Hey everyone.
So Ive recently got a 2007 gs500f non-running, had 0 compression one cylinder, took it apart and both exhaust valves were bent.
Bottom end looked great!
Got another used head as it was easier/cheaper to find than valves, put it on with new shims, 120-130 compression both cylinders.
Cleaned carb and noticed one small piece was missing, fuel bulb vent piece, nr 72 on diagram from partzilla, but i don't think it's extremely relevant anyway?
https://www.partzilla.com/catalog/suzuki/motorcycle/2007/gs500f/carburetor
So anyways, bike starts like a charm now, but it backfires and has trouble with throttle, throttle wont go above 5-7k and bike dies if u hold throttle and it wont rev if you touch throttle right away again, so feels like it's running out of fuel?
And also sometimes after revving, rev keeps up at 3-4k and slowly goes down, again, feels like wrong air/fuel combo.
I confirmed fuel flowing fine through tank and petcock, tried all pri/on/prime, runs identical!
I've set the carb adjust at 2.5 turns after cleaning and tried adjusting a little, runs identical.
Anyone knows what could be the issue or has ran into something like that before?
Stuck on how to try an diagnose this besides maybe ordering whole carb rebuild kit?
Going to try and upload a vid to youtube of its running
Edit: Got the icloud video link https://share.icloud.com/photos/066u1y4ydRKp3tJlMD-kNVIAw
One thing i just remembered when i was typing all this, i didn't open up top part of carbs as the bolts were abused hard and i didn't bother heating/cutting.
Could the rubber piece or something else be busted in upper part and causing constantly too much air or blocking air instead, causing this?
Feels unlikely, but i dunno, out of ideas at this point
If your valves are good, Id get a full rebuild kit. dont use one ball racing. get a quality kit. Pull those puppies down. If you have access to an ultrasonic clean, etc... It would be nice. if not. run wire down every small port you find. With ethenol, it really turns carbs to shaZam!. make sure to check your floats and make sure they are at the right height. hth.
Quote from: DarkCyDE on March 25, 2025, 03:25:34 PMIf your valves are good, Id get a full rebuild kit. dont use one ball racing. get a quality kit. Pull those puppies down. If you have access to an ultrasonic clean, etc... It would be nice. if not. run wire down every small port you find. With ethenol, it really turns carbs to shaZam!. make sure to check your floats and make sure they are at the right height. hth.
Thanks, doing that , ordered a proper kit with new diagphrams.
Update so far: No leak on intake boots, confirmed.
Opened top of carb finally and diaghprams were not teared, but looked extremely soft and bloated, not sitting right. Also noticed when running without air box, the plastic plunger moves up very slow when giving throttle with carb spitting back fuel and if throttle is touched before the plungers are back down, which they do very slow, it sputters and starts dieing.
If i wait til plungers are fully back down, i can momentarily give it a nice rev until plungers are back up, then it starts dieing.
New diagphrams come in tomorrow, will update once i got everything cleaned once again
Update: It now runs after full cleanup, but will not idle without choke, has to be 1/3 on, with rpm at 1500-2000 and idle/mixture adjustement having no effect. Bike fully warmed up.
Can't drive with more than 1/3 throttle as it will instantly backfire and start dieing.
With slow 1/3 throttle it accelerates up fine no issues.
Thinking that maybe they are now heavily out of sync and whoever messed with the carb before royally screwed it up.
Going to get a set of carb sync tool and see if i can get it working, if i cant, for sale it goes.
Sync tool arrives tomorrow, fingers crossed..
My last resort, Ive taken the carb apart so many times now, every single hole and jet is squeaky clean and shines light through, i dunno what else could make it run so bad.
I've got a 2002 Kawasaki 500cc as 2nd bike and the whole carb setup is soooooo much easier, im starting to loose all hope on this Suzuki.
HOLY GUACAMOLE, I WIN AND THE BIKE IS BEATEN FINALLY
You will NEVER in a MILLION years guess what the issue was, holy shaZam!.
As i originally mentioned, bike never ran when i got it and i replaced the head.
I had a suspicion that someone messed with carbs before.
So last night i was sitting and re-visiting Fuel/Carb/Air diagrams on Suzuki and Partzilla, then it struck me.
(https://cdn.partzilla.com/cdn-cgi/image/quality=50/MTE/d/b/MjE2MTAyOQ-be7f7f35.png)
The parts 27 and 16 are both Main jet and are IDENTICAL in size, but the hole is DIFFERENT, one is 60 the other one is 130, what if... someone who messed up with carbs before mixed them up? No way, right?
Took it apart again 10th time this morning and what do you know, the 60/130 were mixed up on BOTH carbs, almost like someone did it on purpose.
Swapped them and bike started up and runs properly now, revs to the iguazuu and flies fast.
Before that, it would die with throttle and couldn't rev past 6k.
So happy, holy shaZam!.
Now to warm it up properly in the evening, re-sync carbs with tool and adjust idle.
Holy shaZam indeed!
Before you fixed it I was going to offer you FREE of charge my almost new complete engine with carbs. Ah well, :icon_mrgreen: missed out!
This was a great read! Thanks for posting!!!!!!!! :bstar: :bstar: :bstar: