Cold Start: Maintaining Tickover - Triumph Forum: Triumph Rat Motorcycle Forums
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post #1 of 33 (permalink) Old 09-09-2019, 07:07 PM Thread Starter
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Evening all,

I have been pondering the issue of getting a decent tickover whilst the bike warms up. This is a common issue with these old bikes; a feature, not a fault. 🙂

The Amal carbs on my bike are Mark 2 type that have a rather rudimentary cold start enrichment system to provide additional fuel rather than the 'real' choke found on more modern carbs. I turn on the fuel tap, wait for the empty carbs to fill (signified on my bike by the sound of air being drawn through the tank cap breather pinhole), pull the lever that says "Choke" (but isn't), which in turn lifts the cold start plungers. I gently kick her over a couple of times to draw fuel in, switch on the ignition and with the throttle about 1/4 open, give her a proper kick and she fires up first time (mostly).

Great! And it has taken quite a while for me to get her to the point of such easy starting. However, I then have to stand with the bike, patiently holding the throttle part way open whist she warms up. If I let go of the throttle too soon (and I often do), she dies. I am sure it is a familiar story for most of you: if the bike is setup to tickover correctly when warm, she will not idle cold.

The PO's advice to me was to suit up, lid and gloves on, garage locked up and have the bike facing the open road. Then start her up and ride away immediately, in the hope that by the time you have to stop (but not always) she will be warm enough to hold idle.

I am not keen on this plan. Cold engines need to be warmed up and ideally be close to running temperature before being used. Also, I like to start them up and leave them to warm up whilst a get my gear on and lock up the workshop.

So, I have been thinking about potential solutions. As an interim, I have been using one of these:
https://www.amazon.co.uk/gp/aw/d/B07...b_b_asin_title
It kind of works but is not ideal. However, what it is doing is great; holding the throttle part way open whilst the engine warms up, but I think there is a better way....

So, I have a question: what is the thread on the end of the throttle cable, where it screws into the throttle please? If I know this, I think I can relatively easily create a permanently fitted method to pre-tension the throttle cable enough to hold idle until the engine warms up. Once I have tinkered and tested, I will report back.

If anyone already has a solution, please let me know and save me the effort 🙂

Cheers,
Ian

Last edited by Boggie; 09-09-2019 at 07:11 PM.
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post #2 of 33 (permalink) Old 09-09-2019, 07:31 PM
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i would suggest that gentle running on a warming motor is not only not harmful, it's the better way to do it.

the biggest part of an engine's wear comes about during the first 30 seconds after starting, i've been told, and the sooner the motor is up to operating temperature after that, the less the wear.

what they used to say was, get it moving, get it hot.

once you are past the first 30 seconds and have oil pressure, there will be enough flow to maintain an oil wedge in your plain bearings, and the sooner the pistons warm up to a cylindrical shape the sooner they will stop scuffing your cylinder walls. gently moving off and gently riding the machine for a mile or two will warm up the carbs quicker, which will reduce fuel puddling and cylinder washing, will adjust the pistons to the cylinder walls, and will let the valves and rocker gear expand to their operating clearances.

riding like attila the hun on a cold engine will absolutely not help it, but letting it idle away on its stand won't help to warm up the transmission gears and bushes. these wear out as well as the motor.

just my thoughts.

i be kevin
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post #3 of 33 (permalink) Old 09-10-2019, 01:58 AM
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Quote:
Originally Posted by Boggie View Post
If anyone already has a solution, please let me know and save me the effort
Different bike but same 'issue'. I don't ride away immediately because I have road junctions very near my garage and the bike will stall. I hold 2000rpm until it's warm enough to idle at about 600rpm and use the time to check oil return, look for any leaks, listen for any new rattles and generally enjoy the exhaust note. Once fully up to temperature idle rises to 1100rpm.

I did once try to adjust the twistgrip tension screw so the throttle would stay open on its own but I gave up on that concluding that the starting ritual is just another fact of life with these bikes.
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post #4 of 33 (permalink) Old 09-10-2019, 03:16 AM
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I took the twistgrip friction/locking setup out and installed a larger knurled bolt setup...I use this both for cold idle and 'cruise control'. It isn't a great cruise control, but its good enough to free my right hand while I rearrange my gloves or something without having to lose speed. And because its a friction setup, if I need to throttle down I can, just have to do it manually rather than rely on the carbie springs. I can also release the tension as well, I need to use my left hand while the right holds the twistgrip.
But it is good for cold starts.

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post #5 of 33 (permalink) Old 09-10-2019, 06:09 AM Thread Starter
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Quote:
Originally Posted by speedrattle View Post

the biggest part of an engine's wear comes about during the first 30 seconds after starting,
Yes this is often true, especially where oil has drained back into the sump overnight and there is no oil pressure. That's one of the other reasons to kick her over a couple of times with the ignition off. Also, cold oil in the system is less effective.

Quote:
Originally Posted by speedrattle View Post
the sooner the pistons warm up to a cylindrical shape the sooner they will stop scuffing your cylinder walls. gently moving off and gently riding the machine for a mile or two will warm up the carbs quicker, which will reduce fuel puddling and cylinder washing,
Not sure I understand this one as I am no expert but I would like to... Presumably the pistons/bores start perfectly round, as that was how they were machined, cold. I would also assume that the pistons would expand linearly, as long as the casting and alloy were consistent similarly with the bores. How do they get out of round?
[/QUOTE]

Quote:
Originally Posted by speedrattle View Post
letting it idle away on its stand won't help to warm up the transmission gears and bushes. these wear out as well as the motor.
That is true. Well, only slowly as heat transmits to the gearbox, but I guess that leaving the engine running a little before riding off would not affect transmission either way, as long as Atilla keeps in mind the fact that the gearbox is cold 🙂

I have always been told that a gentle warm up on idle is best for an engine, albeit not too long on an air-cooled motor. Not directly related but my Bonnie engine definitely weeps less oil from under the barrel/pushrod area if I let her warm up before I head out. Not sure why but this is repeatable so something is different if I warm her up first.

Answers on a postcard..... 😉
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post #6 of 33 (permalink) Old 09-10-2019, 06:16 AM Thread Starter
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Quote:
Originally Posted by tridentt150v View Post
I took the twistgrip friction/locking setup out and installed a larger knurled bolt setup...I use this both for cold idle and 'cruise control'. It isn't a great cruise control, but its good enough to free my right hand while I rearrange my gloves or something without having to lose speed. And because its a friction setup, if I need to throttle down I can, just have to do it manually rather than rely on the carbie springs. I can also release the tension as well, I need to use my left hand while the right holds the twistgrip.
But it is good for cold starts.
Ah, yes. A definite advantage of the older throttles! The chap that works for me has the same on his Tiger. He has permanently set the friction so that the throttle does not return and leaves it slightly open as he starts and warms her up. I prefer your idea though as the last thing you want , if you drop her, is the throttle staying open with the bike on her side.... I will mention your knurled solution. Thanks.
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post #7 of 33 (permalink) Old 09-10-2019, 06:25 AM Thread Starter
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Quote:
Originally Posted by Rusty1 View Post
I did once try to adjust the twistgrip tension screw so the throttle would stay open on its own but I gave up on that concluding that the starting ritual is just another fact of life with these bikes.
Once I know the threadform of the throttle cable, where it screws into the handlebar throttle housing, I think I have a solution that does not need any significant skills or tooling. If it works, I will share all the details here for all.

I am surprised Stuart has not been along with the answer as he is an expert on threads and fastenings....

Ian
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post #8 of 33 (permalink) Old 09-10-2019, 07:20 AM
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Quote:
Originally Posted by Boggie View Post
Quote:
Originally Posted by speedrattle View Post

the biggest part of an engine's wear comes about during the first 30 seconds after starting,
Yes this is often true, especially where oil has drained back into the sump overnight and there is no oil pressure. That's one of the other reasons to kick her over a couple of times with the ignition off. Also, cold oil in the system is less effective.

Quote:
Originally Posted by speedrattle View Post
the sooner the pistons warm up to a cylindrical shape the sooner they will stop scuffing your cylinder walls. gently moving off and gently riding the machine for a mile or two will warm up the carbs quicker, which will reduce fuel puddling and cylinder washing,
Not sure I understand this one as I am no expert but I would like to... Presumably the pistons/bores start perfectly round, as that was how they were machined, cold. I would also assume that the pistons would expand linearly, as long as the casting and alloy were consistent similarly with the bores. How do they get out of round?
Quote:
Originally Posted by speedrattle View Post
letting it idle away on its stand won't help to warm up the transmission gears and bushes. these wear out as well as the motor.
That is true. Well, only slowly as heat transmits to the gearbox, but I guess that leaving the engine running a little before riding off would not affect transmission either way, as long as Atilla keeps in mind the fact that the gearbox is cold 🙂

I have always been told that a gentle warm up on idle is best for an engine, albeit not too long on an air-cooled motor. Not directly related but my Bonnie engine definitely weeps less oil from under the barrel/pushrod area if I let her warm up before I head out. Not sure why but this is repeatable so something is different if I warm her up first.

Answers on a postcard..... 😉[/QUOTE]


I'm not sure if this applies to all production pistons especially on lower tune engines but I believe they are machined oval and also barrel shaped to compensate for the different thermal expansion of different areas of the piston and also to allow some slight movement of the piston in the perfectly round bore due to side loads or thrust from the con rod.
They'll also be an overall Looser fit when cold because they'll expand more than the bore when hot.
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post #9 of 33 (permalink) Old 09-10-2019, 09:17 AM
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Without even reading the other replies, I'll say I like to simply blip the throttle till it can take it without stumbling, and ride away.

Once warm DO NOT set tickover BELOW 1,000 RPM. Air-cooled engines need proper oiling at idle, and you DON'T get it below 1,000 RPM.
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post #10 of 33 (permalink) Old 09-10-2019, 11:13 AM
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tickover ? what do you want a tickover for ? -- as soon as it starts ride it - after a while ride it hard - being stopped at traffic lights or junctions is just a good reason to blip the throttle -
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