is this a carb or a charging system issue???

[snowbeard]

Hey all,
I have been having a very high idle after I get the bike really warmed up, say after a nice shot of highway speeds for five minutes, the idle is set to be right about 1200 +/- when sitting, and I adjusted it some time ago to be pretty spot on. just lately it's started creeping up after a run, but it idles normally at start up after sitting off for awhile...

at first I thought it was a stuck slide in the carbs, but I tried tapping on each one and it didn't change.

then today I realized that my headlight was off, as I did remove the tab that stops it, so that I can start more easily (actually I just can't stand to have anybody tell me not to do something, so I had to chop it :roll: )

I haven't had any real trouble out of my electrical aside from a loose turn signal wire, but I wonder if this might be the result of my reg/rectifier starting to go? or could it just be extra charge building up since I had the light off. I know I've heard that the headlight is pretty critical to the charging system.... anybody got any ideas??

thanks a ton!

[Anonymous]

My GS550 does the same thing. My idle is set to 1200 when sitting, but after I go for a fast run (like on the hwy), it idles around 1400 - 1500. But it can drop back down to 1200 if I do more slower driving after the fast driving.
I'm guessing that my carbs need to be synced?? Just a guess though...

[snowbeard]

perhaps, but I think the carbs are in pretty good sync...

when mine does it it idles up to 2100 usually, the last few days (with the headlight off) it's been more like 2900-3100 8O !!! it did also drop when I turned the light back on this morning, reinforcing my electrical ideas....??

[Mobetter]

Sounds like an air leak to me.
I don't think the headlight and the engine revving
have anything to do with each other.
Merely a coincedence.


Mo

[snowbeard]

not making the connection, what kind of air leak would you think might cause this?? in the carb to engine connection? another? please expound :?

the headlight and the change in idle is an experimentally derived conclusion, I turn off the light and the revs kick up by 2-300 RPM. back on and they drop?

it could still be just a stuck slide, perhaps as the temps rise, the metal expands enough to make it stick, where as they moved fine when I had the carbs off cold...

[Anonymous]

not making the connection, what kind of air leak would you think might cause this?? in the carb to engine connection? another? please expound

That would be a vacuum leak that Mo is talking about. Check your intake manifolds, vacuum nipples, etc. with either brake cleaner, starter fluid or other as described in several threads here.

Mark

[snowbeard]

so it would be getting too much air then? I would think a leak between the engine and the carbs would cause a lack of vacuum and therefore less gas to be pulled in from the carbs thru the idle ciruits...

what would said vacuum nipples be?

thanks for the help guys, I am just getting this small engine repair thing a little slowly!!!


edit:now that I knew what to search for, that makes lots of sense. I'll spray it down soon as I can, I think the water idea sounds a bit better, as I don't relish spraying down the engine with ether!! sounds like a good way to lose a bike!! 8O

[Mobetter]

The air leak could be between your carbs and the engine, between
your carbs and the air box,where your air filter attaches in the airbox
and or where your airbox side covers attach to the airbox.
Any and all of these places are possible sources of leaks.

Use the search feature and search, air leak, induction boots,
manifold O rings, etc. etc.
You find lots of info, it's been discussed to death on many occassions.

Gods Peace
Mo

[snowbeard]

hmmm... I would have assumed that the leak would have to be between the carb and the engine in order to really make a difference in how the idle circuits were pressurized (or vacuumized, however you look at it...)

but that brings up an interesting point. I have not had both clips to close my airbox with since I got the bike, but just recently got one more and now close it all the way... perhaps that could be the source of the problem...? I had been asking about trying to change the airbox out for one of those harley looking cone shaped filters on a stalk, but the concensus seemed to be "don't fix what ain't broke" so I quit the idea.

I did try adding a hole on the outside cover of the airbox (so as not to bypass the filter itself) to make up for the new restriction, as the bike ran pretty nice with only one clip. maybe another speed hole?

[KEITH KRAUSE]

The most common reason for high idle as the engine warms up is the o-rings in the manifolds get hard and crack. The manifolds themselves may be cracking. If you're real lucky, the clamps on the manifolds are loose.
When replacing the o-rings, apply some hi-temp' bearing grease to help them last. Torque to 6 ft/lb.