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Discussion Starter · #1 ·
Hi,
The old queen is being dusted off for riding. 1970 triumph tiger 100. Started on the 2nd kick but have difficulty idling and after 10-15’ heads overheat and produce a white smoke (measured 320F).

I read around here and took some notes to report symptoms.
1-High head temperature
2-At idling speed, have to “pump” the throttle to avoid it shutting down
3-Pops and misfires. Spits fire out of exhaust
4-Blueing on chrome exhaust header
5-Spark plugs black
6-Black soot in exhaust tips
7-oil level normal and oil looks good
8-Bike sat for a while but it’s last run 3 years ago had it overheat too

The overheat issue made me think it was running lean but the black on spark plugs and exhaust tip indicates the opposite. So I am a bit confused. I played around with the carb settings trying to smooth things out to no avail. The only thing I gained was to be able to hold an idle by increasing the idle speed.
Any thoughts? I’d like to learn to troubleshoot it myself before I give up and run to the shop
Thanks in advance
 

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Hi,
I would start by checking all earths (grounds U.S) are making good contact. Does the headlight work and stay on for 5 mins without dimming? (motor off) You didn't say anything about the state of the battery. Try a fully charged one for comparison. Do you have points or electronic ignition? The latter likes nothing less than 11 volts, whereas points will function on a lot less. Still no joy? Check the timing with a strobe and for good measure, buy a new set of plugs. Overheating is a symptom of retarded timing.
I also suspect the idle circuit in the carb(s) is blocked as you say you have to "pump" the throttle or it will shut down.
Just my initial thoughts. Let us know if any of this brings an improvement.
Tony
 

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Discussion Starter · #3 ·
Hi,
I would start by checking all earths (grounds U.S) are making good contact. Does the headlight work and stay on for 5 mins without dimming? (motor off) You didn't say anything about the state of the battery. Try a fully charged one for comparison. Do you have points or electronic ignition? The latter likes nothing less than 11 volts, whereas points will function on a lot less. Still no joy? Check the timing with a strobe and for good measure, buy a new set of plugs. Overheating is a symptom of retarded timing.
I also suspect the idle circuit in the carb(s) is blocked as you say you have to "pump" the throttle or it will shut down.
Just my initial thoughts. Let us know if any of this brings an improvement.
Tony
Thanks Tony. Appreciate the advice! 🙏
The battery was on a tender and should be healthy but I’ll check.
I have points. I was going to try to fiddle the timing a bit to see. Need to figure how next.
Then I’ll get my courage together and tackle a carb cleanup after some education too. But I want to try to solve the overheating issue first as I suspect you are right about the idle circuit and that’s the likely fix.
 

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I'm certainly no expert but I recently brought back a '72 from an extended vacation (28 years). My bike exhibited the same things as yours. When you say that it gets too hot after 10-15 minutes, is that just sitting there idleing? An air-cooled engine will get hot with no air blowing through the fins. I remember measureing mine at 350° after a ride on a 100° day and worrying that there was something wrong. After 700 miles, all is fine.
I am assuming that you are running fresh premium fuel. If so, and the lousy idle can't be corrected by adjusting the "air" screw, then I would think about clearing out the idle circuit with a can of carb cleaner shooting through it and reverse flushing through the 2 little holes near the engine side of the venturi. That did it for mine, you know, after completely cleaning the rest of the carb and getting a new needle. Of course you say that you have soot and black plugs. With choke off this still happens? Could be the float and valve are not working correctly. You will need to clean this up and check the float level. Very easy to do. 2 moving parts. So in short, I'd say go through the carb thoroughly. It is a very simple device. Oh, I did need to run a wire through the idle jet because mine was all crusted up. -Brian
 

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Discussion Starter · #5 ·
Thanks Brian. I’ll try and clean the carb next. I also noticed some oil in the plugs now that I put fresh ones. That may be another issue. Researching...
 

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Hi,
1970 triumph tiger 100. Started on the 2nd kick but have difficulty idling and after 10-15’ heads overheat and produce a white smoke (measured 320F).
1-High head temperature
320F after 10-15 minutes idling is not overheating.

"white smoke" is actually "smoke" and not water vapour from condensation in the exhaust system boiling?

8-Bike sat for a while but it’s last run 3 years ago
Has the original 'white' hollow float been changed for an ethanol-resistant black "Stayup" float? Has the original 'white' plastic float needle been changed for an ethanol-resistant Viton-tipped aluminium one?

3-Pops and misfires. Spits fire out of exhaust
5-Spark plugs black
Are you using the "choke" (which isn't like the "choke" on any other carb. make)? Slack inner cable, the "air slide" is partially blocking the venturi. Tight wire, the air slide should be clear. Nevertheless, because "tight wire" pulls up the air slide, unscrew the air filter and check the wire hasn't broken or the air slide hasn't become detached, in chich case the slide's spring deploys the slide ... 😖

Start with a new pair of plugs and at least a new genuine Amal needle jet and needle, expect to check and possibly reset the spark timing.

Be aware corrosion might have enlarged all jets - something visible to jet gauges only, not the Mk.1 eyeball (at least not without considerable magnification).

Genuine Amal spares costs accumulate rapidly; you might want to consider a new Amal "Premier" carb., which is also made of better materials and had a removable pilot jet?

8-Bike sat for a while but it’s last run 3 years ago
Even if fuel wasn't left in the carb., the pilot jet might still be blocked with corrosion. The pilot jet is on the far side of the carb. from the air screw (the screw into the carb. horizontally).

If cleaning rather than replacing the carb., have a #78 drill bit fitted tightly in an aerosol 'straw'; remove the air screw, hold the carb. so the now-open air passage is pointing downwards, work the the #78 drill upwards across the full width of the carb. twirling the #78 drill in the aerosol 'straw' between your thumb and forefinger. Reason you hold the carb. that way is so any released corrosion falls out. Spray carb. cleaner through the hole in the base of the body, observe the spray exiting both tiny holes in the main venturi on the engine side of the slide indent.

6-Black soot in exhaust tips
Rub some soot between two fingers - if it's oily, it's oil; if it's dry, it's what all infernal confusion engines do, the aforementioned tune-up might reduce it but it can't eliminate it.

The overheat issue made me think it was running lean but the black on spark plugs and exhaust tip indicates the opposite. So I am a bit confused.
Discount "The overheat issue" the bike doesn't appear to have, the indicated richness is either it's burning oil, adjustments (e.g. bigger jets, slide with a smaller cutaway) you made or worn/corroded jets?

4-Blueing on chrome exhaust header
"They All Do That, Sir." Unlike Japanese/modern bikes, exhausts on half-century-old Britbikes were/are only 'single wall'; Japanese/modern bikes are 'double wall' - the tube taking the heat is inside the pretty-looking one. One way of reducing exhausts blueing on half-century-old Britbikes is to chrome 'em without the copper layer.

2-At idling speed, have to “pump” the throttle to avoid it shutting down
Standard Amal carb., when the engine's cold, nothing to raise the slide except the nut on the end of the throttle.

Once you've had a chance to tune-up the carb., or replace it with new, the throttle screw is the one you access at an angle. Start the engine, raise the slide with the throttle, turn the the throttle screw about a quarter-turn or so clockwise and release the throttle; repeat 'til idling while you put on your helmet and gloves(?). Carry the screwdriver in a handy pocket because you'll need to turn the throttle screw anti-clockwise a little a few times as the engine warms and the idle rpm increases.

I would start by checking all earths (grounds U.S) are making good contact.
Unless the bike has non-standard electrics - the harness doesn't show Red wires attached to electrical components and the battery +ve - because the engine runs (after a fashion), "grounds" can't be an issue, except possibly significant corrosion where a Red wire's attached to an engine component.

You didn't say anything about the state of the battery. Try a fully charged one for comparison.
Unless a Voltmeter's connected across the battery (one meter lead connected to each battery terminal), you don't have any idea whether it's "fully charged" or not. Absent a meter, a quick-'n'-dirty 'check' is to connect the bike's battery to another vehicle's (car or truck) battery +ve to +ve and -ve to -ve; if the increased power available from the other vehicle's battery improves the bike's running, time to fork out for a decent multi-meter - by "decent" I mean guaranteed it has electro-magnetic interference (emi) protection (which a lot of meters sold in the US don't appear to have (n)).

points or electronic ignition? The latter likes nothing less than 11 volts, whereas points will function on a lot less.
'Fraid misleading for diagnosing:-

. The bike has a 12-Volt electrical system. However, a 'good' battery fully-charged supplies 12.6V, a 'good' battery half-discharged supplies 12.3V. So, if a meter connected across the battery indicates an actual 12V, something is already very badly amiss.

. "points" might "function on a lot less" but the significant components are the ignition coils; less than an actual 12V, one or both coils might not function correctly, aka "a misfire"; system Volts below 12V and a misfire, you cannot reach any conclusion where the problem might lie.

. similarly, "[electronic ignition] likes nothing less than 11 volts" is equally misleading - some EI makers advertise theirs continue to function down to 8V ... but that's only the EI itself, like the points, it's only a switch, doesn't mean the connected coil(s) also continue working normally at 8V or whatever.

The bike only has a nominally-12V electrical system. However, normally, it should be 'well-'above an actual 12V and, if the engine's running and the charging components are working normally, the actual system Volts can be anything up to 15V.

Does the headlight work and stay on for 5 mins without dimming? (motor off)
A 'good' standard-Ah battery will keep a standard or 60/55 QH bulb going for at least thirty minutes; only five minutes before it dims is a shagged battery.

Hth.

Regards,
 

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Discussion Starter · #7 ·
Thank you Stuart for this thorough and precise help guide. The response on this forum has been overwhelming. Everyone is so helpful and generous with their time.
Much appreciate the help and will report back once I have bandwidth to trouble shoot as you describe.
thanks again!
 
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