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*....

[754]

There certainly are uses for JB and silicone..
 GE silicone is or used to be gas proof, many were not. If you dont believe it, put some gas in a beer can, poke a hole in it, then  silicone the hole, and it should setup with the gas against it.

 I use it on gaskets all the time, and never had a problem.. Dont use it for gaskets if you dont understand the word "sparingly" If you dont apply sparingly, EXPECT problems. I use a smear, not a bead..

[octagon]

i agree it's not a miracle cure for anything, but for repairing cracked sidecovers, jb weld works very well.
if you clean the inside surface around the crack, and sand it lightly, you can apply say a two inch band up and down the crack, one inch on either side. then press a two inch strip of ordinary woven fiberglass (the stuff you get at walmart for use with polyester resin) onto the jb weld. the epoxy will soak into the fiberglass. it's better to use gloves. if you moisten the fingertips of the gloves very slightly no epoxy will cling to them.
the five minute version of jb weld would probably be fine for this but i always use the slower curing kind because it's so much stronger.

  

[Spiider]

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

+1 on the Devcon 

http://www.devcon.com/products/products.cfm?brand=Devcon&family=Aluminum%20Putty%20(F)

Best stuff to fix things like cracks in cases or even stripped threads. You can machine the stuff after a proper application.

[dave500]

i repaired the water cross over ports on an old aluminium v8 inlet manifold and i drove it for years,like 23,i upgraded to a new aftermarket edelbrock one and sold the old one privately telling the guy it needs welding,he was happy as he had already been duded on two ebay ones plus freight,i even had him drive around to my place and i tinkered with his qjet and he was more than happy,this was a 1969 holden five litre his dad bought new,some jerk mechanic in the day told his dad to remove the qjet and fit a holley 350 two barrel?what the?the manifold was a period correct part for his car.i think i had used "selleys liquid metal"

[daytonajoker]

I worked at a Honda shop in the early 70's and we fixed several CB750 crankcases with "MarineTex"when the drive chain hit them in front of the primary sprocket....we always told the customer....I never saw one leak....Recently I used JB weld to fix a 750 I bought from a guy who was told that he needed new cases....500miles later,it's fine....I used some fiberglass tape too between layers of JB...used brake cleaner and a wire brush to prep the surface....if it leaks, I'll split the cases and weld it,til then I'll keep my fingers crossed

[dave500]

yeah daytona the prep is the key,plenty of guys just pour goo over trouble and hope itll work,when it dosent they blame the product.

[somesuch]

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?

You, and Suzuki/Yamaha/etc...... they assemble their engine cases with their respective versions of silicone sealers.  The Suzuki 1207b silicone is very easy to work with, and I use it instead of gaskets on many engine covers that I may have to remove in the future. (assuming that the removal of the gasket thickness is not going to affect anything) Very quick and easy clean-up later with acetone if you need to get in there again. Use sparingly and carefully....Permatex import grey is also OK (but does not seem as good as 1207b) I also like Mercedes brand silicone sealer, but it is a bit thicker.

--Nick

[754]

Seems to me some gaskets you buy are "not fixed properly" due to the sealer sprayed on them..!!

[Tripps]

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

Unless you ride a Harley, then it comes in handy for sticking the bits that fall off back on. 

[Raef]

There seem to be a lot of bad vibes on this thread about silicon, what a lot of people don't realize 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.

most building race or hipo engines (auto) use it everywhere but the head and carb gaskets.

If it is showing up inside the engine it is being installed wrong and applied WAY to heavy.

with that said, there are not many places on a SOHC 4 that I would use it unless I was to hold a gasket in place or I was waiting on gaskets and planned on going back in.

I have never used JB weld on a bike but I whave cast small parts out of it with good results, it machines pretty well

Mark

[import_tuner13]

wait wait wait. i just stumbled in on this thread.     Digger!  i just sent you my carbs.  are these mine we are talking about here?  i dont' want no fake saggy silicone carbs coming back to me 

[SOHC Digger]

Don't worry, importtuner13, I wasn't talking about your carbs.  Yours just look like they have NEVER been apart... which is a good thing because it means nobody has screwed them up!

[Damfino]

.......you may be a redneck!