Airbox volume requirements
 

Hello all.

A buddy and I are working on an alternative carb setup for some old GL1000's and we are thinking of using some VTR carbs. The stock GL carbs are not very tunable and aren't very forgiving.

I'm wondering what the "requirements" are for airbox volume that these carbs need to draw from? The setup would use 1 carb per 2 cylinders.

The stock GL1000 airbox is a "typical" oval airbox with an oval filter (see attached image). Our concern is this might be too small to feed the carbs.

Please feel free to let me know your thoughts. I was thinking I could get a smaller air filter (if it's available) with a dome to increase airbox volume in the existing space. Otherwise, we were thinking of maximizing the size that fits in the stock location somehow... Thank you for your help!!

Dont they just fit VW carbs to them?

That sounds a lot easier than VTR carbs.

Particularly as we know how finicky the VTR carbs are when it comes to the airbox arrangement.

The airbox volume from a VTR will not apply since you are feeding 2 250cc cylinders instead of 1 500cc cylinder. For a given rpm the total flow will be the same but taken in to gulps. Sounds like a fun project into uncharted territory.

I remember reading VW manifold with a Weber twin bore carb are an easy swap. Looked pretty simple to me.

Weber IDF carbs are a popular swap, but they kill knee room and make the bike slightly less usable. We want something a bit more simple to hide. The vtr carbs were a choice since we have some sets sitting around and I have access to 3d print the manifolds at work out of Al, so minimal machining required.

I wonder if a set of VM36's would be a better option...