Exhaust Temps

[dbeardslee]

When you're checking the temperature, you aren't by chance doing it sitting still, running, with no fan on the motor - are you? If you let any of them set in one place idling too long without air moving across the motor they'll get hot. On the dropping 2 cylinders - check your pickup coil wires. Most likely culprit.

[n0lan]

When you're checking the temperature, you aren't by chance doing it sitting still, running, with no fan on the motor - are you? If you let any of them set in one place idling too long without air moving across the motor they'll get hot. On the dropping 2 cylinders - check your pickup coil wires. Most likely culprit.

Thats correct, sitting still, running, no fan. But, this is after 1 - 2 minutes, litterally. no longer.

I'm gonna check outthe pickup wires among other things in a few.



Thanks Again for all teh responses and suggestions.
Nolan

[3Phase]

ok, got it fired up agian just to check the temps.

here is what I got:

Yes, #1 and #2 are hotter than #3 and #4.

The way the bike's ignition works, an ignition problem would usually be with the #1 and #4 cylinder pair or the #2 and #3 cylinder pair. It's probably not ignition.

Usually when you have problems with the #1 and #2 cylinder pair or the #3 and #4 cylinder pair it's a fuel problem.

The fuel is supplied to the carburetors in pairs with a tee between the carburetor bodies. One line feeds the #1 and #2 carbs on the left, the other line feeds the #3 and #4 carburetors on the right.

I can't tell if you still have the fuel diaphragm assembly or not. It's the OEM vacuum operated fuel distribution device for the XS1100 Specials. It requires nine hoses to work so it got nicknamed "the octopus." You would know it's there if you had one and it was hooked up.

So, just then all 4 were obiously hitting b/c of the temp readings. but if i would have run it up the road i would have experienced the 2 cyl loss at some point. temps still seem extremely high tho.

Yes, they're all firing and two are hotter than they should be at idle.

Take off the fuel tank and check to see if the fuel supply to the #1 and #2 carburetor tee is blocked or kinked.

next question:

The vacuum advance line from the #2 carburetor is loose or cracked.
would that be this in the pic?

Its plugged off with a bolt by the PO. maybe the 2 cyl loss i'm experiencing is b/c of loss of fuel and not loss of fire.

Yes, that does look like the vacuum advance is plugged but that by itself wouldn't cause the loss of any pair of cylinders.

The static ignition timing may have been advanced to try to compensate for the loss of the vacuum advance. Remove the left engine end cover and check the ignition timing. See if the vacuum advance is still there, works, and can be hooked back up.

a fwe other mystery items I came across that someone may be able to help me identify.

here is where the fuse box should be. not sure what the PO had attempted.
What are the 3 wires that I have circled for?

Those look like the three wires that should go to the turn signal flasher relay.

how bout this one:

I believe that's the Black/White wire from the TCI to the tip over switch. If the switch is still there and it was hooked up that would kill the ignition when the bike is leaned more than 60 degrees to either side. If it bike is tipped over or laid down on the highway the engine is supposed to shut off.

This looks like some sort of realy or something, not really sure. (red arrow)





notice the white arrow in the pic above. That was the PO briiliant idea to hold the battery in there. Is these any suspposed to be a batery box to hold it?

You have a '79 Special so that should be the lamp check relay. It lights up the red oil warning light on the dash if a stop or tail light bulb burns out. It might check the turn signal lamps too but I don't remember.

Yes, there is supposed to be a battery tray and brackets to hold the battery but as the saying goes, "If it looks stupid but it works it's not stupid!"

under seat wiring:

Was there some horrible accident involving a collision with a pair of wire cutters and a terminal crimping tool?

The long black relay is the turn signal self-cancel relay. It's mounted where the lamp check relay is supposed to go.

The bike looks good!

You can go to the Yamaha web site and look at the parts catalog for your bike. It has detailed diagrams for your bike.

Yamaha Parts and Service

Click on the "View Parts Catalog" button on the left side of the page.
On the next page, click "Proceed to Parts Catalog"
On the next page click step 1 and select "Motorcycle".
After the page updates, click step 2 and select 1979 for your bike.
After the page updates, click step 3 and select "XS1100SF"
Bingo, you're looking at the parts catalog for a 1979 XS1100 Special.


Regards,

Scott

[ross]

just my .02 cents...

hey there nolan....i usually measure on the head of the bolt on the upper side of the exhaust flanges.......have never had a reading above 325 degrees.....(hell, even my gas grill doesn't get that hot!)......and you can confirm that you didn't point the d*mn thang at the tip of a welding torch?!?!.....let us know what ya find.....ride hard, ride safe....ross

[n0lan]

3Phase, all I can say is you're the man!

yes, it does have the octy.

and yes, edward scissor hands must have handled the wiring for the PO.

I'm hoping to have some time tomorrow afternoon to start checking the suggestions in this thread.

I'll report back with my results.

Thanks again to everyone! You guys rock!


Nolan

[n0lan]

Ok guys, I finally got around to messing with this again.

I believe I've figured out why its showing crazy exhaust temps, my bro-inlaw told me today, o-yeah, I put octane boost in the tank.




Duh


anywho, I broke out the DMM and started testing stuff. I wasnt getting any power to the coils, I started inspecting all of the hacked connections, replaced a few here and there, all of a sudden I have 12v to the coils. fired it up and its hitting on all 4 again.

I also bypassed the octy too.


Took off up the road, made it about 2 miles from teh house and she shut down again. no spark on any cyl. I dont think I hit any rough bumps or anything just before it quit to jar anything loose. the PO hacked it all up (wiring)pretty good.

so, I believe I'm just gonna have to go thru each wire, one by one, and resolder/crimp everything


I've read that a coil may test good, but once hot will start acting funny and cutting out. I dont believe this to be the case as now, both coils have no power coming out of them.





NOlan

[dbeardslee]

Octane is one of the more misunderstood concepts. It's not a measurement of the 'explosiveness' of the gas - it's a measure of it's compressibility. Putting stuff like octane boost in a tank is supposed to reduce or eliminate pre-ignition from high compression. These motors don't have particularly high compression - 9.2:1 on mine - at least not high enough for pre-ignition to be much of a problem. As far as making it run hot, I doubt that it would do much more than gum up your plugs.