Extremely Frustrating situation with my bike. HELP!

[The Cable Guy]

Okay, so about 2-3 months ago, my 2005 GS500F started to give me problems (around 28000 mi) . The bike would become extremely hard to start in cold weather. On top of that, if the RPM dropped under 3000 RPM. the bike will eventually die by itself. It basically does not idle. I either have to keep blipping the throttle, or have the choke/idle adjustment screw set so that the RPM is at 3000 RPM. Eventually I gave up trying to ride like this and took it to a shop on a warmer day when I could get the bike running.

Everyone I consulted told me it was probably a carb issue, so I took it to a shop to get the carbs cleaned.
Mechanic was piecing back the bike, and couldn't get it to function right, he blamed it on a vacuum leak. He ripped out all the emissions equipment for CA smog and claimed to have fixed the problem.

About halfway home from the shop, when the bike warmed up completely, RPM jumped again to 3500 RPM. I went home, adjusted the idle knob to about 1500 RPM, it would not hold steady and would either jump up to 3000 RPM or dip under 1000 RPM and die. Problem was not fixed.

Took it to the same shop, they suggested I replace the jets. We did that, still no good. He then blamed it on a leak in the intake manifold and replaced the o-rings. Apparently there was a vacuum leak he couldnt find, and so he gave up and I took the bike home.

I took it to another shop nearby and they performed a compression test and found that the bike had little or no (did not clarify) compression in one of the cylinders, and I was basically running on one. They're dumping some chemicals inside the cylinder to see if they can expand the rings for a temporary fix.

Clearly the first shop had no idea what they were doing, the second shop is on the right track, but I wanted to see what the specialists here have to say.

Could it be a bad/stuck valve causing this? What do you guys suggest I do?

The shop quoted me $1400 to rebuild the motor if it comes down to it, but they suggested I just put it towards a new bike if the motor is bad.

this has been going on for almost 2 months, and I have been forced to sit in traffic this whole time, someone please help! I need to get back on 2 wheels

[007brendan]

Ditch the motor.  I've seen people sell working motors on here for $300-500.  Or, you could part the bike out and put it towards a new bike.

[007brendan]

Two motors for sale right now

http://gstwins.com/gsboard/index.php?topic=53876.0

[BaltimoreGS]

Have you checked the valve clearance?  If one valve is not closing completely it will give you no compression on that cylinder.

-Jessie

[Big Rich]

+1 to the valves.

Get yourself a compression tester from a parts store - they are around $30. Do the test on the low cylinder after the motor is warm - once you get that reading, add a teaspoon of motor oil through the plug hole. Test it again, if the numbers stay the same it's your valves.

[JAY W]

"add a teaspoon of motor oil through the plug hole. Test it again, if the numbers stay the same it's your valves"
This is false (sorry BigRich) it will tell you if there`s a prob with ring/cylinder wear.(the oil seals the pleasure leakage)

[The Cable Guy]

Thanks for all the suggestions guys, I just took the bike home from the shop, they adjusted all the valves and the bike no longer dies. I still notice some high idling that comes and goes, mainly stays though.

[Big Rich]

"add a teaspoon of motor oil through the plug hole. Test it again, if the numbers stay the same it's your valves"
This is false (sorry BigRich) it will tell you if there`s a prob with ring/cylinder wear.(the oil seals the pleasure leakage)

I should have been more specific / thinking clearly - sorry. If the pressure is low on the first test and low after adding oil, then it's a leaking valve. Basically the oil in the cylinders will only change the pressure if you have MINOR leaking around the piston rings. Busted rings will let it right through.

[The Cable Guy]

Okay, no I adjusted the idle screw all the way out, it will not back out any more, and I don't want to force it more than I already have. It now idles at about 1500 RPM, I can't get it down to 1200 RPM.

When rolling off the throttle, it seems to lag at 2900 RPM for a good 8-10 seconds before calming down to idle at 1500 RPM.

No leaks, carbs clean, valves good. Carbs should be synced as well. What else am I missing? Do I need to fiddle with fuel/air mix? If so, how do I do that?

[mister]

Does this idle lag happen when riding or when just sitting there on the sidestand with the wheel slightly turned? Is the throttle returning to its normal position?

Michael

[viggen]

My bike had a weak left cylinder (low compression, around 90psi hot, right was 150psi hot), and I had similar stalling issues.  The bike would idle with the choke on, normal idle range would make it slowly die.  I added oil through the spark plug oil and the compression shot WAY up, so I figured it would be rings.  But I think I added too much oil and took up a bunch of space in the cylinder, effectively raising the compression ratio.  I had a really really tight exhaust valve that had some carbon/burn marks on it when I pulled it.  Lapped in a new valve and put in new rings and she's run like a champ for the last 700 miles *knock on wood*.

You can get all of the parts to do rings for around $200.  Haynes manual or Chilton as well as a place to work is also necessary.  I did not pull the engine.  You can probably borrow a torque wrench and honing tool from autozone. 

When you check the valves, you can see the head nuts.   When you remove these, the head and cylinder block can be separated and removed from the crankcase. 

It was my first time delving this far into an engine.  It was a choice between parting out, selling as-is, or spending the same amount of time learning something cool. 

Good luck, let us know how it goes!

[Big Rich]

Okay, no I adjusted the idle screw all the way out, it will not back out any more, and I don't want to force it more than I already have. It now idles at about 1500 RPM, I can't get it down to 1200 RPM.

When rolling off the throttle, it seems to lag at 2900 RPM for a good 8-10 seconds before calming down to idle at 1500 RPM.

No leaks, carbs clean, valves good. Carbs should be synced as well. What else am I missing? Do I need to fiddle with fuel/air mix? If so, how do I do that?

You shouldnt need to mess with the mixture screw. Check the throttle cable though. It can hang up at the mount to the carbs and around the throttle grip.

[ohgood]

there is a thread about hanging idle. check it out.