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Discussion Starter · #1 ·
hey i was just wondering if anybody can hlp me out... i'm running into the problem of when i bring my throttle back to idle position the rpm's stay up high and don't come down till a few twists... this is weird as it just started this morning on a ride... it does eventually come down but is very annoying to ride... just curious if others have run into this before as i'm confused of why this is happening.

Howie
 

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this usualy means that your linkert needs a rebuild !!

but what also can be a problem is that its having a "false air leakage"
maybe the intake manifold rings are bad ,the nuts are loose ,carb is loose from the intake m.

iff the engine is running at idle speed ,try to spray some brake cleaner around the heads/cilinders and intake manifold ..... if that makes the engine rev. and go up in rpm check that first

can be a couple of things ...but rebuilding a linkert after years of hard work is never a bad thing ;)

edit: did you chack the throttle cable if it works the way it should ??
 

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What motor? Are you using advance weights set-up in your timer? As far as the carb goes drop your main nozzle down from the center and make sure the holes in it are clear and no wear on the stem. Also make sure the spring is good and holds it up in place firmly. While you have the bowl down check your setting on the float as well. Try running without your air cleaner also. Hope this helps some if not contact me with pm. Rick
 

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check where your throttle cable mounts near the Linkert. if it's on the front head with that cheesy clamp, check to see if the cable moves. the heat off the motor softens the cable cover and it'll move when rolling the throttle.

ask me how i know....

hope this helps

 

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Howie!

El DIablo (and FlatironMike) is right about checking your throttle linkage, as the springiness of the coiled sheath may be working against the action.
And he was right that a worn Linkert can also develop these symptoms, particularly from not only wear at the throttleshaft, but warpage of the mating flanges of the carb and manifold.

But his suggestion of using brake cleaner will not display anything but enormous leaks, nor will it pinpoint the location. It will also depend upon RPM, temperature, and other variables.
An absolute, static test that will pinpoint even the tiniest of leaks is simple airpressure and soapy water:
http://virtualindian.org/11techleaktest.html.

Correcting the throttleshaft wear is simple replacement with fitting of new bushings;
Correcting the flanges requires lathe-cutting the carb's flange, and grinding
the manifold's flange back to "flat".

Correcting leaks between the manifold and cylinder can be more complicated. Modern compliant seals from the material called "PEEK" are ideal replacements if the manifold spigots are pristine.
Correcting leaks between the intake nipple and the cylinders however, are major surgery, as discussed in the previous link.

Good luck, we hope it is just your control coil!

....Cotten
PS: Sinner!
He mentioned in his subject that it is an 80" Flatty. The last were produced in '42, although U's made through '48 could be overbored to 80". H-D did not introduce the auto-advance until '64.

The main nozzle has nothing to do with idle.
 

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Thanks Cotten didn't see that he mentioned the motor type till now, just saw "Linkert" then went into reading the question... If the air holes in the main nozzle were plugged I have seen them do some strange thing though.... I'm sure you have seen some "modifications" done by experts in their garages to make Linkerts run better ha ha.
 

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Thanks Cotten didn't see that he mentioned the motor type till now, just saw "Linkert" then went into reading the question... If the air holes in the main nozzle were plugged I have seen them do some strange thing though.... I'm sure you have seen some "modifications" done by experts in their garages to make Linkerts run better ha ha.
Sinner1!

If we believe the Armored School Handbook, a 45" had to reach 30 mph before the venturi kicked in to draw from the nozzle, so a Big Twin may even need more speed.
Up to that point, the nozzle need not even exist.

I have collected several photos of modifications that may or may not have merit. Some are rather common.
But the effects of any are pure conjecture and speculation.

If anyone has a testbed machine, dyno, etc., and and has the time and resources to document some modifications, please email me direct at [email protected]
Thanks,

...Cotten
 

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Really? It seems as though since you know everything about Linkerts you really can't come up with an answer to fix the problem and instead decide to tell me how wrong I am with your superior knowledge in this field. So you have made sealer and floats so you are the know all-be all? I have rebuilt over some 300 Linkerts and even though I am a builder and not so much a tuner I have tried to rule out some issues with the carb that are easy enough to check while you have wasted space with telling all it's incorrect with your fancy words and meaningless dribble. I have met you and you are THAT type of guy so if you feel the need to be SO much smarter then the rest who spend their time TRYING to help then countinue to show us all how smart you are. And really Tom, no need to reply to this and hopefully it gets deleted but not before you read it.... Really spend your time HELPING the man, not showing everyone what you THINK you know. I'm willing to offer suggestions pertinent to the question, not bashing others trying to help. Good day.
 

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common guys this thread (and all the others ) is about helping people in anyway whe can
sometimes someone gives the advise needed and somethimes its not the advice for the particular problem .....but anyone taking the time to help another is what its all about

not the i now it all or better than you ,and my dick is longer than yours .....fuck that !!!!
this thread isn't about that ,this thread is about a bike that runs like shit and the guy is asking if it could be his linkert or .........

lets act like grown ups and help the guy ;)
lets get BOT now please !!!
 

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Discussion Starter · #10 ·
hey thanks guys i have currently changed spark plugs, re-timed the distributor and changed the condenser and points,checked for intake leaks as i made a rig to pressure test the manifold when i built the bike and did it when i got it installed, i also change the plug wires and topped the charge on the battery and bingo it seem to be running fine so i'm not exactly sure what it could have been that fixed it but i know all that shit is good for a while i hope!!! i will be replacing the throttle shaft this winter which is coming up very soon... anyone have any ideas of where is the best place to find throttle shaft bushings? i know they can't be that pricey but anything other than the taiwanese made junk is always the way i wanna go... thanks all of you guy and i have to agree with el diablo..... we are all doing the same thing... just riding and wrenching so i appreciate all the help from everyone. thanks again!

Howie
 

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Discussion Starter · #12 ·
hey diablo i'm living in canada and really there are no sources for decent part for vintage in canada... only down side of livin up here!!! i will be searching high and low all over the place to track something down... i checked out that site you sent me and have found a lot of parts i haven't seen for sale ... even in the states... very good site and i will be purchasing some stuff from there... now all i need is to win the lottery!!! hahaha thanks!

Howie
 

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I think that the air test of the carb and intake manifold is a baseline. Once you have established that baseline, you can see what needs to be fixed.
 

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Discussion Starter · #14 ·
it is the best place to start while the build is in progress... do the leak test then i marked a small paint line on the cylinder and the manifold nut so that i can see if the nut has backed off at all... it backed off slightly a week after i had it going so i tightened and placed a new line... been tight and leak free ever since!!! quick way to see if it has backed off any...
 

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Flathead Howie!

When you order parts to overhaul your carb, consider going to a 1 1/8" venturi, as was spec for 80" models.

You will most likely find that your original venturi has shrank on its OD anyway.

Modern aluminum venturies do not shrink, and need not be as tight a fit as potmetal, but beware of modern productions that copied shrunken originals, and show daylight around them.

Good luck,

....Cotten
 

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Cotten: Do you have a pic of the
JPP!

Colony corrected the problem in later productions.

In my attachment, you can see a gap.
This greatly confounds the nozzle's "accellerator sump" function.

Vibration causes a rattling venturi to wear upon the nozzle as well; Worn venturi's holes and worn nozzle spigots benefit from a seal between them.

....Cotten
 

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Discussion Starter · #18 ·
so where would one find a good production venturi and how will i know if it is the proper one until i receive the thing and install in my carb? as i said earlier the carb is getting a FULL rebuild this winter while she rests!!! thanks
 

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Howie!

Since Colony decided to sell the faulty productions first,
you will have the best chance of getting an accurate venturi from the larger distributors with a greater turnover of inventory.

Aluminum venturies can be swaged oversize, and lathe-cut precisely just like an original potmetal venturi, but a great deal more 'persuasion' is required.

Of course, if you have a lathe, you can always cut venturies from scratch when necessary.
Often oversize throttlediscs as well as venturies must be machined to fully recondition vintage carbs.

....Cotten
 
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