Am I overlooking something

[Guest]

So a little background on my gs. I purchased the bike with a crank no start condition. Upon further diagnosis it was revealed that the bike had no spark (signal generator/pickup coil was shot). I replaced it and got it to throw spark. Bike still didn't start. I pulled the carbs, sonic cleaned everything, checked float height, reassembled and reinstalled, and hooked up fuel andvacuum lines. I primed carb bowls, moved petcock to correct position and it still won't start. Am I overlooking something? Everything is stock. Any help would be great.

[chuck hahn]

Full choke and DO NOT twist the throttle.. If you twist it spoils the venturi and nothing under the sun will make it fire.

[chuck hahn]

Note 2...and if the idle knob is in too far that will soil the venturi too. back the knob out till it just touched the throttle linkage and go in 1 full turn. Choke and start. if it stalls when you let off the choke turn the idle knob at 1/2 turn increments until it will idle off choke.

[Steve]

The main thing you are overlooking is telling us what bike you have.

The ONLY thing we know about it is that it is a GS.

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[Taz1000r]

Bike is an 81 gs850. Twisted idle adjustment screw all the way out, twisted in until just on throttle then turned in one full turn. There is something up though because when I disconnected the vacuum line to the petcock that line was creating no vacuum. I hope someone wasn't in there before me and screwed up cam timing. I'm gonna double check the boots and what not. It sputtered once this am after sitting over night. Haven't been able to get it to do it again.

[chuck hahn]

So the nipple at the back of carb 2 isnt producing vacuum?? Thats weird as it rarely ever gets clogged. Is there suction if you out your hand over the face of the carbs and crank it over?? you should at a minimum feel the cylinder sucking..or trying to suck in fuel and air. So now try the idle knob at 1 1/2 to 2 turns in...add another 1 1/2 turn to the 1 turn you already did.

[Taz1000r]

That was my point too chuck. Im gonna pull the air box here in a minute and see if the cylinder(s) are actually creating vacuum. In theory shouldn't it fire with petcock in the prime position, the float bowls would be full. What's the point of the vacuum operated petcock if the floats dictate fuel flow into the bowls?

[chuck hahn]

The vacuum shuts off fuel flow at the tank just like if it were a manual shut off petcock. The shut off of fuel is because the float needles arent a super solid seal and if the carbs weep enough the fuel will get into the crankcase and contaminate the oil. If the contamination isnt caught then you can turn crank bearings, score pistons rings and other things maybe. You want fuel shut off at the tank and never leave it on prime after it starts. Set it to on and the vacuum should hold the diapram open and allow fuel to flow.

[Taz1000r]

It is making vacuum. I'll have to figure out exactly what's going on with the #2 carb vacuum nipple. Pulled the plugs and they looked terrible. Don't have my feeler gauges right in front of me so I couldn't check gap, but they did have gas on them. I'm gonna either clean them or step up to a hotter plug to see if it I'll fire. I'll keep ya posted. Thanks for the help guys.

[Hinermad]

Maybe a dumb question, but are the plug wires connected to the right plugs?

[chuck hahn]

Blow some air down the nipple on carb two to clear it out. Then put the vacuum line on and see if it has suction when you crank it. The gassed up plugs is probably because you had your hand over the carbs and thus they just sucked up a bunch of gas. Dry the plugs. Leaving them out of the bike will allow a lot of the gas in the cylinders to evaporate over night if you let it set.

[greg78gs750]

nother dumb ?....nice fresh fuel?

[Taz1000r]

Yea it's got fresh fuel. I haven't been to look at it since yesterday. I'm gonna deal with the plugs and then recheck to make sure everything is flowing and sealed again. I'll keep ya posted.

[Steve]

It is making vacuum. I'll have to figure out exactly what's going on with the #2 carb vacuum nipple.

OK, let's get back to basics.

First of all, the carbs (and other parts of the bike) are referenced as if you are sitting on the bike, ready to ride. That means they are numbered left-to-right, 1 to 4.
#1 carb will be under your clutch hand, #4 carb will be under your throttle hand.

Next, the nipple in question is the one that is on top of the outlet of the carb, right next to the pilot mixture screw. There are VENT nipples between carbs 1&2 and 3&4, they will have not have a vacuum on them. If you have one of them connected to your petcock, it will never work.

I am only mentioning this because you have not been around long enough for us to get a feel for your experience and mechanical abilities. Sometimes it takes another set of eyes looking at the problem, or, since we are doing this over the inter-webs, a virtual kick in the pants to make sure things are connected correctly.

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[wymple]

If you primed it and no start you need to revisit the electrics.