after city riding for about a half hour the bike stalls out when I come to a stop. I can always get it started again . . . eventually. I have found that I can keep it from stalling by running without lights and holding the throttle open at stops. It has been suggested to check for a blown fuse but I can’t figure out where to look for the fuse block.
Unless the bike's wiring has been modified, no fuse "block",
just one - standard is a white roughly-cylindrical holder close to the battery negative terminal.
How would that be a blown fuse?
Reason you have received the "suggestion"
is the standard electrics were designed for absolute cheapness - the single fuse will isolate the battery in the event of a short, but not the alternator through the rectifier, is why it can be possible to start and run a bike with a blown standard fuse, but is a stupid idea.
Btw, if the fuse has blown, any "35A" marking is specific British; in the US you should fit a 15 Amp fuse.
Another suggestion is to get a bigger battery.
As you have worked out already, that is also a stupid one. However, also, standard battery, the terminals are already close to the seat pan (check pan and particularly battery -ve terminal do not touch when you sit on the seat), no space for a wider battery in either direction.
Aside, all the electrical components under the seat are close to the pan, consider obtaining some rubber or thick plastic sheet, cutting it and securing it over the electrics?
check if your carb float bowl is hot
Also check if there appears to be an obvious gap about the thickness of a business card between the carb and the manifold. There
should be a gap - filled with a special O ring - no gap, combustion heat will conduct from the cylinder head to the carb.
Michigan hot?
city riding very slow, in traffic, lot of idling--such condition can and do cause engine to die through fuel evaporation (starvation).
No. The hotter the carb itself, the
more fuel it vaporises, causing a
rich mixture, until it is too rich for the plugs to fire. "holding the throttle open at stops" draws in more air, weakens the over rich mixture so the engine keeps running.
think it’s a charging problem
Mmmm ... there are real charging problems and what some new owners perceive as "charging problems" but are not ...
To discover/eliminate any "real charging problems":-
. Connect a Voltmeter (e.g. multi-meter set to Volts) across the battery. Fully-charged battery, all switches off, a well calibrated meter should indicate 12.6V for a "wet cell" (liquid acid) battery, maybe a little (0.1~0.3V) higher for an AGM or gel battery. 12.3V indicates a half-discharged battery, is why any meter for electrical problem diagnosis should be well calibrated.
. Turn on just the ignition (no lights). At worst, the meter should only indicate 0.1V lower; even lower, the battery should be replaced - failing battery is causing a "charging problem".
. Meter still displaying 12.5V or above, turn on all lights including the headlight. Again at worst, the meter should only indicate 0.1V lower; even lower, again, the battery should be replaced.
. Original battery was 9 Amp-hours (Ah), modern AGM or gel batteries (e.g. Motobatt) of the same physical size can be up to 11 Ah. Engine not running, a 'good' battery should be able to power ignition and standard lights for around a half hour before a connected Voltmeter indicates 12V (recharge the battery after this last test
).
. 'Good' battery, turn off all lights, start the engine, raise rpm slowly while watching the meter. Volts should increase with rpm to ~15V at around 3,500~4,000 rpm then stay steady even when rpm is increased above 4,000; Volts should only fall again when rpm falls below the above range. Yes to this indicates nothing basically wrong with the charging.
To discover perceived "charging problems":-
. Remove the headlight bulb from the reflector, examine the bulb closely for any Watts markings. Original bulb was 45W main (high), 35W dip (low) according to the Triumph parts book; in reality, it was more likely to be 40W dip.
. Engine running, just the ignition (coils) draw ~3.5 Amps. If you ride lights-on all the time, standard headlight dip doubles that draw on its own; if the headlight bulb is a higher Watts, it draws even more Amps.
. Standard alternator on your bike produced 9A at 3,000 rpm, 10.5A at 5,000 rpm when new. Not only not specified for low rpm riding with all lights on, is now fifty years old - rotor magnetism attenuates with age, reducing the generating ability of the stator.
The real fix is a new later rotor and stator, 'high output' (~12,5A at 3,000 rpm, 14.5A at 5,000 rpm) 3-phase, an option 79 onwards, standard on electric start twins. However, spendy as standard rectifier and Zener diode or a single-phase combined regulator/rectifier must be replaced with a 3-phase reg/rec. Only option if night riding is considered as a different headlight is needed, the standard headlight lens and reflector are poor irrespective whether an incandescent or LED bulb is fitted.
Daylight riding only, replacing incandescent headlight and tailight bulbs with LED is a cheaper alternative - LED are brighter but draw fewer Amps; however, this does not fix any age problem with an old alternator.
PO had the turn signals removed. He said they caused problems. I’m thinking it probably was because they drained the battery even quicker. A further indication of a charging problem.
As I say, standard alternator produced 9A at 3,000 rpm when new. Riding lights-on, ignition and standard headlight dip draw ~7A, taillight and pilot draw about another Amp ... not much left to keep the battery charged ...
Two incandescent turn signal bulbs draw 3.5A, brake light draws nearly another 2A.
Sitting at a stoplight for any length of time with turn signals and brake on is a lot of Amps being drawn from the battery (at idle, the alternator is not supplying anything); bike has to be ridden at or above 3,000 rpm for some time to recharge the battery, up to the next stoplight is nowhere near enough ...
Worse still, many modern owners of 650 and 750 twins ride them like a hardly dangerous, never even get to 3,000 rpm ...
That said, Triumph did not help themselves with turn signal installation - Lucas turn signals ground through their mounting, Triumph mounted the front ones on
painted and rubber mounted headlamp brackets ...
Unbelievably stupid ...
If you reinstall standard turn signals:-
. Dismantle them. If original, remove all dirt and corrosion between components with a small brass wire brush (brass wire will not damage chrome). I reassemble with graphite grease in the joints - ordinary grease will also prevent corrosion and exclude dirt but can be an electrical insulator, the graphite will conduct.
. Where standard turn signals mount - headlight brackets and rear grab rail - run a wire from each to the nearest existing Red wires snap connector - inside the headlamp shell at the front, under the seat at the rear - Red wires are connected to the battery positive terminal for a much better ground. If you require snap connectors to take more than four wires, British Wiring in the US,
six and
eight wires.
. I replace the turn signal relay with a similar Lucas 9FL:-
... while it is taller than the 8FL, its other two dimensions are the same so it fits in the standard anti-vibration mounting bracket; Lucas supplied these to other contemporary British vehicle makers to work the turn signals as hazard signals, are likely stocked by British sports car parts vendors in the US.
If you search for Lucas 9FL online, you are likely to be returned links to a shorter version as well, the same height as the 8FL, I do not know whether this version is as reliable as the taller version.
What is special about "2,500/3,000 revs", all Triumphs rev higher, where any alternator produces more.
