Fuel tank removal

I have a '79 XS650 Special that I am goin to replace the clutch cable on. I was looking at the bike to see what was required and in looking at the fuel tank removal I'm somewhat stymied. What type of bolt is used on the rear mounting bracket? I would have assumed that Yamaha would have used a plain old hex bolt along with a rubber washer and fender washer, but that's not what I have. The bolt appears like at one time it was an allen type screw that is boogered up. I looked at the parts fiche and it looks like a plain old hex bolt to me. I wonder what I am dealing with. Rather than just dive in, I thought I would consult the experts. Any advice?

Mike

Should be a plain old hex bolt at the back with a fender style washer. Front is held on by rubbers only.

Ensure the petcocks are off and the fuel is drained out of the lines before you start. You’d be surprised how much fuel those lines contain when they spill.

I’ve found the best way to remove is to tilt up the back tank and gently wiggle back and forth while pulling rearward. The front rubbers can also be sticky.

I fought with my tank for years and then got smart and smeared a bit of synthetic grease on the rubbers. Comes off and goes on much easier now.

Most were #3 Phillips or JIS #3 for the purists...
Vicegripped or head drilled off by the get'r done crowd.

Also remove the vacuum lines from the petcocks or intakes..
Agree; Silglide the front rubbers to reassemble with less fighting.

Thanks for the replies. In looking in greater detail it appears that at one time it was either a hex or Phillips screw that was used by Yamaha but at some point in time it was broken off by a prior owner. What appeared at first to be a boogered up allen screw was an unsuccessful attempt at drilling out the broken bolt. As is stands currently, the tank will lift right off of the broken bolt. When I get the tank off to replace the clutch cable, I will try to remove the stub of the broken bolt or drill it out and replace it. If worse comes to worse, there is sufficient clearance under the frame to use a bolt with a backup nut.

Mike

Both of mine ('78 and '83) have a standard M6 hex head bolt. In fact, that's all I've ever seen used on any I've looked at. I don't think Yamaha ever used a Philips or Allen bolt here. A note on the fender washer - it's special and has a larger than normal diameter. Hopefully you still have it .....



Once the tank is removed, you'll see the mount is a post welded to the frame with a threaded hole in it. I'm pretty sure it's a blind hole (doesn't go all the way through). Maybe that was the issue. Maybe a P.O. used a bolt that was too long and it bottomed out in the hole before making the tank tight. They kept tightening it and buggered up the head. According to the parts diagrams, the bolt is an M6 x 16.



I would do all I could to get the old buggered or broken bolt out. Maybe use an EZ-Out.

Whenever I remove said bolt, I loosely thread it into one of the vacant holes behind the battery where I removed the RLU so I don't lose it or it's special washer .....

The clutch cable is replaced. I tried drilling a bit more, then soaking it with PB Blaster and then shifting it with an ez out but no luck so far. I have the tank just sitting on the pin, the way I bought it for now. I'm going to give it a spritz of PB once a week for a few weeks before I try the ez out again. I'm afraid to get too aggressive with the ez out as the last thing I want to happen is to break the ez out off in the old bolt. Been there, done that, don't wanna do it again! Thanks for everyone's advice.

Note; the first 4 years 70-73 didn't use a bolt, the tank just sits on the pin.

So far the earth has not opened up and swallowed the early bikes and riders.

mikesim said:

The clutch cable is replaced. I tried drilling a bit more, then soaking it with PB Blaster and then shifting it with an ez out but no luck so far. I have the tank just sitting on the pin, the way I bought it for now. I'm going to give it a spritz of PB once a week for a few weeks before I try the ez out again. I'm afraid to get too aggressive with the ez out as the last thing I want to happen is to break the ez out off in the old bolt. Been there, done that, don't wanna do it again! Thanks for everyone's advice.

Click to expand...

I assume that the bolt is broken in the hole and not sticking out. If not so there are more options to get it out
If the M6 x 16 is right which it may well be.
I do not believe the full length is needed 16 mm.
typically the same length as diameter of the bolt. ca 6 mm deep.
Think the height of a M6 nut.
depending om material strength. In this case most likely mild steel a little more would be better.
Assume 2 or 3 mm gone then the need to drill is 4 -5 -6 mm.
Starting with a small drill and carefully larger and finish with a screw tap.
If you are lucky the hole is already deep enough with no drilling needed.
Just the screw tap. Perhaps not even that
And as mentioned ..not really a place with forces on the screw.
Some rust dissolving oil into the hole and after some time try to get it out.
But it can be enough with shorter than full length.
A threaded pin can also be put there
and using a nut on the topside

Yeah G, gravity and the front of the seat held the tank down on my '83 for many years.
I've got a bolt for my '77 running the xs750 tank.....talk about a pita to access.......oi.

Hmmmm food for thought. I will try to extract the broken screw 'cause I like things to be original as possible, however there is no reason to open up a can o' worms if it ain't necessary. With the seat down the tank is not going anywhere so I may just let sleeping dogs lie. I do find it interesting however that the early versions just sat on the pin with no further mechanical attachment. It sort of belies the "Japanese attention to detail" that I had grown accustomed to.

Mike