No start after pulling carbs. What am I doing wrong??

[Guest]

OK... so this is the second time this has happened. I pulled the carbs, drained the float bowls in order to check my float heights (I'm trying to diagnose a running issue) and install some missing pieces (vent hoses). The carbs were off the bike for one day.

I just threw them back on, fully charged battery, everything connected right - I triple checked the fuel and vent hoses. Set petcock to prime for a few minutes. This is a brand new petcock, just replaced 2 weeks ago. It just kept cranking and cranking with no start until I eventually ran the battery down.

This exact same thing happened last time I had the carbs off for about a week for cleaning. Only difference was it still had the old petcock. I had myself convinced that I wouldn't have this issue this time, thinking that maybe the old petcock was faulty and not delivering fuel in the PRI position. The remedy last time was to recharge the battery and try the next day - it started right up!!!!

So obviously I am going to try the same thing tonight. All hooked up to the trickle charger and hoping for a quick start tomorrow.

My question is what the hell am I doing wrong?? What could explain why this is not starting right away? Do I need to prime it for a longer period of time? I must have let it prime for at least 10 minutes altogether. Is there some magical voodoo involved here where the GS gods have to give it some kind of overnight blessing? It was starting fine every time before pulling the carbs each time.

Further - I am wondering if whatever is going on here might help point to the issue I am having while running, which is a consistent fluttering / bogging around 5-6k RPM. There's a whoooole other thread for that.

Thoughts?

[loud et]

I am not saying this is normal, but I had an issue with my new petcock where they are new and stiff. I always test mine with mouth suction using the hose on vaccuum port of the petcock.
With the petcoek removed,If you suck on the vaccuum tube, you will hear it pop open, then if you blow on the fuel outlet it should be closed by the time you move your mouth from one tube to the other. Sometimes when new, it stays open for a longer time till it finds its new "seat" On the other side of the coin, when sucking on the vaccuum tube of the new petcock, it is sometimes hard to get it to open/opetate smoothly the first number of times.
In a nutshell, it is stiff from sitting on a shelf or poor quality. My new petcock even got stuck open once in my first week of using it and I saw fuel weeping out from my float bowl gaskets.
Even though its new, it may need an inspection and manual test to make sure its working smoothly.
With it still hooked to the tank and using longer hoses, You can always put the fuel line into a gas can and suck on the vaccuum line and see if fuel flows, and then stops when you stop sucking on the line. It should flow immediately and then stop within a couple seconds.
gosh, that was confusing. lol

[spyug]

You don't mention anything about the state of the carbs. Have they been cleaned recently and rebuilt with fresh o-rings? Have they been bench synched? Vacuum synched?

It would be helpful to know since the fluttering and bogging point toward plugged jets/passages as well as fuel flow issues. In addition, old dried o-rings are notorious for bad running symptoms and in my experience, many of these things can act in concert to cause poor running.

Give us a bit more info please.

spyug

[exzachtly1]

You don't mention anything about the state of the carbs. Have they been cleaned recently and rebuilt with fresh o-rings? Have they been bench synched? Vacuum synched?

It would be helpful to know since the fluttering and bogging point toward plugged jets/passages as well as fuel flow issues. In addition, old dried o-rings are notorious for bad running symptoms and in my experience, many of these things can act in concert to cause poor running.

Give us a bit more info please.

spyug

Yep, had them off a month or so ago for a full year down, soak, cleaning and new rings. I also replaced the rings on the intake boots. Unfortunately I do not know if the problem existed before cleaning as I did not ride the bike hard enough before. Basically I never revved it that high because I was a new rider and just taking it at low speeds around the block. I can say however that the idling and lower rpm performance improved greatly.

I have not yet synced them since I don't have the tool yet. Just bench synced by eyeballing it... As far as I could tell they were pretty spot on already but I'd really like to vacuum sync soon.

If you look through the other thread, you'll see that I'm planning to do valve clearances and a compression check soon, along with replacing the airbox boots and clamps. I'm also going to do some electrical tests to see if that's an issue.

I'll have to test for proper petcock operation but it does sound like its working... I can hear a click or pop when i flip it to prime. If I'm still having issues tomorrow I supposed I will open one of the float bowl drains to make sure theyre getting fuel.

Anyways, I didn't really intend to make this thread a dupe of the other just wanted to see if there were any thoughts as to why I'm having starting issues after having the carbs off.

[koolaid_kid]

When that happens, I pull a drain screw out to see if the bowls are filling. I put a towel under the carb set, of course.

[azr]

Welcome to working on a 30 yr old GS...don't worry after pulling the carbs for the second or third time and going over every electrical connection on the whole frickin' harness and adjusting your timing for the 4th time, you'll come out of the house after a 'cool down' time hit the start button and she'll fire up like she's been running 100% the whole time and you'll never figure out what was actually wrong...

[chuck hahn]

You dont have the vent nipples capped off or the actual vent hoses plugged do you? If so unplug them so fuel will flow thru all the carbs....thats the function of them being tied together with the little black coupler between them. Secondly, did you check to see if the floats and float needles were freelky working before putting the bowls on? I had a few that had hung up and wouldnt let fuel in ( stuck shut ) Third...did you check to see if you possibly had hooked the coil plug ins and theres no spark? Removing and reinstalling the tank has been known to snag them from time to time and unwittingly they are unplugged by accident.

[tom203]

Check for fuel in bowls, make sure throttle plates are bench synced to just about fully closed position, activate "choke" fully (with no throttle input) and hit starter button.
Back to advance mechanism- you should be able to push on little projection (the metal tab that swings by coils) with screwdriver and rotate it 30 degrees clockwise - release and it should spring back nicely. I just checked mine.

[hjfisk]

You dont have the vent nipples capped off or the actual vent hoses plugged do you? If so unplug them so fuel will flow thru all the carbs....thats the function of them being tied together with the little black coupler between them. Secondly, did you check to see if the floats and float needles were freelky working before putting the bowls on? I had a few that had hung up and wouldnt let fuel in ( stuck shut ) Third...did you check to see if you possibly had hooked the coil plug ins and theres no spark? Removing and reinstalling the tank has been known to snag them from time to time and unwittingly they are unplugged by accident.

Ya what he said, you don't have the vents plugged off do you?

[Frank Z.]

When that happens, I pull a drain screw out to see if the bowls are filling. I put a towel under the carb set, of course.

This! ^^^^^
My experience is that the vacuum pulse generated by the engine is not enough to fill empty carb bowls, thus killing your battery. I have to prime my carbs by the old suck-on-vacuum-tube method when the bowls have been drained... but i have the devil-spawn '80's petcock, so your attack may be a bit different.

[exzachtly1]

Welcome to working on a 30 yr old GS...don't worry after pulling the carbs for the second or third time and going over every electrical connection on the whole frickin' harness and adjusting your timing for the 4th time, you'll come out of the house after a 'cool down' time hit the start button and she'll fire up like she's been running 100% the whole time and you'll never figure out what was actually wrong...

Heh. Guess what happened this morning? She started on the first try. I just don't know man. I just hope my brand new petcock is working right.

You dont have the vent nipples capped off or the actual vent hoses plugged do you? If so unplug them so fuel will flow thru all the carbs....thats the function of them being tied together with the little black coupler between them.

I'm pretty sure there was no issue here... part of the reason I took my carbs off was to install the OEM vent hoses that were missing before. So they're on now, and I think routed correctly. So definitely not capped off or clogged.