Hi all, so story goes like this, took my gs off the road for about 3 weeks due to icy weather but now a new issue has appeared when i try to cold start the bike. so whenever i try to cold start the bike, the right cylinder refuses to fire with full choke or none however as the bike warms up on one cylinder, the right one will slowly sputter back to life over about 3-5 mins of holding 3000rpm.
I've replaced both of the sparks as a quick and easy attempt to fix this, confirmed both sparks are firing correctly, and also did a compression test, both cylinders read about 120psi so not good but not the worst and at least they are wearing evenly. so the only thing left really is the carbs but I've never worked on anything more complex than a Chinese 125 carb so just hoping for any suggestions or advise, thanks.
I also want to mention this, I can't help but think that the bike sounds louder at idle than it used to and I can also hear popping, my exhausted has been damaged for a long time since a crash and has always leaked a bit of noise but I may just be imaging it getting louder and just never noticed the popping before. if they are new symptoms, could the bike be running rich?
If spark is good, then check air and fuel. And if it's firing after warm-up, maybe it's an air problem somewhere near metal. Metal expanding as it warms up, sealing a gap that enables proper air/fuel mixture. Keeping it simple, I'd do the following. (1) do the spray bottle test to check for vacuum leaks. (2) check air leaks at both sets boots, if these are ok, then (3) pull airbox and carbs, then learn how to check and clean your carbs. If your exhaust is damaged, your mixture is probably off anyway. When's the last time they were cleaned? There's lots of little o-rings and tight passaged that get gunked up. I clean mine once a year.
I've only owned the bike for a year and haven't cleaned them since I've owned it. The more i think about it, the more i convince myself that its a dirty carbs so i'll take the bike apart tomorrow. my reasoning being that over that last year I've put 5000 miles on it so a lot of fuel of varying quality has gone through it, on top of that i know from mot history that the bike sat still for around 2 years and for all i know they might have not be cleaned since then and finally when i put the bike away for the 3 weeks, I wasn't actually planning on doing so, more like forced by the weather so I'm pretty sure I left a full tank of the cheap supermarket fuel in it.
I'll look up some instructions on carb cleaning tonight and hopefully post a response tomorrow on its success.
Thanks for the reply.
While you're at it, check inside the gas tank to make sure there's no rust. No point in cleaning your carbs if the upstream is dirty.
My first thought is a bad coil, it cools and contracts and causes wherever the insulation is gone to short, once it heats up it expands and a gap forms where the insulation break is and the short goes away. Swap coils side to side to diagnose, if the problem follows the coil, it's the coil.
My next thought is a low float on the bad-cylinder carb or a sticking float needle valve on that side. Especially since while on the side stand gravity is in favor of the left carb having fuel. To check this (before you start it...) put the bike on the center stand and attach a piece of hose to the carb bowl drain on the right carb, run the hose to some fuel container. Open the screw tap and see if the carb drains fuel. If it has fuel coming out then you at least know the float valve is allowing fuel in and you can eliminate this. It's very hard to absolutely diagnose a sticking/intermittent float needle.
And then of course there's always the intake-boot o-ring air leak, which may cause air to leak into the right cylinder at the head port until it heats enough to expand and cause at least a dodgy enough seal for there to be vacuum pulling air through the carburetor (where it can get fuel) rather than from the atmosphere.
If you haven't done any service at all to the carbs then I'd recommend following this procedure in my blog post (https://joshkarnes.blogspot.com/2017/09/fixing-common-gs500-carburetor-issues.html) to freshen up the carbs. Note that to do this you'll have to first arm yourself with a set of o-rings and since you have a risk of bad float needles I'd buy a pair of them too. All in all this is like $20-30 worth of parts, the most expensive being the float needles and the intake boot o-rings. But it's well worth it if you plan to use the bike.
That said, there may be a bit of good-money-after-bad going on here. The carb freshening thing only costs $30 in parts and (for me) takes a couple of hours to do and it may fix your problem. But if you have only 120psi compression in each cylinder, you are coming very close to needing a top end rebuild just to keep the bike running. You might be chasing your tail trying to diagnose phantom problems that really are just bad compression and that's it. So you might ask yourself if it's worth it to spend the weekend of work and money on sorting the carbs, and if you want to invest the $700+ it'll likely cost for a top end rebuild on this particular bike. Now, IMHO GS500s are kind of everywhere but the process of finding a used one and selling yours is a chore, like repairing your own bike is a chore, and it's also a bit of a crap shoot. You might flip your bike and get another one that has another set of problems that cost as much to fix as the known issues with your current bike. I'm a fix-it-not-flip-it type.
Quote from: mr72 on January 01, 2018, 08:54:53 AM
My first thought...
OP listen to this guy and read his blog. It'll save you tons of time and you'll get the job done right.
I agree with mr72 on everything except for the price of the top end job. If you do it yourself, you should be able to get away with a lot less money. You just need to take your time, read the manual, and get good advice from the members of this forum. mr 72 is right about working on the carbs first.
If you hire out the top end rebuild, it'll be about $700.
My guess was someone having this much trouble with simpler troubleshooting might not be quite ready for a top end rebuild. If I had it to do over again I'd DIY for sure but I hired a shop to do mine. It's a big job and you need space to work with and a good relationship with a machine shop, plus some special tools etc.
Sorry for the late reply, life caught up with me and I forgot about this post. unfortunately things didn't go too well, sadly i don't really have much time these days so I tried to rush the carb clean and rebuild and as we all know rushing causes mistakes :icon_sad:. It looks like the carbs haven't been taken off in a long while and a lot of things are rather seized in place which included the float bowl screws, even using a hand impact driver I managed to strip 3 of the screws. I didn't give myself enough time to extract the screws since i needed the bike on the road again so i cleaned out everything i could as good as I can without removing the float bowls focusing mainly on the pilot system. The result is 'better', I am certain more than ever that it is nothing more than a clogged up pilot circuit on the right carb causing the cylinder to run lean. the right cylinder is easier to get running and once its up to temp the popping is gone.
So i'm gonna ride the bike like this until I get another chance to take it apart, extract and replace the float bowl screws.
@mr72
Quotehaving this much trouble with simpler troubleshooting might not be quite ready for a top end rebuild.
I'm not sure if you intended to make this sound as insulting as i read it either way you've misunderstood the context of my post, I had already diagnosed the fault most likely being the carbs, I simply made this post in vain search for a simpler solution since as I stated I dont have much time to work on the bike right now. I've have rebuilt engines in the past however they have all been side projects not my daily use vehicle so I've been able to work on them over a long time. I do plan to take the bike off the road near the end of summer and do a rebuild. One thing i will do as you suggest is replace the boot o-rings when i take the carbs off next since it could be that i just budged them a bit and got a better seal making it run better. I'll see how things go, if the bike starts running better as it get warmer over the coming months I may delay any more work until i do the rebuild.
Quote from: Kits on January 13, 2018, 03:06:34 PM
It looks like the carbs haven't been taken off in a long while and a lot of things are rather seized in place which included the float bowl screws, even using a hand impact driver I managed to strip 3 of the screws.
I had the same problem. I used some vise grips to try to turn the screws, plus a chisel and a hammer to dig a flathead slot into the soft cheese that is the OEM carb screws, then replaced the lot with something which I've actually got the correct tools for rather than alleged 'JIS' screws.
Quote from: Kits on January 13, 2018, 03:06:34 PM
I tried to rush the carb clean and rebuild and as we all know rushing causes mistakes
Hopefully in you're haste you didn't spray carb cleaner on or into the carbs while the slides and diaphragms were still installed.
Quote
@mr72 Quotehaving this much trouble with simpler troubleshooting might not be quite ready for a top end rebuild.
I'm not sure if you intended to make this sound as insulting as i read it either way you've misunderstood the context of my post, I had already diagnosed the fault most likely being the carbs, I simply made this post in vain search for a simpler solution since as I stated I dont have much time to work on the bike right now.
Oh I certainly didn't intend any insult. Just being practical, a top end rebuild is a much bigger job and you never know what experience level people have when coming to this forum. Most are not ready for that kind of job. I'm not! Only information I had to go in was previous post context which made me think you might not be ready for such a serious job as a top end rebuild.