Drsus-
Brother, I have 40 years with Brit bikes and I started with a TRident which we all know is a lot more funky than a Commando and I have NEVER heard of idling too long as being an issue and I live in the southern US where its as hot as the devil's balls right now
yeah, I've done this with many of my bikes and never had issues but some pole here are warning me a bout it so I'm taking that into account. Ive idled the bike for long periods of time in the past with no issues though.
- Always remember that the Commando is an extremely simple motorcycle and that any issue is ALWAYS the simplest root cause. Again - simplest root cause
There are only 3 things involved in a relatively healthy motor starting and running - Fuel, Spark, and timing. That's it, nothing else.
Fuel -
- You mentioned that the float bowls flood as normal, So, it is not the tank vent. If it starts, runs for a short period of time and dies, check the vent. Next, drop the float bowls. You can do that without removing the carbs. Inspect them for something obvious like a lot of trash and clean them with carb cleaner. Next, pull the jets. Again, you can do this with the carbs still in place. Check them carefully and make sure they are not blocked. While the jets are out, look at the bottom of the exposed needles and make sure one is not obviously lower that the other. If the jets are clear and you don't find anything obvious, put them back together. Your problem is not fuel. I caution you not to over think carburetors. Amals are really simple and really reliable and they don't fail catastrophically, they just get sloppier and sloppier as they wear out. I chased gremlins in the 3 trident carbs for years and years till on a visit with Les Williams in England he explained how they work and helped me recognize that my issues were all in the ignition.
I just rebuilt these amals, one of the carbs was sticking and would keep flooding when I tickled it so I went ahead and re did both of them, it was running great aside form dying at idle after ridding for a long time. I was actually letting it idle this ling this time around to see how the idle would behave as the bike got hotter and I had set a good idle for it and then it died for good. Before when it would stall at idle after a long ride it would still kick start juts fine again, this seems like a new issue separate from that
Spark - OK, if all of the above went well and you have ruled out fuel delivery; lets check the spark. First - put the key in the ignition and turn the bike on and check that you have lights and horn. If these systems are not working, you have a short circuit and it should be obvious because the bike was running. start looking for a lose wire or something melted. Assuming that this checks out and you don't have a general short or electrical failure , pull one of the plugs. Clean and gap it and hook it back up to the spark plug lead. Lay it on the side of the motor and with your garage relatively dark, kick the bike over and check to see if you have a spark. If you have spark , the problem is timing which we will talk about below. If not, go to the kill switch on the handle bars and clean the contacts and check again for spark. If you now have spark, you are good to go. If not, the problem is in the ignition system. If you have electronic ignition, check the box. (When you are under the seat be careful. My MK3 has a capacitor that will light you up if you are not careful).
its not spark. I have a good healthy blue spark out of it. I've bypassed the kill switch a while ago, I still tested for spark with the switch moved from one position to the other just for shits, all good
Timing - If you determined that your fuel delivery system is normal. And you had spark at the plugs and it still won't start - the only thing left is timing. Static time the bike and make sure the advance unit moves freely.
Once you've been through this model the bike should start. You should be able to do all of this in a couple of hours. I'm not saying that your problem isn't some bizarre multifaceted cascading multi-system bla bla bla one in a million event - Well, yes that's exactly what I'm saying
Let us know how it goes
Cheers,
Cameron
