06 gs500f running great but now won't start

[Stanley68]

Hi all! I bought an 06 gs500f last week that needed a bit of work before inspection but ran great. Well I finally got everything ready for it to be inspected  and now it won't start. Ever since I bought it and put some gas in the tank it's fired right off with a slight bit of choke and ran perfect. Yesterday I had it idling in first on the center stand to lube the chain fast and it stalled out. I didn't think anything of it because I only had a dollars worth of gas in the tank to make sure it ran. But went to ride it to the shop for inspection this morning and it won't start. It acts like it's going to sometimes but it never does. And it backfires every now and then. It doesn't seem like it would be timing because like I said it ran great the few times I rode it around. But at the same time it seems to spin faster when you have the throttle open trying to start it but not firing off which makes me think an intake valve is opening at the wrong time. Any help would be much appreciated!

[Stanley68]

Forgot to mention yes I put more gas in the tank

[The Buddha]

You may need to put it in prime a few seconds.
Cool.
Buddha.

[Stanley68]

Buddah, tried prime on the petcock like you said, no go unfortunately. Tried starting fluid to rule out fuel after that, also no go. Tested the spark plugs against the frame, got a weak looking yellow spark for both spark plugs. Hopefully this is the issue. Maybe I fouled them and they're not performing under pressure. How quickly can the ignition coils give out on these. Seems unlikely that it would happen as quickly as my experience is. But I'm also not as familiar with these bikes as you are and I would like to be. Thank you for your reply! Very much appreciated.

[The Buddha]

The coils don't give up on these on any regular basis. I actually also would check all the connections as well as the trigger coil - the F has single one isn't it. I got no expertise on those. I don't know their failure is worse or better than the 89-00, but the one on my 89 died @ 2000 or so @ 35K miles.

Someone else may be able to help here I'm sure.

Cool.
Buddha.

[Stanley68]

Buddha, finally got time between work days to work on the bike. Compression test reads nothing. Anything it does pick up goes away quickly. Could it be head gasket between the cylinders? Or maybe it jumped a tooth on the timing gear? As far as I can tell there's no air or oil coming out of the side of the engine.

[The Buddha]

Compression test should be done with throttle WFO.
And is your gauge good ? Is it thread in or press on ? Make sure its not leaking.

And brilliantly like every other clown who builds a bobber or some other convoluted contraption ...
What is the logic behind your troubleshooting ? Is that cos you found a compression tester by the side of the road abd found it fit the GS and had to use it ?

Great then, you need to rebuild the front wheel bearings, change synthetic Blinker fluid and make sure you give some attention to the tail light bulb.

Your bike didn't start after it may or may not have run out of gas. Compression is like somewhere between 20 and 40 on the list.
But while you have the gauge found - do it WFO.

Your bike is perfectly fine, you got some clogged up fuel passage or a crapped out spark circuit. Find those and then complain when it smokes like a mofo then we'll say go do compression.

Compression is a test for before purchase just likely to beat down the seller. Once you rode it home and didn't kill hordes of birds on the way - its largely irrelevant for 1000's of miles.

Cool.
Buddha.

[Stanley68]

Bike rode home in the bed of my pickup. PO lost keys. Made sure bike turned over jumping the solenoid and took it home. New ignition switch and fuel cap later and some gas in the tank and started right up. Three days later after I get it ready For inspection, because PO took stuff off to make a cafe racer or some crap, bike dies while idling. Out of gas I thought. Got more gas and still wouldn't start. Reasoning behind compression is because it stopped working so fast. Tried starting fluid and bike didn't try so that quickly rules out fuel. Checked plugs, coils, pickup coil, battery, all good. Yes I used multimeter and know very well how to properly use it. Next step without taking the bike apart is compression. I own my own compression tester and gauge is good. Thread in because the cones are crap. Checked with wide open throttle. Bounced but went right back to zero. Thoughts are timing chain slipped a tooth making valves open at the wrong time or blown head gasket between cylinders causing air to escape into the next cylinder and be blown out the valves on its stroke. I work on my own vehicles. Just new to bikes.

[The Buddha]

Now that I know you checked all these - how did you check the trigger pickup coils ?
AFAIK - no way to test them.

Then compression test being so low implies rings - the blowing into adjacent cyl doesn't happen cos the cam chain tunnel will get in the way and it will end up in the crank case. So see if the PCV filter is plugged with blow by related crap.

BTW you may just have a clogged up carb, if it sat and you put new fuel in it, you essentially tossed all that crap down the fuel system. This bike has ~2qt's of fuel you can not get out by use. So you had a lot of crap in it unless you sloshed and drained all the fuel and scraped off the crap pockets also.

Cool.
Buddha.