04 gs500 exhaust popping

[mchollan]

I hoping someone out there can point me in the right direction...

I bought a non-running 04 gs500 for some pocket change thinking I could get it running so I could have a bit of fun.  I replaced the starter clutch and clutch cable to get it starting.  I also replaced the oil filter, oil, air filter, spark plugs, and cleaned the carbs up.  Now it starts and runs but I get some popping and loss of power around 4500 rpm. 

My initial thought was I forgot to tighten something or missed a gasket in the carb when I put it back together so I went though and made sure all the gaskets were in place, and everything was tight and but it back together but I get the same problem.

I started to look for vacuum leaks when I noticed the when I get carb cleaner in the right carb the rpms increase (expected behavior) but then i shoot carb cleaner in the left carb i can see the fluid start to evaporate but I get no change in the engine rmps. 

I know that cylinder is firing, the exhaust on that side gets hot after a few seconds of idling and it idles fairly well.

Does anyone have any ideas?

[jestercinti]

Most likely have a lean mixture.  When you said that you "get carb cleaner in the right carb" the RPMs increase.  Are you spraying around the boot, or directly into the carb?

I'd start with the carb boots.  Make sure that the seal is good and tight.

[mchollan]

initially I was spraying around the boot looking for a leak.  When I didn't find anything I sprayed directly into the carb.  Spraying in the right carb increased the RPMS, spraying directly in the left carb had no effect.

Do you think just the left side is running lean?  Can I adjust the needle jet to enrich the mixture on that side?

[Dizzledan]

On the bottom of the carbs are mixture screws (1 per side) that control the fuel/air mix. Normal setting is 2.5 turns from full in I believe.

[mchollan]

I don't see mixture screws, instead there are two "plugs".  I am assuming the mixture screws are behind the plugs but I don't want to screw something up drilling out the wrong thing?  Is the mixture screw behind one of these plugs?

[ATLRIDER]

The fuel mixture screw should be underneath the cap circled in red.  It would be the one visible with the fuel bowl installed. I have removed some using left hand drill bits. Have also used wood screw started into hole in cap and pulled out on screw with vice grips.

When you get them out you'll see a screw head. You'll want to remove the screws and clean inside.  Be careful as there will be some small parts inside. 
- washer,o-ring,spring 
Also be careful upon reinstallation of the screw as not to over torque it.  You'll possible damage the screw tip and o-ring.

Not sure if this will fix your problem but you apparently hadn't cleaned that circuit yet.

Good luck.

[Lancsben]

Checked for holes in exhaust?

[mchollan]

I pulled the plugs that covered the mixture screws.  For anyone wondering, I used short self-drilling self-tapping screws and pulled them out:



I cleaned the passage and the mixture screw tip.  There was a little bit of black gunk in there.  I set them both to 2.5 turns out each and it seemed to help quite a bit.  I can now get the bike into the 8-9K rmps range, but I still get the popping.


Here is the exhaust:



Here is a video of the popping:
http://www.youtube.com/watch?v=7MnAZC1rqAc&feature=plcp&context=C41975a4VDvjVQa1PpcFOMVXNuLZOTZdzlNtLEuYbchDfk0vGM57E%3D

[ATLRIDER]

Have you checked float height. Here's a way to see if they're set right.

http://gstwin.com/float_height_check.htm

What size jets are in there?

[mchollan]

I will pick up some clear tubing from Ace tomorrow and check the float height.  Is this the correct procedure for adjusting an out of alignment float?
http://cgi.stanford.edu/~sanjayd/gs500/Maintenance/FloatHeight  It says this is for the pre '01 bikes.

Thanks again for everyone's input.

[ATLRIDER]

Don't know the spec for the newer carbs.  Found a couple of links for you to look at.

Use the search within document function at the bottom and type in FLOAT or CARB
http://www.scribd.com/doc/60315156/Suzuki-GS-500-F-K4-Service-Manual-Suplement

Tutorial on how to service Suzuki carbs
http://www.gixxer.com/forums/showthread.php?t=159718

Good luck with it.  Getting closer to riding

[mchollan]

The Jets are 130, 60, 17.5  .  I used some tubing to check the float height.  Both carbs looked low. 

Bigger Image:https://picasaweb.google.com/lh/photo/pJwTpUFVuTLjHwyTwcxSejBo8OxAP9N2Dig8GsB3BLo?feat=directlink
To adjust them I can just bend the metal tab (tongue) on the float to get them back to normal correct?

I also noticed that one of the vacuum lines has been capped.  Actually I noticed it several times but never bothered to investigate it.



Is this correct?

[ATLRIDER]

Yeah it looks low. Carefully bend the tabs.

Don't know what to say about the vacuum caps.  Sounds like maybe some hardware was removed and lines capped.

[mchollan]

OK I know its been a while, but a lot has happened since my last post.  Basically what I thought was a simple carb problem turned out to be much worse.

In one cylinder i get about 140 psi compression. on the other I get 10. So its a bad valve or piston rings or a hole in the piston.  I figure the previous owner of the bike did take care of it, never shimmed the valves (24,000 miles BTW) so I might as well do the whole front end. 

I decided to remove the whole engine because 1.) its not that difficult, and 2.) it affords me lots of room to work.  After removing the engine I began to take the head apart so I can see the piston rings.  While doing so I notice one of the camshaft caps is cracked, and even though I was careful to loosen it evenly on both sides little by little it still broke.



I know that these caps are matched to their heads so I can't get a replacement.  I think I am going to try to weld it or JB weld it back together.  I don't think there is a lot of force pushing back on the camshaft against these caps so as long as it doesn't crack and fall apart when I torque it back down it should be good right?

Even though this is a serious enough problem, i have to continue to the original no compression issue.  once the head was off I noticed that on the bad cylinder, one of the valves looks brand new (no carbon deposits) and the piston head had almost no carbon deposits on the center.  I think the previous owner attempted to replace the valve, but didn't lap it in correctly, or didn't adjust the shims correctly afterwords. 




Any comments or suggestions.

Oh and by the way i cleaned up and wrapped the exhaust.  I looks pretty good now!