To expand on many previous airbox modifications to change over to the 3AJ inlet.
I have just completed a further revision of what has been done before.
So initially I had no access to a full 3Aj airbox so I had to modify my 1VJ box to the same principles.

But now having found a 3AJ airbox I have morphed both 3AJ and 1VJ.
Twin Air very kindly produced a new version of their filter to fit the 1986 1VJ filter cage, this I have found to have a larger surface area than the 3AJ, so in theory should flow better.
I have also added thermal foil insulation to the lower of the airbox to help with heat that rises and radiates from the engine.
Little things that hopefully add to a cooler inlet and motor.




3mm thick plastic sheet cut to fit and and bonded with epoxy







Thermal foil on the underside of the box (I resisted the gold version as it’s a bit too formula 1)







The 3AJ filter cage is recessed to accommodate the inlet.





The snorkel is too long to fit with the larger 1VJ filter so is trimmed a bit.






Done, to be fitted to the bike tomorrow.

Good, but why not do away with the snorkel entirely?

I'd be inclined to cut out the filter cover, and use the frame to hold something like a nylon mesh in place to keep the larger particles out.

Two reasons really, if the box was open, water from washing or rain could get into the airbox as it flows between the tank and seat, secondly it’s tidy/looks finished, to me at least.

I did think of just using a mesh as you say, but the hunt for the parts was fun. (Found one 3AJ airbox in Italy and a second in Ireland)
Modding my second 1VJ next as I have just bought another.

That's a good point.

Could you not modify the original intakes so you don’t have to buy a 3aj box?

The filter cover (that becomes the intake) can easily be modified, at its most basic level by drilling holes in it, or if anyone is a Wizz with a 3D printer I suspect a copy or something similar the the 3AJ intake could be printed.

Looks like someones having a go.

Great to see, that would have saved me quite a lot of hunting.

Thanks Simon.

Hi, Im after one of these 3d printed ones. Do you have a link?

You have to get someone to print from the file and hopefully it'll fit. I was quoted £28.
With an ok second hand 3d printer starting at under £100 I was in two minds, as I'd like to print the oil tank cap / dipstick. Not to mention the starter button.

https://www.thingiverse.com/thing:72871 ... e_vignette

simplesimon1 wrote: Tue Feb 24, 2026 7:43 pm Looks like someones having a go.

Hello,

I printed this part and tried it on my 1VJ.
It was not a straight fit. I had to grind a little bit here and there and finally using a heat gun to make it fit properly.