Rebuilding Yamaha Vacuum Operated Fuel Valves (Petcocks.)

Thank you, gggGary, for the post. Acquired a 79 XS650 Special last week. After I put gas in it, started leaking out of left carb while parked. Followed the post and left petcock had the remains of an insect and plastic filament between diaphragms. Put back together, no more leak. Took apart other petcock and cleaned for good measure with good results......
 
I like to use very fine steel wool. OOOO grade. Waded up into a small ball. Put this in the hole where the diaphragm o-ring seats. I then take a pencil with a good eraser on the end, slightly rounded. Just keep turning the steel wool with the eraser head till the seat is nicely polished.
 
Does anyone know where to get just the filters for these petcocks? I bought some without the filters and thought that it would be a pretty easy part to replace but I've yet to really come across any new aftermarket ones. There are some used ones on ebay for about how much a set of petcocks with filters would run, so I thought I'd ask here before taking that plunge.
 
Does anyone know where to get just the filters for these petcocks? I bought some without the filters and thought that it would be a pretty easy part to replace but I've yet to really come across any new aftermarket ones. There are some used ones on ebay for about how much a set of petcocks with filters would run, so I thought I'd ask here before taking that plunge.
Are you asking about the plastic filters that go on the vacuum petcocks?
 
They are still listed at the link blue900 posted. Click the link select your year then model and then the "fuel tank" fiche. Part #21.
 
Which model/year are you looking at, just for reference? The ones I checked has part 21 as a screw. The Filter, as far as I can find (NET, FILTER 1 2G2-24514-00-00) are discontinued.
 
What year are you looking at? Since you failed to give that info, it remains a mystery to us. Screens for the later single vacuum petcock tank petcocks appear to still be available. The dual petcock '78 tank petcocks don't seem to be available. That was an oddball petcock for something like one year only, so it doesn't surprise me the screens are N.L.A.
 
Great write up Gary :thumbsup:
reckon its my next job on the bike ...
 
I'm currently rebuilding my vacuum-operated fuel valve from my '82 Heritage Special. My attached pics show post-diassembly/pre-cleaning and cleaning after soda-blasting and quick cleaning (less than 1 minute) with MC-containing Paint Stripper.

Is it a necessary/worthwhile endeavor to remove and clean out the 90 degree exit (see Post #12 from Gary) and has epoxy been proven (in last 3 years) to be effective?

20150907_142205-1_zpsz0pycxz6.jpg


I plan to polish valve seat with my Dremel and mating surfaces with 1000 3M Sandpaper.

http://www.xs650.com/media/albums/2677/

:bike:
 
I have done a couple of the epoxied in 90's, no problems so far. In truth I have not kept track of what bike they are on or if I still have it. But odds are I still do, and none that I have done have leaked for me.
 
I used the "fat" #26 o-ring from the "fitz none metric assortment in the red case " to replace the skimpy tank to petcock seals. I have used fat o-rings on a bunch of tanks now, some have been on for 3-4 years, they work super. Install per the pic, turn screws to "just" grip the o-ring then push o-ring into the groove, finish tightening, a bit of silicone (lube, not caulk) to help the o-ring slide into place is a good practice. I always remove all the paint from the petcock seal area with a razor blade and sand the metal smooth. This is SOP on every petcock I remove.

Also in the pic; repair of a split brass petcock tube, split tubes are common; wrap the end with fine copper strand stripped from some automotive wire, clean the tube, flux and solder end and split, this repair is 3 years old now. don't let it get too "fat", the petcock slot in the tank bottom is narrow.

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gggGary, nice expo on petcocks. Since becoming a 78 SX650SE rider in 82, I've had good luck using most of the procedures you displayed and you had a few new tips I hadn't considered yet (ex: didn't have a Dremel last time, but will next!). I've had good luck with the rebuild kits 2 times now. Over the years I've successfully used spray silcone, silicone plumber's grease or Amsoil synthetic bearing grease to sparingly lube the various rubber gaskets and anything that would rub them when assembled. The spray is easier but doesn't last. In any case I consider lubing to be essential for longer life of the petcocks and gives me fighting chance to reuse parts likely unavailable in the field. ;)

The comment to use Marvel Mystery Oil to help here is spot on, though I didn't consider it for that reason back in 85 when I started using it often. My main excuses are it's really good at keeping chambers, valves and sparkers clean of carbon. It helps carbs moving parts and resists rust and corrosion anywhere in the fuel system... my tank doesn't rust despite long periods of inaction. The insides of exhaust pipes (and hence mufflers) are gray too. In cars I usually get a few more MPG and always have it in the tank for emissions tests (esp older cars). And oooohhh, that lovely scent of sweetened ATF!!! :lmao:

I don't condone thread wrap in petcocks. Micro-bits tend to shed on assembly or from vibration (and twins vibe, man). Much prefer to use Permatex Gray gasket sealer/maker (carefully applied) on the big petcock to tank screws. For them I use it on the screw threads where they will clinch in the tank threads and just under the screw heads where they will seal against the petcock body. I use Gray on the petcock gasket area where it will seal to the tank. The vacuum barb threads are a good spot, too. In all cases, let all dry overnight to be inert to fuel. This has been very reliable stopping leaks in these areas. A couple times I've had to pull the petcocks on the road some time after a rebuild (see below) and the Gray often comes off clean enough to be reused if the tank paint was good and clean when sealer was installed. A few other reasons: it's easy to remove next rebuild, acts both as a thread lube and a screw retainer, and it's good at protecting threads against all evils. :hump:

One thing that I learned was to use the later 79 model petcock gas filters. One reason I had to repull the petcocks was the OEM 78 filters are in 2 pieces. A couple times, the top part detached in the tank and I had to retrieve and replace it. Happily discovering the 79's were one piece was an easy fix. Never use the 2 piece OEM filters!! :cool:
 
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Hi Guys,

Great thread. Does anyone know why there is a larger bore on the right image? It's a '79 Special, vacuum type.

Many thanks

Paul
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