petcocks for standards and specials

[dontlikeoc]

I ended up getting a set of petcocks for Standard for intended for 1981 Xs1100 special...I didnt realize that they are completely different.

1) Do petcocks for Standard work on a Special? (I can see that the fuel line widths are different...)

2) The ones from Special dont seem to have any removable part other than the position indicator plate coming off to reveal the O-ring around the cock. Are there special tips as for how to further take them apart?

3) On past threads, I read a mention of using generic petcocks. How do they work in terms of fitting gas-leak-tight to the tank?

4) On past threads, I saw "with or without octo" discussion. I am not technically savvy. What is this about? Is there an additional suction device, in addition to tank, petcocks and carb, on specials?

[Athedra]

A good seal between your tank and petcock is normal red hermitite (Not RTV). I have found that RTV comes loose on the two sides and ends up to be just a loose peace of rubber sitting between what ever you sealed with it.

The connection I have on my standard is as follow:

From Carb one's intake, I have a vacuum pipe to my petcock, and the same on Carb four, a vacuum pipe to my second petcock. Then have a two pipes running from my carbs to a T-Piece and then to my petcock. On both sides.

The two pipes on the carbs is basically one going thru the Needle and seat and the other bypassing the needle and seat completely. SO when you switch the petcock to prime, the needle and seat gets bypassed and continually fills the carbs with fuel, while on on, no fuel comes thru until there is vacuum on your pipes (When the motor is turning).

Hope that helps.

[Ivan]

IIRC the special petcocks won't mount up in the standard tank as the hole spacing is different.

Parts 'n More has some adapter plates that will let you use a generic petcock. Or you could just search eBay for standard petcocks. Standard petcocks had a vacuum diaphragm made in the petcock, which is the same valve as the specials "octopus" that every one complains about. Up to you what you do.

[dbeardslee]

I've got the partsmore petcocks installed on my standard, but with the shorter base plate they can be installed on a special. Installation requires some very minor modification to the tank, as the towers are round and won't quite fit in the factory 'slot'. A very small amount of material has to be removed. If you take the base plate sans petcock and attach it to the tank, use a marker to draw around the ID of the petcock hole, and then remove that material from the tank (if that makes sense) they fit great. They use a rubber gasket instead of the o-ring that the stockers have, and are easier to seal than factory petcocks IMHO. Doesn't require any sealants, but you should use some teflon tape on all the threads to keep the unions from leaking. Gotta remember to turn them on and off though. My $.02

[fredintoon]

I ended up getting a set of petcocks for Standard for intended for 1981 Xs1100 special...I didnt realize that they are completely different.

1) Do petcocks for Standard work on a Special? (I can see that the fuel line widths are different...)

2) The ones from Special dont seem to have any removable part other than the position indicator plate coming off to reveal the O-ring around the cock. Are there special tips as for how to further take them apart?

3) On past threads, I read a mention of using generic petcocks. How do they work in terms of fitting gas-leak-tight to the tank?

4) On past threads, I saw "with or without octo" discussion. I am not technically savvy. What is this about? Is there an additional suction device, in addition to tank, petcocks and carb, on specials?

Hi dont,
1) Standard & Special taps don't interchange because they have different attachment bolt spacings.
2) The Special taps come apart real easy, take the plate off and pull the centrepiece out.
3) Depends on which aftermarket tap you get.
4) The "octopus" is the single separate vacuum operated valve that turns the Special's fuel on and off. Some reckon it's a needless complication. The list has a string on the octo pros, cons & how-tos you can look up.
The Standard taps have built-in vacuum diaphragms instead.

[dontlikeoc]

Fred,

Thank you for explaining, especially, about how to take the petcock apart. Well, I took out all the screws but everything looks one piece. I guess I have to believe in the fiche drawing and just yank them apart.

I am coming to hate Yamaha for making Special so mechanically different from Standard...