UPDATE: MullieMotors is having a sabattical.
We hope to reopen in the summer of 2022
New and used motorcycles,
parts, and accessories.
Specialized in vintage Harley Davidsons.
Featured Items: Contents: Legal Stuff:

Pre-sized PEEK seals
Pre-sized PEEK seals!

Mullie Motors is now offering pre-sized PEEK seals for all common (HD and other) plumbing manifolds! Stop those air-leaking intakes that cause engine mal-functioning or even damage. Pre-sized PEEK seals are available in the following sizes:

Order No.Inner diameterUsed onHD part #
H-D 1 1-9/16 1930-48 74& 80 Flathead,
1936-39 61 OHV, 1940-46 WLD
H-D 21-7/161932-73 45 W & G models 1118-30A
H-D 31-45/641940-54 61& 74 OHV (Knucklehead & Panhead),
also K models & WR

These PEEK seals cost 45,- per set (incl. VAT, excl. shipping).

Order your PEEK seals through info@mulliemotors.com

Important note: pre-sized PEEK seals should only be used on intake manifolds that are in excellent condition. That is, manifolds that are round, have an unworn, smooth surface, and have the correct, original diameter. Old manifolds are often worn or damaged. For these, we offer custom-fitting of PEEK seals, see below.

PEEK intake seals

The intake seals on vintage HD's (and other bikes using the "plumbing" design for their intake manifolds) are notorious for leaking. This can result in hard starting, rough running, overheating, and even destruction of the engine. It is difficult to get a perfect seal using the original brass intake seal rings. There has been a lot of experimentation with other type of materials, or even different designs, for the intake seals. A problem however, is to find a material that can withstand the heat and is resistant to (modern) fuel types. PEEK is about the only modern material that is up to the task. The "invention" of the PEEK intake seal rings is courtesy of "Cotton" from http://www.victorylibrary.com, he calls them "Liberty Rings". Since Cotten does not have the time nor the resources to provide the entire world with Liberty Rings, he encourages others to provide them.

Mullie Motors offers the service to convert your intake manifold sealing to PEEK seals. You send us your intake manifold and intake nuts, and we make a pair of intake seals custom fitted to your manifold and intake nuts (for a perfect seal, it is required that your manifold is dressed up, and the seals are made to the exact dimensions of your manifold and intake nuts).

A pair of custom-fitted PEEK seals usually costs around a 90 Euros, depending on the condition of your manifold and intake nuts, and the current price for PEEK stock (which is very expensive and varies with the oil prices).

Contact us through info@mulliemotors.com to have your plumber intake converted to PEEK-seals.

Two examples: Left is an HD WLA manifold fitted with PEEK seals. Right is an Indian Chief manifold reworked for PEEK seals.

PEEK intake manifold seals PEEK intake manifold seals

Below is a brief description of the process.
Mullie Motors is a trademark of Mullie B.V.
For questions, remarks, or further information please mail to info@mulliemotors.com