Fresh rejet, won't start.

[burp reynolds]

79 GS 1000 - I just had my original mikuni carbs rejetted for pod filters, couldn't start the bike, called the carb guy, took his advice and turned in the air mixture screws under the carbs by 1/2 turn, got the damn thing to run (like a sickly child, but it was running) turned them in another 180 degrees, ran well enough to drive to mailbox and back, let it cool down and charge up, tried again next morning, couldn't get it to start. Have turned them in and out a few times now, probably badly out of synch, want to start over. Can I set the screws all to same spot to start over? How? What other adjustments can I try with the carbs on the bike?

Is there a thread that covers this stuff? The forum search fn is useless on this site. Every search yields either no result or at least 500.

I think I have an ulcer.

[Nessism]

You have two adjustments on your carbs; pilot fuel screw and pilot air screw. On a stock bike the fuel screw should be roughly .75 turns open and the air screw about double that. This is a good starting point. It's hard to reach the fuel screw but you can do it with a small screwdriver stub. Be very careful when bottoming out the fuel screws since they have very sharp tips that like to break off inside the carb body. In fact, I'd check this exact thing before you go much farther.

To search, use the advanced search function. I usually use "title only" since it finds more specific results.

Good luck.

[burp reynolds]

You have two adjustments on your carbs; pilot fuel screw and pilot air screw.

Good luck.

Is the pilot fuel screw the one on the bottom? And the air screw on the side? All the shop manual says is to pretend they don't exist. And what do they do?

[Big T]

Fuel screw is bottom front

Neither screw syncs the carbs.

That screw is on the top of the slide, under the carb top (held on by 3 screws)

Exactly what did this carb mechanic do to your carbs?

[burp reynolds]

Fuel screw is bottom front

Neither screw syncs the carbs.

That screw is on the top of the slide, under the carb top (held on by 3 screws)

Exactly what did this carb mechanic do to your carbs?

Thanks. I guess that he took them apart and gave them an ultrasonic cleaning, then put them back together with new gaskets and bigger jets. He said he set the fuel and air screws to the 'factory' settings.
At 1/2 turn tighter than factory I managed to get the thing running, so I really wish I could get it back to that point and tweek it from there. But overnight, I lost my place.
Last thing I tried was to turn them all the way in, and then back them out 900 degrees. I got a little kick when I tried it at that position, but possibly from some leftover ether still in the throats from this morning. So from there, I backed them out 90 degrees, turned it over, in 180, turned it over, in another 180, and so on until the screws hit bottom.

[Big T]

Okay, you're going backwards.

Turn all 4 air screws to lightly seated. Back out 1 1/2 turns - that's your starting point.

Turn all 4 fuel screws to very lightly seated. Turn back about 3/4 turn

Now, you're approximately factory settings.

What size jets did he install? Why? Do you have a 4-1 header? Pods? What brand?

If it starts with ether , but not on its own, either the jets are still clogged or you have another fuel flow problem.

[burp reynolds]

On a stock bike the fuel screw should be roughly .75 turns open and the air screw about double that.
Good luck.

Wait a minute, I guess I read that too fast. So the fuel screw, on the bottom of the carbs should be 270 degrees from the closed position on a stock bike. That's pretty tight. So when I closed them by 180 degrees, they were only open 90 degrees? That can't be right. I'm sure I turned them at least 360 degrees before they stopped, and I think at least 520.

I just drained the float bowls and got some murky leavings out. This gets better and better. So I guess the jets are clogged and I'll have to pull them, right?

Maybe it's just acid reflux.

[burp reynolds]

Okay, you're going backwards.

Turn all 4 air screws to lightly seated. Back out 1 1/2 turns - that's your starting point.

Turn all 4 fuel screws to very lightly seated. Turn back about 3/4 turn

Now, you're approximately factory settings.

What size jets did he install? Why? Do you have a 4-1 header? Pods? What brand?

I guess I was typing while you were typing. Haha.

I haven't touched the air screws yet in light of the fact that it was running once with them where they are.

And the blasted thing was running with the fuel screws more than 3/4 turns out. Go figure, right?

He said he pulled out the #90 main jets and put in #100's. Pods, yes. The cheap kind you can get for 30 bucks on ebay. (I paid Doc Brown 70 out of gratitude for all of the free advice he was giving me at the time. Hell of a mechanic Doc is. Hell of a mechanic. He made half the tools in his shop from scratch.) 4-1, no. Was looking for a Supertrapp on ebay, but project is stalled due to unemployment.

So, is there a way to backflush the jets? I have a bad feeling about the gas.

[Big T]

Sounds like you have a rusty gas tank, or a lot of crud in there. Drain it and have a look.

Cheap pods are pound wise and penny foolish. Take them off and toss them. $30 is not that hard a lesson.

You'll have to pull your carbs and see what crud is in there. Post up some pics.

There is no way to back flush the carbs.

[burp reynolds]

Cheap pods... toss them.

You'll have to pull your carbs and see what crud is in there. Post up some pics.

So, should I go back to the air box, or take out a loan and get some K&N's?

The carbs were fairly clean. a little schmutz down by the drain plugs, I suspect some paint got in there while I was sanding.

Speaking of drain plugs, mine were on their last legs after getting chewed up by thirty years of overenthusiastic screwdrivers, so I covered the heads in epoxy (the only thing on earth I like everything about). When I was done I turned to my wife and said, "That's right, you just watched a man rebuild four bolts with epoxy." I could tell she was impressed, she didn't have to say so.

[burp reynolds]

Homebrewed power siphon

Sounds like you have a rusty gas tank, or a lot of crud in there. Drain it and have a look.

Allright! If anybody ever wants a power siphon, but has little more to his name than a water jug, a motorcycle and a vacuum cleaner, I have a hack for you. I spliced together two carb overflow hoses with an automotive wiring crimp (cut off fat ends of the blue insulator, stuff the crimp into ends of two hoses) burned a hole into the jug with a hot (used) spoke (try not to use torches within 3 feet of open gasoline containers, unless nobody safety conscious is around to criticise) stuff the free end of hose fairly deep into the hole, put tape over the slit you made in the jug while trying to ream out the hole with unweildy knife, apply vacuum to the mouth of the jug, and try to fish around in the tank and suck up as much junk as you can.
See the pictures! Pretend it was your idea! Get totally laid!

http://picasaweb.google.com/lh/photo/yYBJW_c_9o7xGpN0Bzd9JA

http://picasaweb.google.com/lh/photo/B__DO855Hd4R0vOt7VS31A

Ron Paxton: As you can see, it sucks as it cuts.
Wayne Campbell: It certainly does suck. ...

[burp reynolds]

Do I give up?

Damn thing still won't start. Is there any chance I can go back to the original airbox with the bigger main jet I had installed? I just want to drive my motorcycle until it starts snowing. Then I can turn it inside out for three months.

[KEITH KRAUSE]

Just the cheaper pods and totally stock exhaust, no other mod's??
I'd try 115 mains, jet needle e-clip in the 4th position from the top (1 position richer), stock 15 pilot jet try 2 full turns out from lightly seated on the pilot fuel screws underneath, adjust side air screws to 1 1/2 turns out. Bench synch the carbs.
After the bike warms up fully, final adjust the side air screws using the highest rpm method, base idle rpm of 1000/1,100 rpm's. Then it will be ready to vacuum tool synch.
The carbs of course, must be clean, inner o-rings in good shape, suggested new manifold o-rings and be SURE the manifolds are in good shape.
The carbs MUST be bench synched well enough to get the bike running and then they MUST be synched with a vacuum tool.
Before the synch and as a part of basic tuning, the valve clearances and ignition timing must be correct. If you still run points ignition, the points must be in good shape and the dwell set correctly. Use fresh NGK B8ES plugs gapped about .028"
If the above is done right, the bike will run decent but possibly require tinkering with the suggested jetting because cheap pods and stock exhaust are a poor match. But easy enough to re-jet without too much trouble if basic tuning has been done and the bike is ready for the re-jet.
Simply test each jetting circuit at the throttle position each jet operates at. 3/4 to full throttle for the main jet, 1/5 to 3/4 throttle for the jet needle, and idle to 1/5 for the pilot jet.

[KEITH KRAUSE]

Also, if you'd rather go with a stock airbox (which includes the lid), just re-install 90 mains. I'm guessing the jet needles are in the stock position? Try 3/4 turn out from lightly seated for the pilot fuel screws underneath. That will be pretty close to the general factory range. Set the side air screws using the highest rpm method, after it's fully warmed up. Again, bench and then vacuum synch.
Of course, all basic tuning must still be done as said earlier.

[burp reynolds]

I'd try 115 mains...

Ok, I an swallow the rest of that, but 115 mains? That caught me off guard. I was going to try a 97.5 with the stock setup, because I heard these bikes were made to run lean to meet emission standards. I think the carb guy said it came with a 95. He has to deal with a lot of carbs, though. It might be a 90. I need to look again.