The International CBX Owners Association

Hey all.

The carb boots on the CBX are famously tight, with advice for removal and installation including the use of prybars, 2x4s, ratchet straps, and probably most importantly the use of a heat gun to get the rubber smoking hot.

I am in the design phase for custom throttle bodies to replace the OEM carbs. They will install in place of the OEM carbs, which will allow the inclusion of the entire OEM intake tract, plus the OEM throttle linkages and cables.

The bad news is that I intend to fabricate these throttle bodies from a material that is unlikely to withstand the heat required to get the rubber boots smoking hot.

The good news is that I have complete control over the final shape and dimensions of the completed throttle bodies. It's hard for me to understand why they have to be as tight as they apparently do. This might be an unanswerable question, but how much of the difficulty with removal and replacement is due to tightness, and how much is due to the amount of deformation required because of the V-shape of the bank of carbs and the boots that receive them? If the shape or size of the outlets of the carbs/throttle bodies was changed to make removal and replacement easier, would it even make a difference?

Thanks for any advice or insight on this.

Tight is relative. They only have to be tight enough to seal. The clamps do a lot of that work. As they age and withstand heat over the years they seemingly turn ceramic hard and then they’re famously hard to remove. Installing new soft boots isn’t all that hard.

I've been using these for years, about 1/2 the price of stock clamps and they're made of STAINLESS STEEL! (They don't come polished).

https://www.aircraftspruce.com/catalog/ ... /055-9.php

55mm for the boots, 60mm for the airbox. Available in many sizes.

While I'm far from a wizard, Phil, I would say the carb boots should be 1 or 2 mm 'tight' on the diameter. A little stretch is good/necessary. The clamps don't so much seal as they just keep things from coming apart. If the clamps were to distort the boots any, there will be a 'buckle' effect that would, then, be a leak. My numbers are a WAG on my part. I've never bothered to measure new boots to confirm. Maybe someone has a new boot and can measure it for us. Bottom line, though, they do need to be snug.
The use of blasting powder to remove old ones is a matter of aging and heat. Generally, I've found that blasting caps are sufficient! :) Maybe air hammers. (Said the smart ass, here)

Perhaps there's a market for the boots to made from a silicone material, that would be more heat resistant, thus less prone to hardening. Just look under the hood of newer trucks and heavy equipment. Nearly all hoses are now silicone based. Especially turbo hoses which get a lot of heat.

Maybe Viton boots ?

My test for checking the clamping effort is this for stock clamps:

If you push in the screw head with a driver and the clamp rotates, it's loose.
If the clamp ends are butted together, you need new boots.

As simple as that.

While we're on the subject of insulator clamp tightness, new ones ALWAYS need to be re-tightened up after a heat cycle. Do not neglect this.

CBX-tras wrote: ↑

Wed Mar 27, 2024 8:41 am

My test for checking the clamping effort is this for stock clamps:

If you push in the screw head with a driver and the clamp rotates, it's loose.
If the clamp ends are butted together, you need new boots.

As simple as that.

YUP!!

Rick Pope wrote: ↑

Tue Mar 26, 2024 1:44 pm

Perhaps there's a market for the boots to made from a silicone material, that would be more heat resistant, thus less prone to hardening.

I've been thinking about silicone replacements for these boots a lot. I have the means to 3D print some molds and cast my own silicone replacements that match the dimensions of the originals.

That would be most interesting, Phil. Keep us posted.