Re: bike got harder to start each time, now wont start :( part 2

[chicago]

oh my god, it ran when i first got it , then as in my previous post got harder to start then wouldnt run , changed the plugs and then ran ok again , now left in the garage for two days and now back to almost impossible to start and keep running . ive now took the carb off (again) and cleaned everything out. i put the carb back on and still a swine to get to start and really hard to keep running. as soon as you go to give it a little bit of gas when running on fast tick over it goes to die. also back firing a little.
upto now ive changed the inlet manifold gasket's. changed the plugs and set gap to .020  (champion l85c) changed the spark plug caps, cleaned the magneto pickups, cleaned the carb.
i've taken the plugs out and held them against the barrels and there seems to be a healthy blue spark. the only thing i haven't checked is the points. the engine is a 1948 longstroke.
forgot to mention the carb on the bike is a amal monobloc 376/35 as far as i can gather its off a Triumph 498cc 1955-61;TR5, T100.
any sugestions would be very much apreiciated before i end up going crazy  .
all the best, chicago

[duTch]

Can't remember the previous posts, but if the spark is healthy, points indicate ok(probably still worth confirmation), maybe timing has slipped??  Check tappet clearance?? also check holding   right 

[Triton Thrasher]

the only thing i haven't checked is the points.

Why on Earth not?

The first thing you check on almost any starting problem is the presence of fuel. Second thing is the plugs, then points gap and cleanliness.  Isn't it in the owners' handbook?

[Triton Thrasher]

Reading the previous stuff, it looks as if it starts ok for a while after you clean the soot off the plugs. Does it start on a cold morning with no pressing of tickler? It probably shouldn't.

Get correct plugs, gap to 18 thou, then carry out the Amal tuning procedure.

[chicago]

Can't remember the previous posts, but if the spark is healthy, points indicate ok(probably still worth confirmation), maybe timing has slipped??  Check tappet clearance?? also check holding   right 

hi there dutch, with me knowing nothing about magneto's i didnt want to mess with the points untill my workshop manual arrives. same situation with the timing didnt want to start messing with it as theres a a chance i might end up making it worse. i was begining to think it might be a sticking valve ?. just cant understand why the bike would go from running well to almost not at all. i just hope its not the magneto isnt packing up. cheers for the input dutch, much aprieciated.

[chicago]

the only thing i haven't checked is the points.

Why on Earth not?

The first thing you check on almost any starting problem is the presence of fuel. Second thing is the plugs, then points gap and cleanliness.  Isn't it in the owners' handbook?

hi there triton thrasher. with me knowing virtualy nothing about the workings or internals of a magneto and still having to wait for the stupid workshop manual i ordered about a week and a bit ago from ebay i thought it would be best not to mess with it for now. the magneto end cover has like line markings all the way round it and a little brass pointer thing so i thought if i took the cover off it might disturb the timing ? (see very little knowledge) all the best fella, chicago 

[a10 gf]

with me knowing virtualy nothing about the workings or internals of a magneto

That will soon change!... welcome to the joys of classic bike ownership. Regarding the mag, maybe take a look at my mag topic, which should give you a good introduction to what's going on in there. Many more good & helpful topics in the Lucas board.

btw, am very proud  of my test and timing system.
 
edit: just read the post about tickling, maybe you're lucky? But good to learn some stuff about the mag, one day it'll be helpful.

[chicago]

Reading the previous stuff, it looks as if it starts ok for a while after you clean the soot off the plugs. Does it start on a cold morning with no pressing of tickler? It probably shouldn't.

Get correct plugs, gap to 18 thou, then carry out the Amal tuning procedure.

hi again fella, not sure to be honest, ive only had the bike about two weeks and ive never tried starting it without tickler, it does however start without airlever/choke. would the plugs i have be the correct plugs for the bike ? (champion l85c ?). cheers for the input, all the best, chicago

[bsa-bill]

Hi Chicago
The carb on your bike if on original settings would have a main jet of 220 where as the 48 longstroke carb would be 140? much richer but mitigated somewhat by the needle position (4 for the Triumph and  1 or 2 ? for your bike ( would be so nice if here was a chart with correlation of main jet to needle position).
So it's quite likely it's running rich and sooting up your plugs, main jet and needle position would allow starting with clean plugs but soot them up and deffo make staring difficult next time.
Trouble is sooty plugs can be either running to rich or poor spark, you need to get in there and check points, plenty help here if you get stuck we've all been learners here and still learning thanks to those who know and share their knowledge

I can sympathise with you as I went through similar problems with my last build I had a lot of help from the forum and in particular a couple of members who know magnetos  

[chicago]

with me knowing virtualy nothing about the workings or internals of a magneto

That will soon change!... welcome to the joys of classic bike ownership. Regarding the mag, maybe take a look at my mag topic, which should give you a good introduction to what's going on in there. Many more good & helpful topics in the Lucas board.

btw, am very proud  of my test and timing system.
 
edit: just read the post about tickling, maybe you're lucky? But good to learn some stuff about the mag, one day it'll be helpful.

hi there a10gf, just had a look at your post about mags, very impessive post and test bed setup ect, it does help me a bit having photos of a magneto in bits. just hope i dont have to start striping mine  . cheers fella.

[chicago]

Hi Chicago
The carb on your bike if on original settings would have a main jet of 220 where as the 48 longstroke carb would be 140? much richer but mitigated somewhat by the needle position (4 for the Triumph and  1 or 2 ? for your bike ( would be so nice if here was a chart with correlation of main jet to needle position).
So it's quite likely it's running rich and sooting up your plugs, main jet and needle position would allow starting with clean plugs but soot them up and deffo make staring difficult next time.
Trouble is sooty plugs can be either running to rich or poor spark, you need to get in there and check points, plenty help here if you get stuck we've all been learners here and still learning thanks to those who know and share their knowledge

I can sympathise with you as I went through similar problems with my last build I had a lot of help from the forum and in particular a couple of members who know magnetos  

hi there bsa bill, when i was stripping the carb the other day i did notice that the idle/tickover jet was a 25, and the needle was on the third notch down from the top.
i think as you and others have suggested im going to have to check the points. is there anything in particular that i should be aware of when checking them ?. it does give me a lot of comfort knowing i have the backup of the forum members with all your collective knowledge. all the best, chicago
***edit*** sod it im off to the garage and going in for the kill. im gonna take the end cap off the magneto and check the points. i'll post some photos of the points later to see if anybody can spot anything obvious. wish me luck. cheers fella's, all the best, chicago

[Triton Thrasher]

There are probably online BSA manuals somewhere.

Your symptoms could be caused by a slightly too-rich idle screw setting, but there's more to consider.

If other carb settings are wrong, you do risk overheating the engine.

You're in something of a tricky position, having a faulty 60-year old bike. You need a mechanic or enthusiast who is used to working on very old bikes.  If you can't get that sort of help, you have to learn it yourself.

[chicago]

There are probably online BSA manuals somewhere.

Your symptoms could be caused by a slightly too-rich idle screw setting, but there's more to consider.

If other carb settings are wrong, you do risk overheating the engine.

You're in something of a tricky position, having a faulty 60-year old bike. You need a mechanic or enthusiast who is used to working on very old bikes.  If you can't get that sort of help, you have to learn it yourself.

hi again triton thrasher, cheers. would a rough setting for the idle screw be screwed in all the way, and then turn out again 1 and a half turns ?.
the exuaste pipes seem to be a very light shade of gold just at the first 5-6 inches with no sign of blueing so maybe not overheating/too lean ?.
unfortunatly ive spent every penny i had on buying the bike + £500 owed to my missus so a experianced mechanic or new parts looks like out of question for a while. i dont mind learning stuff myself as that makes me more able to deal with stuff in the future but im just a bit flustered with having problems so soon. lucky ive got this forum. cheers for the advice though fella, it is aprieciated. take care and all the best, chicago

[Triton Thrasher]

Yes you could start with the mixture screw one and a half turns out. Then when the warm engine is idling, slowly screw it in until the engine slows and rhythmically chugs. That means it's too rich. Slowly screw it out until it runs steadily, with both cylinders firing. Then the idling mixture is probably not too far out.

You have to control engine speed with the throttle stop screw as well and probably slightly retard the spark lever, if there is one. There's no denying it can be a bit tricky!

Even with correct idle mixture, a too-small throttle slide cutaway, worn needle jet, or needle in wrong clip can soot up the plugs.

[chicago]

Yes you could start with the mixture screw one and a half turns out. Then when the warm engine is idling, slowly screw it in until the engine slows and rhythmically chugs. That means it's too rich. Slowly screw it out until it runs steadily, with both cylinders firing. Then the idling mixture is probably not too far out.

You have to control engine speed with the throttle stop screw as well and probably slightly retard the spark lever, if there is one. There's no denying it can be a bit tricky!

Even with correct idle mixture, a too-small throttle slide cutaway, worn needle jet, or needle in wrong clip can soot up the plugs.

cheer's to you and all the forum members the bike now runs. i went in the garage but before i did anything i tried again to start it but no joy at all (sore foot though). so i turned the idle mixture screw all the way in and back out 1 and a half turns then kicked it over about 5 times and she roared back into life  . what a relief. she now runs more even than she did before. it now even re-starts after turning off , excellent, nice one fella's. all the best chicago