Linkert popping

[59Panman]

Just got my new throttle cable and on, "thanks for the assistance to mksbeam for the Palmers reference", and have one last question regarding my Linkert. Sometimes at low speeds the Linkert will pop like when you crack the throttle to fast, and it sounds like it is flooding and then it will run ok. Could this be that the low speed screw is too rich or does it sound like it is too lean? Anyone have any thoughts or suggestions.

By the way, I have new manifold orings, manifold gaskets and new plugs and pressure tested OK.

The bike is a 59 Pan with a Linkert M74B.

Couple more questions, is it necessary to polarize the generator when a solid state voltage regulator is installed? And, what should the maximum output voltage be that is sent from the regulator to charge the battery? I don't have a amp meter and would like a easy way to check my charging system.

Thanks!

ozwick

[dude]

poping or coughing out the carb is generally a sign of too lean a mix.. Richen it a bit & see..

[Cotten]

Oz!

Several things can affect accelleration.
Let us assume your timing and valve adjustments are dead-on.

To begin with, the main nozzle well, which acts as an "accellerator pump" will not empty itself effectively at low velocities. The common notion that Harleys should idle at a slow lumpity-lump is not correct. It not only impedes off-idle carburetion, it does not oil the motor properly either. Set the idle up to where it smooths out the pulse of the motor.

Next, remember that the needles overlap in effect.
Your lowspeed needle not only meters fuel at idle and low speeds, it meters additional air when the circuit reverses itself at moderate speeds.
Adjustments require trimming back and forth between the two needles are required to find their optimum setting (which may change with varied fuels.) Trim the idle needle at idle and very low speeds, and trim the highspeed at speeds of 35 mph and higher.

Beyond adjustment, there are wear concerns within the carb that can affect the overlap of the two circuits. The three common areas of wear are at the throttle shaft/bushings, throttleplate against the carb bore, and venturi/nozzle spigot.

The bushings and shaft are easily replaced if they are loose enough to admit air.

If the throttleplate wear forms a groove that extends all the way to the idle bleed holes, then you lose the ability to tune for the separate circuits. (Repair is to bore for an oversized plate.

When venturies shrink from age, then not only does an air gap form around the outside, the venturi can rattle and wear a 'girdle' around its spigot for another leak. Your M74B actually came with a phenolic gasket between the venturi and nozzle to aid sealing at this point. The cure is to swage the venturi back to a pressfit, and solder the spigot damage and dress it to mate the worn venturi hole.

And last, the connection of the carb to the manifold is a difficult one to test. The double-gasketed phenolic spacer between them invariably allows fastener distortion of bronze carb flange, and moderately to the manifold flange as well. The carb casting's idle gallery ridge stiffens the flange around the gallery plug thus holding it back from fastener stress, creating a gap:



They can easily be ground flat by hand with emerypaper upon glass, or a very large stone, before re-assembly.
(Sealers that may be attacked by modern fuels should be avoided.)

And last, beware of some modern airfilter elements that are overly restrictive.

Good luck,

...Cotten

[64DUOGLIDE]

My linkert is doing something wierd, at higher RPMs, the more I open the throttle, the more it tends to stumble/surge...been thinking about if a couple of days. Last night while riding, I moved the choke about halfway to the first detent and accelerated, the surging was gone and it accelerated as normal, which tells me it is to lean. I'm gonna try opening the high speed jet a little and see if that helps. Is this normal behaviour? My last pan had an S&S from day one, this is my first Linkert.

Thanks

[Cotten]

64duoglide!

Linkerts are forgiving to an extreme, although they need to be pretty fresh if you expect them to be 'perfect'.

But before all other concerns, the manifold assembly must be absolute.

Please pressuretest your manifold assembly @ 15psi with soapsuds as per http://virtualindian.org/11techleaktest.html" onclick="window.open(this.href);return false;

When those variables have been eliminated, then the carb issues can be addressed.

Good luck,

...Cotten

[64DUOGLIDE]

Thanks for the advice...I will pressure test tomorrow. I turned the high speed jet open one half turn...performance improved slightly, another half turn made it worse.

Does it sound like a fuel/air problem? It almost feels like a rev limiter is kicking in if I ope the throttle to much. If I pour on the throttle slowly and let the speed catch up, it runs like it should.

Thanks again

[59Panman]

64duoglide,

I have found that my Linkert problems to be with the low speed jet. Once your bike is warmed up, turn the low speed in slowly until the engine begins to stumble then back it out until it runs smoothly, then adjust the idle screw so the engine runs at a good idle. Use this as a reference point to dial in the carb setting / sluggish throttle. I would play with this setting by even a couple of turns richer, again you will need to adjust idle after every adjustment as this will affect your performance. Then dial in the high speed setting last to see how your plugs are burning.

Good luck,

ozwick