Linkert Snap Back Throttle - Internal Throttle Type
Linkert Snap Back Throttle - Internal Throttle Type
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What Throttles does this work with?
This version is for INTERNAL throttle that PULL the wire into the sheath at wide open throttle. The throttle cable must enter from the carburettor intake side of the engine with this product.
All parts are provided to allow this throttle to work with Internal throttles in PUSH or PULL configuration, you can ever use it to turn the carb throttle anticlockwise if you wish!
No more janky spring setups, no more flex, this thing is SOLID and is designed to look good against the period of the machine to which it will be fitted.
What Carbs Does This Fit?
This Snap-Back throttle linkage has been designed to retrofit to 3 & 4 Bolt Linkert "M" Series carbs with 1/4" throttle shaft and 5/16" mounting bolts commonly used on 1930-1952 Flatheads, 1936-1939 OHV Harleys and some Indians.
It will also fit Schebler DLX carbs with 1/4" throttle shafts, and 5/16" mounting bolts used on very early machines.
It does not fit Schebler HX Carbs, or Linkert DC carbs, I will have kits for them soon.
What Option Do I Need?
There are two options available:
- Overhead Valve (OHV) - Knuckle, Pan, and Shovels
- Side Valve (SV) - WLA, WLC, Model U, Linkert/Schebler DLX equipped J-Models. this version is a mirror image of the OHV version.
What Configurations Should I Avoid With this Product?
There are only FOUR configurations across both models for which I STRONGLY recommend you purchase the "Linkert Snap Back Throttle - External Throttle Type" Instead. It is lower cost and will give you a cleaner more reliable operation.
Side Valve (SV) Motor/Carb/Cable configurations that DO NOT work with this throttle:
- PUSH throttle with cable entering from the RIGHT hand side of bike
- PULL throttle with cable entering from the RIGHT hand side of bike
Overhead Valve (OHV) Motor/Carb/Cable configurations that DO NOT work with this throttle:
- PUSH throttle with cable entering from the LEFT hand side of bike
- PULL throttle with cable entering from the LEFT hand side of bike
What Comes with the Kit?
Rear Plate - Mounts behind the manifold, sandwiching the manifold between the rear plate, 1/4" Thermal Spacer and the Carburettor using the stock mounting bolts that should already be on your bike (not supplied).
Lever - Drilled to 6.35mm (1/4") this is a very snug fit. You can spread the opening a little if you want but I find there is rarely the need. what I do is tap it in place with a small drift, then adjust the butterfly position once installed. The lever is further clamped in place with am M4x0.7x16mm screw and spring washer. Only 1/2 to 3/4 of a turn should be required to lock it down.
A spare hexagonal head screw is provided should spanner access be easier for you.
Sheath Clamp (Later versions supplied with Long AND Short) - This is where your cable sheath enters the linkage, this is my invention, it avoids you having to clamp your sheath to your motor. The sheath clamp rotates on a shouldered nylon washer. It is held in place with a M1.6x16mm split pin. The sheath is clamped in place with an M4x0.7x8mm screw and spring washer.
Again, a spare hexagonal head screw is provided should spanner access be easier for you.
Cable Clamp (Later versions supplied with Long AND Short) - This is the component that holds the inner wire of the throttle cable. It is mounted to Lever through a shouldered nylon washer. It is held in place with a M1.6x16mm split pin. The sheath is clamped in place with an M4x0.7x8mm screw and spring washer. Under this Clamp is a Spring Bobbin.
Surprise! another spare hexagonal head screw is provided should spanner access be easier for you.
2 x Long Pin - This Blanking Pin is mounted on the Rear Plate toward the rear of the bike and serves only as a mounting point for a spring bobbin.
2 or 3 x Short Pins (Later versions) - These Blanking Pins are mounted serve as aesthetics and to prevent loss of the nylon bushes in certain configurations.
Spring Bobbins - On this version the extension spring can be "Underslung" between the Rear Plate, and the Lever, we use these to make that happen. Each one is located by either a Long Pin, Long Cable Clamp, or Long Sheath Clamp. Each spring bobbin is secured with a M1.6x16mm split pin.
Spring Bobbin Pins - These spring bobbins allow for an Overslung spring in certain scenarios. The choice of Overslung, or Underslung springs is often an aesthetic choice, but I have left the decision up to you :-)
Springs - Six springs are supplied:
- 35mm x 0.8mm x 10mm
- 30mm x 0.8mm x 10mm
- 25mm x 0.8mm x 10mm
- 35mm x 1mm x 10mm
- 30mm x 1mm x 10mm
- 25mm x 1mm x 10mm
All are Stainless Steel extension springs with Closed Double English ends to ensure they cannot come off!
Now, Throttle feel is subjective, very personal, and is also affected by cable type, length, and condition. To that end I have made my Bobbins slightly undersized, and cross drilled them to allow you to experiment with rubber bands hook end springs etc etc. This was done so as not to lock you into my preference, but also to allow you multiple options on the road to repairs.
Do not use 12mm diameter springs, they will be too large and could come off.
Carb Spacers (and how they affect spring length)
If you use spacers larger than 1/4" between your manifold and carb then you will need a longer spring.
Mc Master Carr, and Ebay stock a wide variety of springs, this image is a quick filter of what was in stock on 27/04/2025
Installation
Remove the Carb and Manifold.....your fingers will thank you.
Split Pin Notes: If the split pins are to tight for you, just use one side of them, or get a smaller one. I supply 1.6x12mm split pins but sometimes the combination of tolerances in the parts and nylon washers can lead to a tight fitment.
Bolt the rear plate behind the manifold using the stock mounting bolts that should already be on your bike (not supplied), then you Made from 316L Stainless steel it is built to last. If you are using a three bolt carb make sure to take some time to ensure the plate is nice and level when tightened. if it is not level your Idle and Wide Open Throttle (WOT) screws will not align with the Lever correctly.
Next, Clean up your throttle shaft and remove any burrs, or corrosion.
Align the lever and press it on the Throttle shaft till the base of the lever meets the carb. Don't worry about butterfly position (that's not yoga!) untill the lever is pressed into position. This lever is shipped to be SNUG and I often TAP it onto the shaft with a small pin hammer, in extreme cases I open up the clamping gap with a screw driver while tapping.
Now to set the CLOSED POSITION. Hold the butterfly closed with your fingers, while adjusting the lever till the spring "Just" starts to open. You need a very slight amount of spring pressure (where the coils just start to separate). Camp the lever in place with its M4 screw.....DONT go nuts cowboy! You may need to work on this on the side of the road while you are high so just enough to compress the spring washer so it can do its job.
Now to set the WOT position. Sight down the carb and set the lever into the WOT position, then wind in the WOT screw so that it prevents any over travel. Now depending on your carb and your preferences the spring on the screw may be too long, jut trim it to suit with some side cutters. If you want you can replace with any 5mm I/D spring that holds the screw to your liking. I have also supplied longer WOT screws for you just in case the fitted ones are two short.
TWEAK the IDLE. Let everything go and the Lever should return the butterfly to the closed position. Add two full turns to the Idle screw so that it adds some extra spring tension. As with the WOT screw spring, I ship the springs over length so that you can trim to suit to get the the tension just right. I have also supplied longer IDLE screws for you just in case the fitted ones are two short.
Remount the Carb.
FIT THE SHEATH Insert the Sheath into the Sheath Clamp and tighten the M$ screw so that it holds the sheath but does not hinder cable movement. Remove any rubber sheath that you need to. If the sheath is too thick the M8 bolt may be too long to allow engagement of the spring washer, move to an M4x6mm screw (supplied) in this scenario.
Later models have two threaded holes to allow you to place the screw on the side of the clamp that allows best clearance.
FIT THE CABLE Insert the inner throttle cable into the Cable Clamp, rotate the throttle to closed, tighten the M4 screw on the cable clamp till it holds the cable in place. If the Cable is to thick the M8 bolt may be too long to allow engagement of the spring washer, move to an M4x6mm screw (supplied) in this scenario.
You can rotate the cable clamp 180 degrees to position the clamping screw wherever it allows most clearance.
Fire up the bike
Set the Idle
Hug your family, tell them you love them, then go for a ride.
Safety and Words of Wisdom
- It is YOUR responsibility to ensure the safe operation of this part and its legality on the roads of your country. By building a custom bike you take on the responsibility for your work, respect that responsibility and show the next generation how to respect it so they continue the traditions!
- If you are not qualified to work on motorcycles please seen an approved professional to perform the work for you.
- I will not help you tune your carb, seriously! don't even call about that!
- If you loose a part, break a part etc. I can sell you individual spares.
- Some slight fettling of the part may be required. My quality is consistent but the product will ALWAYS vary between production runs....small batch life baby!
- I'm one bloke in a shed, in Australia, with a Wife, Dog, and 9-5 Job. I'm not a corporation, I'm not rich, and I don't intend to become rich of the backs of you lot so my profit margins are LOW so that you can do cool shit. Please remember this when dealing with me, lets all work together.
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