POST 5: Blue bike; Fuel Tank, Petcock and Oil tank

I hadnt meant to clean and sort out the tank since its my intention to sell this bike as a project... albeit a running one using a temporary fuel supply. However, forced to wait for parts, I needed something to do anyway.

Removing the tank

I started by removing the saddle... it tips forward on a hinge plate revealing 2 flange nuts beneath.

The nuts come off showing the washers and rubber mountings beneath. 

The hinge plate then lifts off with the mountings leaving the studs. I reattached the flange nuts for safe keeping.

The tank is fixed at front and rear; the front of the tank is retained by a short m8 bolt each side.

 Bolts removed

The rear is held by 2 vertical studs accessed from below... their position is indicated here by my finger.

The view beneath shows the nuts are screwed  onto long studs and need a deep 12mm socket to unscrew them.

Tank then lifts off revealing the stellate rubber mountings beneath.

Rubber mounting pads

Underside of tank showing petcock installed.

Removing and reconditioning the petcock

Underside of tank shows fuel tap attachment. The fuel tap (petcock) is a 22mm nut and unscrews to release it from the tank.

The petcock is released leaving the internal filter tube inside the tank. You can see the base of the internal tank filter and a sealing ring still in the tank.

Fuel is filtered through the in-tank filter before entering the tap which contains a second filter screen and sediment bowl. The base/sediment bowl unscrews easily. This reveals the in-tap filter screen and its sealing ring. The sediment bowl was also full of solidified sediment. 

The tap has a second filter screen and sealing ring.

The ring and internal screen lift out. Even the top of this tap is dirty.

Sediment is caked and dried in the sediment chamber.

I scraped out the worst

It was difficult to remove the internal tank filter because it was solidly gummed in. The sealing ring was brittle and broke on removal.

In the end I removed it by screwing an M8 bolt into the filter,  cutting its own thread in the plastic. I could then grip the bolt loosely with pliers and tap them up smartly with a hammer. This pulled it out without damaging the outside surfaces.

And tap the pliers upwards from below. The filter tube was horribly gummed up

Reconditioning the petcock (fuel tap)
I cleaned all components in the sonicator which improved things greatly, but although the tap turned easily, I couldnt get fluid to flow through it in any direction and in any position. Its seems clear that the inside of the tap is going to be as gummed up as everything else and I think I'll have to open the tap to clear it properly. Sadly the tap is rivetted and not made for servicing. However this is a nice item;  with its 2 filters and sedimentation chamber its a pretty sophisticated tap. Simple replacements are cheap, but nicer ones are very expensive so its worth trying to repair this one.

I started by drilling out the rivet heads holding the front plate.

Heads off and...

Lever off the cover plate.

Immediately beneath the cover plate is a wave washer and a shim

The tap unit can then be pulled out which revealed a lot of sediment in the petcock and the  U chanel in the tap section was also full of congealed sediment.

Tap section removed. Crud on top of rubber sealing washer and also jamming the U channel in the tap.

The rubber valve plate could be levered off. It was choked with sediment and its surface had deteriorated.

As this is a non-serviceable item no spares are available,×× however they can be made. I stamped out some discs from 3mm nitrile rubber strip using a16mm punch (you must use a fuel proof rubber).

I pressed one of these blanks into the petcock unit so that the 4 openings left witness marks indicating where the holes should be punched.

I punched 5mm holes in the places so marked. The projections are actually only 4mm  but I found holes made with a 4mm punch were too small- or my punching was too inaccurate! The other point is that of the 4 projections, one is not actually a petcock fuel channel. Looking more closely at the original.it seems that the hole corresponding to the blank projection didnt originally penetrate right though the rubber. However I was unable to punch "half a hole" so I punched through completely and hope this will be ok.

New rubber disc in place with 5mm holes located over fuel openings. Note the left hand hole locates over a peg not a hole. I also cleaned out the U channel in the tap unit.

... and inserted the tap to protect the interior of the petcock. I could then drill out the remainder of the rivets using a 3mm drill.

And tap the holes to M4. One could be tapped all the way through, the other was a blind hole and so bottom tapped.

The tap could then be reassembled. Its important that the screw heads dont obstruct the movement of the tap so I used M4 countersunk screws (countersunk the holes in the plate). Low profile flanged Allen screws might look better. I used 10 and 5mm screws in the different depth holes.

I also fitted a new O ring in the sediment chamber. The original was I think a square section but the mating flange inside the chamber has an obvious chamfer and should work well with a round sextion... which is obviously easier to source.
The tap seems to work when tested with water but I've yet to see how it stands up to fuel (which is thinner) and a pressure head. I may need to make a new washer but for the time being I'm hopeful.
** I have found that petcock spares are available, and although 16mm is an unusual size it is shared with the Simson SR50, KR51 and Schwalbe. However these seem only available in bulk from Germany but if you can get them youre quids in! Also there is a 15mm seal from honda for the GX range OEM No.16957-ZE1-812 which might work.

Cleaning the tank

Im sure its no surprise that the tank was also full of congealed fuel varnish although there was no actual liquid fuel left. I shook it extensively with m8 and m10 nuts rattling in a mix of washing-up liquid, diet cola and water. It needed several changes until the wash started to emerge clearer. This is a very tiring process! I then blocked the tap hole and filled the tank with 2% citric acid in detergent and let it stand for 3 days. Rinse and repeat.

After a week the cleaning effect was disappointing and patchy. In all the ranks Ive done this sticky coating is unique. Problem seems that the residue is stuck fast and being greasy prevents the acid from reaching the metal. If doing this again I'd use sodium hydroxide first. However another change for fresh citric acid did eventually clean it up well. I rinsed it thoroughly with water, then methylated spurit and finally sprayed tge insidexas thoroughlyvas I could with wd40 to coat and protect the fresh metal until I could add fuel.

Oil Tank

This bike had obviously siezed for a reason. Im assuming this is either pump failure, incorrect oil, hose blockage, or simply over revving. Given both my bikes were siezed, it seems this could be a problem with these bikes. Im pretty sure the oil pump works now... its a simple design and works via a screw on a pinion wheel so if it turns it pumps. That means I need to examine the tank and oil feed.

The tank is held to the rear carrier via one bolt underneath.

And it clips on at the front of the rack with  this hook-like mounting and 2 rubber feet.

Undo the rear bolt.. raise the rear of the tank and slide it backwards to disengage. The tank is then held only by the oil feed pipe. This can be pulled off but obviously this will reease the oil so detach the carb end and direct the flow into a collection vessel. Note that there is a filter at the tank spigot and this in-tank filter comes off with the pipe. In my case it was clear so I just cleaned it out with carb cleaner (forgot pics)

The side bubble is a sight window that should show immediately when the oil needs topping up.

In my case the sight window was obscured with blue gelatinous material  and the indicator yellow ball was missing.

I drained the oil- to my surprise it was blue. There were some blue gelatinous lumps in it which could have interruped the oil feed? The blue oil was a mystery- I've never seen it before. The tank label refers to "two stroke injection oil"... dont know what that is- or whether this blue stuff is it. I am familiar with 2 stroke premix oil but that is red. Opinions from fb suggest its either a Lucas 2 stroke oil or a specialist marine oil. In any event and although Uve hot a lot of this I cant afford to risk it in the rebuilt motor so Im draining it.

I cleaned the jelly like material out if the sight bubble and it returned to transparency. I found the yellow ball in the drained oil and refitted it in the sight bubble. I rinsed the tnk in paraffin and drained it before refitting.

Before refitting the tank and reattaching the hose... ensure the filter is present. This is held in only by the oil tube which seems odd.