1980 GS550L will not idle when hot

[Mfraumeni]

I recently purchased a 1980 GS550L that seems to idle fine off choke after warming it up and can rev without issue. The problem is that after I ride it a bit and it gets really warm/hot it will not idle. When this happens it can be hard to restart as well, but I have always been able to get it restarted (I did bump start it once since I was at the top of a hill and could not get it to restart using the starter). I have read it could be bad coils, sticking valves, bad rectifier, clogged carb and more. I was wondering if anyone has had a similar issue and how you fixed it.

[Nessism]

What maintenance have you done? Adjusted the valves? Checked the charging system voltage?

You might want to check the Newbie Mistakes thread linked in my signature.

[Mfraumeni]

Hi,
I have not done any of that. I had a mechanic that works on older bikes do some work like new tires, bars (since the stock bars are awful) and to adjust the carbs. He didn't touch the carbs because he said it was running perfect but added some seafoam just in case. Igot it back and it did the same thing. He could not get it to die and asked me stupid questions like if I kept the choke on while riding, but he obviously was not test riding it long enough. After arguing with him and letting him know I am not an idiot he agreed to test ride it again for a longer distance. He did and it died on him once he came to a stop. He charges quite a bit per hour so I was not going to have him dig into it since he thought he was going to have to replace the valves. I posted here because I heard people say they had idle issues caused by the coils when they got hot. I was asking for examples of similar experiences. I can change coils. I do not know how to adjust or replace valves.

[Grimly]

Nobody knows how to adjust valves when they're born.
Honestly, it's not a big deal to do, even the first time. Second time's a breeze and after that it holds no fears.
There is lots of help here and other places should you decide to do it yourself.
If you want to run one of these older bikes, you really can't afford to pay a mechanic's time to do all the small but essential stuff it needs. It ends up being a money pit. Apart from that, most mechanics these days know next to nothing about any bike older than ten, maybe twenty, years old.
Valve clearances are essential maintenance. Without them being done, it runs like a bag of crap, then gets damaged internally, and the cost of fixing it would put it beyond economical repair.

[Nessism]

Honestly, I strongly suggest you read the newbie mistakes thread and then ask yourself if you want to own a 40 year old motorcycle. Unless you have a lot of money to pay a mechanic, plus you can find a good mechanic, you are going to have to do the work yourself.

[Rob S.]

And if you decide you want a mechanic, look for a racer. Not in his 20's. Does he have examples of old, air cooled bikes in his shop? Racers, builders, tuners are the best mechanics (men in their 50's). Does the shop have a dino?

Otherwise, read everything you can. Watch (live or on-line) others doing the work.

[rphillips]

Yep, what he said. A good rule of thumb, find a mechanic that is older than your bike.