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It seems as though a lot of riders are looking for replacement intake boots because the rubber is cracked. Why rubber?? Why is it a non metal substance? Cars don't use it. Straight metal. I don't have a problem with the rubber per se, just that they break down, are expersive and hard to find, unless you buy new $$$.
 

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It seems as though a lot of riders are looking for replacement intake boots because the rubber is cracked. Why rubber?? Why is it a non metal substance? Cars don't use it. Straight metal. I don't have a problem with the rubber per se, just that they break down, are expersive and hard to find, unless you buy new $$$.
nope,you cant use metal.they are heat insulators.

cylinder----heat-----carb----petrol.

bad mix
 

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Bike carbs don't use a manifold as such so the carb is bolted almost directly to the head. The rubber I beleive is used in an attempt to avoid too much heat reaching the carb.
 

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Heat, and vibration. You don't want the carb to be shaking like crazy. The carbs aren't mounted to the frame, just the rubber boots, which give a little flex. Otherwise with every cycle of the engine it would shake like crazy.
 

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The old British iron Triumphs BSA Nortons etc had carbs that bolted directly to the cylinder heads with no more than an insulated gasket to protect them. Those old machines used to vibrate a darn sight more than any ol` CX that I know of yet they ran perfectly OK.
 

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It's a combination of factors. Rubber insulates heat and vibration. Rubber is no stronger than it needs to be, and is cheaper than metal. Hose clamps are quick and easy to assemble at the plant.
 

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The old British iron Triumphs BSA Nortons etc had carbs that bolted directly to the cylinder heads with no more than an insulated gasket to protect them. Those old machines used to vibrate a darn sight more than any ol` CX that I know of yet they ran perfectly OK.


I've owned many BSA's and a Norton or two, I never had the pleasure of owning one that ran "perfectly OK" for more than an hour or so.
Few bikes made it to 10K in the "good ole days" without a complete rebuild. You have to go pretty far back to find a BSA, Triumph et. al. which doesn't use a rubber insulator.
 

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My old CZ250 had carbs bolted via alloy manifolds direct to the engine, but had rubber boots to the airbox.



Carbs tend to stay cold, air and petrol mixing together create a cooling mixture. I suppose it depends how hot the country is you live in.



They certainly didn't effect the performance, or vibrate to bits, or set on fire.



:)
 
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