?
Please forgive my english.
Claudius

[paul.w]

the next question if I may;

Its a 1931 Model 9.  I've done a couple of hundred miles now, and I have an irritating carb problem.  When I first rode it in anger I found I couldn't get above 50mph because at anything above about 3/4 throttle the engine would die on me.  If I snapped the throttle open it'd cut completely, if I teased it open I'd get a couple of more mph then it'd start missing.  Fairly obviously a mixture problem so I took the carb apart to clean out jets etc - which didn't help so I've been playing with needle height.

It was initially in the second slot.  I've tried progressively moving it up a slot at a time and by the time I got to the 4th slot (so I've increased mixture by quite a bit) I found that it would get to about 58mph before developing the same missfire.  I did also try dropping the needle to slot 1 to see what would happen just in case it was over-rich at high revs but that didn't help at all.  However it is now less able to tick over without stalling.

So, it looks like I have a carb problem.  I've checked the numbers and they are:-

The carb is 289/001 (or it may be 00R)
Slide No. 4
The brass insert in the carb body is stamped 54
Needle  25
Jet 170

Can someone tell me if these numbers make sense, or does the carb have the wrong sized components in it?  If it was an SU I'd know what I'm doing, but I'm not so familiar with AMALS (and don't have a bucket of old  spares to play with).
On the upside, it is a delight to ride compared to my old BSA Sloper and now I can get 58mph out of it I feel that, even if I've not sorted it, I'm getting there.