Linkert Problem Question????

[Hollywood]

A friend brought a 55 Pan over with an M74B on it. The carb was recently "rebuilt". The bike won't run right and will only run with the low speed needle backed waaaay out. He started it up and while running I removed the low speed needle completely and it ran better than with it in...I've never seen this before in 35 years of messing with these things. I haven't looked at anything yet but figured I'd run it through the Forum...
Any Thoughts?

[50Panhead]

Is the intake leaking?

[T. Cotten]

Hollywood!

Always check for vacuum leaks first: http://virtualindian.org/11techleaktest.html
O-rings don't like modern fuels (unless Viton).

If the manifold assembly is sound, then sorting out the carb will be much easier.

....Cotten

[Hollywood]

Thanks. I, of course, gave it the shade tree combustable test....which it passed. It has all new clamps and O rings. I haven't gone any further than that. Just wondering if the condition I described rang any obvious bells...

[T. Cotten]

Hollywood!

Lots of machines have passed the shade tree test and still seized or burnt a hole in a piston.
"It ran great before it blew up..."

Any stone unturned hides something that will bite you.

You're going to take the carb off anyway to see what's been done to it, and its not hard to make a tester (attached).

...Cotten
PS: Here's what common P4gas does to common O-rings. (Fresh one sitting on top of one soaked in fuel.)
PPS: The interface between the manifold and carb cannot be bubbletested, so the flanges should arbitrarily ground flat. Please see if the last "rebuild" included that.

[Hollywood]

Understood. I'll give it go when the carb comes off.

[Rubone]

Hollywood,
It likely ran better because you allowed a large volume of air to enter the low speed circuit by removing it. Check the needle to see if it is long enough, and if the needle is installed in the lever correctly.

[T. Cotten]

Hollywood,
It likely ran better because you allowed a large volume of air to enter the low speed circuit by removing it. Check the needle to see if it is long enough, and if the needle is installed in the lever correctly.

Hollywood!

Your lowspeed needle should be 3½" long. There is only way to install it within the lever, however it may be above the spring rather than below it within the knob.
A shorter needle would allow more volume, not less, as it would not reach its seat. Beware also that needle controls fuel, not air, until the flow reverses itself at moderate RPM.

At low RPM, more fuel would be needed to accomodate a vacuum leak.

Please note if the spring collar beneath the lever is in place, and moves freely.
Please inspect the surface beneath the collar to assure that it is not "eroded": http://www.antiquemotorcycle.org/bbo...ng+collar+seat

Let us know how it goes...

.....Cotten.

[koanes]

Last one I saw with these symptoms was missing the idle passage plug at the manifold end.

[KNUCK]

Hollywood!

Lots of machines have passed the shade tree test and still seized or burnt a hole in a piston.
"It ran great before it blew up..."

Any stone unturned hides something that will bite you.

You're going to take the carb off anyway to see what's been done to it, and its not hard to make a tester (attached).

...Cotten
PS: Here's what common P4gas does to common O-rings. (Fresh one sitting on top of one soaked in fuel.)
PPS: The interface between the manifold and carb cannot be bubbletested, so the flanges should arbitrarily ground flat. Please see if the last "rebuild" included that.

Changed mine last week in the pan and the "O" rings looked just like that nasty one you show!

[Hollywood]

Well I removed the carb and the first obvious issue I saw was the spring washer/needle guide was missing on the Idle side...not the root cause {turns out it was the root cause Thanks Cotton!} just an obvious omission and a sign of things to come...when I popped off the bowl the root cause {Not the Root Cause!} was staring me right in the face...the "jet" and plug were reversed...the "jet" was on the idle side. I switched them back, added the propper washer to the spring and reassembled. I started from scratch with the adjustments and everything worked as it should. All low speed adjustment was back. I dialed it in and she starts on one kick and runs like a dream!

Photo6507.jpgPhoto6509.jpgPhoto6510.jpgPhoto6511.jpgPhoto6512.jpg

[T. Cotten]

Hollywood!

The positions of the jet and gallery plug caused nothing, as they both lead to the nozzle well.
The spring collar, however, is critical, as it meters air.

All may seem well, but Linkerts are so forgiving, that minor aspects are often overlooked.
Often the lowspeed needle, and the collar,is worn where the spring collar guides the needle. This is where air is metered to mix with fuel to make an emulsion. Please inspect for wear.

.....Cotten

[Hollywood]

Cotton...Really? So it was the spring collar all along??? Wow! I thought the opposite...every other carb I have has the the jet and plug in the opposite position from the troubled one so I thought that was the main problem.

Thanks for straightening me out on that...and making me look like a dumb ass

H. Wood

[T. Cotten]

Hollywood!

Not to make you or anyone look like anything, but did your replacement collar slide freely upon its seat?
If not, the wear I pictured above will occur, as the lever moves the needle and collar in an arc.
Once again, the condition of the seat can be an issue, as extra air will leak under it: http://www.antiquemotorcycle.org/bbo...ng+collar+seat.

Linkerts are enormously forgiving, but we certainly want them to be all they can be, and the more of the loose ends that you can tighten up, the longer and sweeter they will perform.

.....Cotten
PS: Folks, I have fellows who desperately need Schebler levers; If anyone is currently reproducing them, I would be most greatfull.