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Discussion Starter #1
The piece that goes into the top of the petrol tank with the 8 little grub screws around it ( that the opening part of the petrol cap sits in ). It ( should ) has that green o-ring on it to seal against the tank, and then the weather seal at the top. Some brightspark DPO didn't have the weather seal fitted, and of course water and stuff has gotten in there and now that piece is seized to the tank ( the alloy tank on my 851 :( ). I need to get it out to fix the petrol pump wiring. I've drowned it in CRC556 for days, made a small slide hammer at work that picks up the three screw holes that the cap screws into, but no luck getting it out. Tried twisting it out, doesn't even budge the slightest amount.

I bought another one, thinking that I might have to cut the seized one in half with a hacksaw blade so I can collapse the halves inwards to get it out, but then I'm going to get a tank full of swarf with won't do anything much good.

So has anyone got any tricks I can try before it gets ugly?
 

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so you got the grub screws out? i had a monster one last week with two seized and rounded screws. eventually got on to come out with the valve paste trick, the other i went a rescue bit on to remove it from the equation. as you have done, penetrant around the outside and wiggle wiggle. i use a hammer handle / old fork tube / large screw drive handle in the hole for leverage and start gentle.

if it's just stuck, i could only see slicing it up as the way to get it out. you can clean the debris out of the tank later.

aluminium piece in aluminium tank shouldn't be corroded in though? heat the tank, cool the insert?
 

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Discussion Starter #3
Yeah I've had a big hammer handle in the hole trying to get it to move, but the whole top of the tank starts flexing. Yes I'e got the grub screws out.
 

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I had this problem, the PO had actually used a smear of gasket sealer. I used this, along with the slide hammer technique. It took several applications around the edge and in the grub screw holes over a week to penetrate. I also used several nylon paint lid openers I got at HomeDepot to pry into the edges. If these had not worked I was thinking through how I could use a toilet plunger and compressed air but never had to.


980534
 

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The piece that goes into the top of the petrol tank with the 8 little grub screws around it ( that the opening part of the petrol cap sits in ).
part #13 appears to be a threaded ring nut.keep a heat gun on it till you start feeling some movement IF you can firmly grab it to twist CCW.
 

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Sure, twisting can help but #13 is not threaded - the drawing makes the O-Ring channel and grub screw lip look like that - the grub screws are supposed to be the only thing holding it in. If I didn't make clear before, try removing 13,14,15 together as one unit by prying with nylon paint lid tools, squirting liberally whatever solvent you got over a few days. Once you get that out, it is easy to separate 13-14
 

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Missing #14 ? That would leave a large gap all around. If so, put some cloth padding down and thin pieces of metal or wood to spread the force across the tank surface and apply a pair of crowbars to it with a friend. Sucker should pop right out then, especially if soaking for a few days in penetrating spray.

I get back to the idea my PO had when they did not have the ORing to put back in, the AH put gasket goo on it, so it mine wasn't rusted but glued in place so normal penetrating spray had little effect but the gasket remover ate it away leaving the paint OK. I peeled away the rubber lip weather seal around #14 which appears to be missing in the drawing given, in order to squirt down in there. This also gave me just enough gap to wedge the nylon levers in there to help. OP says it is the thin little rubber bit that was missing, not the metal ring.

Since I destroyed my weather seal, the smart lady at Ducati of Omaha had to check another source to get me the part number for that. Like $10 as I remember, or was the green ORIng and this part was $25? Order both anyway.
 

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When I had to remove my fuel cap assembly to replace the fuel pump mine too was very hard to get out -I doubt it had ever been removed from my bike. I removed the grub screws, sprayed some CRC power lube around the the fitting let it soak over night. I then used a slide hammer hooked on the inside lip and worked it out--It took more force to get out then I thought it would but it did come out without damaging the tank. But it was a steel 900SS tank, not an alloy 851 tank as I think I saw the poster said he had
 

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900SS has both the stepped rubber and an aluminum trim ring in a steel tank. Didn't know the 851 was that different. Yeah, aluminum to aluminum over time could stick very firmly. White vinegar or Muriatic acid?
 

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900SS has both the stepped rubber and an aluminum trim ring in a steel tank. Didn't know the 851 was that different. Yeah, aluminum to aluminum over time could stick very firmly. White vinegar or Muriatic acid?
by "aluminium trim ring" you mean #13, the big cast aluminium insert?
 

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I
900SS has both the stepped rubber and an aluminum trim ring in a steel tank. Didn't know the 851 was that different. Yeah, aluminum to aluminum over time could stick very firmly. White vinegar or Muriatic acid?
would try apple cider vinegar, that seems to work better
 

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New parts are the exact same for a later model 900SS.....at least with regard to 900SS’s and steel tanks.

The aluminum tank is a different animal all together when combined with the aluminum carrier ring.

I don’t know what manner of penetrant fluid the OP has at their disposal but look into aviation maintenance supply.

There are a number of products available from aircraft maintenance suppliers for dealing with alloy to alloy corrosion. Corrosion X is one that I can think of but I don’t know how widely available it is.

I’ve not used it personally but have heard a good deal of feed back on its use from some of the A&Ps I know.
 

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When you get it apart, remember to use an appropriate lube when putting the O-ring and other parts back together. I used petroleum jelly as it is compatible with fuel.
 

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Discussion Starter #16
Well after squirting WD40 around the edge and into all the little grub screw holes twice a week every week since I posted this thread, yesterday I finally managed to get it out. Used the big wooden hammer handle method. Not a pretty sight, the things some people do really defies belief. Anyway, bit of a cleanup job ahead now

20200328_103534 by JAFA851, on Flickr

20200328_103731 by JAFA851, on Flickr
 

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Some people have no business EVER touching a motorcycle
 

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Seriously, getting the proper parts isn’t that hard nor expensive. I despise the use of RTV in places where it isn’t called for.

I agree completely, some people shouldn’t be allowed to work on anything, much less an 851.
 

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Discussion Starter #20
It's not a regular 851 either, it's an SP3. The whole bike is like this. Some peanut left the rear sprocket nuts loose and they backed off and chewed the side out of the swingarm, so to "fix" it they filled the massive gouge up with epoxy resin. Chopped up wiring to accommodate cheap shitty knockoff indicators instead of buying the correct indicators, extra wires spliced into the main loom at random places for who knows what, most of the bolts have been swapped to stainless but instead of buying bolts of the correct lengths just buy 1 length and cut them all to suit but don't clean the cut end up and chamfer it just wind them in and wreck the threads, the list is endless. It's cost already, and still costing me, a fortune to buy ( when I can find stuff ) the correct parts to rebuild the bike back to original. All this on a supposedly "good sound bike, just give it a polish and ride it". Fuckwits
 
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