I am stumped

[BA80]

So the issue with the miss is back. It's not carbs, it's not coils, it's not the TCI box, the plugs or plug caps. I have switched out all those components with know good ones from my hop up bike.
So.... do I start thinking about defective pickups? Do I replace the pick ups with the ones on my hop up bike or is there something else I should be looking at before I do that.
The miss is not as bad as it was last year. is affecting # 1 and #4 and is present across all throttle settings.
Perhaps it's just an OLD WEAK ignition system?

It's that alien mother ship that passed over.

If it's 1 & 4 it has to be a coil or a pick up coil.

Have you ohmed out the pickup coils?

I had a set that drove me crazy on an SG a couple years ago. They ohmed out at slightly lower readings than the spec range. This bike WOULDN'T start (no spark) if the temperature was below 40º F. If I heated the timing cover it would eventually start and run on 2 cylinders until the engine warmed up a bit then the other 2 would kick in. Swapped out the pickups and it works fine to this day. Go figure.

[79XS11F]

It's Back

So the issue with the miss is back. It's not carbs, it's not coils, it's not the TCI box, the plugs or plug caps. I have switched out all those components with know good ones from my hop up bike.
So.... do I start thinking about defective pickups? Do I replace the pick ups with the ones on my hop up bike or is there something else I should be looking at before I do that.
The miss is not as bad as it was last year. is affecting # 1 and #4 and is present across all throttle settings.
Perhaps it's just an OLD WEAK ignition system?

[TopCatGr58]

Hey Rob,

Glad you were able to finally able to figure it out, but as we've seen many times with other bikes, your carbs were having ELECTRICAL problems!!

When you say the plug leads looked good after the first 1/4" trim....do you mean you could see the copper just on the ends of the cut wires, or were you able to see the copper color on the sides of the wires? My guess would be that there was still some copper corrosion on the sides of the wires with just the 1/4" snip, and so the plug cap screw that screws into the wire was still not making very good contact with the corroded sides of the wire strands. So....then after further snipping you were able to reach uncorroded wire farther up into the wire leads, and THEN the plug cap screw was able to make good purchase/bite into the non-corroded sides of the wire strands.

I know you know this, just stating it for newbies that may read this.

T.C.

[79XS11F]

Mack's update is correct but the bike went back to being problematic a few days later so I checked the electrical again. I knew the carbs were not the issue because Mack's loaned carbs are as perfect as carbs can be. When it was all said and done the issue proved to be the coil leads. In spite of having cut the ends back a few times in the past and seeing good looking wire inside the lead ends, the connection was still not good enough. I ended up having to cut between 1/2 and 3/4 of an inch more off the ends to finally get into good wire inside the leads. Once this was done the missing went away and the bike is running well. All I can say is... the cutting off of the typical 1/4" may not be enough when spark is weak. Cutting off the recommanded 1/4" of lead wire can not by default be concidered as a cure even when the wire 1/4" into the leads looks good. Alway make sure the leads will still reach the plugs in any case.
Rob

[mack]

Update

Rob probably won't come back on and post an update, but since this turned out to be a long thread, I thought I'd let you know what the final result was.
I took a set of known carbs to his house on Friday and popped them on his F. Bike fired right up and 2 minutes later it was sync'd and idle was set. The bike was purring like a fat cat at 950 rpm, no issues at all.
So the problem was carb related and he gave his carbs to me to run down what it was. I can't get to them right now so I left him with my set to finish the season off with. We'll hook up in the spring and give him his originals back.
Since he's having computer issues, he asked me to extend a big thankyou for all the imput on this thread.

[79XS11F]

Hey Rob,

You've been busy trying to troubleshoot your bike, so you may not have seen this thread I started a few weeks ago!

http://www.xs11.com/forum/showthread.php?t=42622

You may find it interesting in a little better understanding of the pilot circuit, and the places that can get clogged up due to varnish and fuel gum....ie. the pilot screw hole as well as the other 3 transition ports/holes that are on the top inside of the engine side of the carb throat.

What's interesting is the revealing info about where the aeration of the pilot circuit occurs....AFTER the end of the pilot jet....so the side holes in the jet are MOOT, just the END hole is the important factor...as you found out...the proper size.....and that what we found with the K&L jets are that the side holes were NOT in themselves the problem, just the incorrect sizing of the metering hole vs. GENUINE MIKUNI jets.

T.C.

I will be pulling the carbs again to see if I can "really" get them clean.

[TopCatGr58]

Hey Rob,

You've been busy trying to troubleshoot your bike, so you may not have seen this thread I started a few weeks ago!

http://www.xs11.com/forum/showthread.php?t=42622

You may find it interesting in a little better understanding of the pilot circuit, and the places that can get clogged up due to varnish and fuel gum....ie. the pilot screw hole as well as the other 3 transition ports/holes that are on the top inside of the engine side of the carb throat.

What's interesting is the revealing info about where the aeration of the pilot circuit occurs....AFTER the end of the pilot jet....so the side holes in the jet are MOOT, just the END hole is the important factor...as you found out...the proper size.....and that what we found with the K&L jets are that the side holes were NOT in themselves the problem, just the incorrect sizing of the metering hole vs. GENUINE MIKUNI jets.

T.C.

[79XS11F]

I just switched out the Accel coils for the stock units and it did not correct the stumbling so there must be something else going on in the carbs.
Rob

[79XS11F]

Judging by the embarrassed face he put up it's something he may not want to admit.

IT WAS THE PILOT JET!!! The pilot jet has 3 hole in the side of it and 1 hole in the nose. the 3 holes on the side were clean and i could push my syray gun cleaning wire through them easily. The hole on the nose was however, somewhat smaller and i did not know that the hole at the nose was suppose to be the same size as the ones in the side. The holes at the nose on these jets in # 1 and #2 were about the size of a twist tie which is TOO SMALL. I only noticed this when I got out some jets from my jet kit that I have in storage for future use. So it looks like just seeing light thorough the opening is not good enough. The holes must be spec size.

[79XS11F]

Thanks TC.
The original coils and for that matter all electrical components were OEM components, exactly as was used on the bike when I took her to NY for the XS11 get together. The bike was running like a top at that time. Then the bike sat unused or only used occasionally for 2 -3 years. Life got in the way. Thinking that my issue was electrical I installed the Accel coils from my hop up bike. Your information might however tell me why the bike is sill missing under acceleration. She is back firing (bubbly) in the pipes on down shift but if the coils are not correct (BS is still in place) that could be related to this issues. I will return the stock coils to this bike given that the issue did prove to be carb related after all.
Rob

[QUOTE=TopCatGr58;448522

With your last posts about getting fire on only 1 of the each plug of a coil pair, and this quoted info in your first post....but you didn't say what you original coils were? Also, someone posted about the ballast resistor, your bike OEM had one, but I thought you had some high power coils ie. Dyna, but not sure if you had used the 1.5 ohm style with the ballast resistor, or 3.0 type and removed the B.R.? But you then stated you had swapped the Accel coils onto the bike. Again, not knowing if they were 3 ohm type, or 1.5 ohm, but I'm thinking that you are running the B.R with 1.5 ohm Dyna coils, but when you swapped in the Accel...they were 3.0 ohm type, and so WITH the B.R. in place, the coils were getting LOW VOLTAGE, and so were only able to generate enough spark energy to fire 1 plug of the 2 plug coil set...which is the rare incidence where folks can have a no spark or 2 cold cylinders that are not normally electrically paired....ie. 1 and 2 or 3 and 4 , and the problem is STILL electrical and not carb. That's my theory, hope you enjoyed the ride, and look forward to your REVEAL!

T.C.[/QUOTE]

[BA80]

Judging by the embarrassed face he put up it's something he may not want to admit.

[MaximPhil]

I got it ) she's running ion for and synced and idling at 1K I'll post what it was later. Time to ride

Hi Rob,
Please do not keep us hanging too looong
Hope you are having a great ride and look forward to hearing what you found the problem to be.
Phil

[TopCatGr58]

My restored 79 XS11 Standard is not running right. It is missing at idle, during acceleration, and at any held speed in any gear.

- Confirmed that the coils are good by installing a set of excell coils from my other bike.
-
Rob

Rob,

With your last posts about getting fire on only 1 of the each plug of a coil pair, and this quoted info in your first post....but you didn't say what you original coils were? Also, someone posted about the ballast resistor, your bike OEM had one, but I thought you had some high power coils ie. Dyna, but not sure if you had used the 1.5 ohm style with the ballast resistor, or 3.0 type and removed the B.R.? But you then stated you had swapped the Accel coils onto the bike. Again, not knowing if they were 3 ohm type, or 1.5 ohm, but I'm thinking that you are running the B.R with 1.5 ohm Dyna coils, but when you swapped in the Accel...they were 3.0 ohm type, and so WITH the B.R. in place, the coils were getting LOW VOLTAGE, and so were only able to generate enough spark energy to fire 1 plug of the 2 plug coil set...which is the rare incidence where folks can have a no spark or 2 cold cylinders that are not normally electrically paired....ie. 1 and 2 or 3 and 4 , and the problem is STILL electrical and not carb. That's my theory, hope you enjoyed the ride, and look forward to your REVEAL!

T.C.

[79XS11F]

I got it ) she's running ion for and synced and idling at 1K I'll post what it was later. Time to ride

[motoman]

Have you already eliminated or by-passed the ballast resistor?