Lambretta Atomic ultimate reed-valve kit

Lambretta Atomic ultimate reed-valve kit

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  • 101101 (150/175cc)
  • 101100 (200cc)
444 grams


  • Awesome. easy to start.
  • The reed kits are ace by the way, I recommend them to all who ask.
  • I fitted an Atomic Ultimate large reed block to the barrel & quite a lot was removed, no affects whatsoever.
  • I wouldn't worry about trimming fins as its on the cool inlet side plus the nice big lump of ally you are adding as a reedblock will act as a heatsink
  • I fitted one of the ATOMIC ones last year & have thrashed the arse off my scoot for 3000 odd miles thus far with NO issues at all. 

Atomic Performance high-quality bolt-on reed valve kit for standard Lambretta cylinders.

We have 2 reed-valve kits, this one and our mini reed-valve kit.

This kit is the "ultimate" because it allows for the most performance and is the best available anywhere - including those at twice the price!

What is a reed-valve? Basically a flap that opens and allows fuel in as the pressure in the cylinder needs it, then is pushed closed when not needed. You gain power and responsiveness down low, a huge improvement in fuel efficiency and no spit-back from the carb. People making the change rave about the smoothness of the power delivery.

You do not need a highly tuned motor to use this kit. It is great for regular motors too.

The kit includes everything needed and features:

  • top quality reed-valve
  • fits under the panel
  • rubber manifold with 34mm opening to fit our PWK 24-30mm carburetors (might also fit Dellorto 26-30 PHBH, VHSA 28, Mikuni TM24-30 but check your carb first)
  • 200cc manifold comes pre-matched to an Indian GP200 inlet; the 150/175 type is pre-matched to an Italian 150. You can open either type wider.

Reed-valve features:

  • top quality Atomic reed-valve for Yamaha RD350/TS1. No other kit comes with this excellent reed-valve! We also have spares.
  • alloy body
  • fiberglass reeds for optimal Lambretta performance (not carbon for super high RPM motorbikes)
  • rubber coated

See our tech notes for modifications needed. As you can see from the photos, when fitting this kit or similarly sized ones elsewhere, you need to trim some cylinder fins. (Our mini reed-valve kit fits without trimming fins if you prefer.)

Choose an option based on your original bolt pattern, 200cc or 150/175cc.

Tech Notes

  • You will need to shave down some fins on the cylinder above the inlet port to fit the reed manifold - any similar size kit has the same requuirement if fitting under the panel. Allow a mm of clearance. 
  • Check your jetting when making the change. You usually need to upjet a lot. See our tech page for how to do a plug chop.
  • Match your cylinder inlet port to the new manifold, and open the manifold as much as you want to allow more flow. 
  • A standard Lambretta only opens the inlet port when the piston is out of the way. To take advantage of the reed-valve you should make some changes to allow fuel to enter whenever it is needed. You do that by drilling 2 large holes in the piston inlet side (or use a piston already made for a reed-valve) such that you can see into the piston through the inlet port. You can also add a boost port in the cylinder up from the inlet to the top of the transfer ports. Raising the exhaust port slightly will help increase power. Please consult a local shop for tuning assistance.

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