Hi All,

I've been lurking for a while, looking at the huge number of other "Bike won't start!" threads and I can't seem to find what I'm looking for.

I bought a 1990 GS500 in a semi-functioning state a few months ago, with the intent to fix up some of the more obvious problems myself. Issues on purchase:

• Hadn't been ridden in 12 months
• Both front and rear tires had leaky valves
• Muffler needed repacking
• Wouldn't start - but had run ok 12 months ago
• Fuel petcock had been removed and a single line was running from the RES to the carb
• Tacho doesn't work - the cable needs replacing

Since I bought it, I've fixed the tires and the muffler, replaced the oil and filter, bought new fuel lines and new petcock to rerun the fuel lines properly however now I'm stuck. I can bump start the bike and I can get it to turn over with starter fluid but it won't stay idling for more than a second or two. Bike has a new battery and the electrics seem fine (all lights work, all cables are intact, putting out acceptable voltage etc).

I'm pretty confident the issue is a fuel flow issue but I'm fast running out of ideas of what to look at, and since its now summer in Aus and the weather is incredible, I'm jonesing to get out on the tar.

In terms of things I've done to make sure the bike will actually run, I've cleaned the carbs and there's no damage on the seals or the diaphragm or needles. I'm thinking that the filter in the tank could potentially be the problem since the bike wasn't running for 12 months and wasn't stored with fuel in the tank. Haven't yet looked at that but I'm guessing that'll be where I go to next.

If that's not the issue, does any one else have any ideas for where to go to next? I've been putting away at fixing this in my weekends over the last few months, but I'm bang on the cusp of taking it to a mechanic for a better assessment.

Can anyone point me in a better direction for investigation? Or have an experience with a similar problem? Or even point me to a thread that I might have missed that could help me here?

I'd really appreciate any help I could get at this stage.

Cheers,

Evil Muppets

Are the spark plugs wet with gasoline after you try and start it? If they are bone dry (and not soaked with oil) than I would look at the pilot jets & choke circuit.

Also, when were the valves checked last?

The spark plugs are getting something through, they're definitely not bone dry. They look like this:
http://farm5.static.flickr.com/4035/4623452986_bd1991e23d_b.jpg (someone else pic, but pretty close to how mine look).

The choke is odd though, it doesn't lock in when you put it on. It springs back pretty much immediately, and I need to hold it fully open to get a response. I figured that may have been because of the lack of fuel pressure?

Have you tried running it on prime?
When you say petcock was removed, do you mean the vacum valve? If so this may indicate to some previous problem. I ask because without petcock fuel would gush from tank
Are you holding the choke open -ie stop it jumping back? It should not jump back seems a friction problem on the lever.
Make sure the choke mechanism on the carb  does actually move as it should.
Double check fuel piping - it changed over the years, there are errors on the manual and it is easy to make a mistake there.
Vacuum line connected and not leaking. 
I have a small bottle type standalone fuel supply that I use when balancing cars etc that one can use to troubleshoot  . Ie known good fuel source.
Wish I was going into summer, -12 in Montreal today, but in a week I am off back to south Africa for a months holiday. Wish I could take the bike with! !!

"Wouldn't start - but had run ok 12 months ago"

•Fresh Fuel
•Fully Charged Battery
•Large Hill

Quote from: Suzuki Stevo on December 06, 2014, 08:52:26 AM

•Large Hill

But true

Haha I tried a large hill. Made the mistake of kitting up too before trying it down. Managed to start but it cut out prior to me being able to get it back up. Ended up pushing it home which was not super pleasant. But yeah its got new fuel, and the battery sits on a trickle charger between attempts.

BMF,  yeah the previous owner had removed the vacuum valve. He was running a line straight from RES to the carbs. I replaced the valve and added new lines. I figured originally that the carbs were flooding from the straight run from the tank.

With the new valve,  I left it on prime while trying to start it. No joy.

I did the routing based of kerry's hose routing diagram, so I hope I did that right. With the choke, I do have to hold it open. I've had the carbs off a couple of times and set the choke line connection back to how I found it initially.  No guarantees that's correct though. It responds when you move the choke but for the life of me I can't figure how it would lock off. I might grab a photo and chuck it up to see if I've popped it on wrong.

Cheers for the suggestions by the way. I really appreciate the assist. I might try the bottle trick too. Good idea to troubleshoot so I don't need to keep putting the tank back on to test!

So many people riding bikes around me  while mine is in the shed is making me sad. But I guess if I wanted to ride straight away I shouldn't have bought a fixer - upper!

Just in case, (your prob is probably not this but you never know). Re: your comment about your choke not holding fully on. Had this was on a CX Honda... the choke knob never held the full choke position, it would always settle back a couple of mm, and this made a big difference to cold starting. Just a tired cable. Once I sussed this I would hold the choke knob hard up fully whilst I hit the starter button.

So I just checked the choke position on the bike and I'd put it in the right place when I re-attached it to the carbs yesterday. Could be what Joolstacho is saying and a tired cable. I've never checked the valves - so no idea if the shims are completely gone, or if there is a valve issue on the bike. It would make sense given the previous owner completely nixed the vacuum circuit. If there's not enough compression I can see why it wouldn't be starting.

Gonna have a crack at checking out the valves next to see if they are problematic. Might look at a replacement choke cable too.

+1 on putting the petcock to prime, mine won't start if it was sitting for any amount of time unless I put it on prime to get the gas flowing to the float bowls again. Also, try starting it with the gas cap open. If it starts, your vents in the gas cap are clogged with dirt or something.

There's an excellent tutorial on cleaning and lubing the gas cap here I'm pretty sure.


Here it is:

http://gstwins.com/gsboard/index.php?topic=41061.0

Roaring via Tapatalk.

As it starts to get warm, a mariginally tight valve will hang open making that cyl not run. So yea could be your issue.
You could also have a crank trigger go bad as it gets warm. That you can try to compensate/prove by removing the right side cover and spraying the 2 pick up coils with canned air from a can turned upside, which would be cold. Be careful, it will ice over very rapidly.
You could have a simple carb issue as well. Blocked jets or passages.
Fuel flow issue also possible, so make sure the carbb floats are full before you start, and you'd eliminate that.

Cool.
Buddha.

Quote from: The Buddha on December 07, 2014, 11:38:57 AM
You could have a simple carb issue as well. Blocked jets or passages.
Cool.
Buddha.

+1 Pilot jets generally will not come clean with carb cleaner and air blast. They need to be probed carefully with a wire that is smaller than the orifice.

Also the issue with your choke needs to be sorted. If the choke isn't working properly the bike will not stay running during start-up.

Soak carbs overnight 12+ hours in a gallon of carb cleaner. Completely stripped of all plastic or rubber parts