rejuvenating, rubber bits?

anyone know a way of softening up rubber bits that have gone hard over time, i'm thinking mainly about cam cover donuts. was going to try soaking in diesel for a bit on an old knackered one.
my donuts are in decent shape there just hard on the surface, anyone any tricks to try?
thanks
Stu

 

I’ve never tried it myself, but have heard that Wintergreen Oil is effective at softening rubber.
Regards
Charlie

 

I tried it, even bought the good wintergreen oil. Worked a little on the stuff that was kinda pliable but anything that was rock hard it didn’t work.

 

thanks guy's , looks like the diesel worked enough for me to re-use the donuts. though i wouldn't leave them in there for more than a couple of days, as i soaked a brake calliper in diesel for two weeks, to get the calliper half bolts out, and the piston seals were nearly double the size of the new ones when i took them out, they had swelled so much they doubled up out of their grooves.
winter green seems quite expensive here for a small amount, but i suppose if it works - then --------
thanks
Stu

 

Brake fluid will soften up sone types of rubber...it's commonly used as a temporary fix to soften up some types of woofer surrounds on speakers

 

interesting , -- may try that too

 

I had the same problem when trying to find wintergreen, but discovered some cheaper sources on Amazon. As always, for things that have a vaguely medical application, you'll find re-packagers of it that charge as much as they can get away with.
Also, I came across mention that the wintergreen can be diluted into acetone or IPA, which will really expand its use. If you use it neat a lot of it will be wasted.

 

I used Berryman's B-12 Chemtool on the carburetor diaphragms and it cleaned/softened them up quite well.

 

Silicone spray lubricant will also help , but you have to really soak it in lube .

 

I followed a process on Practical Sportbike in UK wher they boiled airbox rubbers in diluted wintergreen with water (can't recall the ratio maybe 10:1).
It works but you need to be careful as it can make the outside of the object sticky and kind of off-white IIRC. Diluting with alcohol and submerging
sounds safer..

Another thought - could you make a mould and cast them in silicone?

 

The biggest issue I had was the rubber parts had shrunk and could not be reinstalled. This was an odd one year bike where the part only fit three bikes in a three year span so I was desperate. Took years of searching and eBay searches to find one intake duct. I did not try brake fluid, that might make them swell up but I don't know if that would be a long term repair.

Valve cover donuts are easily sourced though, why not just replace them?

 

SOFTENING RUBBER:

A solution is to purchase some Methyl Salicylate (it may be called “oil of wintergreen” at some sellers) and mix it up with some solvent, such as mineral spirits or isopropyl alcohol (the purer, the better) and then soak the parts in that mixture for 24 hours or so….....the solvent opens up the pores in the rubber, and the wintergreen oil replaces the "softening" compounds in the rubber, which have evaporated/de-graded over time and causes the rubber to shrink and/or become hard.

METHYL SALICYLATE a/k/a wintergreen oil a/k/a oil of wintergreen
99+% ISOPROPYL ALCOHOL (ISP) (note: do not use drugstore 70% alcohol, has too much water in it. Another note: very flammable)

Mix:
1 part x Methyl Salicylate (wintergreen oil)
3 parts x 99% Rubbing Alcohol

or:

Toluene or Xylene will work also: Mix 60% toluene or xylene / 40% wintergreen oil. Toluene as the solvent does cause the rubber to expand somewhat --- but it also gets the methyl salicylate into the rubber quicker --- and you’ll then need to leave the parts out (not in the fluid mix) for a few hours for them to return to their original size.

NOTE: always soak in a glass or metal container! These types of solvents (including the 99% alcohol) will have undesired results when put in contact with plastic


Note that whatever method/mix used, that the process may need to be repeated every couple of years, as the wintergreen oils aren't exactly the same material that is used in rubber compounding originally, and the wintergreen oil will eventually "evaporate" out of the rubber, as did the original chemicals.

The the wintergreen + whatever-solvent-used mix can be stored in a tightly sealed container and then used over-and-over again.

 

hi all,
thanks for the other replies, i'll give them some thought
internet been offline for a week, so couldn't reply.
cheapest "donuts i could find were £3 GBP, which makes it £36 GBP!!

 

A UK source of wintergreen oil, much cheaper than the rip-offs on amazon.
https://mistralni.co.uk/products/wintergreen-fragrance-oil?variant=213253535

 

Another thought.. I wonder if you could 'make' some from stacking some different sized o-rings - maybe 'glue' them together with black silicone. O rings are pennies usually.

 

i've put the "renovated " donuts back on, i already had a new rubber gasket, sealed gasket and donuts with blue Hylomar, gasket sealant, and all seems ok, havent started the motor yet, as its still on the bench.
p.s. couldn't get hold of the Permatex gasket stuff without paying stupid prices

 

@bensalf https://www.motorcycleproducts.co.uk/cylinder-head-mounting-rubbers/yamaha-xj600-1984/5/33983/31931

Are these the ones you need £17 plus postage for twelve?