The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Lucas, Ignition, Charging, Electrical => Topic started by: BSA500 on 24.04. 2026 13:28
-
Hi,
The A7 specced as a SS is confusing me. It will start ok and seem to run ok. As it gets hotter the bike refuses to tick over and just dies. Sometimes being difficult to start. I have wound in the throttle stop to raise the tickover to help but even then she wants to die. Thinking it might be the mag I pull the plugs and they spark really well nice fat blue sparks. Plug condition sooty so rich. So fiddle with carb settings. You can see where its going a muddle. Also as she gets hotter start to notice a lack of power. So perhaps points gap.
What I am really asking what should i be looking at. The mag is a Andy from Priory mags put in a couple of years ago. Carb has had a recent clean in an ultrasonic and compressor blow through, new pilot jet,needle and needle jet. Carb spec 1 inch 376,30 pilot, 106 needle jet, 270 main B7ES plugs.
Plan is check and reset if needed points gap, check regap plugs, check compression because I can, check valve gaps, check/clean slip ring. Check throttle cable is not snagged, wind throttle stop down and open a little. Anything else??
thanks in advance
-
Points gap and lubrication is routine maintenance.
Got to keep on top of that, as well as the other service items.
-
Vent hole in petrol cap clear?
-
Yes a service is on the list and the vent is clear.. I am basically resetting and checking all the normal stuff and see what happens. I have fiddled around too much I think
-
Hi,
The A7 specced as a SS is confusing me. It will start ok and seem to run ok. As it gets hotter the bike refuses to tick over and just dies. Sometimes being difficult to start. I have wound in the throttle stop to raise the tickover to help but even then she wants to die. Thinking it might be the mag I pull the plugs and they spark really well nice fat blue sparks. Plug condition sooty so rich. So fiddle with carb settings. You can see where its going a muddle. Also as she gets hotter start to notice a lack of power. So perhaps points gap.
What I am really asking what should i be looking at. The mag is a Andy from Priory mags put in a couple of years ago. Carb has had a recent clean in an ultrasonic and compressor blow through, new pilot jet,needle and needle jet. Carb spec 1 inch 376,30 pilot, 106 needle jet, 270 main B7ES plugs.
Plan is check and reset if needed points gap, check regap plugs, check compression because I can, check valve gaps, check/clean slip ring. Check throttle cable is not snagged, wind throttle stop down and open a little. Anything else??
thanks in advance
How worn is the carb? A worn slide often causes an erratic idle, albeit the idle speed usually goes up when hot, as air leaks past it.
-
NGK plugs could be your problem, If not made in Japan.
-
Found it. Checked mag,plugs,carb all good compression 110 psi both cylinders . Last check valve clearances , timing side inlet drive side exhaust no gap, timing side exhaust drive side inlet about 3 thou. That'll do it the hotter the engine the worse it ran
-
Would also account for the power loss, logically. Well sussed!
-
Nice to have a clear reason for once. Thought the valve clatter was quiet *smiley4*
-
Occam's Razor again..
-
Now you know why there’s a maintenance schedule.
-
If the compression was reasonably good, probably no damage to valve seats from tight / negative clearances *dunno*
-
She seemed OK after resetting no issues
-
Remember, a noisy tappet is a happy tappet *smile*
cheers Klaus
-
They’re not called “tappets” for nothing.
Richard L.
-
Even when they're really "rockers"... *smile*
-
True. I slightly mispoke and appeciate the clarity. Looking for some personal redemption, I found this part of a definition allowing for it to apply to a lever (rocker?). It describes a mechanical component, such as a rod or lever in an engine, that imparts intermittent motion by tapping or touching another
Richard L.
-
Went like a scolded cat this morning and ticked over even when hot, its a miracle
-
True. I slightly mispoke and appeciate the clarity. Looking for some personal redemption, I found this part of a definition allowing for it to apply to a lever (rocker?). It describes a mechanical component, such as a rod or lever in an engine, that imparts intermittent motion by tapping or touching another
"Tappets" is the older name for cam followers, and was used in the days of Side Valve engine tappets which worked directly on the cam lobes. On OHV engines the adjustable rockers are a fair distance from the camshaft.
-
Well, like I said, I misspoke. I was only exploring the word for etymological redemption. *smile*
-
Depending on the geometry of the the rockers, checking the 'valve clearance', 'tappet clearance' is all the same. Checking the clearance at the rockers gives the same reading as the clearance at the cam / cam follower (i.e. tappets) provided the rocker arms are the same length and the angle between the pushrod and the rocker is 90 degrees.