keep cracking carb connecting rubbers, why?

[Davidsquaredson]

My manifold is 36mm, carb 36mm. Remote K&N air filter on a bellows. I keep going through connecting rubbers. Clearly I am not setting it up right. I find they crack along the clamp around the manifold. Is it that I am clamping too hard? I have been using the MB rubbers, they are ID=35mm. For a change I am trying BGM that are 34/34. I had to heat it up to get it on. There are also Polini (34/34) and Malossi 35/35.

I thought the weight of my filter was not helping so I ran it sideways, added a loop to the pastic top, and zip tied it to part of the frame.

Anyone find one of these manufacturers lasts the best? MB, BGM, Polini, or Malossi?

If I am clamping too hard, whats your technique?

Clearly I am not doing it right.

Tx
David

[eden]

Is the carb close enough to anything that it can hit it when the suspension travels, like the tool box? if so it makes the carb twist when it hits it which kills the rubber.
Just a stab in the dark

[Donnie]

Only ever used one of the manufacturers ones many years ago and had the same issue, changed to using a piece of car radiator hose (about 10 years ago) and only replaced that with a new one about 2 years ago due to age. Never actually had a problem with it.

When tightening the jubilee clips my techniques always been to tighten them both up until they are just nipping the rubber, then see if i can twist the rubber on the manifold first and nip up a bit more until i cannot do so by hand, same on the clip on the carb. Never had an issue doing it like this.

[shocky]

Are the ribs on the rubber in the correct place in relation to the carb and manifold , like donnie ive used top hose from a land rover and I use the just just nipped up method

[Davidsquaredson]

Thanks Gentlemen,
I'll give rad hose a go and tighten the clips as you suggest. Do you go for an inside diameter the same as your manifold/carb, or if smaller, by how many millimeters?

Tx
David

[Donnie]

I've always gone for the same, ie the inner diameter of the hose = outer diameter of the manifold.

[Grumpy225]

What kind of clamps are you using? There are the really cheap kind, usually stamped "ideal" and they will cut in to the boot.

The good ones have rolled edges and the teeth point out from the boot. German made and usually seen on a lot of Volkswagen. Haven't split a manifold boot ever when running the German ones.

Also match the boot to the manifold, if you have to stretch it to fit you're doing it wrong and it WILL fail.

[Monty]

I thought the weight of my filter was not helping so I ran it sideways, added a loop to the pastic top, and zip tied it to part of the frame.

This is what stood out to me if its too tight you may be pulling against the carb when the engine moves up and down. Just a thought

[Burnside]

Over tightening can cause them to split, running an MB rubber on one of mine and it's been on there for 5 years now without any issues

[shocky]

My last hose was a tight fit tbh I never measured it it was tight and boiling water was used to soften it up im gu3ssing it was 38mm or so becouse the carb was a large body 30mm and had the 39mm connection stub I have no idea what a standard TS1 connection stub is as that was the other end