1932 W32-6 running problem

[Billington]

Hello

I’m looking for some help with my 1932/33 BSA W32-6 500cc side valve.

When I attempt to start the bike for the first time after a week or so it starts first time but only runs for a few seconds before cutting out. After this it is difficult to start; turn the petrol tap off and leave it for a few minutes and it will run again for a few seconds.

When I tickle the carburettor some times fuel comes spurting out the top of the float chamber (type 64/079). The carburettor is a Amal 6/112 fuel is seeping out of the primary air holes as it should, which shows fuel is getting through.

How do I know if this issue is relate to the pilot air screw, throttle stop adjusting screw, advance retard ignition lever or air valve lever.

What do you think the problem is? How can I diagnose the problem and how do I get it to run reliably?

If you have experience of working with this type of vintage bike I would love to hear from you. Thank you for any advice.

I’ve taken resent ownership of the bike and here is a list of the jobs I’ve done.

•   Cleaned out the tank and relined it with a professional kit.
•   New petrol tap
•   Cleaned the Amal carburettor (Amal 6/112)
•   Replace the float chamber on the carburettor because it had a crack then broke
•   Changed the engine and gear box oil

I live in the Black Country, Cradley Heath, England

[iansoady]

Nice looking bike - as for the rider.......

When you say "some times fuel comes spurting out the top of the float chamber " what happens other times?

I'm assuming you know how the advance / retard and air lever work.

Fuel should not really seep out of the holes as the level should be slightly lower than these. It sounds as though the fuel level may be high giving you a rich mixture.

[Rex]

Get hold of a manual (possibly download an E version if nothing else) and see the early pages as there's normally starting instructions, as in where to position the A/R etc. Look and see what the basic carb settings are in the manual and check those too, and although I doubt it's ign related, check the timing, points gap and give it a new plug too.
That bikes looks restored but not run...it's very clean.

[Billington]

Thanks insoady for your response. I do understand what the advance / retard and air lever do; I also understand the throttle stop screw and the pilot jet screw. However I have a book knowledge (academic knowledge) which is different from a life experience of what makes your bike work best in different weather conditions.

I’ve been a circuit racer in the past and understand how engines can be affected by barometric pressure. I was always changing the main jet on my two stroke Honda as different weather fronts moved in during a race day.

Insoady you said “Fuel should not really seep out of the holes as the level should be slightly lower than these. It sounds as though the fuel level may be high giving you a rich mixture.”

I think I may start by screwing out pilot air screw. If this does not work I will try lower needle one or two grooves. How does this sound?

Thank you all again for helping me, I’m a newbie who is just starting to learn one end of an Whitworth spanner from another.

[Billington]

Thanks Rex, you are perceptive about having been restored to a high level then not ridden. I believe the bike was restored in 1980/81 then taken off the rode in 1984. The two previous owners had left it as part of their estate, hence they were old gentlemen who wanted a toy in the garage, but did not ride it. This did give me some problems with the DVLA and taxing the bike; I’ll spare you the story.

I’ve changed the spark plug just to be sure; however I think the old one was okay.

I have had the bike running and I’ve travelled about 25 miles on it, but out of the three trip I returned home on the back of a recovery truck on two occasions. The first time because the tank was full of 37 years of varnished petrol. The second because I convinced myself that it had broken down again when it stopped but actually it was due to not enough fuel in the tank. The tank has a forward slope which makes it look like there is fuel in the tank, but actually not enough to reach the fuel tap at the back. What a fool!

When I rode the bike previously it was in the winter so the air temperature, humidity and barometric pressure were very different. I live in the UK and it’s summer at the time of writing.

Thanks again Rex and everyone else for your help.

The above picture is the bike in 1980. Someone else did the hard work of restoration.

[R]

If the carby flooding is the problem, and you can get it to start, the usual process here is to give it some throttle, and see if you can rev your way out of trouble ?
Too much fuel needs lots of air....

If its cutting out due to being too lean to run when cold though, it may need some choke applied.

Removing and inspecting the spark plug in either of these scenarios often helps.
If the plug is damp or wet with fuel, you know it has too much.
If its dry as a bone, its not getting enough.

[iansoady]

The jet needle doesn't affect whether it floods or not, but of course does affect the mixture at throttle openings between about 1/4 and 3/4. I suspect that either the float needle / seat is leaking allowing a higher level in the float chamber than it should be, or that either the float is punctured and has some petrol in it or isn't correctly attached to the float needle. Is it top- or bottom-feed? If the latter, you can actually take the top off and see what the petrol level is in the chamber.

These old bikes are generally much less sensitive to minor adjustments than are modern ones so will run even though not strictly correct. Amal "chokes" (strictly air slides) are pretty crude affairs and have variable effect depending on throttle opening which can confuse.

[Rex]

That is one lucky bike! Better bikes than that were being weighed in 1980 so this is a lucky survivor.
With respect, until you understand about A/Rs etc you can't make diagnostic decisions what is or might be wrong with your bike.
Is there no-one locally who could give it a swinging kick for you?
As has been said, these bikes are simple, and it never pays to compare with later bikes and make judgement calls based on them.

[chris mac]

Just a quick suggestion, try removing the petrol cap and see if that helps

[Billington]

Okay, I’ve been playing in the garage. I realised that after rebuilding the carburettor I had left the pilot jet (air screw)  full in. The bike would start but only run for  two seconds before stopping despite encouragement from the throttle. So I started to think that my problem was due to the air/fuel mixture being to rich. Easily solved I thought.

After attempting to start the bike with the pilot jet (air screw) at varying positions from fully out to fully in and seeing no affect I realised that it was not going to be that simple. Any way the pilot jet only comes into effect when the throttle is fully closed because it is part of the idle circuit and I usually open the throttle about one eighth open when attempting to start.

I then had a look at the spark plug. It was dry and black; a light rub showed a nice grey brown colour. The spark plug is a new KLG super M30 so I changed it back to the old KLG M30, but this had not noticeable effect.

I did have one miner success. The fuel was some times coming out of the top of  float chamber. It is a bottom feed float chamber. I looked inside the float chamber which is new and realised that the float needle had two notches so I placed the needle retaining clip on the lower notch, which means the fuel level will be lower in the float chamber. This stopped fuel coming out of the top periodically but did nothing for starting the bike.

The bike has been on the road running since I cleaned the tank out, replaced the petrol tap and rebuilt the carburettor, however at the moment it seems to only fire for two seconds then die. After this it will not fire at all unless I leave it for about 1 minute with the fuel tap off. What is this telling me?

AMAL 276 PRE-MONOBLOC CARBURETTERS




Do you need one thousand words or just one picture?

[R]

After this it will not fire at all unless I leave it for about 1 minute with the fuel tap off. What is this telling me?

That your magneto spark is weak ?
Hard to tell really, we are not there to inspect your work.
It sounds like it might be flooded, but it could be starving.

I always keep a brand new plug handy for these sorts of occasions, so you can inspect it immediately this sort of thing happens, and not have to 'brush off' previous combustion residues.
If its wet its flooded, if its dry it needs more fuel.

Tip an extra spoonful of petrol down its throat, and see if it runs longer or drowns it.
Watch that stray fuel may be a fire hazard...