I am currently rebuilding an 1953 A10 that I have owned since 1980. It suffered a spectacular engine failure in 1996 (left hand big end oil starvation, the sludge trap was full).... The mag was rebuilt only a few months before the engine blew up.
It has taken me until now to give the bike a full rebuild, the engine has been rebuilt over a scattered period of 15 years. The rest of the bike has been a Covid lockdown project.
I have got to the stage of starting the bike..... It fires, revs, then stops.... I'm pretty sure the timing is good, it is firing on both cylinders but just will not run continuously or tick over.
When I bought the bike in 1980 it had a monobloc carb.... I never used to have any trouble with carbruration so I never changed any jet sizes, I never needed to. During the rebuild I dismantled and cleaned the carb and bought a rebuild kit (with the original jet sizes) and carefully treated it to a full overhaul....
I'm now at a loss as to why it will start but not run, both cylinders are firing (hot exhaust both sides) but I can't keep it running or ticking over.... I've checked everything I can think of and have run out of ideas.....
I'm reaching out to the experts for help now.....
Jon
Hi Jon. Can you explain the symptoms a bit more? For example, does it fire into life and then refuse to rev and die as you open the throttle or does it run ok and rev for a short time and then die? Will it start again afterwards and do you have to tickle the carb again?
It fires into life then dies straight away.... No backfiring
Actually, it fires into life, revs and then dies, it won’t continue to run, rev or tickover. It will fire again without tickling but float level is not something I have checked so that’s a job for tomorrow.
hello,
impossible to diagnose that fault from emails.
i ve heard the saying on forums that most carb issues are electrical and vise versa.
i am having similar ongoing issues with richness even with electronic ignition and suspect its the latest fuel.
have you checked the fuel flow from the petrol tank is good? new petrol? is the petrol being contaminated with water from the petrol tank? drain the carb and check the jets are clear.
the next option is to substitute a good working carb and magneto.
Had this been a fully functioning bike that had just started to give a problem, it would have been much easier to diagnose the cause. However, because the engine has just been rebuilt, it unfortunately makes this much more difficult.
From what has been said, it looks as though the magneto and the carb were working properly previously and so there should not be a fundamental problem there. Nevertheless, it would be worth double checking both have been assembled correctly - with the magneto, that all the electrical connections are 100% - with the carb that everything is as it should be including the float needle valve, throttle needle, fuel flow into the carb and the mounting flange is perfectly flat with a good O-ring.
Unfortunately, if the magneto and carb look good, you may have to consider that there may be a problem with the engine itself after the rebuild. The compression is easy enough to test but it may be worth double checking the valve timing which could cause problems similar to that being experienced if it is out. Also worth checking the tappet adjustments.
Hopefully, it is just a simple problem which the tests will reveal?
I had a similar problem as this when I re-built my A10, a 1952 plunger. At that time I was running a magneto too. I went back through the timing process again and this seemed to sort the issue. However, I think this can also be a symptom of a failing magneto. I know you said yours was re-built, but... My magneto started to fail last year and the symptoms were rough idle, poor pick up and occasional back firing. I have since switched to electronic ignition and this has transformed the running of the bike.
Hi,
As Spaceman says. Check everything over again. You have a spark and some fuel is getting into the combustion chamber so it almost definitely down to settings and adjustments.
Dave.
:) :) :) :)
I cant remember from my last A7/10. But it sounds Mag? Does this mag have a condenser, Cos thats a good place to look with your symptoms. Certainly if I was doing a big old tractor engine that would be an early port of call.
Mike 8) 8) 8) 8)
:) :) :) :)
Quick follow up. Get someone to hold the tickler down straight after it starts. Might give you some indication about fuel.
Mike 8) 8) 8) 8)
Always go for the simple things first this could simply be a blocked or partialy blocked pilot jet. I have had similar problems with my A65 and it was a partially blocked pilot jet, you have overhauled the carb some years ago I assume you are using fresh fuel but after standing for so long there could be sediment in the fuel tank or fuel lines that could cause a blockage in the pilot jet. It only takes a few minutes to remove the jet and clean it of any obstruction.
:) :) :) :)
Hi. Any joy with this one yet. Be interesting to know the cure and the outcome.
Mike 8) 8) 8)
blocked filler cap vent hole
Still no joy with this....... Stripped and cleaned the carb, checked float height ok, blew out with compressed air..... did the timing again.....same issues.....starts easy, revs then dies.... Firing on both cylinders..... just did a compression test and I've go 100psi on both cylinders (which seems about right on 7:1 pistons..... my auto advanc unit seemed like it doesn't close properly so I've cleaned that and put new springs on the Bob weights..... wish me luck :)
my plunger has electronic ignition, does not get used and when the wet sump is drained, battery charged and clean fuel always starts within a couple of kicks. the B40 was temporamental to start after rebuild but is easy now Ive fitted electronic ignition.
I did try new bob weights and springs but with all the play electronic proved so much easier.
if its racing away , that would suggest air leak.
one thing I did find, has the tank been coated inside? I have a jerry can that I kept oily old fuel in, then while draining some last week, a big sheet of paint from the inside came into view. could be its starting and the vacuum letting the fuel flow, coating covers the inside of the fuel tap.
Hi John,
I would say that there is still a problem with fuel. Assuming that you 'tickle' the carb to cause a rich mixture for starting, the initial rich mixture is firing as would be expected but this surplus is quickly used up. There must then be not enough to keep the engine running.
Try firing it up again but keep the tickler down. This will keep the mixture rich. If the engine keeps running with the ticker down then the problem is almost certainly with the pilot part of the carb. Even with enthusiastic cleaning there could still be a partial blockage. Blow some brake cleaner through the tiny drillings and see if it getting through in copious amounts. Use the air line as well. If this fails you will have to poke a thin wire through - not ideal but needs must unless you have a sonic cleaner. Also, make sure there are no leaks at the carb to head joint. Do not over tighten the carb. nuts.
Dave.
Dean mentioned this a while ago but did you check the petrol cap vent hole? I had symptoms very similar to yours on my Norton Model 18 and that's what it was.
try without the petrol cap on.
Hi,
Try without the petrol cap but I would think that a blocked/partially blocked cap would not cause the problem you are having as not enough fuel will have been used to cause a partial vacuum in the tank. The petrol vapour above the liquid will to some extent pressurise the tank.
Dave.
Thanks for the replies...... I'm using a temporary fuel tank made for the job, not my bike tank.... Leave the lid off every time. I'll try holding the tickler down as you suggest. I replaced then auto advance Bob weight springs and retimed the ignition.... Still the same issue.... When the bike was running before, I didn't have a carb drip plate in place.... I thought it might be safer to have one. However, this has more potential to introduce leaks so I'll try running it without.
Thanks for your helpful suggestions
Have you checked for air leaks when you removed the drip tray do the mounting studs have a thread free portion?
I haven’t removed it yet, job for next week I’m away at the mo.
My year and model of A10 has the carburettor mounted with bolts rather than studs….
Well, I've tested compression, 100psi on each cylinder which seams reasonable for standard pistons. thanks I've removed the carburettor drip tray, cleaned out the carbs twice with carb cleaner and an air line, overhauled the advance and retard unit, new pickups and brushes, new spark plugs,
Timing checked again and seems good but it's still no good.... Starts and revs on first kick but still will not run continuously or tickover.....
nothing has changed...
Sticky inlet valve or magneto?
I know it's awhile, but how did you get on with this? I had a similar issue where are used a brand-new idle jet screw and for some reason it just did not work so went back to using the original one which was significantly better. Also I opened up the points gap to 0.012 and my 350 empire star is running so much better now.
:) :) :) :)
Dont know this particular set up but it sounds a bit condenser.
Mike 8) 8) 8) 8)
After a bout of illness I'm back on the starting of my 53 A10. I decided to change the cap in the mag for an easicap. Easy to do and cheap... much fatter spark and starts OK.... running a bot rough but managed together it ticking over, all sounds good... I noticed that one cylinder got hotter than the other... I recon the timing is still off, a bit of popping and banging but it's a runner
Fitted an easy cap thing to a mag on my douglas 350, after a few miles wouldn't start, points gap was gone, adjusted gap to find after a few miles the bike started running rough, this time points gap was wider than it should have been, to cut a long story short found that the static point contact, the one that clamps the easy cap down, was for want of a better description moving which affected timing and spark. Ended up having to completely strip armature and put in a proper condensor. Dont know if it was me not tightening the screw down enough but after rebuilding the mag using the original parts there was no problem with the bike, at least there wasn't till the big end roller cage collapsed.
I'm getting there, it ran better (but still a bit rough) after fitting an easycap to the magneto. Got it to tickover but stalls a bit when opening the throttle but runs with a few bangs at higher revs, bu8t its better than it was.. The rocker box leaked so I've taken it off and treated it to some copper gaskets. I managed to refit it ok, using the comb to guide the pushrods back in and all seems to be operation fine, I even got it to run but the timing was way out this time. I'm not happy about one of the inlet rockers the tappet sits much higher than any of the others... I think that its working on the rocker and operating the valve but maybe not properly seated in the rocker cup, I don't want to remove the rocker box again, has anyone had any luck reseating a stray pushrod without removing the rocker box?
I'm thinking to loosen off the tappet and trying to manoeuvre the pushrod into its seat but I cant see a thing.
An update to this post... It's now been three years since I posted... I tried everything, rebuilt mag fitted easicap, cleaned the carb numerous times. New jets. Many attempts at timing... Always the same... Starts first kick, revs then dies.. nothing would make any difference...ended up buying a brand new Amal carburettor... Problems sorted, first kick, runs beautifully.. Thanks for all the helpful comments but the only solution was to chuck some money at it lol... Now to sort out those oil leaks.. ::)