Topic: If you are fixing your bike with silicone...

[SOHC Digger]

Please people, remember...

If you are fixing your bike with silicone, you are not really fixing it.

There are very VERY few mechanical applications where silicone or RTV are the preferred sealing methods.  If you are using it where something else is intended, you are creating a world of sh*t for yourself or someone else down the line.  Silicone breaks off and finds any orifice it can, and clogs it, whether it's an oil passage, air line, fuel jet, etc.  Do the right thing, repair it correctly.

"Why the rant, Digger?" you ask.  Well, I have seen silicone used it horrible places, but this past week was probably the topper.  I tore down a set of carbs for rebuild and the previous shade-tree decided that silicone made a better float bowl gasket than the rubber o-ring Keihin designed for it.  Gee, can't imagine why the bike wasn't running right.

Please people, be professional.

[Fritz]

And not to forget: Silicone is the perfect stuff to ruin your paint job

[Kong]

And as long as we're talking about stuff that has no place on a motorcycle (or anything else) how about JB-Weld, the most overused crap on the face of the earth that is always, and I mean absolutely always, used in the place of the proper fix; there had never been a case in the world where anything that was "fixed" with JB-Weld was fixed properly.

[Elan]

silicone breasts work great on a bike

[Damfino]

silicone breasts work great on a bike

I prefer them in my face!



Thanks to Kit for the pic!

[OneWheelDrive]

JUXTAPOSITION WIN!

silicone breasts work great on a bike

I prefer them in my face!



Thanks to Kit for the pic!

[KingCustomCycles.com]

And as long as we're talking about stuff that has no place on a motorcycle (or anything else) how about JB-Weld, the most overused crap on the face of the earth that is always, and I mean absolutely always, used in the place of the proper fix; there had never been a case in the world where anything that was "fixed" with JB-Weld was fixed properly.

Seals gas tank holes from dent pulling just dandy.  Aircraft fuel tanks are made of epoxy so I would guess it is a permanent fix.

[Kong]

Use it if you like but I still think JB-Weld is both expensive and an inappropriate product for auto body work situations.  If I want to fix dents in metal gas tanks then I'll use automotive body filler properly applied.  By the way, you know as well as I do that there isn't an airplane on the face god's good green earth that has its fuel tank repaired with JB-Weld, at least not one that's legally licensed to fly.

[Lavis500]

I can't speak for ALL aircraft, but on military helicopters the fuel cells are a bladder style bag with self sealing capabilities.  Here is how a fuel cell is constructed on a blackhawk:

Cells are constructed of several layers to make them crashworthy and ballistic tolerant. The inner layer is BUNA-N or nitrile rubber, which is fuel resistant. The next layer is a nylon film barrier followed by two layers of nylon or other type of woven cloth; these two layers are the “load carrier” layers. Between the load carrier layers there are two layers of UNCURED NATURAL GUM RUBBER SEALER. Lastly, there is a rubber or polyurethane outer surface.

From what I've been lead to believe, all aircraft have to have a fuel cell that allows for expansion of fuel due to pressure changes.  Though they may not all be as tough as this one, I would think other aircraft have a similar style fuel cell.

I'll tell you without hesitation that we use silicone sealant and RTV ALL OVER aircraft.  There are some spots where we DO make gaskets out of RTV!  However, this is never anything in direct contact with the engine.  It may be sealing the engine compartment, but not an engine component.  We also have a 2 part chemical adhesive called hysol, and it is used the same way you would use JBweld.  It doesn't hold up forever, but it allows for easy removal and replacement of components.  JBweld, just like any other chemical and tool, has places where it should be used and places where it shouldn't.

Oh, and Kong you might be surprised at the fixes (or not fixes!) that are allowed to fly!

[City Boy]

Hi gang.I agree wholeheartedly that silicone sealer or rtv and JB Weld are both used very often in the wrong applications.However,in my view they all have their place at times and they all reside in my box of tricks.Ironically,I just finished with a spot of JB within the hour!  Rock On

[SOHC Digger]

Hi gang.I agree wholeheartedly that silicone sealer or rtv and JB Weld are both used very often in the wrong applications.However,in my view they all have their place at times and they all reside in my box of tricks.Ironically,I just finished with a spot of JB within the hour!  Rock On

I would say if they will get you home, go ahead and use them.  Then, once you are home, go back and repair it correctly.

The difference between amateurs and professionals:  professionals fix their mistakes.

[Retro Rocket]

Sikaflex is a better product than silicon,silicon is acidic and you would be surprised to see how many people repair a leaking windscreen with the stuff only to have the whole thing rust up. Sikaflex is better ,stronger and is paintable, just don't use it to make gaskets unless you are really stuck for a quick fix,like silicon, it likes to block oil passages..

Mick

[Jordan]

There is a school of thought in restoration arenas that if a mechanic has to use any sealant other than gaskets and o rings the engine was designed to use then said mechanic should not be allowed to touch an engine. Some are fanatical about it. Used as a temporary fix is ok with me but with the intention of fixing the leak properly asap. Never used jbweld so can't comment yea or nay. If something has a lot of value to me I would look at finding a machine shop to fix it properly.

[thehammer]

i've seen jb weld fix some serious sh**. Cracks in transmissions mostly. I've also used too much silicone on my floatbowl gaskets and wrecked my carbs. on the floatbowl gasket, the challenge is sometimes fitting the oring in right. a dab of superglue in the corners does the trick, doesnt wreck yr carbs.

[andy750]

I need to disagree with you Kong...my HM300s exhaust have had their small rust pinholes sealed using JB Weld and after 2 yrs its holding well. I also had a CB750K4 with a broken cylinder fin repaired using JB weld and it held up fine over the years.

cheers
Andy

[Retro Rocket]

I need to disagree with you Kong...my HM300s exhaust have had their small rust pinholes sealed using JB Weld and after 2 yrs its holding well. I also had a CB750K4 with a broken cylinder fin repaired using JB weld and it held up fine over the years.

cheers
Andy

I agree, when i was working in a bike shop in Sydney i used Devcon {similar to JB} to rebuild brake master cylinders that had gravel rash or worn off corners from a slide down the road, when done properly and painted you couldn't tell the difference from new and i never had one fail....

Mick

[SOHC Digger]

The one time that I was satisfied with a JB weld repair was when I was working on a Cummins semi-truck engine that had thrown a rod and put a hairline crack in the side of the block.  We overhauled the engine and JB welded the crack after v-ing it inside and out.  That repair held for at least the two remaining years I was with that company.  It saved them from buying a new engine.  Other than that, I have rarely seen it used with good results.

[swellguy]

I think as a metal filler JB weld works fine.

I also use it around gas tank filler caps running a thing film over the edge of the paint and primer to prevent gas from getting underneath the edges and starting the paint to bubble. For this, it has worked like a charm

[ZoomyZen]

JUXTAPOSITION WIN!

HAHA!!

[dave500]

i assemble crankcase halves with silicon,spead it on one side then smear lighty wiping off excess then press together,ive never had any show up in filters,i use more care than most maybe?

[parrotbasher]

RAF pilots are taught how to recover from a spin flying a 1960s Hunter jet. Wings regularly repaired with.......Araldite!

[trueblue]

There seem to be a lot of bad vibes on this thread about silicon, what a lot of people don't realise is most car engines now a days are glued together, from factory, with a silicon type product called three-bond, there are a lot of engines out there that have a tappet cover gasket and head gasket and that is all, the rest is just stuck together with the three-bond.

[Elan]

wow this thread just keep trucking along huh?

so the moral is:

Silicone should not be the first resort to bike problems, but in some circumstances it might find its way on your bike- forum discretion is advised.

[florence]

I feel the honour of silicon must be defended.  It is a marvellous invention and has a whole host of practical uses.  I use it on my bike at every opportunity.  It is currently the only thing keeping water out of my electrical system.

Other useful things for the practical mechanic include; gaffa tape, baler twine, baked bean tins, old engine oil and clothes pegs.  In fact, apart from a few bits of rusty old japanese metal, that's pretty much what my bike is made of.

 

[ZoomyZen]

....but in some circumstances it might find its way on your bike...

Indeed.  Especially if you're single and the bike is really hot *bada-boom*....