A10 Golden Flash Carb

[peteb]

Hi,

Have just bought my first BSA, a 1953 A10 Plunger Golden Flash.  I bought it as a none runner so expect a few problems getting it back on the road. 

The carb is a 626 concentric without the connection to the air filter box, and by partially blocking off the intake I can get the engine running (and it sounds good).  I've had a good look around this and other sites for information on this carb fitted to a A10 but most of the posts concern the 276 and 376? monobloc. 

Ideally I would like to get hold of the rubber connector between the filter box and the carb but there seems to some debate on whether those available are for the A7 or A10.  Is there anyone supplying the correct connector?

I have considered using a round filter on the carb but there does not appear to be enough room to fit one.  Would a bell mouth fitted with a guaze be O.K.?

The other option I quess is to change the jetting.  At present I have a 190 main, 105 needle, 25 pilot with a No. 3 slide and with the needle on position 2, is this standard jetting for this carb? and if I want to run without a filter how should I change it?

Are there any other options?

I should add that the magneto is a good re-conditioned unit producing a good spark and the timing is spot on.

Any help and advise on this will be much appreciated.

Thanks

[fido]

Have you read the thread about these air filter rubbers? The one you can get is for the airbox outlet at right angles to the carb intake. You can't get the type where the airbox outlet is inline with the carb.

[a10 gf]

Welcome to the forum, I hope you will enjoy the discussions and find the help you may need.

Regarding the jets, I have not seen or heard of a 626 on an a10, so it may be difficult to find a "normal" value. It may be fine as it is. As I understand it a 626 is 26mm size, and the A10 with f.ex a 376 uses a 1 1\16 inch, = 26,9 mm, so the size should be right (? don't know really if that applies to different carbs).

You may know all this already, but anyway, some standard tests & symptoms: no black smoke, the tickover is good, accelerates evenly trough the various opening stages of the carb, looses power or gets better if you give it some choke at speed, the plugs looks ok (too rich much better than lean) etc. If it runs good, then keep it that way and finetune over time with roadtests, jets and plugreading. If there is some obvious problem, try to find out at what carb opening it occurs, and adjust settings \ jets applying to the particular spot. On http://www.amalcarb.co.uk/ there are lots of different jets and slides available.

Others here may have clever carb adj. tricks to share.

Of course, it's best to use an airfilter, but the engine will still last a long while without (unless one does 20000 miles a year, no oilchange + ride in sahara sandstorms ).

regards
e.

[peteb]

Thanks for the info.

From the work I've done so far I am convinced that, basically, there is little wrong with the carb that is fitted other than the fact that the lack of a filter is making the mixture too weak for the bike to start.  (I've been using a copper saucepan scouring pad over the carb intake to reduce the air flow and with that fitted the bike will start and run with no real problem, if I remove this temporary filter when the engine is running it immediately stops)

Not too concerned about having a filter to protect the engine although in an ideal world one should be fitted.  Not too concerned either at originality for the moment.

My airbox is behind the battery holder and as such I need the angled connection piece but the threads I have seen discussing the connection pieces all seem to think that the only ones available are the ones for the A7 and not suitable for the A10 due to the difference in engine height.

The only place that seems to have any in stock is a place in Sweden but I don't want to spend time and money having one sent to the UK only to find that it will not fit.

If I was to revert to a 376 monobloc or the earlier 276 will the bike run without a filter on the standard jetting?

All help fully appreciated

[groily]

Hi Peteb,  Quite a few possibilities here methinks. Many people (like me) don't have air filters for the reason you're finding out. Most bikes will run just fine without, though the Sahara sand comment is more than valid. (I've never had a Brit bike with an air filter, though, ever.) It's quite possible that a bike won't START without something restricting the air - a choke slide for example! Especially when it's freezing cold. But it should certainly run when it's warmed up a bit. My swing-arm A10 likes a generous tickle and a hand over the bellmouth for starting on sub-zero days (no choke slide fitted) but after 30 seconds of spluttering it then settles down. With a monobloc. If your beast won't run at all with the strange carb that's on it without having something rammed up it, my first thought is that the cut-out on the slide is too big and is letting too much air in; my second is that there is an air leak at the flange mounting to the head - Concentrics are legendary for bowing if the nuts are tightened up what you and I might call properly); my third is that there is a problem with either the fuel level in the bowl of the concentric, or that there is a partial blockage. I can't remember off hand how you adjust the fuel level on them, (and Mk1s and 2s might be different anyway - all a bit modern for me), but it can be done and the link to the Amal tips page might tell you how. If you happen to have a Monobloc lying around, I'd try that before getting too bogged down. Whatever it is, it ain't that serious as the beast does at least run and sounds good . . . Good Luck. Groily

[G/F DAVE]

Hi, Peteb I run my 52 A10 plunger with a 376 monobloc standard jets no problems no air filter as I have mentioned earlier. I use jet/choke size as per later swing arm goldflash A10 that used 376 monobloc as standard fitment. A 626 concentric carb should  be a good conversion for your bike properly jetted..........Dave.

[a10 gf]

Never seen one, so have to ask, is there no choke arrangement \ choke jet to check\adjust on a 626?

You may simulate an airfilter with a piece of foam drenched in some oil, and see if that makes it start, and also ride with it strapped on the carb, checking  performance under different loads, speeds and rpm, and do some plug reading.

[G/F DAVE]

No choke jet on concentric,it has a cable operated slide as on monobloc and 276 carb types .There are two types of concentric one is for two stroke engines,other four stroke. The two stroke type has a chamfered brass insert for needle jet, if you look into carb venturi from manifold side you will see this insert.Your A10 should run ok without a filter with a concentric carb fitted.I would check jet sizes & slide cutaway  if all is ok with these maybe internal airways are blocked.I have encountered this before I think its due to old unleaded petrol leaving a residue which block the small airways in the carb.I just replace the carb body if this happens as I have never managed to clean carb out properly. Dave....

[RichardL]

Gents,

I am a little confused about the enthusiasm for running without air filters. First, let me say that most, if not all, of you have more riding, building or repairing experience than I do. I have only owned one motorcycle in my life, and I have owned that since 1973. It is the one you have probabaly seen in photos on this forum. That bike has spent far more time in the shop or rusting away than it has in any state of good repair. Nevertheless, I have a long background in things mechanical, and studied automotive mechanics for two years when I  was in high school, back before car radios had FM and fuel injection might have been seen on an Indy car but not on a street machine. Way back then, my sainted auto shop teacher told us that an engine should not be run for any length of time without an air filter (of course, he was referring to street machines). Reqular-old air, it seems, has adequate particulate to offend an engine. At the same time, you never know when a cloud of dirt is going to be kicked-up by the wind, the car in front of you, or droped by a dump truck in front of you. Now, all you experienced riders are saying that all has been fine. Well and good, I believe you. Just one thing, is it possible that our engines need repair for other reasons more often than the repair cycle that might be due to dirt particles in the intake air?

So, if I venture to give advice to newbies, it would be, "use an air filter."

Richard

[groily]

Manosound's quite right - we all should, no doubt about it. But for all sorts of bad reasons we don't . . . one of which is the inability to get the connecting pipework for the things, coupled with reluctance to screw on a pancake one (if there's room). But to be honest, I've been running an AMC twin for 32 years without one for want of the correct parts, and no space for an aftermarket job, it has done mega miles and not needed frequent rebores and valves .  . in fact it's on the same valves and guides that were in it it in 1976, and has had one rebore. But that may be down to luck and the right climate. I ought to put one on the A10 (which does have room) though, and shall now chastise myself every time I look at it until I do! Groily
PS re the carb query that started this: Peteb - are you sure you've got the right needle in there? No idea what it should be, but the 'wrong' one could do all of the things you're having trouble with and more. A 376 Mono, if memory serves, takes a C needle on the middle notch for starters . . .

[fido]

I've never ridden any of my bikes in desert conditions but would certainly make sure any bike I put to such use had an air filter. My A7 is doing well if it does 1000 miles a year so the engine should take a while to wear out, even without an air filter.

[G/F DAVE]

You have to remember that a lot of old bikes were never fitted with a air filter hence those nice little bell mouths fitted to AMAL carbs. Also here in the UK there use is more likely to keep out rain than dust. A good example of no air filter is my civillian 1950 BSA M20 as per factory spec, when the army used WM20 in the desert it was fitted with a huge vokes filter on top of the tank. Obviously BSA thought the english weather didn,t warrant a filter,or they couldn,t be bothered  !!!!.The only reason I don,t run with a filter on my plunger A10 is as I have said earlier is I have a home made battery carrier for a large 12 volt battery with no space for a filter.Once I have rebuilt my TRIBSA (with air fiter) I will rebuild A10 to standard spec & use my rare filter/battery carrier (I have managed to source a correct rubber connecter). If you have the space use a filter as it will increase engine life especially top end, unless like my old M20 it was never fitted with one Dave.......

[RichardL]

Speaking of weather and environs, I guess I should point out that I (and my motorcycle) grew up in Los Angeles, California, which is much drier and dustier than Great Britain or, even, Chicago. Regardless, an air cleaner is probably still a good idea anywhere (if it fits, etc.).

Richard

[peteb]

Thanks for all the info and advice so far.

I have worked on engines all my life and have to agree that an air filter is better than no air filter, (unfortunately the "cathedral" ships engines that I am more use to don't come fitted with an Amal carb of any sort  ).  The problem at the moment is that I can't source the correct rubber connector between the filter box and the carb so in this case it is a question of 'needs must'.

Groily - I should have thought about the carb flange getting bowed - I've seen it before.  The fact that I have to partially block of the intake should have suggested to me earlier that air may be being pulled in somewhere else so this could well be the fault.  Having fallen foul of blocked pilot jets before I have ultrasonically cleaned the carbs and checked that everything is clear.

I did look at the needle but the number was a new one on me - 1U or U1 can't remember offhand which.  Along with the rest of the carb internals I have no idea which is the correct part for this carb on this bike.  But I believe the bike was running using this carb at one time so have fairly sure everything is the correct size. 

I shall have another go at the carb over the weekend and post what I find. 

[groily]

Can't say anything useful about the needle Peteb, but you might also check that pilot air screw setting. If it's an air bleed, screw the darn thing right in to cut the air out, try it and then undo a bit at a time till it sounds right. 'Normal' is probably somewhere between one full turn and 1.5 full turns back from fully screwed in (on a monobloc!). Also, if the carb top has a hole for a choke cable etc and there isn't one fitted, bung something in it (I use silicon sealant gunge) to stop air being sucked straight in from up top. Could be you have a combination of little things conspiring against you, particularly if it ran with this carb before. But if you can make one of those maritime monsters below the waterline work, this is kindergarten stuff! Groily