78 gs550 cylinders 1&4 not firing

[jrom3897]

So I think I've narrowed down my issue to incorrect ignition timing, I've set the points according to the manual and got the bike running and everything seemed ok. But when i tried to start the bike the next day after riding I had the same issue with cylinders 1&4 not firing, they feel cold while 2&3 are red hot, also if I try to give the bike gas it dies. This scenario has occurred several times could there be something else going wrong other than the points? Ive checked the plugs for spark and they seem fine so I dont think it could be the coil. Any Ideas?

[tom203]

Run the bike for a while on just 2 and 3, then pull spark plugs 1 and 4- are they wet or dry? put bike model/year in your signature. Have you read up on carb cleaning?

[jrom3897]

1978 gs550 the plugs are dry but ive cleaned the carbs and the jets are clear.

[Nessism]

If the plugs are dry, that means no gas is getting though. Try opening up the carb drains on #1 & #4 and see if any gas come out. Could be a gas flow issue. If fuel comes out, and you still have spark, the carbs are the obvious issue.

[jrom3897]

there is fuel in the float bowls, but again ive taken apart the carbs and nothing is clogged

[tom203]

there is fuel in the float bowls, but again ive taken apart the carbs and nothing is clogged

So it ran for a while on 2 and 3, you found plugs 1 and 4 dry,then found fuel in 1 and 4 bowls, so why doesn't this fuel make it to plugs? I would think the low speed jets are plugged, but I'm not familiar with the VM carbs.

[Killer2600]

So a problem with spark has been ruled out...

This is where I'd spray a shot of ether to see if cylinders 1 and 4 light up.

[jrom3897]

So while i had the bike running (with only 2&3 firing) i sprayed starter fluid into 1&4 the revs picked up but briefly and if i kept adding starter fluid the bike seems to run. any ideas as to what this means?

[sedelen]

So while i had the bike running (with only 2&3 firing) i sprayed starter fluid into 1&4 the revs picked up but briefly and if i kept adding starter fluid the bike seems to run. any ideas as to what this means?

Yeah, those cylinders are starving for fuel.

[jrom3897]

ok but the float bowls have gas and the jets arnt clogged so why arnt they getting gas?

[Nessism]

Did you hold up the pilot jets up to a light and make sure the small orifice is open? Did you replace all the O-rings inside the carbs and on the intake pipe boots? Did you verify the pilot fuel screw tips are not broken off in the carb bodies, and set the screws at 7/8's of one turn open from lightly seated? Did you set the pilot air screw at 1.5 turns from lightly seated? Did you bench sync the carbs before you installed them?

Something is obviously wrong. You keep shooting down our suggestions.

[cowboyup3371]

Everybody is right here and you'd do well to listen. How did you verify the carbs were clean? Did you dip them per the tutorial or just look at them and decide they were since there was little gunk laying around? Remember, there are passages you cannot see that MUST be clean for fuel to flow to the cylinders properly.

[BassCliff]

Greetings and Salutations!!

Hi Mr. jrom3897,

With these old GS bikes, everything starts with properly cleaned carbs. You'll find several tutorials collected on my website. Once that is done, go through the maintenance lists linked below.

I've been away so I apologize for being late with your "mega-welcome".

Let me dump a TON of information on you and share some GS lovin'.

I just stopped by to welcome you to the forum in my own, special way.

If there's anything you'd like to know about the Suzuki GS model bikes, and most others actually, you've come to the right place. There's a lot of knowledge and experience here in the community. Come on in and let me say "HOoooowwwDY!"....

Here is your very own magical, mystical, mythical, mind-expanding "mega-welcome". Please take notice of the "Top 10 Common Issues", "Top 15 Tips For GS Happiness", the Carb Cleanup Series, and the Stator Papers. All of these tasks must be addressed in order to have a safe, reliable machine. This is what NOT to do: Top 10 Newbie Mistakes. Now let me roll out the welcome mat for you...



Please click here for your mega-welcome, chock full of tips, suggestions, links to vendors, and other information. Then feel free to visit my little BikeCliff website where I've been collecting the wisdom of this generous community. Don't forget, we like pictures! Not you, your bike!

Thanks for joining us. Keep us informed.

Thank you for your indulgence,

BassCliff