79 sf,need your advise

[mrtkayak]

Work done
1. Carbs clean and bench sync
2. Valve adjustment.
3. Checked the vacuum advance wires are healthy

problem
1.start bike w/no problem.idle steady but fluctuate every once in a while.
2. Check the exhaust pipe, 3 and 4 not getting hot,1 and 2 sizzles when spray w water bottle.

*need advise,heard about marvelous magic oil (wat a name).
Do you guys used this?
Do you think my rings are stuck?
Pls. Reply. Thanks

[Ranger_xs1100]

I had the same problem on my bike. I really didn't do any troubleshooting though. I just swapped out the ignition unit from my other bike because it was something quick and easy to try.
So the bottom line is...I just got lucky and all 4 were getting hot immediately!

[kboehringer]

Compression?

SNIP.....*need advise,heard about marvelous magic oil (wat a name). Do you guys used this? Do you think my rings are stuck?

MrKayak,
What is the actual compression in each cylinder? Do you have a compression tester?

I have successfully used Marvel's Mystery Oil (MMO) to resolve what seems to have been stuck rings on my XS11. I had very very low compression (basically across the board) and the compression problem was a combination of poorly adjusted valves and stuck rings. Strangely, the bike would idle fairly decent and ran semi-OK with the crappy compression. I started with compression ranges 65#->80#. After properly adjusting valves and several doses of MMO I'm at basically 135# +/- across the board. Stock/perfect compression (according to Clymer Manual) is 142+/- 14psi.

If your compression turns out to be poor.

• Remove your plugs and put a couple TABLESPOONS of MMO in each of the cylinders.
• Turn it over a couple times, preferably by HAND using the timing bolt, otherwise it'll shoot out everywhere.
• I place my plugs back in ONLY A thread or two to keep foreign material out. Leave it sit for SEVERAL HOURS if possible, OVERNIGHT is even better!
• Remove the plugs and crank the engine over several times to eject the MMO down the exhaust and out the plug holes. Place a clean rag over the plug holes (don't ask why I know to do this!) FYI Pistons don't compress liquids and if you accidentally got too much in there you could cause some severe damage if the plugs are not removed.
• Install the plugs and run the bike to temperature.
• Stop & check compression
• I had to do this three times to get to the 135# I have now.

HOT PIPES
Personally, I have no idea why one set of pipes would be hotter than the others unless you were very lean on one side compared to the other. However, you mentioned a nice idle with an occasional hiccup. What do the plugs look like on the apparently hotter side vs. the other side? If your idle is a nice as you say, I wouldn't think one side wasn't getting gas? The 1&2 / 3&4 carbs are on separate fuel feeds.......

CARB SYNC.
Do you have the gauges to do an actual running sync? Personally, I've never had any luck getting the carbs right on the bench.

Looking forward to your responses. Hope this helps.

KURT

[mack]

fuel

When 3&4 fail to fire it's usually a fuel delivery issue. Check the petcock is flowing. Check the fuel line for a kink. Check the fuel and vent t's are clear.

[TopCatGr58]

Hey MrTKayak,

As others have eluded, the 3-4 cylinders are linked via Carbs/fuel, same for 1-2. The cylinders are linked electrically 1-4 and 2-3, so if the pickup coils, ignition coils were bad, they USUALLY show up paired electrically.

Are the 3-4 pipes getting a little warm, or totally cold? If warm, then they are getting a "little" fuel, probably from the mains, but not from the pilot circuit. Start it up and try running it at ~3500 rpms for a minute or so, and then retest for heat/sizzle. If then a bit warmer, then you've confirmed that the pilot circuits are probably still clogged, but the fuel is getting thru the mains enough to then fire at the 3500 rpm zone. IF the pipes are still cold, then you've got some more serious fuel flow restrictions going on....again as mentioned, petcocks, or inlet T's clogged, or the screen on the bottom of the float valve seat is clogged, or the floats are not dropping letting fuel in, etc.!

There IS a more rare electrical condition where fire can be lost on the otherwise normally fuel paired/linked cylinders....like too low voltage to the ignition coils...so that each coil can only fire it's PRIMARY plug....but not enough juice/voltage to push thru the head and back up the other plug. You've got a 79, it uses the ballast resistor system, and the connections can get corroded. When the engine is running power is routed thru it to keep from burning up the OEM coils so the voltage at the coils will be around 9 volts instead of 12 when just starting....power is routed around the BR during starting to provide stronger starting spark.

Other conditions can be corrosion between plug wire and cap, resistor within the cap. As Motoman/Brant likes to say, you need to make sure your carbs aren't having electrical problems!

Keep at it, test, and report back as needed, as well as just to let us know what you find....feedback for us!


T.C.

[mrtkayak]

MrKayak,
What is the actual compression in each cylinder? Do you have a compression tester?

I have successfully used Marvel's Mystery Oil (MMO) to resolve what seems to have been stuck rings on my XS11. I had very very low compression (basically across the board) and the compression problem was a combination of poorly adjusted valves and stuck rings. Strangely, the bike would idle fairly decent and ran semi-OK with the crappy compression. I started with compression ranges 65#->80#. After properly adjusting valves and several doses of MMO I'm at basically 135# +/- across the board. Stock/perfect compression (according to Clymer Manual) is 142+/- 14psi.
I dont have the actual readings on
If your compression turns out to be poor.

• Remove your plugs and put a couple TABLESPOONS of MMO in each of the cylinders.
• Turn it over a couple times, preferably by HAND using the timing bolt, otherwise it'll shoot out everywhere.
• I place my plugs back in ONLY A thread or two to keep foreign material out. Leave it sit for SEVERAL HOURS if possible, OVERNIGHT is even better!
• Remove the plugs and crank the engine over several times to eject the MMO down the exhaust and out the plug holes. Place a clean rag over the plug holes (don't ask why I know to do this!) FYI Pistons don't compress liquids and if you accidentally got too much in there you could cause some severe damage if the plugs are not removed.
• Install the plugs and run the bike to temperature.
• Stop & check compression
• I had to do this three times to get to the 135# I have now.

HOT PIPES
Personally, I have no idea why one set of pipes would be hotter than the others unless you were very lean on one side compared to the other. However, you mentioned a nice idle with an occasional hiccup. What do the plugs look like on the apparently hotter side vs. the other side? If your idle is a nice as you say, I wouldn't think one side wasn't getting gas? The 1&2 / 3&4 carbs are on separate fuel feeds.......

CARB SYNC.
Do you have the gauges to do an actual running sync? Personally, I've never had any luck getting the carbs right on the bench.

Looking forward to your responses. Hope this helps.

KURT

I dont have the actual readings on the cylinders. (Dont have the tester)but it looks as the 2 side (hot) and 2 sides (only warm). I ll do the MMM tonight. Now i believe what it can do.
Thanks Buddy!

[mrtkayak]

When 3&4 fail to fire it's usually a fuel delivery issue. Check the petcock is flowing. Check the fuel line for a kink. Check the fuel and vent t's are clear.

ill do check this out tonight.Thanks

[mrtkayak]

[QUOTE=TopCatGr58;477249]Hey MrTKayak,

As others have eluded, the 3-4 cylinders are linked via Carbs/fuel, same for 1-2. The cylinders are linked electrically 1-4 and 2-3, so if the pickup coils, ignition coils were bad, they USUALLY show up paired electrically.

Ill check out my the fuel sysytem tonight. Carb, Tank and Petcock
Thanks TC

[mrtkayak]

I had the same problem on my bike. I really didn't do any troubleshooting though. I just swapped out the ignition unit from my other bike because it was something quick and easy to try.
So the bottom line is...I just got lucky and all 4 were getting hot immediately!

Good for you..Me.I need to check everything out bec. I dont know the History of this bike.
no contact w the PO.But thanks. Put ingnition on my to do list

[mrtkayak]

Hey MrTKayak,

As others have eluded, the 3-4 cylinders are linked via Carbs/fuel, same for 1-2. The cylinders are linked electrically 1-4 and 2-3, so if the pickup coils, ignition coils were bad, they USUALLY show up paired electrically.

Are the 3-4 pipes getting a little warm, or totally cold? If warm, then they are getting a "little" fuel, probably from the mains, but not from the pilot circuit. Start it up and try running it at ~3500 rpms for a minute or so, and then retest for heat/sizzle. If then a bit warmer, then you've confirmed that the pilot circuits are probably still clogged, but the fuel is getting thru the mains enough to then fire at the 3500 rpm zone. IF the pipes are still cold, then you've got some more serious fuel flow restrictions going on....again as mentioned, petcocks, or inlet T's clogged, or the screen on the bottom of the float valve seat is clogged, or the floats are not dropping letting fuel in, etc.!

There IS a more rare electrical condition where fire can be lost on the otherwise normally fuel paired/linked cylinders....like too low voltage to the ignition coils...so that each coil can only fire it's PRIMARY plug....but not enough juice/voltage to push thru the head and back up the other plug. You've got a 79, it uses the ballast resistor system, and the connections can get corroded. When the engine is running power is routed thru it to keep from burning up the OEM coils so the voltage at the coils will be around 9 volts instead of 12 when just starting....power is routed around the BR during starting to provide stronger starting spark.

Other conditions can be corrosion between plug wire and cap, resistor within the cap. As Motoman/Brant likes to say, you need to make sure your carbs aren't having electrical problems!

Keep at it, test, and report back as needed, as well as just to let us know what you find....feedback for us!


T.C.

Ill check my Fuel system tonight. Carb, Tank and ,fuel lines and Petcock.Thank you Sir

[motoman]

Work done
1. Carbs clean and bench sync
2. Valve adjustment.
3. Checked the vacuum advance wires are healthy

problem
1.start bike w/no problem.idle steady but fluctuate every once in a while.
2. Check the exhaust pipe, 3 and 4 not getting hot,1 and 2 sizzles when spray w water bottle.

*need advise,heard about marvelous magic oil (wat a name).
Do you guys used this?
Do you think my rings are stuck?
Pls. Reply. Thanks

Pilot jets are still patially pluged, Use a magnifying glass and LED lite to check for a clear round opening at atomizing end of pilot jets. They HAVE to be blown clear FROM atomizing end in order to be perfectly cleared. NO wire made will fit that teeny atomizing hole, and highly NOT reccomended if you were to find one small enough anyways!

[mrtkayak]

Sorry Guys for the late reply

Finally did find sometime today...

Done:
1. Checked the tank and fully emptied just to found large pieces of
sealant maybe the PO tried to fix some leak but I could not find any.

2. Use MMO and left overnight, NOW the 3 and 4 cylinder is firing and getting
hot, not the same as the 1 and 2 cylinder but it is a good improvement. YOu guys made me a believer what this oil can do for your rings and probably your valves.

3.Now,I took down the carbs again and checking the pilot circuit especially the pilot jet. Im using 42.5 on 1 and 2 . 45 on 3 and 4. this might be the cause of idle problems .

Thank you GUYS, try to keep you posted.thanks again

[TopCatGr58]

Hey again Kayak,

Okay, you got the pilot jets in the wrong carbs.....IF you really want to bother with staggered jets. 1-4 should have the 42.5 and the 2-3 pair should have the 45. Richer jets are supposed to help the cylinders to run a little cooler since they don't get as much AIR flow cooling. Yamaha also used different MAIN JET NEEDLES=emulsion tubes to help keep the central cylinders cool. The nozzles with more holes go into the 1-4, the ones with less holes in 2-3, again they should be a little richer. But Yamaha soon learned that it really wasn't necessary, and so just went to using the same sized jets and emulsion tubes across all 4.

SO....it's your choice. IF you have enough to make them the same across all 4, then put them in, otherwise, stagger as stated above.

T.C.

[mack]

It's been

my experience that the pilots should be the same accross all four carbs. (42.5) and the mains the same as well provided you have the 266 and 301 emulsion tubes. However this winter I've stripped down three sets of early carbs and in each one the emulsion tubes were the same accross all four but the mains were larger in 2&3 so...... yamaha wasn't very consistant with what they wanted to do.

[BA80]

Mack is correct TC. The pilots are all the same, some bikes had bigger mains in 2 &3 though. For cooling purposes in theory.