ST4s died while riding - Page 3 - - The Ultimate Ducati Forum
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post #21 of 22 (permalink) Old Aug 2nd, 2019, 6:05 pm Thread Starter
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Location: Cody, WY, United States
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Ok, the Duc flies again. While I was waiting yesterday for the o-rings to show up I cleaned the (Bosch) pump screen, a little debris there and in the well of the flange where it sits. Removed the Permatex sealant and resealed the drain plug with Seal All and let it sit overnight (instructions say 2-6 hours).

With the tank inverted on a piece of carpet laying on the concrete driveway. I sacrificed two o-rings to the god of learning before I figured out the trick to getting the pump flange seated.

The English portion of the SM says to grease the o-ring, put it in place and "Drive flange fully home onto to the tank" which implies a dead blow hammer or such but that didn't work for me.

The complication is that the entry surface of the tank that the o-ring contacts is slightly beveled such that the flange rocks side to side instead of being guided straight in. If they would only have made the 3 flange mounting studs another 1/4-3/8 inch longer one could use the nuts to evenly cinch the flange into place.

On the third try I got over the top of it so I could use my body weight and both hands to steady the flange and push it in far enough/straight enough so that I could finish the job with the nuts but lo and behold, it popped right in, flush with the bottom of the tank, unlike how I found it when I first removed it to fix the detached hose - there was a gap of about 1/8 inch at the rearward portion of the flange. Apparently that part of the assembly was done by the same person that didn't get the hose properly secured to the pump : /

Another point to note about this process: I tested the tank for leaks before putting it on the bike by sitting it astraddle of a couple pieces of 4x4 lumber I keep on hand for such occasions, and putting about 1 gallon of gas in the tank. This was sufficient to test for leaks at the flange and drain plug but still allowed the flange to be removed after inverting the tank to replace the broken o-ring without gas running everywhere. The point being, I don't think it would be wise to test for leaks by mounting the tank on the bike and pouring gas in the tank.

If anyone is interested, the size of the drain plug is 10 mm x 1.25 and the size of its copper washer is 14 mm O.D. x 10 mm I.D. x 1 mm thick. I have not yet looked for any sort of petcock that might fit the tank.

Thanks to all that helped with advice and knowledge!
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post #22 of 22 (permalink) Old Aug 2nd, 2019, 6:48 pm
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Location: Coventry, CT, USA
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Originally Posted by DucInTheDesert View Post
"Drive flange fully home onto to the tank" which implies a dead blow hammer or such but that didn't work for me.
On the 916, with the bolts instead of nuts, I walk the flange on using bolts just long enough to grab a few threads with the o ring sitting on the edge. It's been a while so I don't remember for certain if you can do the same with the nuts of the ST tank. If you can get one nut to just catch, maybe you can work it on by leveraging that one post until the gasket gets over the edge. It seems like I remember doing something like that last time the ST was down for a filter.

Dan. "Painfully mistaking my big talk for the truth" Samantha Fish.
2003 ST4s (The Truck)
1995 916 (Junk Yard Dog)
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