Author Topic: Engine failure troubleshooting  (Read 896 times)

Offline owain

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Engine failure troubleshooting
« on: 18.09. 2019 08:48 »
My A10 has been running well for the last few months and I've managed to put a lot of miles onto the newly built engine. However, yesterday it broke down on me in North Wales. To make matters worse it was whilst being filmed by ITV for a TV segment ;D. I ended up having to get my A10 loaded in the van and taken home.

Today I'm going to try and repair it but of course wondered whether anyone could shed some light on the symptoms to find the cause of the problem. In brief, I first started to notice the engine fluttering (i.e. not combusting) at when in top gear and at speed. I pulled over and checked the carb, they looked pretty good, albeit a perhaps a tiny bit too lean. Set off again. A few minutes later the motorcycle started fluttering but now at mid-speed (30-45mph). Dropped the speed and kept riding a little a few minutes longer but then the motorcycle fluttered and stopped combusting entirely. I pulled over, Tickled the carb until the float is flooded, engine starts straight away. Ride 800yds. Engine flutters and stops. Tickled the carb again, engine starts, ride another 800yds and repeat again.

My initial thought was that the engine is using fuel at a faster pace than it is replacing. So I knocked on a campsite receptions door and asked to borrow a socket set to remove the tank and get to the carb. I removed the carb it's float bowl, the main-jet holder had vibrated loose, so I tightened it back up, thinking I had found the problem but had the same symptoms. Eventually the distances I could travel after tickling the carb reduced more and more (600yds, then 400yds, then 200yds) until the engine wouldn't start at all.

Does anyone have any ideas about the possible cause of this problem? Thanks guys!
Sweden & North Wales
'50 BSA A10
'69 BSA A75R

Offline duTch

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Re: Engine failure troubleshooting
« Reply #1 on: 18.09. 2019 09:07 »

 
Quote
...... I pulled over and checked the carbs, they looked pretty good, albeit a perhaps a tiny bit too lean.........

 
Quote
......... I pulled over, Tickled the carb until the float is flooded, engine starts straight away. Ride 800yds. Engine flutters and stops. Tickled the carb again, engine starts, ride another 800yds and repeat again.........

 How many carbs do you have, one, two or two into one *conf2* ?- I suspect  the first ^^quote^^ means two S-plugs....The first think that comes to mind is a blocked vent in the tank cap, and next that you're low on fuel or crap in the fuel lines/tank filter....other than that requires thought *dunno*
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
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Offline owain

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Re: Engine failure troubleshooting
« Reply #2 on: 18.09. 2019 09:20 »
Possibly. I did remove the fuel cap to see if that remedied the problem whilst riding but no luck. Fuel lines also appear clear i.e. if I detached one and open the opposite fuel tap, petrol comes running out of the fuel lines. I'll give it a look...I'll also edit my grammar haha

I should also mention that I recently modified the exhaust with a mute, that would certainly increase exhaust back pressure but it's been running fine with it on for a week or so before this incident.
Sweden & North Wales
'50 BSA A10
'69 BSA A75R

Offline Swarfcut

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Re: Engine failure troubleshooting
« Reply #3 on: 18.09. 2019 09:28 »
Ha....The curse of the A10 strikes again, frustrating your chance of stardom.

Ok, duTch is on the money here, anything that stops that fuel vapour getting to the inlet manifold is suspect, from a blocked tank breather, to a blocked main jet and anything in between. So start with the easy stuff, fuel taps, tank filters, float, needle. Establish fuel is getting to the carb, then move on to jets, internal drillings, sealing washers, correct assembly, air leaks. Good chance its the tank, recent enthusiastic riding has shaken up some sediment....taking the fuel taps out may reveal all! A couple of cheap in line fuel filters are worth fitting, and give visible indication of fuel supply.

Swarfy.
















Online Greybeard

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Re: Engine failure troubleshooting
« Reply #4 on: 18.09. 2019 09:29 »
I once had a blocked tank cap vent. I was able to drive for a couple of k before the engine stopped. After a bit of fiddling the engine would start again and off I'd go for another short run. Rinse and repeat!

Online Klaus

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Re: Engine failure troubleshooting
« Reply #5 on: 18.09. 2019 09:58 »
There is also a gacefilter in the top of the floatbowl, may be the is some dirt.

cheers Klaus


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Online Greybeard

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Re: Engine failure troubleshooting
« Reply #6 on: 18.09. 2019 10:16 »
Has the magneto been serviced? A faulty condenser tends to fail when the bike is hot.

Online bsa-bill

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Re: Engine failure troubleshooting
« Reply #7 on: 18.09. 2019 10:27 »
try both taps turned on - might show or eliminate something
All the best - Bill
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Online ironhead

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Re: Engine failure troubleshooting
« Reply #8 on: 18.09. 2019 10:28 »
I'll put my money on Klaus's suggestion.
SA

Offline owain

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Re: Engine failure troubleshooting
« Reply #9 on: 18.09. 2019 12:02 »
Righto, I just tried starting the bike before reading all these comments and the damn thing caught fire! Looked like it started at the carburettor. Fortunately it was a very small fire and I had a fire extinguisher within arms length of me, so it was out within a few seconds.
Just how I like start to the morning *lol*

I've cleaned it up now and I've just removed the carb. I'll drain the tank and remove the petrol taps. I also noticed that air is escaping from the timing side cover via one of the screws when I kick it over...not sure if it is note worthy how the bike is? I'll check back on the forum regularly throughout the day to keep you updated and see how things progress!

Also to answer Greybeard, Yep the magneto has been serviced by APL magnetos a few months ago. I'd be hugely disappointed if the mag is playing up already.

Image is from post-fire extinguisher antics:
Sweden & North Wales
'50 BSA A10
'69 BSA A75R

Offline Swarfcut

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Re: Engine failure troubleshooting
« Reply #10 on: 18.09. 2019 12:53 »
A fire is perhaps an indication of another fault. Sure it was the carb? A petrol soaked magneto is an obvious a fire source, but for a carb to light up means it has fired and spat back through the inlet manifold.  If a compression check and tappet clearances are OK, meaning the valves are sealing, could be the ignition timing is out, and it fired while the inlet valves were slightly open....or the valve timing has moved, key on camshaft sheared and cam no longer correctly timed, but here ignition will stay correctly timed to the crank. Unlikely scenarios, but something to bear in mind.

Swarfy.

Online Flashgreubon

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Re: Engine failure troubleshooting
« Reply #11 on: 18.09. 2019 13:28 »
Just to remind you that there are a lot of faulty soft mag brushes around that wear to nothing in no time!

Offline owain

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Re: Engine failure troubleshooting
« Reply #12 on: 18.09. 2019 13:29 »
Thanks Swarfy, perhaps I need to recheck the tappet clearances again since rebuilding the engine. I haven't got my compression test kit with me at the moment, just a toolbox with the basics. The only compression test I've done is placing a thumb on the spark plug hole. Very rough test. I've removed the point assembly to give the points a quick clean and lost the little rubber grommet that sat between the metal arm and the points lever. Is this just to keep the lever in place i.e. I can replace it with any piece of non-conductive material?

An update on checking the fuel lines though. I've taken the carb to bits. Jets are clear but the tube that accommodates the float needle had a small piece of material in there. Not sure if it was large enough to cause a stoppage but then again anything where it shouldn't be isn't helpful. There was some a few rust particles from trapped behind the gauze filter in the carb. I removed the petrol taps and they both seemed pretty. I gave everything a clean and will removed any bits. I'm off to B&Q to get some clear tube to replace my fuel lines which look like they could crack at any moment.
Sweden & North Wales
'50 BSA A10
'69 BSA A75R

Offline Swarfcut

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Re: Engine failure troubleshooting
« Reply #13 on: 18.09. 2019 13:50 »
Thanks Flash... Carbon clogging up the slip ring will fire both plugs at the same time if the HT is strong enough to track around the slip ring, so a nice clean  and a check on those brushes will eliminate another potential cause. Could account for the spitting back.

 Any insulating material  shaped to size will do in the short term to replace the missing tit.

Swarfy

Offline mugwump

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Re: Engine failure troubleshooting
« Reply #14 on: 18.09. 2019 15:55 »
Not too sure that B&Q sell ethanol proof fuel line though! If that starts to disintegrate then you will have blocked jets etc.

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