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My thoughts on carb/brake cleaner vs rubber and plastic components

Started by lucas, June 01, 2016, 10:43:34 AM

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lucas

Edit:  I originally wrote this in a thread that wasn't about carb cleaners. So instead of derailing that discussion I moved my comments over here. 

The arguments about brake/carb cleaner on rubber and plastic have been raging forever and there are a lot of contradictory ideas out there.

The trouble starts because every brand of cleaner has totally different solvents in their products.  All carb cleaners are different, so it is impossible to adequately generalize.  Further there are several types of rubber and plastic and some can be safely sprayed with a cleaner while others will swell or rot away.

There are brake cleaners and carb cleaners out there that are safe for plastics and rubbers.  Look for explicit statements on the packaging that claims it won't harm rubber/plastic.  If the packaging doesn't clearly say it, then it is safe to assume it will harm rubber.  The non-chlorinated CRC Brakleen can still be harmful to rubber due to the acetone content while Berryman chem dip is easy on rubber parts.

Some of the chemicals that harm rubber and plastic are acetone, chlorinated solvents, and some alcohols.  I found a cool resource showing the relative reactivity of several chemicals with plastics.

Any solvent branded as carb or brake cleaner is going to be made of very reactive chemicals what for the quick dissolving of gunk.  Plastics and rubbers are made of polymers - long chains of molecules that are susceptible to attack by reactive chemicals.  When the right kinds of reactive molecules come by they can attach themselves to the polymer, link multiple polymers, or break polymers thus degrading the material.  So cleaners need to be specially formulated to minimize damage to plastics and rubber.

Any anecdotes of the form "I've used X cleaner for  Y years and never had a problem with seals going bad" have to be taken with a grain of salt.  It may be true that the specific cleaner and that particular rubber material are compatible, but that doesn't mean that it is safe for other types of rubber.  Without special knowledge it can be hard to determine what kind of rubber a seal is made out of.  Also, the person with the anecdote might be incorrect, they may not be able to detect visually that the rubber is now more brittle or less elastic than it once was.  Most damage to rubber and plastic from solvents is not going to be extreme or obvious but will probably just result in premature failure somewhere down the road.

Don't just take a leap of faith with cleaners by spraying and praying.  When you're cleaning your carbs disassemble them as much as possible, remove plastics and rubber, and separate dissimilar metals.  It is impossible to completely disassemble the carbs though since the throttle valve is locked in and the copper tubing is brazed in place.

You can get all the plastic and rubber parts off though.  Even the plastic slide guide (white plastic) can be removed from the carb body with either a 5mm screw or using the jet to push up on it from underneath the carb body, can't quite remember which.  But in my experience trying to pull it from the top was useless.


Watcher

"The point of a journey is not to arrive..."

-Neil Peart

ShowBizWolf

Awesome read!  :star:

I'm guilty of doing my fair share of spraying Brakleen on various things and praying it wouldn't damage anything... I've been lucky and I love it as a cleaner for stubborn dirt that just won't come off.
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Kijona


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