Fuell gallery o-rings

Last fall, I got a hell of a deal on a "project bike",
(You can STOP your laughing/screaming!!!) its a red 1983 XJ900.
The previous owner had overhauled it from the front axle back as far as the
carbs.

I got into the carbs this spring.
I doubt theyve ever been cleaned in the history of the bike.
You know the sludge that builds up on the outside of car engines?
These things had it inside & out of the carbs.

Now the problem:
They tell you never to unrack the carbs, but I was never going to get them
clean.unless I did it.
Exposure to air has caused the fuel gallery o-rings to shrink and now they wont seal as I reassemble the carbs.
Yamaha parts is no help at all.

I suspect the rings are SAE type " OB-70-012 "
Can anyone confirm this ?

Also, what size is the recess allen plug in the top of the front forks ?
16mm ? 17 mm etc ?

 

Texx, I carry the correct replacement or-ing for the fuel supply tubes in stock.

The inverse hex fork tube cap bolt is 17mm.

 

I'm not sure who they is that says don't break the rack. It's the only way to replace the throttle shaft seals. Those seals do wear/dry out over time.

 

Yamaha says that it is usually not necessary to break the rack in their service manuals, but of course their service manuals were written about the same time that the bikes were built, so of course for typical service procedures being performed at that time, in that era, their advice was to not break them (although a later Technical Service Bulletion they published to resolve some fuel tank rust issues, which might have possibly contaminated the carbs, tells the service technician to break the rack IN ORDER TO GET THE CARBS FULLY CLEANED..........).

 

Interesting they also told us not to adjust the idle mix. I don;t see how you get carbs fully clean without breaking the rack. I wouldn;' do it every time but sometimes you gotta...

 

Re: Fuel gallery o-rings

The local Yamaha dear is no help at all on non FI bikes.
They dont deal with "that old junk".
I found a mechanic in Oakland who specialized in old Japanese bikes.
His reaction was "NEVER un rack em ! You will let the magic chi out of them !"

Interestingly enough, Ive unracked the 750 carbs with no problems but over a month, the 900 rings just went to hell.

Im curious about the " OB-70-012 " rings though because I can get them fast &
cheap. If not, Ill have to bug Chacal for them.

For the fuel tee, I have another problem, it has bumps which also shrunk and nowhere to put o-rings. Unless anyone has better ideas, Ill have to buy a new
one. Bdesigns up in canada makes new brass tees that have slots for o-rings.

 

Wow. That's what we've all been doing wrong.

Finally, a rational explanation.............

 

Success !!!

No disrespect to Chacal, but I wanted to see if i could do it with local
suppliers.
Ill go to Chacal when I need something bigger.

Heres what I learned:

ON-70-010 is the SAE number for the right part.
Your local Grand/Kragen/Schucks/Oreilly uto supplier has Buna Nitrile o-rings
for fuel injectors. 1/4" id, 3/8" OD, 1/16" cross section area fit despite the
fact that they are not metric.

They sell them in baggies of about 8 for a little over $2 (US) per baggie.

I tested with low presure air (more than a gravity feed will ever generate)

The same o-ring fits the fuel conduit as well at the carb vent tees.
My fuel feed tee still seals, so I didnt mess with it.
The original fuel feed tees usually didnt take o-rings.
They were coated with a rubbery gunk which was thicker where it went into the carb.
bdesigns.com sells a replacement fuel feed tee that takes o-rings if you need one.

 

I would get those new o rings on the fuel T as well... why not? For so cheap, you already have the carbs off.

For the money - anytime someone tears apart their carbs first time after buying a pre-loved/hated XJ, they might as well nail out the rubbers and gaskets in there all in one swoop. Helps rule out those being a problem later on.

 

My fuel tee does not take o-rings.
Im on a tight budget, being out of work a while.
Im hoping to get this thing running so I can save money on gasoline.

In a more perfect world, Id replace the tee with one that takes the o-rings.
But it works now and that will save $30 bucks which I deperately need to do.

I realize that sometime later, Ill have to go back in again.
Ill eventually have to replace the vacum diaphragms, but cant afford now.
Hopefully I can use some RTV to seal the pin holes.

 

My carbs don't have the o-rings in the fuel overflow tee either. I discussed this with Len as it appeared a sloppy fit however we both agreed that the overflow tee is not under any pressure and if the fuel flow shuts off when the float rises, then it shouldn't overflow!

I have re-assembled and it is fine. I am not going to worry about something that isn't a problem!

When refitting the fuel gallery connectors (with the two o-rings each side) I somehow managed to pinch one and it leaked. I re-did it but didn't have any silicon grease to hand so I just put the silver connectors with the o-rings in the freezer for half an hour, moistened them, and they slid in just fine after that.

Do take care that those connectors are seated correctly. :wink: