Post by rob on Jul 25, 2014 14:16:11 GMT 1
A couple of weeks ago I was mid-way through a light restoration of my NTV 650P which had stood idle for 14 years in the garage. Most of the stuff I had to do was pretty straightforward but I'd left the tank with a litre or so of petrol in it which, when drained, revealed a lovely rusty brown deposit in the bottom of the tank near the outlet spigot - enough particles to block the petcock filter once it got sloshed around with fresh gas.
Naturally, there's lots of advice on the web on how to clean your tank but I wasn't about to chuck rocks or star washers or chains and diesel in there without very good reason. The most "convincing" solution I could find was this article on Real Classics. In my opinion, Les Howard's piece is worth close reading - especially the safety tips about personal protection - these are corrosive chemicals. The only problem for the NTV is that both the caustic and the Spirit of Salts acid used would eat the aluminium filler cap and the process calls for sealing and inverting the tank.
So this is what I did:
1] Removed the tank and the petcock and removed the filter, then fitted a narrow pushbike inner tube to the spigot and secured it with a jubilee clip. A couple of bulldog clips acting as a temporary on/off switch on the inner tube.
2] Removed the whole filler cap assembly and covered the entire painted surface of the tank with insulation tape and bits of plastic sheet, especially around the filler hole. Took a while but it was sort of therapeutic.
3] The tank was then secured to a workmate bench with a strap and a 'leash' through the front bolt hole so I could rock it without it falling off the workbench. The tank has to perch overhanging the bench for the lowest part to drain properly.
4] Ran water from the garden hose through the (pretty well empty) tank, allowing it to fill and empty several times - straight down the drain.
5] Once drained, I poured 500g caustic soda into the tank and then filled it half with water. Rocked it a minute or so and then filled it up with water to the neck. I covered the filler hole loosely with the cap from a can of Halfords brake cleaning spray. Then I left it overnight. The caustic won't shift rust but it will move any petrol varnish and loosen the crud it had formed. Next day, I had to syphon the strong caustic solution out as some of it had crystallised in the spigot hole
Still, repeated filling and syphoning (use the length of hosepipe filled with water to prime your syphon - not the suck method) meant it was diluted enough to turn the tank upside down and gouge out the caustic plug with a screwdriver. Obviously I hadn't sufficiently agitated the tank to dissolve all the crystals. The peaty brown liquid going down the drain showed that something had happened. I also filled the bath upstairs and immediately flushed my strong solution with a lot more water. There was a deposit of hard white caustic soda inside the tank around the spigot hole but this eventually dissolved by running more water through the tank.
6] The next bit worried me as it involved rotating the tank in both axes when it contained strong acid solution, so I did a dummy run with just 2 pints of water in the tank. Sure enough, the lip on the filler hole prevented any drop from coming out - just be gentle.
7] So, after another good rinsing and reattaching the rubber inner tube, I added a pint of water and a third of the pint container of Spirit of Salts. Rotated it thoroughly for about a minute and then added another third of the bottle. Same rotating again and because I thought I might as well, added the last of the acid, rotated it and left it for 20 mins. The point of rotating the tank is to cover all the surface of the tank so all the rust scale comes off and gets converted to something else.
8] Then I emptied the acid down the drain through the inner tube by removing the bulldog clip and again repeatedly filled and emptied the tank with fresh water, making sure that it got a good sloshing around to rinse all the acid away. A quick peek inside the tank and there was no sign of rust - just clean metal. To neutralise any acid sitting in the seam, I dissolved a couple of tablespoons of bicarbonate of soda in a pint of pater and slooshed that around, taking care to rock the tank on its long axis all the way to get into all of the seam.
9] Almost there.... a bit more hosepipe rinsing (to flush the bicarb) and I removed all the tape and stood the tank on end between the open jaws of the work mate front end uppermost and played a hot air gun on lowest setting around the tank until it seemed to be dry. Then I dithered about how wise it would be to spray WD40 into the tank to dispel any residual water. What the heck, I sprayed away and tried to cover all angles but especially the seam again. Needless to say that my once dry tank was now wet again and there was a milky pool of emulsified WD40 and water collected at the bottom of the tank. I lashed a small piece of sponge to a garden cane and mopped it out as quickly as I could. With a tank this clean, rust is just waiting to attack.. again.
10] Last bit. I put my 5 litres of fresh petrol in the tank along with the contents of a bottle of Wynns Dry Tank and hoped it wouldn't go rusty again before I could fill up properly at the petrol station. I had a couple of days wait while my forks were being serviced (within my abilities but I caved in as the seal sets and fork oil as well as a new fork cap hex key meant the price for the service didn't hurt too much) but when everything was back together the bike fired-up first time in fourteen years - of course it did.
The petcock filter was a bugger to get out so I resorted to needlenose pliers. I think the force with which I had to tug on these might have caused the tiny tear in the filter gauze. I repaired this with a miniscule dab of two-part epoxy as it seems to be petrol-proof. I also needed a new O-ring for the petcock - 14mm diameter I think - which I got in a Halfords' assortment of "Large" O-rings.
My personal protective equipment was full waterproofs, heavy duty marigolds and motorcycle helmet and wellies. Oh yes and a helper on standby with a hose pipe in case of splashes/accidental skin contact. He got bored quite quickly watching his dad dressed up for winter on the hottest day of the year - so he ended up being a bit of a spare part. He's doing chemistry A-level so he was useful in telling me what was happening and even why.
The result is a good clean tank with a reserve that works and so far, at least according to the idle revs, petrol seems to flowing cleanly. More importantly, I'm back on the NTV and learning how to perfect that idiotic biker's grin again. Happy days!
Naturally, there's lots of advice on the web on how to clean your tank but I wasn't about to chuck rocks or star washers or chains and diesel in there without very good reason. The most "convincing" solution I could find was this article on Real Classics. In my opinion, Les Howard's piece is worth close reading - especially the safety tips about personal protection - these are corrosive chemicals. The only problem for the NTV is that both the caustic and the Spirit of Salts acid used would eat the aluminium filler cap and the process calls for sealing and inverting the tank.
So this is what I did:
1] Removed the tank and the petcock and removed the filter, then fitted a narrow pushbike inner tube to the spigot and secured it with a jubilee clip. A couple of bulldog clips acting as a temporary on/off switch on the inner tube.
2] Removed the whole filler cap assembly and covered the entire painted surface of the tank with insulation tape and bits of plastic sheet, especially around the filler hole. Took a while but it was sort of therapeutic.
3] The tank was then secured to a workmate bench with a strap and a 'leash' through the front bolt hole so I could rock it without it falling off the workbench. The tank has to perch overhanging the bench for the lowest part to drain properly.
4] Ran water from the garden hose through the (pretty well empty) tank, allowing it to fill and empty several times - straight down the drain.
5] Once drained, I poured 500g caustic soda into the tank and then filled it half with water. Rocked it a minute or so and then filled it up with water to the neck. I covered the filler hole loosely with the cap from a can of Halfords brake cleaning spray. Then I left it overnight. The caustic won't shift rust but it will move any petrol varnish and loosen the crud it had formed. Next day, I had to syphon the strong caustic solution out as some of it had crystallised in the spigot hole
Still, repeated filling and syphoning (use the length of hosepipe filled with water to prime your syphon - not the suck method) meant it was diluted enough to turn the tank upside down and gouge out the caustic plug with a screwdriver. Obviously I hadn't sufficiently agitated the tank to dissolve all the crystals. The peaty brown liquid going down the drain showed that something had happened. I also filled the bath upstairs and immediately flushed my strong solution with a lot more water. There was a deposit of hard white caustic soda inside the tank around the spigot hole but this eventually dissolved by running more water through the tank.6] The next bit worried me as it involved rotating the tank in both axes when it contained strong acid solution, so I did a dummy run with just 2 pints of water in the tank. Sure enough, the lip on the filler hole prevented any drop from coming out - just be gentle.
7] So, after another good rinsing and reattaching the rubber inner tube, I added a pint of water and a third of the pint container of Spirit of Salts. Rotated it thoroughly for about a minute and then added another third of the bottle. Same rotating again and because I thought I might as well, added the last of the acid, rotated it and left it for 20 mins. The point of rotating the tank is to cover all the surface of the tank so all the rust scale comes off and gets converted to something else.
8] Then I emptied the acid down the drain through the inner tube by removing the bulldog clip and again repeatedly filled and emptied the tank with fresh water, making sure that it got a good sloshing around to rinse all the acid away. A quick peek inside the tank and there was no sign of rust - just clean metal. To neutralise any acid sitting in the seam, I dissolved a couple of tablespoons of bicarbonate of soda in a pint of pater and slooshed that around, taking care to rock the tank on its long axis all the way to get into all of the seam.
9] Almost there.... a bit more hosepipe rinsing (to flush the bicarb) and I removed all the tape and stood the tank on end between the open jaws of the work mate front end uppermost and played a hot air gun on lowest setting around the tank until it seemed to be dry. Then I dithered about how wise it would be to spray WD40 into the tank to dispel any residual water. What the heck, I sprayed away and tried to cover all angles but especially the seam again. Needless to say that my once dry tank was now wet again and there was a milky pool of emulsified WD40 and water collected at the bottom of the tank. I lashed a small piece of sponge to a garden cane and mopped it out as quickly as I could. With a tank this clean, rust is just waiting to attack.. again.
10] Last bit. I put my 5 litres of fresh petrol in the tank along with the contents of a bottle of Wynns Dry Tank and hoped it wouldn't go rusty again before I could fill up properly at the petrol station. I had a couple of days wait while my forks were being serviced (within my abilities but I caved in as the seal sets and fork oil as well as a new fork cap hex key meant the price for the service didn't hurt too much) but when everything was back together the bike fired-up first time in fourteen years - of course it did.
The petcock filter was a bugger to get out so I resorted to needlenose pliers. I think the force with which I had to tug on these might have caused the tiny tear in the filter gauze. I repaired this with a miniscule dab of two-part epoxy as it seems to be petrol-proof. I also needed a new O-ring for the petcock - 14mm diameter I think - which I got in a Halfords' assortment of "Large" O-rings.
My personal protective equipment was full waterproofs, heavy duty marigolds and motorcycle helmet and wellies. Oh yes and a helper on standby with a hose pipe in case of splashes/accidental skin contact. He got bored quite quickly watching his dad dressed up for winter on the hottest day of the year - so he ended up being a bit of a spare part. He's doing chemistry A-level so he was useful in telling me what was happening and even why.
The result is a good clean tank with a reserve that works and so far, at least according to the idle revs, petrol seems to flowing cleanly. More importantly, I'm back on the NTV and learning how to perfect that idiotic biker's grin again. Happy days!