The magic just wore out.

[fredintoon]

Years back I was fixing and refixing my carbs on a monthly basis and I wearied of the blood & broken knuckles involved in R&Ring the stock airbox to get at them.
So I deep-sixed the stock airbox and installed four pod filters.
(NOT the el-cheapo pods that block off the carb peripheral air holes, the nice pods from MikesXS that say XS on them)
I reckon those pods were magic because the carbs have acted perfectly ever since.
Until today. I reckon the magic just wore out.
Took a short trip to Canadian Tire to get a new bag of oil absorber.
(The zero-spill oil change is another trick I need to learn)
Just got to CT's parking lot and the leftside exhaust starts popping and banging.
Bought my bag of absorber and the bike sneezed and staggered back home.
Runs good on all 4 above 3,000rpm, only on 2 below that. No fun at all in city traffic.
Borrowed the wife's car and went back to CT for 2 cans of carb cleaner and lots of plastic fuel line to build a 4-line manometer.
If I gotta clean the bastards I may as well try and synch them too.
Wish me luck.

[DGXSER]

Fred,

Are you certain it is not a pick-up coil wire issue? Loosing two cylinders at a time...only below 3k...seems likely anyway.

[CRXSi90]

Running on two? You don't think it's pickup coil wires???

*you beat me to it!

[motoman]

As an 'old school' wrencher, you know 'ignition before fueling' when diagnosing...

[fredintoon]

The other magic?

Thanks guys,
3 out of 3 say "first, check the pickup wires" and my son quoted me what I quoted him years ago "Most carb failures are ignition faults"
But a while back I fixed those bastards, too.
Mebbe it was the electrical magic that failed?
Mind you, I once spent a week chasing #4's suspected ignition problem before I fixed it by spending a half-hour cleaning #4's carb.
OTOH, I bought all that plastic hose. Seems a waste unless I make a manometer to balance the carbs.
But First! Check the pickup wires.

[TomB]

Fred, I recently had 1 and 4 coil do that, would run on 4 cylinders above 3K rpm but cut out onto 2 cylinders below, bugger to start too as you're trying to start on 2 cylinders.

I suspected pick-ups first as they are the usual suspects, eventually found a small split in the coil casing near the square steel mount bar with brown powder around it where the coil had been arcing.

[fredintoon]

Fred, I recently had 1 and 4 coil do that, would run on 4 cylinders above 3K rpm but cut out onto 2 cylinders below, bugger to start too as you're trying to start on 2 cylinders.

I suspected pick-ups first as they are the usual suspects, eventually found a small split in the coil casing near the square steel mount bar with brown powder around it where the coil had been arcing.

Hi Tom,
thanks for the input. If I tug on the pickup wires and don't find a stretchy one I'll swap the coil & plug wires over and see if the other side acts up instead.

[BigRed]

This is funny... I just logged on thinking that somebody probably needs to be told to check their pick-up coil wires. For me, having fixed it the first time didn't solve my problem for all that long. Not too long after fixing my pick up coil wires, I found that I had made one of the loops just long enough that it could contact the timing plate under the right (wrong) circumstances. That wore through the insulation and grounded the pick-up coil wire through the timing plate. Another time, I had the whole timing assembly come loose... the two screws that hold it on had come out. Unfortunately for me, I was in the middle of experimenting with changing out jets, and wasn't happy with any of my results (turns out because the timing was off) and didn't find the problem until after I went back to the stock set-up and the problem persisted.

So, let me be the fourth out of four.

I've been thinking that the next time I need to do this, I'm going to make a quick connect/swap out set of wires so that I don't have to jerk around with a soldering iron on that last 1/8" of wire. Then I could just make a spare set and have it ready.

[fredintoon]

This is funny... I just logged on thinking that somebody probably needs to be told to check their pick-up coil wires.
So, let me be the fourth out of four.
I've been thinking that the next time I need to do this, I'm going to make a quick connect/swap out set of wires so that I don't have to jerk around with a soldering iron on that last 1/8" of wire. Then I could just make a spare set and have it ready.

Hi Red,
sounds good but you'd need really small plug-ins at the senders as there's not much room in there and the whole plate is being shaken about by the vacuum advance?
Weirdly, I fired the bike up this morning and it ran perfectly.
For about a mile.
Then it was back to running on 2 below 3,000 rpm.
But before looking at the bike I will have to clean out the garage.
I'm sure there's a floor down there someplace and I'll find it if I keep digging.

[TomB]

Hi Red,
I'm sure there's a floor down there someplace and I'll find it if I keep digging.

Really!!!!???? theres floors in garages!!!!?? I ain't seen one in mine!, wow I'm going to go have a root around in there now.



.

[trbig]

Have you checked those little rubber caps over the vacuum tubes? Mine starts sputtering, spitting and running bad when they go bad. Many times they LOOK fine, but inspection shows the tops nearly cracked off.

[TopCatGr58]

Hey Fred,

Well, I'll be the devil's advocate and say have you tried some Sea Foam in the tank?? I don't recall or remember if you use any kind of carb cleaner in your fuel periodically? Drop out and poor throttle response below 3K is also in the Pilot jet/circuit range, and it's an easy thing to test/do, and will help your carbs even if it's not the problem!

Also, would suggest disconnecting the vac. adv. and see if it still misbehaves. Of course the timing plate will still move with the cent. adv. mechanisms actions, but it's usually at it's end around 3500 rpm, but can still flex/rotate below the 3500 threshold. Anyways, hope you find the culprit and that it's an easy fix whatever it is.

T.C.

[Rasputin]

Fred, you Old Fart. You probably forgot more than I ever knew about these bikes so what are you up to? Did you find a brand new problem and you are testing us to see who knows? You know more people, old bikes, and have had more experience than almost anyone on this forum By the way are you coming up to the vintage show in Ponoka later this month or is Red Deer your only Alberta trip?

[oldyam80sg]

My bikes vacuum caps looked good but when i got a closer look the caps were cracked.A trip to the auto parts store and they are good to go after replacing them.No more spitting and sputtering!

[fredintoon]

Mr. Stupid strikes again.

Hi Guys,
all those good ideas and sound advice and you were all WRONG.
After pulling on the ignition sender wires to find they had zero stretchy I was psyching myself up to do the carb teardown.
The gas tank was already off so I sidetracked myself by draining it to double-check if my last year's swapping the gas tap levers right to left had worked as planned to swap Prime/Run/Reserve/vacuum into On/Off/Reserve/manual.
That showed me two things.
1) The lever swap works. Forward is On, down is Off and Back is Reserve.
2) As gas didn't come out of the rightside tap when switched to On but flowed when switched to Res I deduced (and then checked) that my thermistor level sender is broken.
The gas lines are X-ed over so the failure of #1 & #2 was plain ol' running out of gas symptoms.
Who'da thought it?
But WTF, the tank is already off and I already bought all the stuff to make a 4-way manometer so now's the time to finally balance the carbs.
BTW, thanks everyone for all those good thoughts.
Without them I'd have gone straight into a needless carb teardown and still not found the problem.