carby manifold/boots..........

[GS750]

A few quick questions please.

Im in the processes (3mths now) of getting my GS750 back on the road after major dramas with the engine rebuild.

I noticed when I removed my carby inlet manifold/boots and discovered that they had loads of corrosion under them.

The parts manual shows that they dont have an O ring under them but it looks like it has had something in there........ There is no grove for an O ring on any of the 4 boots.

Should I use a thin (1 or 2mm) viton O ring under them when I reinstall them even though there is no actual groove to hold them in place, or should I use that high temp engine silicone?

The boots themselves are in good nick, still soft, no cracks etc etc.


The cost of the new boots is not something I can afford at the moment after having just managed to justify to the family how I have spent almost AU$1200 on the rebuild and some other additions / repairs / mods.

[Dave8338]

750 16-valve (years)? - no o-rings. Make sure that the mating surfaces are all clean and then give them a thin coat of the blue RTV silicone and put it back together.

[Nessism]

1977 model GS bikes, at least some of them, didn't have O-rings on the boots. Not sure if there was a gasket or not. Not sure what to recommend but do know that silicone is not the answer since it won't last.

[Dave8338]

1977 model GS bikes, at least some of them, didn't have O-rings on the boots. Not sure if there was a gasket or not. Not sure what to recommend but do know that silicone is not the answer since it won't last.

And the next best solution is...........? He could try and soften the boots with silicone spray (I've used it and it works great) and reinstall. Form A Gasket may be another option if leaks follow after a "dry" install.

[hampshirehog]

The very first 750s as Nessism correctly points out weren't of the O ring type. They used a paper gasket instead, the same part number as one of the TS trail bike range, though I can't remember which model. I suggest you make your own as it's easy enough.

[bwringer]

Silicone gasket-makers and sealers are no good for sealing against gasoline (and gasoline vapor).

If these indeed used paper gaskets, buy or make some -- don't use an o-ring where there's no groove.

It's very, very likely you'll need new boots, through -- do replacement boots come with an o-ring groove?

[Calvin Blackmore]

maybe this stuff will work
Permatex? Hylomar? HPF Gasket Dressing and Flange Sealant

[GS750]

And the next best solution is...........? He could try and soften the boots with silicone spray (I've used it and it works great) and reinstall. Form A Gasket may be another option if leaks follow after a "dry" install.

The rubber sections are actually still very soft and supple, it is only the mounting surface which I have an issue with.

Silicone gasket-makers and sealers are no good for sealing against gasoline (and gasoline vapor).

If these indeed used paper gaskets, buy or make some -- don't use an o-ring where there's no groove.

It's very, very likely you'll need new boots, through -- do replacement boots come with an o-ring groove?

I dont think I need new boots, these are stil soft and no cracks in the rubbers at all.

I have previously used viton O rings on carbys with just a dab of grease to hold them in place for fitting. At least the Oring seems to provide a definate seal and is easier than the gasket cutting.

I was just asking so I could find out what others have done with the same situation, and hopefully on a GS installation.

Like I said previously, new boots are out of the question as Im looking at another AU$150++ for the set of 4 and I really cant justify that at the moment.

I have decided that I will go with the gasket paper method since I have loads of it laying around and I will also spray some hylomar onto the surfaces prior to installation.

Thanks everyone for the assistance

[80GS750]

hylomar is very good stuff and WILL hold up......

[SqDancerLynn1]

Do yourself a favor and order new boots & they will have O rings so order them too. It will eliminate a lot of headaches later. In the mean time use automotive gasket material, (thick kind) and make some gaskets.

[hampshirehog]

Do yourself a favor and order new boots & they will have O rings so order them too. It will eliminate a lot of headaches later. In the mean time use automotive gasket material, (thick kind) and make some gaskets.

I'd take the opposite view. If your rubbers are still soft, and they've done pretty well if they are the originals, keep your cash and go down the gasket root - loads of bikes use that method. My BSA A65 and my CZ both use paper gaskets and one of those has kept going for 42 years. (Alright, it's not the original gaskets in there but you know what I mean.....)

[GS750]

I decided to do the gasket only route, the gasket material I used is 1.2mm thick and temp compatible

Now I just gotta get the barrels installed.

Thanks for the suggestions

[silverhorse47]

Thank you for that information Andrew. Please keep us posted on the performance of the product after you have had the bike up to temp for a few thousand miles. This is where the real information will come in handy.
S.