GS500 WON'T START, LUNCHBOX + SLIPON & REJET

[halffttime]

"I'd get new gas, 1.5 yrs is long enough to have it turn back into a dinosaur."

Thats funny buddha, best joke I ever heard about old gas. Youre right too, Ive had ethanol gas go bad in less than a year without stabilizer. One time I thought the gas in my chainsaw had turned to kerosene, but it turned out I had just been drunk and premixed kerosene.

Change the fuel out dude, and put some damn lucas in before you park it again.

Okay. So I poured out the old fuel and put new 91 premium fuel in the tank. Still no go... However, upon close examination... I can now hear a very faint start, but it just won't go over the hump and start altogether.

I got new spark plugs that I put in yesterday, but didn't gap it because I didn't have the gapping tool. Hmmm...

I'm at a loss for words. I'm thinking it's either something with the carbs, or the k&n filter is messing up with the air/fuel mixture... Either those, or I need to push start this bad boy.

Arghhh.... I just want to hear the new muffler already!!!

[mr72]

Okay. So I poured out the old fuel and put new 91 premium fuel in the tank. Still no go...

Did you drain the fuel from the carburetor bowls? Fuel lines? Petcock? If not, it will take a LOT of cranking to cycle out the old fuel. You need to turn off the tank petcock and unhook both tank fuel lines (so air can come in), hook a drain hose to each carb bowl, and open the drain screw and drain until all of the fuel runs out of each carb bowl. Then turn the petcock to prime and do it again, which should drain the fuel hoses. Hook everything back up, turn the tank petcock back on, and keep the main petcock on prime. This will begin to fill the carbs with fresh fuel. Now you won't have a LOT of cranking, just a lot of cranking before it will be getting fresh fuel.

However, upon close examination... I can now hear a very faint start, but it just won't go over the hump and start altogether.

That's because of the odd firing order. It's normal. It doesn't mean it's really "trying to start". It will do that with no fuel at all, or even with the carbs completely off the bike.

I got new spark plugs that I put in yesterday, but didn't gap it because I didn't have the gapping tool. Hmmm...

Really? Being dead honest here, you are really overlooking a lot of super simple, obvious things. You need to begin with the fundamentals and forget about your mods. The plugs were probably pre-gapped but you should check, who knows what they were pre-gapped to, and really, they sell the plug gap tools at the register at every Autozone in America for like $2.

I'm at a loss for words. I'm thinking it's either something with the carbs, or the k&n filter is messing up with the air/fuel mixture... Either those, or I need to push start this bad boy.

It MAY be something with the carbs, like bad o-rings or something put together wrong. It is NOT the K&N filter because it only affects the mixture when you are way above idle RPMs and not at the like 100 rpms used to start to the bike. Even with stock jets it will start with NO air filter if everything is working. You need to just erase this from your list of things to check. No start means either no [or bad] fuel, no [or inadequate] fire, or no [or weak] compression, and THAT'S IT! You're not tuning here, you're just trying to get it to run. One you get it to start THEN you might have issues with lean mixture or the wrong plug gap or whatever but until then you need to solve the basic, simple problems.

Arghhh.... I just want to hear the new muffler already!!!

No offense, but this might be part of the attitude that prevents you from finding the real problem. You could take the new air filter and muffler clean off of the bike and THEN try to get it to start. They have absolutely nothing to do with your starting issues and thinking about them will not help you solve the problem.

1. It had old/bad gas. You have to fix this, absolutely, first. This means draining all of the old gas from the carbs and fuel lines and everything.
2. You had the carbs off of the bike, and partially disassembled. This means you MIGHT have made a mistake assembling, not noticed something was put together wrong, or unintentionally damaged something (I have done all three of these, in the past month!). If it won't start with new fuel, VERIFY THIS NEXT. Don't put the carbs back on the bike until you are absolutely sure they are assembled correctly and there are no bad o-rings or overly worn parts. And when you put them back on be very careful to make sure the boots can't leak.
3. New plugs are a good idea but you've probably already soaked them in [bad] gas. So you should pull them again, clean them, and then GAP correctly just to be absolutely sure this is not wrong.

It's not rocket science and without that airbox in there you could do all of these checks in like one hour flat. If you can find someone local who understands CV motorcycle carburetors, then hands-on help and another set of eyeballs is probably a huge benefit.

[halffttime]

thanks for your reply mr72, it was very helpful.

Okay, so I've gapped the spark plugs accordingly and checked for spark. They're good. The fuel is good, it was getting into the carbs fine. The battery is fully charged to 14.4V (ballistic).

So... I got the bike to "fire" and start for about half a second before it died. I'm definitely getting closer. I even sprayed starter fluid in the intake, and the K&N air filter. When I start the bike, I can hear it firing up, even closer to starting than before, however it just won't go over the hump. I tried covering the muffler close to create more back pressure, still no go.

Okay... So I pulled out the carbs and I'm going to do a second check at all the screws, o rings, gaskets, etc. and clean it up...

What I did discover when I pulled out the carbs was that I had the idle screw at full open, meaning it wasn't tightened at the very least to touch the springs that compresses the butterflies.

Question:
1. When starting the bike, should the petcock be on prime? Forgive me if this is a stupid question.
2. When starting the bike, should the idle screw be all the way loose, all the way tight, or somewhere in between?
3. Should I throttle while i'm pressing the start button? Or throttle before, to get some fuel into the carbs?

[W201028]

Yes, put the petcock on prime. Is it necessary to start the bike? No. But this bypasses any vacuum problems you might have with the petcock. You said you have fuel in the bowls, so this likely isnt a problem.

The idle screw should not be loose, this is likely the problem. The idle screw should be somewhere in the middle, its not figured by turns, you just set the idle speed on the tach.

Should you throttle? Ideally you dont have to, but I think you should. Try starting the bike with the throttle 1/4 turn. If it fires and runs, tighten up the idle screw. Hell, tighten up the idle screw anyway. If the throttle plates are closed theres no chance of the bike running

[halffttime]

Yes, put the petcock on prime. Is it necessary to start the bike? No. But this bypasses any vacuum problems you might have with the petcock. You said you have fuel in the bowls, so this likely isnt a problem.

The idle screw should not be loose, this is likely the problem. The idle screw should be somewhere in the middle, its not figured by turns, you just set the idle speed on the tach.

Should you throttle? Ideally you dont have to, but I think you should. Try starting the bike with the throttle 1/4 turn. If it fires and runs, tighten up the idle screw. Hell, tighten up the idle screw anyway. If the throttle plates are closed theres no chance of the bike running

You've been very helpful, thank you very much.

Okay. So upon examination of the carburetors, I can see that the butterflies aren't opened to the same amount. At full close, one of the butterflies is slightly open while the other one is fully closed. Is this where "carb sync" comes into play? If so, where is the carb sync screw? I think this is the problem....

[mr72]

You should set the balance by eye and then adjust correctly once it is running. That won't cause it to not start but it will cause it to idle rough and stall at idle.

[halffttime]

You should set the balance by eye and then adjust correctly once it is running. That won't cause it to not start but it will cause it to idle rough and stall at idle.

That's what I did. Balanced it with the naked eye.

I sprayed starter fluid in the intake, and the air filter. Still no go. I did get a loud backfire pop though.

Don't know what else to do.

[halffttime]

could bad engine oil or fuel in the engine cause the bike not too start? forgive me if dumb question.

[The Buddha]

1. Do not spray starting fluid anywhere near the bike.

2. You have a clogged fuel passage - likely the air screw passage or the choke - and you are using the choke right ?

3. Your bike should spin over nice and fast with a charged battery, none of that anaemic spinning will get a bike that's been sitting for 1.5 yrs working. Make sure its got good spinning speed. 300-400 rpm for the engine is needed to get it started.

Cool.
Buddha.

[mr72]

could bad engine oil or fuel in the engine cause the bike not too start? forgive me if dumb question.

Not sure what you mean by this but you should change the oil if you are worried about it. But bad or low oil in the engine will not cause it to not start. It might cause it to wear out quicker if you ever get it to start.

I don't know what you mean "fuel in the engine" but if you have liquid fuel in the cylinders then it may "hydrolock," which is a genuine concern if it is flooding. And it might very well be flooding, and adding starting fluid may not be helping. You can always pull the plugs and let it sit overnight so that whatever fuel is in the cylinders will evaporate, then ensure it's not flooding (that's float height, float needle valve, float o-ring, float needle valve o-ring...), and don't worry about it.

If you mean you have fuel in the crankcase then you have to be seriously concerned about how it got there. Ordinarily this is a combination of bad rings and flooding, or tons of effort to start the bike with no spark or whatever, where lots of fuel gets into the cylinders, slips past the rings, and piles up in the crankcase along with the oil.

You don't need starting fluid. If you do, then you still have bad gas, or otherwise no fuel getting to the engine, as Buddha said, perhaps clogged carb orifices. With bad gas it doesn't take much to clog stuff up, INCLUDING THE PILOT JET which will make it impossible to start!

[Janx101]

GS's are cold blooded... a little grumpy anyway when starting...

There surely are many more experienced folks here with carbs etc than myself.... but I've never! Had 'extra success' with using throttle of any amount while starting! .. set 'choke' lever and hit the button!.. if anything trying to feather the throttle to get it firing made things worse! .. that's just my limited tests though...

Also. .. waaaaay back at the start of the thread... bike on centre stand- fair enough.. but what purpose does 'starting it in first gear' serve?! ... I must be missing a secret technique there?!

.. also also... yes the bike has carbs.... yes they have the same basic function as carbs on a car...

however on the bike... the 'choke' isn't one! ... the adding throttle isn't really like pumping the gas pedal on the old junker in the back shed! Its a way smaller/twitchier system!...

There is a missed step/missing part/incorrect assembly in there for sure! ...

Errrm... the coil wires are firmly seated in the coils yeah?

[halffttime]

Here's a video of me trying to start the bike.

https://youtu.be/EsliJCMw6_A

What do you guys think?

I forgot to mention that I did I shimmed the valves. I'm now thinking that I might have messed up somewhere there. The intake valves, I shimmed to spec, between 0.04mm to 0.08mm. However, I went a little looser on the exhaust valves because I read somewhere on the site that it's advisable to do so. I believe I went between 0.11mm to 0.13 on the exhaust valves. I'm wondering if this might be the problem.

I'm going to put everything on the bike back to stock and see what happens with that. Then I'll open up the top end again and check valve shims again, and also engine timing. I'll also check the sparks again...

If neither of these starts the bike, then got damn.

[mr72]

Your valve adjustment is fine. I won't say whether it is ideal or not, but it is not what's causing the bike to not start. If you screwed up the valve timing by turning the cams while the tensioner was loose etc then that might cause it to not start but didn't you say it started and ran for a few seconds then died?

Did you pull the carbs and check the pilot jets, make sure they are not clogged? Also the pilot air passageway, etc., verify they are not clogged? If you have #40 pilot jets then that's 0.4mm or 0.0157", you should be able to run a 0.015" wire through them to clear them (I use old guitar strings). I ran a 0.013" guitar string through the other orifices in the carb to ensure they are clear.

If you spray starting fluid in and it starts for a second, but it won't run on its own, then more than likely your low-speed fuel supply is clogged. That's the pilot jet and the fuel orifices for the pilot circuit. Given the fact it was sitting with bad gas, I would say this is highly likely to be the problem.

Seriously you need to pull the carbs and absolutely, without fail, ensure they are completely cleaned and there are no leaks. Clear all orifices. Blow compressed air through them, run the correct gauge wires through, etc. It's very important to low-speed running, which includes starting.

[SirHansford]

Here's a video of me trying to start the bike.

https://youtu.be/EsliJCMw6_A

It's your socks with flip flops.  The bike is disgusted with your fashion sense and refusing to start.  J/k ,  thought i'd offer an attempt at comic relief    I have nothing helpful to offer, sorry. Good luck man! Hope she gets better soon.

[Arpee]

*snip*

I forgot to mention that I did I shimmed the valves. I'm now thinking that I might have messed up somewhere there. The intake valves, I shimmed to spec, between 0.04mm to 0.08mm. However, I went a little looser on the exhaust valves because I read somewhere on the site that it's advisable to do so. I believe I went between 0.11mm to 0.13 on the exhaust valves. I'm wondering if this might be the problem.

I'm going to put everything on the bike back to stock and see what happens with that. Then I'll open up the top end again and check valve shims again, and also engine timing. I'll also check the sparks again...

If neither of these starts the bike, then got damn.

Did you remove the cams when you did the shims?

[halffttime]

*snip*

I forgot to mention that I did I shimmed the valves. I'm now thinking that I might have messed up somewhere there. The intake valves, I shimmed to spec, between 0.04mm to 0.08mm. However, I went a little looser on the exhaust valves because I read somewhere on the site that it's advisable to do so. I believe I went between 0.11mm to 0.13 on the exhaust valves. I'm wondering if this might be the problem.

I'm going to put everything on the bike back to stock and see what happens with that. Then I'll open up the top end again and check valve shims again, and also engine timing. I'll also check the sparks again...

If neither of these starts the bike, then got damn.

Did you remove the cams when you did the shims?

Yea, i had too... i didn't have the tool to remove the shims. I re-timed the engine after though. 18 pins between the two arrows.