Gas consumption is way too HIGH, Mileage too low

[RichV]

Well I rode the bike today and I've got good and bad news.

First, the good news. The speedi sleeve fixed the seal leak problem. No more oil on my boot. I also got up to a very high speed and there was power to spare.

Now the bad. The engine still sputters and #2 plug still foals. A little bit of black oil still drips out of the exhaust pipe joint when stopped (not alot).

I seem to still have a small leak in the front center of the head gasket. Oil from the cam chain gallery.

So I don't know what's going on. None of my swaps seemed to have any impact on the engine. My only troubleshooting test I have left is to swap the #2 and #3 leads and put in the hotter plug. I'll can also check the head bolts again before I go out.

I also found some smaller leaks like around the oil pressure sensor and one corner of the valve cover. Small stuff easily fixed. Now that the seal no longer leaks, I can ride the bike more.

As for the problem with #2, I'm running out of ideas.

[RichV]

Yesterday I swapped the #2 and #3 wires and re-torqued the head bolts. I also tightened up some things and stopped the leaks. I actually had a loose valve cover bolt. The oil pressure switch was also loose and took over a full turn to tighten. It was the source of my major leak on associated with the tail pipe.

I still have the bad mileage (20-25) and the stutter on medium acceleration. It seem to exist in the lower RPM range mostly.

The problem still exists but the fouling seems less. The #2 plug was less fouled and the oil leak from the exhaust pipe appears to be gone. So is the leak at the front center of the head gasket. That all could be from the re-torque. #3 looks the same as before so I don't think it was the wire swap.

Today I will try the hotter plug and check the torque again. I hope I'm not doing something to the studs. When I originally disassembled the engine I removed all the studs except the two between the #2 cyl and the cam chain gallery. They would not come out and I didn't want to break them. It's odd that my only "problem" with the engine seems to be coming from this point.

Once again thanks for the help.

[Bonz]

I am bummed for the bad gas mileage you still have. I have read and re-read the thread and the issue with your stutter on medium acceleration in the lower rpm range has been a constant even when the bike is running "great". Are you able to tell a lean stutter from a rich stutter? This bike should be running pig rich, and one cylinder or carb to my mind wouldn't be causing the issue on a bike that runs well then goes south after 20 minutes of riding or miles and miles of riding. It is a cumulative affect of too much fuel going into the engne that is causing the issue, not a wholesale "dump" of fuel that all of the sudden happens when the bike starts running worse.

My gut tells me the carbs, despite all your hard work, are not doing what they should. Mid 20's for gas mileage is really low for these bikes even on the worst day of flogging on a twisty road. Forgive me if i missed somethng, but here goes.

Air filter is in good condition? Do the needles have an adjustable clip position (shouldn't on an 80+ model)? If you have the correct non-adjustable needles, are any shims being used to adjust the needles? Are the diaphragm lips seated/sealed under the carb tops? Is the enrichener disengaging completely when pushed in? And all the float needles, float seats are genuine Mikuni along with new o-rings on the needle seats that aren't damaged or nicked (I have pinched them when pushing the needle seats in). Are the needle seats seated fully when you push them in? None should be an easy push in or an easy removal, they should be downright tight. Cam timing hasn't been altered or thrown out of whack?

I am just going through the checklist of stuff that leads to the bad gas mileage that I didn't see specifically asked about or stated already, but again, my apologies if I missed stuff that was stated.

[RichV]

I am bummed for the bad gas mileage you still have. I have read and re-read the thread and the issue with your stutter on medium acceleration in the lower rpm range has been a constant even when the bike is running "great". Are you able to tell a lean stutter from a rich stutter? This bike should be running pig rich, and one cylinder or carb to my mind wouldn't be causing the issue on a bike that runs well then goes south after 20 minutes of riding or miles and miles of riding. It is a cumulative affect of too much fuel going into the engne that is causing the issue, not a wholesale "dump" of fuel that all of the sudden happens when the bike starts running worse.

The problem has migrated over time with the implementation of various fixes. One of those fixes took care of the "works for 20 minutes" problem. I think it was the a #3 spark plug cap that broke down over time and bad jets which I replaced. Now I have the "stutter" at low RPM and low mileage. I started at 10 MPG and I'm now at 20+ MPG so things are improving.

So right now it all seems to center on #2 carb and a fouled #2 spark plug.

Air filter is in good condition? Do the needles have an adjustable clip position (shouldn't on an 80+ model)? If you have the correct non-adjustable needles, are any shims being used to adjust the needles? Are the diaphragm lips seated/sealed under the carb tops? Is the enrichener disengaging completely when pushed in? And all the float needles, float seats are genuine Mikuni along with new o-rings on the needle seats that aren't damaged or nicked (I have pinched them when pushing the needle seats in). Are the needle seats seated fully when you push them in? None should be an easy push in or an easy removal, they should be downright tight. Cam timing hasn't been altered or thrown out of whack?

1. New air filter.
2. No adjustable clip and the needles I have are the right one. I've also swapped #2 out with one from a good carb. I assume the lips are sealed but I will add some RTV just to make sure. I can't see any holes in the diaphragm.
3. Is the enrichener disengaging? Don't know but this sounds like an excellent next step to check. This could be the smoking gun. Today's test indicated that this "might" be it.
4. All float needles are working and seats are all the way in. I've over tested them and swapped them out. I've adjusted the float heights and tweeked them over and over. I've tested the fuel level while static, mounted, and running. I even swapped the needle and seat from a known good carb.
5. Cam timing is correct. Valve shims are also correct and recently double checked. I have them on the high side of the adjustment range.

Today I checked the idle needles to make sure they were working properly. I removed them and checked the holes to make sure they were clear. I installed them to 1 1/4 turns and re-balanced the carbs.

Now the fun starts. I adjusted all in a normal fashion. I closed them and the engine RPM dropped raised them and it dropped then found a center point. I have to do it by ear since I don't have a tach or colortune.

#1. Didn't change much
#2. RPMs did not drop when closed or opened. Smoking gun?
#3. A little richer (runs very hot right now).
#4. No change.

So something is keeping fuel going to #2 when the idle adjustment is closed. I suspect it's the enricher (what else can it be???) but I'll need to pull the carbs and check. I've become an expert at pulling these carbs quickly.

More to report later.

[Bonz]

Hi, use rubber cement to seal the edges of a diaphragm lips. The stuff you used as a kid to do art projects in school. Holds great, and comes right up. Trust me, it works great!

[GLoweVA]

Rich, i have an idea, how about i drop by a set of carbs off my SG and you run them for a week or two and see how it runs.
I'm going to be on that side of the HRBT Sun afternoon.

I suspect that your #2 problem may be the float post issue. Seems that if the float stuck open then the bowl would overflow past the needle and feed the cylinder all the time, not so much a problem at mid throttle, but at idle too much fuel would foul the plug.

[RichV]

Rich, i have an idea, how about i drop by a set of carbs off my SG and you run them for a week or two and see how it runs.
I'm going to be on that side of the HRBT Sun afternoon.

I suspect that your #2 problem may be the float post issue. Seems that if the float stuck open then the bowl would overflow past the needle and feed the cylinder all the time, not so much a problem at mid throttle, but at idle too much fuel would foul the plug.

I'm in the process of putting the carbs back together right now. If my current "fix" does not work I would like to try your carbs. Let me know when you can drop by tomorrow.

Do you remember where I live?
9050 Barnes Road, Toano, VA 23168

[MPittma100]

Carbs

You should put fuel to the carbs with a remote fuel source while the carbs are off of the bike. Observe and check for leaks. Leave in this position for about an hour or longer to verify no leaks. Tilt them to simulate being on the side stand. Finding and repairing any leaks while off of the bike is much easier and faster.

[tarzan]

I read through this thread loosely and noticed the subject of P/U coil wires mentioned briefly. I would look closer at that if I were you. You mentioned you have a second set of them. Why not swap them out to rule it out. I have had a few of these bike have that issue. One I worked on yesterday on another guys bike had a completely broken wire. It would stumble off idle pretty bad and then die. He had previously been able to ride it with a stumble.Depending on the break, it could be intermittent at first and get worse. JAT

[RichV]

You should put fuel to the carbs with a remote fuel source while the carbs are off of the bike. Observe and check for leaks. Leave in this position for about an hour or longer to verify no leaks. Tilt them to simulate being on the side stand. Finding and repairing any leaks while off of the bike is much easier and faster.

I have a bench setup I use to static test the carbs. I smack them a few times and jiggle them about to see if the level changes any. I then leave them there over night. After all that, I load them on the bike, level the bike and carbs and static test them again.

Finally, while syncing the carbs I have a tube attached to the bottom and I watch the float levels to see them change.

My problems center around #2 carb and cylinder. When I turn the idle mix down to closed, the RPM does not drop like it does for the other carbs. The vacuum does go up a touch knocking the carbs slightly out of sync and returns to where it was when I open it slightly.

I'm no expert at this. I'm learning as I go. Right now I'm focusing on the sympton presented by the #2 idle mix screw. I tore #1 and #2 appart again last night and adjusted to enrichers making sure they close whem the level is all the way in. I also RTV'ed the edges of the diaphragm to make sure they are sealed.

The fouled plug remains a problem along with the dark oil dripping out the exhaust pipe. As of now, I have tested, changed or swapped:

1. All valve seals and clearances.
2. Piston rings (and rechecked them later).
3. Cleaned and Rebuilt the carbs completely using authentic jets.
4. Cleaned and sealed head gasket using a copper sealant.
5. Swapped out all electronic components with spares I have including the ignition unit.
6. Replaced all plug caps and replaced the plugs repeatedly. Swapped out the coils and reversed the wires.

I fixed a lot of little problems along the way as well but the one mentioned above is the only one remaining and it's kicking my a$$.

[RichV]

I read through this thread loosely and noticed the subject of P/U coil wires mentioned briefly. I would look closer at that if I were you. You mentioned you have a second set of them. Why not swap them out to rule it out. I have had a few of these bike have that issue. One I worked on yesterday on another guys bike had a completely broken wire. It would stumble off idle pretty bad and then die. He had previously been able to ride it with a stumble.Depending on the break, it could be intermittent at first and get worse. JAT

I have a second set but I don't know how good they are. They were submerged. I tested the wires and cleaned the connectors. I also replaced the cover for the wire bundle.

I was under the impression that the problem would exist in both cylinders in the pair (#1-#4) (#2-#3). I only see this in #2. #3 works fine and does not foul.

My symptoms currently are:
1. #2 fouls with a wet black substance. This has gotten better over time and a hotter plug may have helped.
2. Stutter during acceleration (gets worse with time)
3. Oil like substance out of the #1/#2 exhaust (#2 is the source). Not much and it doesn't seem to affect the oil level so it might just be gas and carbon which I've been told can "look" like oil.
4. Fuel smell/smoke out #1/#2 exhaust. It's also a little loader that #3/#4 exhaust.

[RichV]

Thank you George for dropping by that rack of carbs to try. With you great help we were able to confirm that my #2 is definitely causing the problem.

As it turned out, #2 was not firing at all. The plug was sparking but the gas wasn't there. We swapped out the entire rack with a set from an 80 and it started right up.

#2 is now firing and all that oil in the pipe made a lot of smoke.

But why is #2 messed up? It's unique in the set so I have to find a new one.

Once again, Thanks George.

[MPittma100]

Problem Identified

That is good news - problem found. Just have to fix it now. I have not seen or heard of a carburetor doing this before. Would be interested in finding the exact failure in that one. Carbs are available on eBay and Craigslist occasionally. Check with Andreas Weiss on this site to see if any are available. May find it a little more difficult to find a single one. May have to buy a set.

eBay set:

http://www.ebay.com/itm/81-YAMAHA-XS...e19fd5&vxp=mtr

[red bandit]

You never know what the PO did. Might have used a drill to remove jets and ruined one or more bodies.

[RichV]

That is good news - problem found. Just have to fix it now. I have not seen or heard of a carburetor doing this before. Would be interested in finding the exact failure in that one. Carbs are available on eBay and Craigslist occasionally. Check with Andreas Weiss on this site to see if any are available. May find it a little more difficult to find a single one. May have to buy a set.

eBay set:

http://www.ebay.com/itm/81-YAMAHA-XS...e19fd5&vxp=mtr

Don't know what I would do with a set. Maybe someone else needs one of the others and is willing to go 50/50 with me.

I did an experiment, at Georges suggestion, with a wet/dry vac to see if I can find any leaks. I added some other steps in order to get measurements.

I opened the drain at the bottom of the carbs and attached a clear hose stretching it to the floor where I had a bottle of water. I then ran the vac on the intake simulating engine vacuum. The water level in the tube rose evenly for all four carbs about an inch. If I put my hand over the intake, the water level rose to a few inches below the carb on all but #2. It sucked in the water filled the bowl and into the chamber. I don't know if that means anything but are there any exterior vents on the carb?