cold headers

[CatatonicBug]

I have a strange situation. I had noticed that the right exhaust was not puting out as much heat/pressure as the left side. I knew I needed to rebuild the carbs, so I didn't worry about it too much. I finally got the rebuild kits and took care of that today. Got it all put back together, and the problem did not go away. I am able to start the bike (struggles to start when it's cold) and it runs relatively well after a short warm-up. The left side heats up to the point that I cannot touch the headers (like they are supposed to), but both of the right side remains COLD! There is a good amount of air pressure coming from the tailpipe, but something is obviously not right.

I know I am getting fuel to the carbs (the bowl drain lets fuel out when I open it), and I am getting spark to the plugs. It seems like there is something that is keeping the two from getting together in the cylinder. Any idea where I should start?

[DiverRay]

I think you will have to look at the carbs one more time. If the bike runs well at speed, try looking at the spark plugs at idle. Check to see if the two right side plugs, 3 & 4, are sooty or white. That will be the start of your search.
3&4 point to a fuel problem, even though you have "fuel out of the bowl" when you drain it. If the fuel line is kinked, or the octy has a bad/plugged outlet, you can have the problem. After a good nights sleep, two cups of coffee, and a good breakfast, you should be ready to look into it some more.

[CatatonicBug]

The plugs are sooty. I don't know if that means that it works sometimes, and not always, or if the soot is left over from a previous time when it did work properly. Unless someone else has any other ideas, I think I will concentrate on the fuel lines first. I didn't remove the fuel lines from the carbs when I cleaned them. I have already rebuild the octy, but maybe there is something between the octy and the carbs that I didn't get out. Could it be that a small amount of fuel is getting through, but not enough to make the cylinders run properly?

[DiverRay]

If the plugs are sooty, you CANNOT do anything until you change them. Try switching the plugs from 1&2 to 3&4, and run it again. If they get sooty again, you are RICH, and flooding. Too much fuel WILL keep the cyl. cold, just as no fuel will.
I would double check the floats, and bench test everything BEFORE you install the carbs again. As a final note, are you running pod filters, or the stock box??

[CatatonicBug]

I don't have a bench to test on... I do all my work on top of my trash can in my open carport (kinda cold out there ) As far as I can tell, everything on my bike is stock, including the airbox. I double checked the floats, and I know they are not sticking. I will play with the plugs in the next few days and see what I find.

[oldyam80sg]

MY SG did almost the same thing as yours.It would idle fine and be ok when i took it on short trips around the block.But when i touched one of the exhaust pipes it was lukewarm at best.Finally came down to crap under the needle valves.Those little screens were plugged with gunk and very little if any fuel was getting into the carb.If the plugs are black with soot then you need to change them or swap them like DiverRay said.Good luck. P.S. I had to work on the bike in a storage unit parking lot and the owners complained every time i went and worked on it.The day i finally got it good enough to ride out of there was a relief.

[TopCatGr58]

Just to add more confusion!

Hey Bug,

Most likely it's the carbs as has been stated. But there has been a situation where one side/pair of cylinders misfiring was actually electrical related, even though they were not the proper pairing ie. 1-4 or 2-3 for the commonly shared electrical components. The problem was a weak voltage going to the ignition high tension spark plug coils. They would generate enough power to fire the PRIMARY spark plug, but not enough to flow thru the engine, and fire the secondary plug in the shared circuit!

So...aside or after you double check your carbs, ensuring you have the proper float heights, no obstructions in fuel and AIR flow, etc., you can then check the ignition side. Check the spark plug caps themselves for resistance, should be 5-8kohm, when rmoved from the plug wires. Inspect the wire ends for corrosion. Once removed the plug caps for all 4 wires, check the secondary resistance of the coils, between the spark plug wire ends for a matching pair, 1-4 and 2-3, should be about 15kohms.

Also, check the red/white power wire to the coils using a voltmeter, should have ~12 volts with key on.

Good Luck!
T.C.

[tarzan]

If you didnt change or at least take out and clean your plugs before trying to run it ,there is a good chance you just have two fouled plugs from before the carb rebuild.I would buy new plugs and install them first.
Then if you still have the problem look elsewhere.This is assuming you got all the circuits inside the carbs clean.Did you look at the o-rings under the needle seats.That is often a flooding problem.

[oldyam80sg]

You can also take the spark plug caps off,snip off a little bit and screw the caps back on.Sometimes the wires go bad on the ends and a snip is all it takes.This has happened to me also.Good luck!

[planedick]

Let's don't forget

Proper syncronization is key to proper running engine.

[Ivan]

Lets go back to the rebuild. What did this entail?

I have seen some "rebuilt" carbs that were merely sprayed down with autozone carb and choke cleaner and blown dry with compressed air.

When I refer to rebuilt carbs, it means that I have taken the carbs completely apart, not one piece still assembled to another, the bodies and metal parts soaked in caustic, and every hole or port blown through with either spray carb cleaner or compressed air.

My way is a tad over kill, but it was the way I was taught. I suspect you, having only a carport to work with probably pulled the carbs, cleaned them with spray cleaner, and replaced the main and pilot jets, needle and seat, and bowl gaskets. Now, I am not saying you did anything wrong, as that should most likely been a good enough cleaning. Like I said, I do overkill.

I would suspect if your pipes start getting hot when you rev the engine to about 2500 or 3000, the problem is in your idle circuit. If you bought the kits that had new pilot jets, and you replaced them, that would mean there is an obstruction in the hole past where the pilot jet sits. Pull the pilot jets out and stick the red spray tube of some spray cleaner in there and spray until you see it come out the throat of the carb. Make sure those idle circuits are clean.

If the cylinders stay dead at all rpms, I would suggest that the needle and seat may be passing fuel, but there is an obstruction to where they just can't keep up. Seeing that you have the right side not firing, I would pull the hose off and open the petcock that feeds it and drain some fuel into a cup. Just enough to see that the petcock is flowing enough fuel to fill the carb bowls. Your sig has a MNS listed so you should check both the "Prime" and "run" positions. Also, look into the cup and see if there are any chunks of crap that came out.

If you have good fuel flow and quality there, hook the hoses up to the petcock again, and pull the hose off the T. You will have to put some vacuum on the "octy" and make sure fuel flows through it as well.

If you have good flow through the octy, you'll need to pull the needle seat out and be sure there isn't any gunk behind that.

Also, I only ventured down the trail of the carbs, since that seems to be where the evidence leads. It may be smart to pull the airbox bottom end off and squirt some carb cleaner in the holes of those carbs to listen for an rpm change. if the engine revs a bit when you do this, it is a fuel problem, or an excessive air problem. Also, spray some carb cleaner around the rubber carb boots and the cylinder head, and listen for an engine sound change. There is a possibility that they are cracked and letting too much air in. This would cause a definite miss at idle, but not be as bad at higher engine loads.

That's all I can think of for now. I need more coffee

[CatatonicBug]

My rebuild included most of what you mentioned. I replaced all of the parts included in this rebuild kit, except for the small round silver plug thingy (center right) and and the tiny o-ring next to it. I couldn't figure out where these go.

Only things I didn't do was separate the carbs from each other and remove the butterflies.

I was sure to spray carb cleaner through each and every port and made sure it came out the other side. The plugs are relatively new, as I replaced them in October right after I got the bike. I will try swapping them around to see what happens.

I know I need to sychronize, but that will be the finishing touch after I get everything running the way it should be. My neighbor has the synchronizing rig, but I only want to have to do it once, after I am done with everything else.

[bikerphil]

When the bike is idling, if you pull the plug wires off 1 at a time, do you have a dead cylinder? I've had a coil go bad before (mikesxs), and I replaced the coils with ones from an XJ and all is fine. The coil would only fire one plug. Just looking at the electrical angle of things since you are pretty confident about the carbs being clean. HTH

[prometheus578]

"And there's the answer..."

I replaced all of the parts included in this rebuild kit, except for the small round silver plug thingy (center right) and and the tiny o-ring next to it.

(Forget about the plug... that's to replug the tower where the pilot screw sits)

Pipes don't get hot at idle... Idle circuit messed up.
Those little O ring thingies are part of the idle circuit.
They go next to the little metal washers shown there... which go on the ends of the pilot screws.
Now... unless one knows beforehand that there are those little O rings in the carbs, they are easy to overlook... being down deep in the pilot screw well.
So... you get to pull your carbs again.
Take out the pilot screw, the spring and the little metal washer. Fish down in the well for the O ring with a dental tool or something sharp and hooked, etc.
You can also blast the area with compressed air, though you'll never find the o ring afterwards.
Two things could have happened when you cleaned them the first time. On the cylinders that aren't firing, when cleaning the carbs the old o-rings fell out and you didn't notice, or....
And I have seen it a'plenty.... the old O rings where crap, fell apart and chunks of them are blocking the idle circuit.
Pull the carbs, make sure the old o rings aren't in there, install the new o rings and try again.
The order of assembly is Take the pilot screw...
put on the spring... put on the metal washer.... and then put on the O-ring... then put the pilot screw into the hole and adjust it.

Oh yeah, and like everyone is saying.... replace the fouled plugs.

"My bike doesn't run, but I don't know if it's because of the carbs... or the fouled plugs"
Trying to diagnose a bike that has fouled plugs is impossable... 'cause you don't know if it's the plugs causing the problem.
Replace them!

[Ivan]

If you didn't remove the throttle shafts, and you used "carb dip", the brown stuff in a bucket, chances are your throttle shaft seals are shot. Behind the levers on the throttle shaft, there are small seals that keep air from entering around the throttle shaft.

The small oring in the kit goes along with the small washer and spring below the idle needle. If you dunked the carbs, that is probably shot as well. I used a bread tie with the plastic stuff partially removed and a J bend in it to remove them prior to cleaning.

The aluminum plug is for covering the idle screws. They are part of the EPA's save the world from idiots campaign, in which some mystical beast misadjusts idle screws on carburetors and destroys baby seals, the arctic ice caps, turns Mars red, and makes our coffee taste bad. IOW, they aren't necessary. Also, 1980 and newer vehicles up to 1992 (?) only had 85 mph speedos, because people won't go faster than 55, if their speedos only show 85. This will save lives, because anything over 55 is so close to the speed of light, that matter may interchange with energy and set off a nuclear reaction with the fumes from your mis adjusted idle jets.

Ok, I am off my soap box now.

If you just used spray cleaner, you're probably OK, since it won't eat rubber like the caustic stuff does.

If you did dunk them, don't worry, find an old mechanic in an old shop and see if he can dig through his extra stuff from rebuilding carbs since 1902, and find some like seals. You probably still have the small orings, so you can replace those as well. The hard part about removing the throttle shafts is that the screws are staked from the other side of the shaft. You'll either need a really good fitting screwdriver or a dremel to grind the back of the screws off. The important thing is to remember to stake the screws again when you replace them.

Now, back to the bread tie. It can be used to give your carbs a "Kansas Synch" by making sure the butterflies are all the same distance from the throttle body. I did this and got the synch screws within a half turn of what the gages finalized to.

One other thought. Some times the idle screws get a ham handed adjustment by a PO and the tip breaks off in the body. There are several tech tips on removing them if you need to.

Hope you get it runinng. And DON'T GIVE UP!