Dies On Idle

So I've just got my 1973 CL350 all synced and tuned up. I have about a 17 miles trip to work, about 40% of it stop and go traffic. The rest is just a straight line of some pretty steep rolling hills. By the time I get to work it just doesn't want to idle. It will start right up again just fine I just have to give it some steady gas to not die.


What am I doing wrong? It idles perfectly at 1100 rpm's until the last 5 minutes of my commute, which is about 30 minutes, then it just seems to get tired.


Any suggestions?

If it idles fine when cold but dies when hot, I would check your valve clearances. Is it difficult to start when hot?

bob.

Running a bit lean can also cause this.

Jacob, you're in Denver, right? If your bike was originally delivered to a showroom closer to sea level it would not be uncommon to experience that problem if it were then brought to the mile high city but never rejetted. My own 360 suffers from this exact issue when I take it into the mountains and start getting above 3000 ft.

Yup I'm in Denver and I just rejetted it to match the altitude. Sparks plugs show that I'm not running too lean or too rich. I should also mention that the carbs are Mikuni 30mm with K&N's. I'm wondering if oiling the filters would make a difference. I oiled them up before installation but they are starting to look a bit dry.


As for the valve clearance, I'll have to give that one another look. No issues started at all when warm. It starts up with just one light kick everytime.

Cool. That's one less thing to worry about (probably).

After the bike dies in these last five minute of riding, will it start right back up again and idle just fine or does it continue to die?

It always starts back up and idles for about 15 seconds then just slowly dies. Once it's cooled down, it's back to normal again.


Thanks for the help.

I'll stick with my original guess and say it sounds lean.

Turn each of your mixture screws out half a turn and see if the problem is better or worse.

I've been in Texas all week for work so I haven't had a chance to mess with the mixture screws at all but I was thinking... Is the reason you believe it's running lean because once it's hot it atomizes the fuel before ignition?


Sorry if this is a dumb questions, I'm a noob.

Jacob Agaetis said:

I've been in Texas all week for work so I haven't had a chance to mess with the mixture screws at all but I was thinking... Is the reason you believe it's running lean because once it's hot it atomizes the fuel before ignition?


Sorry if this is a dumb questions, I'm a noob.

Click to expand...

Actually, you want complete atomization of the fuel prior to ignition. Only atomized fuel burns; liquid fuel does not. This is precisely why a choke is required when the engine is cold. You need to add extra fuel because it doesn't atomize as well during cold operation and so you toss in the extra amount. The additional fuel atomizes just as poorly, but because there is more of it, the atomized concentration with the air increases.

Also, please forgive me, but I got things switched up in my head and was telling you the wrong info in my previous posts. As I just described, cold engines need more fuel in order to achieve the correct atomized fuel/air ratio. If an engine runs better cold than it does hot, then it's getting too much fuel. Turn the screws IN half a turn, not out.

Also, what Bob said. Valve clearances could be an issue as well. As the engine heats up, the valves and rockers all expand by a slight amount. This can lead to valves opening too early or closing too late and it's possible that this can lower the compression enough at low RPMs to affect the running of the bike. Interesting enough, this also has the effect making the bike run stronger at high RPM.

Which part of the ride is the stop and go? In the beginning, or at the end? I've heard the 350's don't have a great charging system, and you have to idle at 3000 RPM to even start charging. If you follow Rocan's build, I believe he mentions this many times.