Strange Idle Pattern

[Guest]

1. My 1980 GS550 will idle normally (about 1100) at cold start, once it's off the choke.

2. Once moderately warm (after about 15 minutes of riding) it will bog and stall at stops.

4. When hot (like after riding for an hour on the highway in yesterday's 85-degree temps) it will idle way too fast. Sometimes it will come down if I blip the throttle but usually not. I did lube the throttle cable two weeks ago.

I hope this pattern means something simple is out of adjustment, that I can fix when we sync the carbs next weekend. Ideas welcomed with much thanks.

[hampshirehog]

Sounds like there's an air leak. Have you replaced the inlet stub O rings?

[Nessism]

How about more information on your bikes maintenance? What is the condition of the carbs (clean and O-ring condition), valve adjustment, carb sync, intake boots and their O-ring condition, are their any mods on the bike, gas tank clean and free of rust, etc. It's impossible to troubleshoot unless all the maintenance is up to date and any mods are thoughtfully applied.

[FiremanBob]

Thanks. I only bought the bike about four weeks ago. I have changed the oil (and it has stayed at the same level since) and done a coil relay mod so far. Have not yet taken the carbs off. The intake boots seem to be fairly fresh, with no visible cracks.

When the parts arrive next week I'll be doing a valve check, sync the carbs, compression check, and install new choke cable.

[Nessism]

Thanks. I only bought the bike about four weeks ago. I have changed the oil (and it has stayed at the same level since) and done a coil relay mod so far. Have not yet taken the carbs off. The intake boots seem to be fairly fresh, with no visible cracks.

When the parts arrive next week I'll be doing a valve check, sync the carbs, compression check, and install new choke cable.

Okay, good job. It's best to take care of maintenance tasks like you are up front instead of waiting for the bike to break down.

I strongly suggest that you go though the carbs too while you are updating everything. The intake boot O-rings are almost sure to leak unless they have been updated lately, and the carb O-rings have been soaking in gas for 30 years so they are do for a refresh too. If the carbs are not overly dirty you won't have to dip them long so the entire cleaning job can be done in one day. Check my signature for a link to the carb rebuild tutorial.

Good luck and keep up the good work.

[Steve]

. Have not yet taken the carbs off. The intake boots seem to be fairly fresh, with no visible cracks.

That's OK, you can rely STRICTLY on appearances.

If I remember correctly, these boots APPEARED "fairly fresh, with no visible cracks".


See that gap in the o-ring just left of top center? Yours can look like that, too. If so, that's the source of your problems.

As I just posted in another thread, ...
We keep telling you guys and telling you guys, ... THERE ARE NO SHORTCUTS.


.

[JEEPRUSTY]

Okay, good job. It's best to take care of maintenance tasks like you are up front instead of waiting for the bike to break down.

I strongly suggest that you go though the carbs too while you are updating everything. The intake boot O-rings are almost sure to leak unless they have been updated lately, and the carb O-rings have been soaking in gas for 30 years so they are do for a refresh too. If the carbs are not overly dirty you won't have to dip them long so the entire cleaning job can be done in one day. Check my signature for a link to the carb rebuild tutorial.

Good luck and keep up the good work.

I had my bike acting the same as yours until I replaced carb o-rings.
It was flooding when it warmed up for want of a better term.

It would flood so much when it got warm it would stop running completely even when running at high RPM.

[Allie]

That's OK, you can rely STRICTLY on appearances.

If I remember correctly, these boots APPEARED "fairly fresh, with no visible cracks".


See that gap in the o-ring just left of top center? Yours can look like that, too. If so, that's the source of your problems.

As I just posted in another thread, ...
We keep telling you guys and telling you guys, ... THERE ARE NO SHORTCUTS.


.

Oh come on, sure there are! Just slather gobs of RTV around your intake boots! Oh wait, that's the shortcut to being hunted down like a dog by the GSR posse.

[FiremanBob]

Thanks, guys. I know the hard way the ZAMM lesson that you can't cheat machinery. Guess I'll be pulling the carbs then next week, too. What I need is a full day of rain and 70-degree temps, but we're supposed to get the Midwest heat wave next weekend.

What's the most cost-effective source for carb boots and o-rings?

While I'm asking, what size are the adaptors for the carb sync ports? I have some 5mm ones from my old Honda.

[Allie]

Thanks, guys. I know the hard way the ZAMM lesson that you can't cheat machinery. Guess I'll be pulling the carbs then next week, too. What I need is a full day of rain and 70-degree temps, but we're supposed to get the Midwest heat wave next weekend.

What's the most cost-effective source for carb boots and o-rings?

While I'm asking, what size are the adaptors for the carb sync ports? I have some 5mm ones from my old Honda.

http://cycleorings.com/ for all your o-ring needs! You may not need boots, at least not yet, if they are truly crack free and pliable. If you have the money it's probably easier to replace them while you have them off, cause it's only a matter of time.

Don't feel bad, it only took seeing my intake boots spitting water all over the place after starting a wet bike to light a fire under me. Ahhh denial...

[FiremanBob]

Thanks for the link. I just ordered o-rings and 16mm screws.

[Steve]

To answer your other question, the 5mm sync adapters are fine.

.

[Allie]

Thanks for the link. I just ordered o-rings and 16mm screws.

I forgot - yes, those allen screws are verrruh nice!

[FiremanBob]

Just to close out the original question: Last weekend I installed the new o-rings and re-installed the carbs. The bike runs better than ever now, idles smoothly without stalling or racing at any temperature.

Thanks for all the good advice, and kudos to Robert Barr for his excellent products.