just got a 1985 GS550E (-ES?) and idle issue

[Dybz]

Hi,

I haven't been keeping up with this thread, and I didn't take the time to read the whole thing. So forgive me if you've already considered the following.

I really don't think engine overheating is your problem. It is possible to have a thermally intermittent ignition component, like the igniter or coils. But check the simple stuff first. Is the gas cap venting properly? It can be disassembled and cleaned. Make sure the hole in the filler neck is clear. This can get clogged when you paint or seal the fuel tank. Make sure your fuel line has no kinks and no "uphill" path to the carbs. Inline fuel filters are usually frowned upon because of the fuel restriction they can cause.

What do the plugs look like?


Thank you for your indulgence,

BassCliff

plus look like it might be a slight bit rich, but then i just figured it's from idling at stops for so long around the city. i'll look more into them via some chopping.

i don't think it's a fuel tank -> carb issue, as it continued sputtering during tuning when i had a temporary tank set up as per your carb sync DIY. i'll check the vent, but i have a feeling it's not the issue.

[Dybz]

here's a quick vid of the idle after about 15 minutes of riding. this "good" idle lasts from about 5 minutes after getting going to about 40 minutes, then the bike starts sputterring and dying. the carbs are synced as per all instructions at slightly above idle, and at idle they are just slightly <2 mm Hg off of each other as per the manual. another reason i don't think it's a fueling or tuning issue is because of this: fuel/engine has fully warmed up well before the 40 or so minute mark, so i don't think it's running rich or lean. something just happens after long riding, and only thing i can think of is overheating. i appreciate/respect any input you guys give me as i really hope to have the GS running properly.

if you guys want i can get the sputterring/dying on vid too, but probably not until the weekend. all it does it sputter/die so nothing really to gain from it i think. the carbs don't become unsynced or anything, and idle screws obviously don't move. if i let the bike sit for about 10 minutes, it runs great again until it seems to get hot... again.

http://www.youtube.com/watch?v=OlZl43Mc1rc

edit:
oh, and bikecliff, here is the vid of me tuning it. shows morgan carb sync and how it idles when warmed up. i'm all ears if you have any other suggestions or catch anything i missed in the video or something.

http://www.youtube.com/watch?v=GwkuCMMLbZY

[cowboyup3371]

How many turns out are your mixture screws?

[Dybz]

varies from 3.5 to a bit over 4. one guy i was talking to mentioned that the GS550E idle screws have much finer thread, and that the couple 550E's he's had have been out there as well due to that. i tried starting off at 2 as per bikecliff's DIY from his 850, but the bike definitely did not like that and barely ran.

[Dybz]

only checked battery during idle with volt meter for now, but it sits around 13.8, normal as per bikecliff's info. when bike is off it is around 12.8, and with ignition in on position and light on it's at 12.3... again, normal. i'll ride it around this weekend and see if it goes hay-wire after a bit of riding, but for some reason i doubt it will lol. any other ignition system spots i can test voltage after riding?

[Dybz]

battery voltage is solid before/during/after riding. i took plugs out and they seem in bad shape. ordered a set of new ones and plug boot/seals on top of that since old ones seem to be in a bad way. i kinda said screw it and reset all idle screws to 2.5 turns out today before checking plugs, and bike seemed to run better/longer on that than when i had them "tuned" in... it did still ended up starting to sputter and die after about 10 miles of riding.

tried to get it in garage to tune while it was sputtering, but nothing seemed to fix the issue. fueling is not the issue as fuel is flowing through the inline filter, even when it's throwing its fits. checked the gas cap and petcock and everything fueling related as well, all good.

any other suggestions?

[Dybz]

got a compression test tool today and all cylinders fall right around the 1100 kpa mark (normal as per manual = 1000-1400). waiting for the new plugs/boots next week. leave the country for 3 weeks next thursday, hoping the parts get here before then.

[Dybz]

replaced plugs/plug boot seals yesterday. rode the bike for a good 18 miles today and it seemed to still be decently happy at the end of the ride. seeing as it's a nice balmy 95 or so here today i'ld say we have success. i did also retune it after a long ride yesterday and i think i set all the screws about 3-3.25 out rather than the 3.5-4.5 they were before so that may have helped as well. it's a bit tougher to warm up and take off the choke now, but who cares if it's running right during the actual riding.

thanks to everyone for all the help. hopefully this'll be my last post in the "issues" portion of the forum haha.