Halfway To Thunder

A Stealth Intake Mod for 1500/1600 Engines


This tip relies on an adapter from Thunder Manufacturing, which has ceased operations.
If you know of another source for the intake adapter, let us know.

thunder backing plate stock airbox cover

Ok so you want to open up the intake on your engine for more power but you really don't want to be looking at the filter as you will with most other mods including the Caddmann, most of Thunder's round air kits and Baron's Big Air Kit. You also ride in the rain a lot and don't like the idea of having the filter hanging out in the air sucking up H20. Not a problem.

Most riders who open up the intake by putting the filter on the right side remove the air tunnel and air cleaner assembly from the left side of the bike. For this mod (like the Caddmann intake mod) that is not absolutely necessary. If you do choose to remove what will become superfluous parts you might want to check the instructions posted on this page. If you don't like the 'naked' look of the left side once the air cleaner is removed you have plenty of choices for replacements, some of those are shown here.

This mod uses a Thunder Manufacturing adapter plate, part of a Thunder Round Air Kit and your stock air box or air cleaner cover to produce what you see in the picture at the top of the page. Looks stock doesn't it? Well it isn't.

The filter that comes with the Thunder kit is just under 7" in diameter and 2" tall. Your air cleaner cover is about 8.5" in diameter and 2" tall. Result, you have about 1/2" of clearance between the cover and filter all around, the two are the same height but the adapter you'll use leaves the entire outer edge of the cover uncovered so you're drawing lots of fresh air straight into the throttle body.

This project will cost you about $230 which is a bit less than most aftermarket kits but quite a bit more than the $30 Caddmann which uses an automotive type air cleaner. Then again, saving money isn't why you're doing this right? It's to pick up about 10-15 hp and at least 10 lb ft of torque while hiding the filter.


What You'll Need
thunder adapter 20203a

  • 1- Thunder adapter kit as shown at right for Vulcan 1500/1600 FI part number 20203A. If you have a different bike or carb rather than FI you'll need a different adapter.
  • 1- Thunder kit part number 30101A-NC. The "NC" means "No Cover." What you're buying is a plate the K&N air filter sits on and the filter. Essentially the round air kit but without the outside piece which saves you $20.
  • 1- Strongly suggested, an aftermarket fuel management computer like a Dobeck TFI or Dynojet Power Commander


How to Do It

  1. If you never plan to take the intake back to stock, remove the left side air cleaner and backing plate, air tunnel and right side air box cover and backing plate. If you want both sides of the engine to look the same when you're finished just leave the stock (left side) air cleaner in place and remove the right side air box cover and backing plate.
  2. Screw the air temperature sensor (brass colored thing) you removed from the air box backing plate into the hole provided in the Thunder adapter. Connect the crankcase vent to the supplied plastic elbow and bolt backing plate to throttle body using supplied bolts. Plug the brass pipes that used to supply vacuum to the cold idle solenoids with the supplied rubber caps.
  3. Attach the filter backing plate to the adapter with supplied bolts
    thunder backing plate 20203a
  4. Place the K&N air filter that came with the 30101A-NC kit on the backing plate
    thunder backing plate wk nfilter 7x2
  5. Pick one of your OEM covers and place that over the top of the filter and attach it to the backing plate using the bolt style of your choice. There may be one supplied with the backing plate but it will look like the one in the photo at the top of the page. Not pretty.
  6. Tune your TFI or other aftermarket computer as needed. If you haven't installed a TFI yet you'll find instructions and suggested settings here.
  7. Go ride and enjoy the extra 10 horsepower and 10 lb ft of torque you just granted yourself.


thunder backing plate odyssey coverIf you ever decide you don't want to use the stock air cleaner cover anymore Thunder has a huge choice of covers that use the same backing plate and filter. This is the Thunder "Odyssey" style cover that bolts to the adapter and right on top of the filter.

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