'79 XS1100F Carb Issues; Poor Performance on the Main Jet.

[cajun31]

If you decide on the replacement coils make sure you make your mounting brackets out of steel not aluminum.

[bikerphil]

I haven't had a chance to look yet but doesn't the XS110 have some of those weird resistors in line that are suppose to lessen the draw that the coils take?

Yes, there is a single ballast resistor mounted to the frame, under the front left side of the fuel tank. When replacing your coils with 3 ohm type (factory units are 1.5 ohm), you will need to bypass it.

[banzaibob]

Update on the update.....

I checked my parts stash and the only decent 3 ohm coils I had without cracks in them were a set of TEC coils from a '96 Honda 600 Shadow. They actually measured something like 2.7 ohms...close enough. I'm actually trying to decide if the results are as dramatic as they are. My first high speed run of the day with the new (old) coils rigged up pulled pretty strong and revealed some new questions sort of. In 5th gear, past 4500 rpm it pulled WITHOUT the usual rough running and loading up. There was however a hint of that rough running past 5500-6000rpm...very brief, very transient. At that point I'm doing 85-90 mph (I guess). At that point it feels that it is simply not pulling as strong yet it keeps climbing. Conclusion? New coils DEFINITELY improved conditions. By how much? Don't know, need to ride it a bit more.

All of this was without the air filter or the bottom half of the air box hooked up. I can only guess that it may not run quite as good as it does without the air filter in place....more tests to follow.

I was able to do another high speed run shortly after that and discovered something more. I have a Motion Pro test tank that I rig up with a hook on the handlebars that has a fuel line down to the carbs. Holds about a quart of gas. I have been filling it from one of the 5 gallon cans I have sitting around. This one was starting to get a little light and getting near the bottom. I filled up the test tank and headed down the road only to get a 1/2 mile from the house. It cut out and barely got running again. Come to find out this can was FULL of water. This may account for my "air leak" and even some of the high speed crap....shoiulda known better.

So....the second high speed run that I made was a little better still. It still has what I would categorize as the "same" sort of problem....rough running that mimics an overly rich main jet. But that effect is now very transient and almost appears to be associated with a narrow rpm range (5500 or so?) as opposed to throttle position. Plus, once it passes that point and does it's little "shudder"...it almost acts like it wants to clean up and keep revving. I also did a plug chop, one after a mile at 50mph in 4 gear relying only on the pilot circuitry and the second, a full throttle plug chop from high gear at about 90 mph.

So.....Any recommendations for high performance coils that won't kill my battery or charging system?

[bikerphil]

Dynatec DC1-1 coils are what most of us use as high quality replacements.

DW-200 is the solid core wire kit.

[banzaibob]

Dynatec DC1-1 coils are what most of us use as high quality replacements.

DW-200 is the solid core wire kit.

I have a set of these on a dual-plugged BMW R90/6. Very happy with them.

[bikerphil]

Yep, they're good ones, super hot spark, super reliable, beware of cheap imitations. You'll need some small L-brackets and short bolts to mount them to the stock location though.

[DEEBS11]

I put Dyna coils on my XS11. Big difference in performance.

[DEEBS11]

..........

[DEEBS11]

And make this jumper to eliminate the resistor. BTW, the only reason the resistor is there is so the ignition circuit outputs to coils that equal 3 ohms (impedance). The stock coils are less than 3 ohms so they have the resistor there to add up to 3 ohms. If you use 3 ohm Dyna coils, you can just jump out the resistor and the circuit will equal 3 ohms. If you eliminate this resistor with stock coils, the circuit will run very hot and eventually burn out which I'm sure has happened to many bikes that don't run/run right.

[DEEBS11]

And also, your old coils were fine, the wires were old and cracked. It's the classic high rpm fail that bad wires act like (not to say you don't have some carb issues as well). Coils either work or they don't work. Everybody misses the wires because they "look fine". When the bike is at idle spray some water from a garden hose on the spark plug wires. If the wires are good it will still run perfectly. If it sputters or shuts off, you have bad wires.

[jetmechmarty]

Several years ago, I bought a kit from XJ4Ever.com. It came with Dyna coils, clamps, wires and everything to complete the job including detailed instructions. I upgraded my coils in the driveway in 20 minutes. Whatever I paid for that kit it was money well spent.

[banzaibob]

Been talking to LEN from XJ4Ever. Guy definitely knows his ****. Here is what I told him today:

I was able to do another test run today. This time I attached the air filter and the bottom half of the air box. Due to the way things are sort of cobbled together right now on the bike, it's not perfectly sealed up so I imagine some air is able to come in around the seams. Subsequently, at full throttle in top gear from about 4000 rpm it "shuddered" about the same if not very marginally worse.

However, I'm going to walk away from it for a few days. The bottom line is that it IS running MUCH better than it was. The problem now is that I may be reading things wrong. Taken in total, it just seems that I may be missing something. After today's run and also yesterday's, the spark plugs are showing lean. The insulator is bright white and the side electrode is clean. The only thing that is puzzling is that the shell or rim past the threads that is exposed to the combustion chamber is sooty. Also there is a noticeably lean spot in the throttle position. From 2000 to 3500 rpm with light throttle settings it is sort of lethargic. Once past 4000 with more aggressive throttle, it comes on strong (almost too strong). When it "hits" it comes on strong until about 5000-5500 rpm, it then does it's little "shudder" thing....and then sort of smooths out. With an aftermarket less restrictive exhaust and the plug tips showing nice and white, I'm a little scared to lean out the main jets any more than stock 137.5.

Also upon cold start with the choke on, there is quite a bit of popping and backfiring in the mufflers. After a minute or two of warm up when taking off (with the choke off) it will pop and spit through the intake. Eventually is sorts itself out but warm up is in no way smooth.


It almost seems as if things are now so mismatched that it could be too lean on the pilot jets....still too rich on the needles.

The reality is that things ARE getting better and there are some cosmetic and ride ability issues that I need to fix in the next couple of days.

[bikerphil]

Well, it seems like now that you have the weak spark sorted out somewhat, it may be time to put the carbs back to conventional jetting, maybe 42.5 or 45/137.5 (140 or142.5 may be ok too) and needle clip either center position or maybe one richer if needed. As for the leaking air box, not helpful, maybe make some type of gasket.

Golden rule: make sure the ignition system is tip top before carb adjustments are made.

[banzaibob]

The thread that refuses to die......

I was able to find some ACTUAL 5GZ6 needles. They have the original Yamaha part #s (2H7-14116-06-00) and the seller displayed actual photos. These are not the brass Y265 needles that come with the K&L kits but appear to be alloy needles with what appears to be the original Mikuni "square in a square" markings. They will probably get here in a couple of days. The tension mounts....... I'll keep you posted.

[bikerphil]

That's lucky that you found some. I wonder why the PO changed them to the Y265, maybe they could have been worn out? They get scratches in them after higher miles and cause a dead spot (rich) mid RPM.
The emultion tubes wear too and can get egg shaped at the carb throat side.