Have a new 2023 Bonneville T120 bought in October; have put on 170miles. Quite cold here in Indiana today; 40F, 4C BUT the sun is shining, sky blue, couldn't resist a 2 mile ride around the subdivision. What a rush; price was Popsicle cojones. I let the engine warm up for about 10 minutes in my 40F garage and then took the ride. Engine has original factory supplied oil. Now for the discussion and confluence of opinions: Considering the cold temp and its effect on the oil, better to not run the engine???
For a bike in storage or laid up for the Winter, I would say better not to run the engine. If you're actually riding it, albeit infrequently, I would say no problem. I use my Street Scrambler all year round in temps close to freezing and usually let the engine warm up for a few mins beforehand. If it's a relatively short town journey I let the bike idle in the garage, until the fan kicks in, on my return.
I discussed this issue with some mechanics in the past for a long time. Our/their conclusion was. You can ride your bike at any (very low) temperatures. Just keep the engine speed at a low level for the first 10 kilometers to give the engine and all fluids some time to warm up. After this "slow" ride you can speed up without any issues and worries. In their opinion a warm up in a garage is not useful.
I am guessing that the reason for a warm up in the garage is not good is that at that time, fuel injection is at full rich especially on a cold day; hence, dumping more gas into each cylinder that can be burned and maybe getting past the rings and diluting the oil.
And it does tend to set-off my smoke alarm in the basement if I let it run more than a couple of minutes.
On a cold start, especially in cold ambient temperature, condensation will form inside the engine crankcases which will tale a LONG time to evaporate, if it ever does, by just letting the engine sit there idling. Riding the bike will not only warm it up quicker but you will get better crankcase ventilation with higher engine revs and load. This is ESPECIALLY true with diesels which generate comparatively little heat idling with no load. Bore wetting from unburnt fuel is also more of a problem on diesels, hence their need for glow plugs or some other intake charge heating device to achieve sufficient combustion during the first few seconds of cold running.
You should warm it up a little bit before taking off depending on the temperature and the oil you're using. Cold, thick oil will flow thru the bypass valve rather than the filter when the engine gets revved up too soon.
I strongly agree with Pegscraper. With idling in your garage you prolong the cold start period quite a lot which takes strain on the engine. If you immediately (ok, maybe after 20-30 seconds idling) start to ride, your engine will warm up much quicker and hence the cold start period with increased wear will be shorter than the way you do it. In Germany it would actually be forbidden (!) to keep your engine idling for warming up. Every car engine works exactly the same way - you also don't idle your car for 10 minutes before you go, isn't it? Just don't (regardless of the outside temperature) do high revs before the engine is warm and you should be fine.
Am impressed by the feedback on the idling on cold days; great sharing of info by the forum members. To round the idle question off, I took a look at the oil and ambient temp spec in the 2023 owners manual on page 111; looks like the synthetic low end range for 10W40 and 10W50 is 14F (-10C) degrees; can't imagine ever running below 40F anyway; well, might get desperate once in a while. I have now changed my startup habit for my engines. Thanks a bunch!!! Update: Couldn't resist going into the garage and starting up the Bonnie; nothing like that Triumph exhaust rumble; right up there with the rumble from a HD.
