Board index Flathead Power-Technical Questions, Answers, and Suggestions 45 Flatties Linkert parts

Linkert parts

Moderators: Curt!, Pa

Post Fri May 06, 2011 12:13 pm

Posts: 604
Location: Largo, Fl

Does anyone know where i can get an OVERSIZE Throttle Plate for a 1 1/4" Linkert? Thanks, Indianut

Post Fri May 06, 2011 6:26 pm

Posts: 3134
Location: Central Illinois, USA
Indianut!

You can cut discs individually to any size you want with a simple thirteen degree mandrel.
DSCMNDRL.jpg

That way, you can minimize the amount of bore you must hone away for each carb.

The effect of shortening the idle bleed tract is still an unknown.

1 1/4" model discs are easily cut from a worn 1 1/2" disc (and 1" from worn 1 1/4" discs.)
But I must cut and punch blanks for the 1 1/2" models. I am in the process of over-thickness discs to salvage a small lot of worthless Eastern shafts that have too wide of a slit. (Fortunately, I scrounged a very old door kick-plate that is of thicker stock than the conventional .050"!)

I have a new Tedd 9/X disc that is good for nothing else but cutting down, as it is .0035" undersize right out of the package.

....Cotten
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Post Fri May 06, 2011 6:38 pm

Posts: 604
Location: Largo, Fl

Great Info!!! Thanks!! I take that to mean 13 Deg. is the spec for the 1 1/4 Carb? Thanks

Post Sat May 07, 2011 6:15 am

Posts: 3134
Location: Central Illinois, USA
Indianut!

Palmer lists thirteen degrees for all H-D 1 1/4" Linkerts, and it was the same for '41 and later Indian Chiefs and SS.

The degree is stamped on all Linkerts and DLX Schebler throttlediscs (7 to 14), and installed to the right when viewed from the carb's exit.
14DEGREE.jpg

HX Schebs had no degree stamp (just "L" for left?), but I guess them at ten degrees.

How a degree of difference can be significant eludes me.

....Cotten
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Post Sat May 07, 2011 1:50 pm

Posts: 604
Location: Largo, Fl

Thanks for the info. Now I have a Project for tomorrow!

Post Mon May 09, 2011 3:10 am

Posts: 32
Hmmm this is all new to me - I've noticed the numbers on my throttle disk but never knew what they meant.
So what do they mean - what are the degrees?

Cheers,
Steve

Post Mon May 09, 2011 6:54 am

Posts: 3134
Location: Central Illinois, USA
Steve!

Throttlediscs are oval, cut at an angle, and that angle is the degree.
This creates a disc that will shut with a flat edge against the bore, instead of just coming close if it were a circle.

But then the disc should never touch the bore in service anyway (as the idle screw holds it open), so I don't get it either.

It must have something to do with how air is deflected into the idle bleeds, and then drawn back out.

....Cotten

Post Mon May 09, 2011 8:22 am

Posts: 32
Thanks for that, Cotten.

I'm still a bit puzzled. Surely every 1 1/4 linkert should take the same throttle disk? The bore is the same.

I can't remember what my number is - does it make any significant difference?
Anything to do with bore wear?
Thanks,
Steve

Post Mon May 09, 2011 6:24 pm

Posts: 3134
Location: Central Illinois, USA
Steve!

I have been studying this for a good while, and I have not learned much at all.

You can quote me on that.
Excluding DLX Scheblers and carbs upon other marques, we can generalize Palmer's to show that 1" models were commonly 12 degrees, 1 1/4" models were commonly 13 degrees, and 1 1/2" models returned to either 12 or fell back to 9 degrees.

(K's were akin, but 8 degrees.)

The M74B series (four variants at least...) introduced the 9/X to denote a chamfer behind the leading edge at the idle bleeds.
(Great subject for a separate thread.)

As I posted previously, the effect of a degree is lost upon me.

I regret that Panic is not here to contribute, as any insights at all into this too simple of carburetion system would be appreciated.

.....Cotten

Post Mon May 09, 2011 9:55 pm

Posts: 87
Panic describes the function of the disc angle in his Linkert booklet, noting that the angle of the disc changes the relative richness or leanness of the mixture during the "tip-in" period, i.e., when the throttle plate is 1st moved from the idle position, and partially controls when tip-in occurs. Lower angles are richer and provide better off-idle response and higher angles are leaner. Many of the performance Linkert models employed the smaller angle throttle disc (8 deg) , e.g., MR-3, M-53, M-53A1, etc.

Panic's recommendation was that if off-idle response was not crisp with a 1.5" bore Linkert having a 12 deg throttle disc, it should be replaced with an 8 or 9 deg disc to improve response. If tip-in throttle response is good, but black smoke appears, this suggests that a leaner (higher angle) disc may be indicated. He had additional disc modification suggestions for dealing with situations where no disc angle options exist (1" and 1.25" bore carbs).

In the Linkert carb series the 1" bore employed a 12 deg disc, the 1.25" bore employed a 13 deg disc and the 1.5" bore employed 8, 9, and 12 deg discs.

Post Tue May 10, 2011 4:53 am

Posts: 32
Would you say it's worthwhile to sharpen the leading edge of the disk to streamline air flow - also, polish the bore and venturi for similar reasons?

Post Tue May 10, 2011 7:00 am

Posts: 3134
Location: Central Illinois, USA
Steve!

One problem I have with Panic's theory is that the mixture has already been determined before it ever gets to the idle bleed.
According to the Armored School Handbook, the lowspeed mixture is determined by the needle, and the air orifice around it.

The angle of the the disc cannot add fuel, it can only add air;
Air travels in the front hole to push emulsion out the rear hole.

So if Panic is correct that the mixture is changed, it would mean that low angles push less air in?
Or draw more emulsion out?

The chamfer behind the bevel on the 9/X disc is often found copied on others.
BVLDISC3.jpg

Note that this is downstream of the bleeds, not ahead of it.
Does it create a low-pressure region to disperse the emulsion further into the stream?

Or is just merely knife-edging the disc enough to make off-idle acceleration more "crisp"?

....Cotten
PS: For all practical purposes, a Linkert in fresh condition is "polished": If blasted, everything should be "soft"-brushed anyway.
For all we know, a roughed venturi may atomize better!
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Post Tue May 10, 2011 12:03 pm

Posts: 87
Cotton!

As you noted earlier, it is unfortunate that Panic isn’t here to speak for himself. Perhaps his stint in the office is almost over and he can rejoin the class soon.

One problem I have with Panic's theory is that the mixture has already been determined before it ever gets to the idle bleed.
According to the Armored School Handbook, the lowspeed mixture is determined by the needle, and the air orifice around it.

The angle of the disc cannot add fuel, it can only add air;
Air travels in the front hole to push emulsion out the rear hole.


The above is true only when the disc is totally or nearly closed. At nearly closed disc positions the idle slot acts as you describe - air enters the upstream side and air/fuel emulsion exits the downstream side. As disc opening progresses, i.e., the tip-in period, it reveals a continuum of different idle slot entry/exit ratios, and hence different air/fuel ratios. When the disc has moved sufficiently to reveal the entire idle slot, the slot becomes a constant source of fuel (fuel feeds from the entire slot length), rather than functioning as a mixing chamber, with air entering one end and emulsion exiting the other end of the slot, as it did at nearly closed disc positions.

So if Panic is correct that the mixture is changed, it would mean that low angles push less air in?
Or draw more emulsion out?


As described above, as the disc opens, the idle slot feeds more and more fuel for the reasons stated above. The disk angle determines the number of degrees of rotation that the disk interacts with the slot, and in turn the relative richness or leanness of the mixture emitted from the slot. Beveling a disc, e.g., an X-9 disc or altering the disc angle alters how the disc interacts with the slot, and hence the relative richness or leanness of the tip-in period.

If one decides to knife edge the leading edge of the disc, be aware that you will be altering the tip-in region for all the reasons mentioned above. However, knife edging the trailing edge is without consequence, so long as the outside disc dimension is not altered.

Post Tue May 10, 2011 4:34 pm

Posts: 3134
Location: Central Illinois, USA
WZ507 wrote:
Cotton!

As you noted earlier, it is unfortunate that Panic isn’t here to speak for himself. Perhaps his stint in the office is almost over and he can rejoin the class soon.

One problem I have with Panic's theory is that the mixture has already been determined before it ever gets to the idle bleed.
According to the Armored School Handbook, the lowspeed mixture is determined by the needle, and the air orifice around it.

The angle of the disc cannot add fuel, it can only add air;
Air travels in the front hole to push emulsion out the rear hole.


The above is true only when the disc is totally or nearly closed. At nearly closed disc positions the idle slot acts as you describe - air enters the upstream side and air/fuel emulsion exits the downstream side. As disc opening progresses, i.e., the tip-in period, it reveals a continuum of different idle slot entry/exit ratios, and hence different air/fuel ratios. When the disc has moved sufficiently to reveal the entire idle slot, the slot becomes a constant source of fuel (fuel feeds from the entire slot length), rather than functioning as a mixing chamber, with air entering one end and emulsion exiting the other end of the slot, as it did at nearly closed disc positions.

So if Panic is correct that the mixture is changed, it would mean that low angles push less air in?
Or draw more emulsion out?


As described above, as the disc opens, the idle slot feeds more and more fuel for the reasons stated above. The disk angle determines the number of degrees of rotation that the disk interacts with the slot, and in turn the relative richness or leanness of the mixture emitted from the slot. Beveling a disc, e.g., an X-9 disc or altering the disc angle alters how the disc interacts with the slot, and hence the relative richness or leanness of the tip-in period.

If one decides to knife edge the leading edge of the disc, be aware that you will be altering the tip-in region for all the reasons mentioned above. However, knife edging the trailing edge is without consequence, so long as the outside disc dimension is not altered.


Uh, WZ507,

Once the disc is beyond the idle range the whole idle circuit reverses itself..

Are you aware of that?

....Cotten

Post Wed May 11, 2011 6:13 am

Posts: 67
So I'm not the only one who misses Panic.

Post Wed May 11, 2011 7:40 am

Posts: 976
Location: Markt Einersheim, Germany

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Last edited by George Greer on Tue Jul 12, 2011 11:26 pm, edited 1 time in total.

Post Wed May 11, 2011 9:34 am
Pa Site Admin

Posts: 5807
Location: Ohio USA

Though not a guru in Linkerts, and not taking a closer look at the plate function, could the bevel be for clearance issues, such as when the plate seats in the body ?

Post Wed May 11, 2011 5:21 pm

Posts: 3134
Location: Central Illinois, USA
Pa wrote:
Though not a guru in Linkerts, and not taking a closer look at the plate function, could the bevel be for clearance issues, such as when the plate seats in the body ?

Pa!

If the disc were a perfect circle, it could never seal perfectly, as either the leading edge would touch first, or if smaller, it would have a gap. The disc must seal when moved in an arc, and a beveled edge allows that.
But either circumstance is purely rhetorical, as the disc should never be fully closed anyway!

The wear aspect is the greatest concern: as play of the throttleshaft within the bushing grows, then vibration and engine pulses can beat the disc against the bore to make an 'eyebrow" groove.

This is the only way a Linkert or Schebler can truly wear out, and regular maintenance of the shaft and bushings do much to prevent it.

A decent lube would help immensely:
The only non-soluble lube I can find is baked-on moly disulphide.
Unfortunately, the "market" is not accepting an extra $20 treatment to an ordinary re-build.

...Cotten

Post Wed Jun 29, 2011 9:29 am

Posts: 28
Location: Texas

Really enjoyed reading this thread. Here's a little vid of the nozzle action.

http://www.youtube.com/watch?v=4FhckJbMa5k

Post Wed Jun 29, 2011 5:22 pm

Posts: 3134
Location: Central Illinois, USA
Mr. Big!

That is quite revealing!

The most obvious aspect is all of the raw fuel drooling around the disc from the "rapping" of the throttle.

The spray would not be like that in normal operation of course, but it still shows the folly of "rapping" at idle.
Not only is the motor stressed from lack of load, but it fills the intake tract with puddling fuel.

One can only wonder how much better competition machines could get off the line if they avoided it:
If your cams won't allow an idle, yer snotted up for the launch.

....Cotten

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