Hard Start.. Rough Idle

[Metalman77]

Ok guys..  I'm new here and am looking for a little bit of advise.  I just bought a 93 GS500E for cheap, sorta fell into my lap.  The bike ran pretty rough, really didn't want to start and idled all over the place.  So I took out the carbs and gave them a nice cleaning, replaced some of the rings, etc...

I put the carbs back in and the same problem.  The bike turns over FOREVER and eventually starts.  After starting it idles really high and is super sentive to any throttle input..  It will usually stall if I touch it.  After the bike warms up it will idle and run ok but when I give it throttle it revs and VERY slowly comes back down to idle.  I'm fairly new to bikes and carbs but the float height seems to be ok and I think I have the mixture screw set about right ~3 turns...  Also, a little blue smoke comes from the exhaust after it's been sitting for a while, but then clears after it warms up.  Valve seals???

Thanks for any help ahead of time..  I just really want to get this thing running tight so I can hit the road.

[garciabooboo24]

 i would check the timing you will need a timing gun,change the plugs,bbut it sounds to me like your floats are getting stuck. :

[scratch]

Welcome, both of you!

You cleaned the carbs, did you visually synchronize them, so they both open at the same time?  Otherwise, have them vacuum balanced.

Bike turns over forever - could be not enough compression from improper valve clearance.  A valve adjustment may be needed.

Idles high and stalls if you touch the throttle, tells me that the choke is being left on.  The choke (enrichener) is a black lever on the left handlebar, between the switchbox and the mirror mount; pull back to open the plungers in the carbs to allow more fuel to be added for starting when the engine is cold; turn it off after a couple of minutes and ride; use the throttle to keep rpm's up til the bike is fully warm.

Rpm's coming down slowly means the carburetion/jetting is too lean, or the idle is set too high.  What rpm does it idle at when fully warmed up?

[Metalman77]

Thanks for the replies guys. 

G24: 
For timing I haven't checked it, but I'm not really sure how I would go about changing it if I had to.  Is there an adjustment on or around the stator?

Scratch: 
Carbs - I only visually synched them, they open and close at the same time and are visually equally spaced when in the closed position.   However, I haven't done any feeler gauge measurments or vacuum balancing.

Valves - I haven't even checked the valves yet.  There is no clicking when the motor is running so you think the valves spacing is too large?  I will check them with some feeler gauges in accordance to the 'How To' on this site.  If I need larger spacers, do you know where I can get valve spacers for a reasonable price?

Choke - Well when it does stall the choke is usually on and the engine is cold.  However, even if you roll the throttle slowly it will cut out and stall.  I know on other bikes you can give it throttle with the choke still on, it will just idle higher.  I set the idle to about 1600 RPMS once the engine is warm..  I think I read somewhere that was the correct setting.  I guess I can try to richen up the mixture with the set screws.

Thanks again for all the help.
Josh

[MarkusN]

RPM's coming down slowly can also mean false air is being drawn. Are the rubber boots tight? Status of the diaphragms? Vacuum line to the petcosck installed and tight? vacuum pickups capped? O-rings at sid pickups in place?

Idle warm should actually be around 1200 rpm.

[Metalman77]

Hmm...  The rubber boots are tight, I did the WD-40 trick by the boots and there was no increase in RPM.  The diaphragms look good...  The vacuum line to the petcosck is also tight.  Pickups are capped..  Unsure of the O-rings at the SID pickups, what are they and how do I check?  Is there an easy way to check all vacuum lines?

Thanks.

[scratch]

There's only one vacuum line.

Click the link in this post describing the o-ring, part no. 26: http://gstwins.com/gsboard/index.php?topic=18570.msg168837#msg168837

[Metalman77]

Ok guys..  I'll double check everything and get back to you..  Hopefully I'll have this think purring by the next time you hear from me..  Thanks again for all your input.

[BaoQingTian]

I'm new here, and probably have no place posting advice, but I've asked a lot of questions and spent about 25 hours wrenching on my GS.  When I bought it, it ran about like you describe.

My biggest problem (after dirty carbs which made floats stick) was float height.  Kerry wrote an excellent U-tube method for checking it.  IMO about as accurate as calipers and you leave your bike assembled.  Mine was way too high, causing it to run rich, and flood.  It would take forever to start (cause carbs were always flooded) and if I so much as breathed on the throttle it would die.  Now I have other things that I could fix, but the bike runs pretty good.

Blue smoke is bad.  Comes from burning oil- like you said valve seals, or I think piston rings can too.  Whitish smoke is ok, just condensation burning off.

Like someone said, idle staying high is a symptom of lean running, which is exactly opposite of what I said above.  So that's kind of confusing.

Anyway, first thing I'd do is check float heights with u-tube method.

[Metalman77]

UPDATE UPDATE!  Sorry for the hold up fella's..  It's been pretty busy these days.  Well, ok the starting issue was solved!  I double checked and readjusted the float height and now the bike starts really nicely.  So that's outta the way..  OK, now the bike is varies RPM's quite a bike while idling (usually warming up).  The RPM's will race up to about 4K and then come back down randomly..  Hmmm...

Also it seems when the bike is HOT the it runs pretty rough and stalls super easy.  Just letting out the clutch a little bit will kill it if you don't hammer the gas..  So are we talkin lean or rich here? 

I think I need to replace the choke cable too..  It was looking pretty beat up.  And it will mostly but not FULLY unchoke the carb..  Are these common symptoms with a bad choke cable?  So far so good though..  Learning alot and I got you guys to thanks for it!

Thanks, Josh

[scratch]

Maybe spin the slack adjusters all the way up the choke cable sheath, so there's no threads showing; that would be completely backed off/slacked.

Can you push the choke plunger slide closed?