silicon on fuel rails

Reassembling my carb rack, again. I bought some silicon gel to use on gaskets and such. Is silicon also good for o-rings, specifically the ones on the fuel rails between the carbs?

 

silicon as in gasket in a tube or silicon as in grease ?
the grease is good on o-rings, but i wouldn't use gasket stuff in the carbs

 

Yup, as in grease. So don't use the stuff for the bowl gasket... should I use something else? Or just put in new carb bowl gaskets dry?

 

Oh wait, gotcha - there are tubes of silicon, gasket-forming material. I'm not using that. I am using a tube of silicon grease. I've applied it to the fuel rail o-rings; is it also appropriate for the carburetor bowl gaskets I'm about to put on?

 

sure a little on the bowl gaskets would be ok, under the carb "hats" on the edges of the Diaphragm works well too
the rtv/silicon gasket stuff tends to turn to snott under fuel

 

Silicone or silicone grease? There's a difference, unless I miss my guess. Me, I'm using the silicone grease I got from Chacal.

 

The silicone GREASE is what you want to use on the fuel pipe O-rings, the carb diaphram edges (if necessary), on ANY rubber parts (petcock selector lever o-rings, etc.). It's great stuff; it makes the world go 'round, smoothly.

You can also smear a thin dab of it on the gaskets so that they become "non-stick" to the mating surface.

Thinking quickly, I don't know if there's ANY place on these bikes that you'd want to use silicone GASKET MAKER material. At all. Ever.

 

Let me say again, I'm using a tube of silicon GREASE purchased from chacal. I used it on my fuel rails, I'm about to go put a little on the new gaskets I'm putting in the carb bowls, also purchased from chacal. I just wanted to make sure that if that stuff got into the fuel (which I guess a little will if I'm lining the carb gasket with it) that it wouldn't harm the engine.

 

Oak....no, the miniscule amounts of silicone grease that may get into the fuel system will NOT hurt anything.....although, again, all you need to use is a VERY thin smear of the grease on carb bowl gaskets, etc......the grease is not being used as "gasket material", it's being used as an "anti-stick coating".

There is no need for any type of gasket maker material on the carb bowl gaskets. They won't leak even if installed dry. The smear of grease is to allow future bowl removal without tearing the gasket, by preventing the gasket from "welding" itself to either metal surface.

By the way, when I rebuild carbs, I always take a piece of fine grit sandpaper (let's say, 400-800 grit), and place it on a KNOWN perfectly flat surface (glass, or a piece of milled metal), and then wet the sandpaper with WD40, and then with a back-and-forth hand motion, run the top surface of the bowl against the sandpaper so you can "surface-cut" the bowl gasket mounting flange.....getting it as smooth and flat as possible. Make sure to clean the bowl afterwards with some carb cleaner, especially down the (hopefully---perfectly cleaned!) starter jet passage in the bowl.

On the carb piston diaphrams, the silicone grease around the edges serves only as a "glue" to hold the outer edges of the rubber diaphram in place---in that recessed groove of the carb body---while installing the carb hats. On many of these carbs, the rubber diaphram shrinks just a bit over time, and thus as long as the piston is elevated, the outer ring of the diaphram fits snugly into that recessed groove. However, as soon as you let the piston "drop" into the bore, the slightly shrunken diaphram pulls itself out of the recessed groove either in spots, or all the way around. If you then screw the carb hat down---while the diaphram edges are in a displaced position, out of its little groove---you can pinch, tear, or otherwise distort the diaphram. The diaphram must be able to move freely to allow the piston to rise and fall smoothly in response to engine vacuum. In order for the piston to rise and fall smoothly, the diaphram must be able to flex freely, and without enduring injury---and for that to happen, the outer edges of the diaphram must be completely within that recessed groove of the carb body, so that when the carb hat is installed, it captures the outer edge of the diaphram IN that groove, and not on top of it.

Sorry for using so many words!.....but, I think yours is a good question, and something that many people might overlook when doing their carb rebuild. The proper operation of the vacuum piston is crucial to the proper operation and performance of these carbs.

 

Thanks for the info, fellas. I do love this site.