The neoprene washers are much thicker than the old squished fiber washers (1.36mm vs .39mm) so I hope that doesn't matter. They should take up to ~270 F, so I think will be fine on the pump, but not for the cylinder connection. No riding today because of rain, but I'll put some miles on it next week and see how they hold up. I'll also check one good local auto parts shop next week (closed today for Easter) to see if they have fiber washers, but this will be an experiment.

Old one on the right:

Long ago i cut the ears of an oil pump mount gasket or similar to use as sealing washers.
Maybe something bigger as pump one would be 5mm.
Too long ago, but wasn't a fiber style gasket so not the best plan with a bolt head screwing against it on the top half. Worked at the time.
Back when i had a Suzuki Quad they ran a rubberized washer on two of the rocker box 6mm bolts but might be too thick for the bolt length when adding two of them.
Shouldn't be necessary though.
www.partzilla.com/product/suzuki/09168-0...431315d935656cef883a

Well, forget about using neoprene washers. I took it back apart, just to confirm that the washer wasn't too thick and interfering with the hole in the banjo bolt, also to make sure I had the spring in correctly, and the washers already seem like they were softening up. It was to the point that if I cranked down on them they would distort, and slip out from between the surfaces. I'll just have to dig up some fiber washers, or order the copper, but at least I learned something. I also got the ball bearing out while I had the pump off, and it wasn't clogged. 

I tried using neoprene to cut new sealing washers for a couple gas caps. They worked perfect until I opened them to refuel. The neoprene turned to jelly. So I cut new sealing washers out of gasket material. I stacked two in order to have the same thickness as the original gasket that hardened and cracked. It has held up well so far.

Schu, when I first started working on this CT-1, the old original gas cap gasket was completely gone. I tried to make one for it, but it just didn't seem to fit right. Then I found an old 1 gal metal gas can that was rusting away, but the gasket for the cap was perfect, and it fit my Yamaha cap like it was made for it. Been using it ever since.

I cannot find any fiber washers this size locally, and a Harbor Freight assortment that I thought may have had the ones I need (from a previous thread) only had much larger fiber washers. However, they did have an assortment of copper washers, which has 20 that fit perfectly. So I'll see how these work after a few miles. I also did a better job cleaning the pump mating surface to the case, using 2000 grit wet/dry on a flat surface. The gasket is new from a year ago.

Rode 12 miles up and down PCH and checked it, no sign of leaks yet 

Tom I used the copper from Harbor freight for my CT1C with no leaks on the engine 

That's good to hear that someone else has used these. It's really a great deal, the whole assortment is $6, and you get 20 of the ones that fit the pump.. If you buy one Yamaha copper washer I think it's about $5, plus shipping.. Actually when she rung it up it was $3.99, and I said, "oh it's on sale". She said  "no, that's a regular price". I looked at the receipt after I left, and the she had scanned in an assortment of screws. 

I didn't read this whole thread, but I'm guessing no one realizes that the sealing washers are special.

The original fiber washers (and the still available Yamaha copper washers) are approximately 0.5mm in thickness.
That will reduce the check ball spring effective length by 1.0mm.... which is how it was originally engineered.

When you put in thicker washers, you move the bolt (and the spring) further from the check ball which reduces or even eliminates the close off force.

While you may think that you have saved a few cents, you may now have to deal with the oil tank draining into the crankcase from gravity.