Some questions about carb tuning and a couple other questions

[79XS1100SF]

I had to replace the outer left carb on my 79 XS1100 special with a set of carbs from a 79 that I bought on Ebay. After I got them, I decided to just pull the left carb off of the set that I bought to replace the broken left one of mine. I stripped my carb apart since it was clean and used the parts to put into the other carb I bought, since they were dirty. I stripped the new carb down and cleaned the heck out of it and then installed the clean internals from my old carb. By eyeballing the carbs the new left one was really close in sync with the original 3 carbs from my bike.

When I got it started it was running great. It had good throttle response. But I had borrowed my friends mercury sticks to sync them anyway, so I prepared the bike by turning the gas tank around and hooking it up to the fuel lines, removing the vacuum line from the vacuum control splitter, the vacuum caps off of carbs 1, 3, and 4, and turning the petcocks to the Prime position. I had hooked up the vacuum lines from the mercury sticks to 1-1, 2-2, 3-3, and 4-4. Before I sync'd the carbs the bike was idling very smoothly. I started by syncing the 1 and 2 carbs by adjusting the adjusting the slotting screw between the 1-2 carbs until the mercury in tubes 1 and 2 were even. Then I adjusted the 3-4 carbs in the same manner until the 3 and 4 carbs were even on the mercury sticks. I did notice that the bike was still idling but not as smoothly though. I wasn't trying to die either. Lastly I adjusted the sync screw between the 2 and 3 carbs to bring both pairs together. I noticed that the bike was idling less smoothly then it had before I sync'd the carbs, but it was still idling without trying to die on me.

Then I removed the mercury sticks and installed the tank, fuel lines, and vacuum caps back on the intake manifolds. I did notice that it was a little more hard starting compared to before I sync'd the carbs, and it didn't help that my battery wasn't fully charged up. But it would crank over and start with a somewhat charged battery. So I jump started the bike and had it running, and it revs great when you blip the throttle or just roll on the throttle.

I did notice that it smells a little more rich compared to before I sync'd the carbs. I'm wondering if the idle mixtures screws need to leaned out some? When I replaced the idle mixture screw in the left carb that I replaced, I counted how many turns it was out from a gentle seat, and it was at 3.5 turns out. I read on another thread on this forum that they came factory at around 1-1.5 turns out from gentle seat. Is that correct? I have a Yamaha manual but it says nothing but that the idle mixture screws are set at the factory and don't need to be adjusted. How many turns out do you think I need the idle mixtures set at for 1800' elevation? I'm assuming that I'll need to get them set and then resync the carbs again right?

Also, I noticed that my Neutral light is staying on even though I'm shifting into all the gears, and it didn't do that last fall. Where do I need to look at for that? The last question is, I was letting the bike idle while it was parked and I noticed that a little motor oil had puked out from what looked like was under the front of the seat towards the left side of the engine and it ran down the left side of the air box down to the transaxle drive shaft area. What could've caused this? I installed a new oil filter and Mobil 1 synthetic oil in it last fall, but I can't remember if I had the bike on its center stand or the side stand when I filled it with oil. So I'll have to put it up on its center stand and check the oil level. Could it be that it just got hot enough from idling with no air flow going over the engine to make it puke out a little oil? Is there a crankcase vent tube up near the top of the frame under the seat?

[79XS11F]

My 7911F idle screw required 1 and 1/4 turns out from lightly seated.
Rob

[excess11]

Carbs

After carb snyc set idle where it should be adjust idle mixture screws on each carb until you get peak rpm from each carb but make sure to keep idle speed is where it should be during this process it will creep up on you as you peak out each carb. To find the peak idle mixture on each carb. Remove air box. Start bike warm it up. I usually put a box fan in front of the bike to keep it from getting really hot while idling for extended period. I Start with the left hand carb and work right. Does not really matter. On left carb adjust mixture screw in until the rpm's drop then slowly turn screw back out about 1/8th turn at a time and then wait for idle to stabilize again. Take a can of carb cleaner and give the carb the tinyist shot of cleaner and listen if rpm's go up or down. If the mixture is still lean idle will go up if rich idle will go down. Adjust the screw in or out by what ever the idle responce is. You will eventually find the peak setting for this carb. Once you do this reset the idle speed to correct rpm then proceed to the following carbs until you are finished. This is the best and most acurate way I have found to set the idle mixture.

[TopCatGr58]

Your neutral light staying on could be a simple as the wire grounding to the frame, check it where it connects to the engine down under for wear/rubbing, etc. Remove it and see if light is still on, if so, then it's grounding to the frame somewhere!?

Secondly, your oil leak could be several sources, but most likely the valve cover and rubber half moons. Synthetic oil is much more slippery and can leak out thru otherwise good sealing gaskets!!

The crankcase vent goes to the airbox, that large hose. The smaller hose from the middle gear is what is vented up under the tank.

You need to get a FAN and put it on high infront of the motor while you're synching carbs and such! I remember posting a copy of Ken Talbot's pilot screw tuning technique by ear in the tech tips!
T.C.

[79XS1100SF]

Thanks for the info! I really appreciate the knowledge that others have especially since this is my first street bike. I've been around motocross bikes, 3 wheelers, quads, snowmobiles, etc. But each machine is different from the others in certain aspects and I'm trying to learn what I can to obtain that knowledge as well. I called the local Yamaha shop to speak to a friend of mine that runs it, but he was gone today. The other guy there said that 3.5 turns out seemed like a lot. I'll look at the bike tomorrow and see if I can get it tuned up more so I can ride it to work on Monday.

What's kind of weird for me, is that I turned 41 this last April and I've been riding enduro bikes, motocross bikes, 3 wheelers, and quads since I started riding them at 9 yrs of age. I never thought that I wanted to ride a street bike because of the idiots out on the roads that don't watch for motorcyclists. But with the fuel prices the way that they are, I'm tired of spending $60 a week on gas in my Toyota 4x4 to drive to work for 5 days a week. So I finally took the Team Oregon Motorcycle Safety Course and passed it. Then all I had to do is present my Certificate to DMV and they gave me my motorcycle endorsement after giving them $74. The Yamaha XS1100 I got free from a friend that didn't ride it anymore. I spent $105 on a new battery, spark plugs, oil, filter, new fuel lines, and a front tire. Of course then I had to dole out $140 for a lost title and transfer into my name and new license plate registration tags. I bought the carbs for $112 off of Ebay. So all in all, I got a nice street bike for around $350 or so.

[TomKat]

ONLY $350.00? You are SOOOOOO wrong my friend. Classic rides are an addiction, as you will see and will continue to feed for years to come. The "Free" ride your friend gave you will turn into an obcession that many on this site happily share.....

[79XS1100SF]

I know where you're coming from Tomkat. I plan on getting a different seat with a back rest for my wife when she wants to go take a ride with me. I'll definitely need to get some kind of saddle bags for it too.

I have a 66 GTO hardtop that I bought from my uncle almost 2 yrs ago that I really enjoy driving. I have a different camshaft and lifters to install in it, as well as, a HEI distributor, Edelbrock intake, etc. But at the moment I'm trying to find a radiator for it without breaking the bank so to speak.

[TADracer]

Rob, I recommend you do a complete carb tuneup and there is a certain order you should do this in, considering that your carbs are clean and floats are set right. Here is what I do and it seems to work well for me down here in the thick Louisiana air.

1, warm up bike with a fan infront of the engine. Set idle to 1,100 RPM and dont use the bikes tach, it is not accurate enough. Use an alternate tach with a fine scale because you will keep watching the tach alot.

2, Set your idle mixture. Start at 1 1/4 turns out from lightly seated and the turn each screw out in 1/4 turn increments until you get past the highest and smothest RPM at idle and the engine begins to run rough. Then turn back in in 1/4 turn increments until the idle smooths out. The mixture screw final setting may be different if you change pilot jets or make other mods.

3, reset your idle RPM to 1,100 again and then sync your carbs. if using a carb stick, do not rev the engine or else you may suck in some mercury.

4, reset your idle RPM again to 1,100.

It takes patience and a fine touch and you must wait about 15 seconds between changes in the mixture or sync screws for the engine to level out at the new adjustment. But you will be rewarded with a smooth idle and a kick off the line.