Not another idle problem

[smokedogg]

Hi guys,

This may sound kind of noobish, but please bear with me.

Ok, now I have tried all the tricks in my own book and the FAQ on GSTWIN and need some expert advice.
Bought a GS 500 mod. '95 with some minor problems. One of the problems being that it is not able to idle below 3.000rpm without dying.
I'm able to hit the golden spot when using the throttle, but it may suddenly jump from 1500rpm to 4000rpm. This would suggest a leak, but I'm not able to detect it.
The bike goes really nice when driving. I just can't get the bleeping thing to idle. 

I've done the WD-40 test with no result. (Engine intake, and above and below the carbs)

I've checked chooke/throttle for proper action

I've ripped both carbs apart several times and inspected all o-rings. All of them look fine. Carbs have been cleaned in carb. cleaner with a toothbrush.

I've reset the AIR adjustment screws to 1and7/8

I've tried a lot of adjustments with idle screw, but either the result is an idle above 3000rpm or an engine that shuts off. 

I've tested the vacuum tube to fuel chicken for proper vacuum (no leaks in hose or carb intake)

The only thing I've not tried yet is adjusting valves. Is this really the only thing left, that can be causing the problem if all of the above is OK?

BR
Allan

[waiho]

had the same problems, and did the same as you did

to realize I just need to check the valvel clearance. Had a friend help me with that

if it's not that, then I dunno 

check here for help http://cgi.stanford.edu/~sanjayd/gs500/Maintenance/CheckValves

[ohgood]

1 adjust your valves, they smooth out allot of things
2 sync your carbs, this smooths out things too
3 make sure you have new spark plugs, and do plug chops (google "plug chop howto")

did you already rule out electrical problems ? you may have an intermittent short.
is your choke circuit working ?
got good compression ?

i'm betting there is a cracked plastic cap, or a cracked nipple on the plastic cap. possibly a split rubber vaccuum boot.

are your slides moving freely ?

good luck !

[smokedogg]

I'm pretty convinced that the Valve adjustment thing is a pretty good idea. Unfortunately I can't check it before I find thickness gauges in the right range.
Pretty hard to get a hold of anything below 0.05mm around here. I have done some measuring on the shims with a 0.10mm gauge which was all I had. It didn't fit in any of the valves. But that doesn't really tell me a lot. Will try to track down the tool tomorrow.

I've just replaced my rotor and pickups, because of spark trouble on right cylinder. Haven't seen spark problems since. The bad idle did not change after this operation. Also checked the wires / resistance in coils / connectors when i changed that. All seems OK. Including the new spark plugs I put in.

Fine compression as far as I can tell.

No cracked plastic on top of the carbs either. At least not visible.

But the search goes on. . . 

[smokedogg]

Quick question:

Just ordered a thickness feeler ranging from 0.04mm to 0.08mm. Just like the one Kerry is using is his excellent valve video. 
But it being the holidays and all, the thickness gauge won't reach me until next week at best. I need the bike for transport everyday, so I need some tricksters to greenlight my little idea below:

I have in my possession a gauge on 0.1mm.
If 0.1mm gauge won't fit in any of valve clearences, the shims can't be more than max 0.01mm bigger than the spec.

And if I can freely spin all of the shims/buckets, the shims can't be dangerously tight.

That should keep me rolling until the more sophisticated tools arrive. Right ? ? ?

[smokedogg]

Well I just checked my valve clearence. All was able to move freely except the left exhaust valve. This is very tight. I'm able to spin it with some force. I'll have that changed.

Just took a picture of my intake boots. Is the rust critical and shouldn't there be some kind a gasket between the cylinder head metal and the boot metal?
http://img187.imageshack.us/my.php?image=billede001ae1.jpg

[smokedogg]

Today I finally found myself a used carburator + intake boots + CDI. Replaced all parts and said my prayers. But nothing changed. Still can't idle. . .

Guess I'll just have to live with either stall or 4000rpm when idling at the stop light. 
Or perhaps to buy my bike at the other side of the street next time.

[beRto]

Did you finish the valve adjustment yet? How about the carb balancing?

Thanks for following up with this thread!

[smokedogg]

Hey

I did as mentioned earlier check for free shim rotation and found one exhaust valve to be very tight.

I'm awaiting tools to do the job. Suki lift-tool / 0.4-0.8mm gauge. My Suzuki mechanic told me that tight exhaust valves usually isn't the cause for idle problems. But what do I know? I use to drive Honda. 

I don't own a vacuum tool for sync. But I tried adjusting it with no real improvement either counter- nor clockwise.

[beRto]

Hey

I did as mentioned earlier check for free shim rotation and found one exhaust valve to be very tight.

I'm awaiting tools to do the job. Suki lift-tool / 0.4-0.8mm gauge. My Suzuki mechanic told me that tight exhaust valves usually isn't the cause for idle problems. But what do I know? I use to drive Honda. 

I had read that you found a tight valve, but it was unclear if you fixed it. If I understand you, the tight valve has not yet been fixed.

I don't own a vacuum tool for sync. But I tried adjusting it with no real improvement either counter- nor clockwise.

You can build your own tool for next to nothing. There are some related threads on GStwin. I like this description: http://www.powerchutes.com/manometer.asp  I used 2-stroke oil in mine and it worked well.

Be careful adjusting without a gauge because small adjustments can have a big effect.

Another thing to consider is the air filter. What is its condition? Any holes or problems on the sealing surface?

[The Buddha]

I've reset the AIR adjustment screws to 1and7/8

BR
Allan

Why 1 and 7/8th, why not 1 1/2 or 2, 1 and 7/8th huh ... extremely precise there aren't ya ... especially since I cant even tell if its actually 1/4 ... must be old age telling ...
Anyway 3 is the minimum for it I'd say, more like 3 to 5 for most people. Rare cases are under 3 and almost never under 2.5. Stock is 2.5 and its lean - olsen twin lean.
Cool.
Buddha.

[smokedogg]

I found the 1 and 7/8 turns specification in the Haynes Chapter 4.

UK K,L,M,N and P model - 2 1/4 turns out
UK R & S model - 1 7/8  turns out
UK T and V model - 2 turns out

One complete turn is easy. Then I imagine the screw is a clock and I turn it 52,5 minutes.
In my book that should be 1 and 7/8. 

[smokedogg]

I have build my own carb sync tool following the instructions given by beRto. Will be trying it out tomorrow.

One thing confusing me quite a bit: Why is the Main Jets in my carburators not the same?
122.5# in the right and 125# in the left. That doesn't make much sense to me? My local mechanic gave me two 120# jets he asked me to install instead.
What do you guys say?

[smokedogg]

Update:

Had to start the bike when going home from work. It was freezing and snowing very much. Like 10 degrees fahrenheit. The bike just couldn't start and after a minute the battery was dead. Next day I recharged the battery and bang she finally started.

I need the bike everyday, so I brought it to my local Suzuki dealer. He replaced 3 shims and cleaned the carb. She runs like a charm now. Nice idle and easy to start. I peaked at 180km/h on my little testride. Impressive I must say. I think she can go even faster under right conditions.

Unfortunately the certified help, put me down $550. Vampires.

But now I'm finally running... 

Thx for your help

[beRto]

Update:

Had to start the bike when going home from work. It was freezing and snowing very much. Like 10 degrees fahrenheit. The bike just couldn't start and after a minute the battery was dead. Next day I recharged the battery and bang she finally started.

I need the bike everyday, so I brought it to my local Suzuki dealer. He replaced 3 shims and cleaned the carb. She runs like a charm now. Nice idle and easy to start. I peaked at 180km/h on my little testride. Impressive I must say. I think she can go even faster under right conditions.

Unfortunately the certified help, put me down $550. Vampires.

But now I'm finally running... 

Thx for your help

Glad you got it sorted out!