HO 50K 2

The slow process to com­ple­tion con­tin­ues as Cap­tain' Mark Hay­cock makes his nal as­cent on his K2!

Classic Motorcycle Mechanics - - COTENTS -

Mark Hay­cock starts to line the tank.

When look­ing over a prospec­tive pro­ject bike, you will prob­a­bly take a uick look in­side the fuel tank and per­haps be slightly hor­ri­fied by the un­ap­peal­ing sight. Af­ter years of stor­age the in­side sur­face will be rusty and dirty, with pos­si­bly the re­mains of old fuel or at least de­posits from it. This need not put you off as it can be sorted out, by ap­ply­ing a new lin­ing. ou might have heard a lot of sto­ries about the fuel cur­rently avail­able from pumps dam­ag­ing tanks and among the non­sense there is a small amount of truth. t is prob­a­bly best to line tanks now as mod­ern fu­els do con­tain a pro­por­tion of ethy­lene which can give rise to more rust­ing than in for­mer times. know peo­ple get rather hot un­der the col­lar about this, but if you just spend a lit­tle time pre­par­ing for it then in my ex­pe­ri­ence± mod­ern Bri­tish fu­els work per­fectly well with old en­gines, though that may not be the case with what' s avail­able in other coun­tries. So even if the tank ap­pears to be in good shape, a lin­ing makes sense. There are one or two pro­vi­sos here: 1) The process has to be car­ried out in a thor­ough man­ner. 2) The lin­ing ma­te­rial must be suit­able for new-style fu­els, both now and in the fu­ture. t is uite likely that the paint on a pro­ject bike is not per­fect and you will want to re­spray it, so it makes sense to do the lin­ing be­fore the paint­ing. What am go­ing to look at then is how to pre­pare the tank, choose the lin­ing ma­te­rial and ap­ply it. When look­ing at ad­verts for tank lin­ers you will of­ten nd that the sell­ers also of­fer a prepa­ra­tion kit and for many that will of­fer the sim­plest so­lu­tion. But this mag­a­zine is for en­thu­si­asts who like to do it them­selves, so shall show you how do it from scratch. am not say­ing that this is the way to do it but just what works for me. f you are lucky, you will look in­side the tank and nd it to be empty, clean and shiny. Re­turn­ing to the real world, it will be any­thing but. f it has the re­mains of some sort of mo­tor fuel in­side, in a way that is a good sign as it shows the tank is not com­pletely full of holes. ou need to drain it out and savour that de­light­ful smell it pro­duces af­ter years of stor­age. be­lieve it is caused by a re­ac­tion catal­ysed by the steel tank, but the fuel is now com­pletely use­less and just a li­a­bil­ity: what do you do with it? Please do not tip it away at the end of the gar­den or even down the drain, but in­stead con­tact your lo­cal au­thor­ity for ad­vice. Now you can test whether or not it holds wa­ter lit­er­ally, as this will show you whether or not you need to carry out re­pairs

to make it fuel-tight. A very slight leak is okay as the liner will seal it, but any­thing more will need weld­ing. f the test is passed, you can go ahead to clean it out. f the fuel tap is ac­tu­ally work­ing cor­rectly you can keep it on for this but other­wise you will need to take it off and nd a way to tem­po­rar­ily block up the hole. In Photo 1 we see the tap for my CB750 K2 which, apart from a gen­eral over­haul, needs to come off for re­pairs as the sec­ond lit­tle brass tube has be­come de­tached. Af­ter tak­ing it off, cleaned up the mount­ing (Photo 2) and cut a small steel strip to cover the hole, AET ting it and cover­ing the whole lot, in­clud­ing the mount­ing screws both ex­ter­nally and on the threads, in sil­i­cone (Photo 3) . es, it looks a mess but it is tem­po­rary and it needs to seal. us e the su­pe­rior oxime-based sil­i­cone (Photo 4) which gives me a bit more conae­dence t hat it will work. This type is dis­tin­guish­able from the or­di­nary stuff as it does not smell like vine­gar when cur­ing. We are go­ing to ll the tank with a home-made clean­ing uid but it is best to use some­thing other than the nor­mal ller cap to seal it as they of­ten do not pro­vide a her­metic seal. A large rub­ber bung (or stop­per, as they are known) seems to work okay (Photo 5). They are sized by a slightly ar­cane num­ber­ing sys­tem: have used my num­ber 11 (ta­per­ing from 56 to 48mm di­am­e­ter) on sev­eral ller necks with suc­cess, but maybe yours is par­tic­u­larly big or small: who knows? Now the tank is ready to be cleaned out and for this use a hot, strong so­lu­tion of in­dus­trial de­ter­gent with maybe a lit­tle caus­tic soda added. have found that if it is spilled on the out­side, this will not dam­age paint pro­vided that it is washed off im­me­di­ately. ou need some­thing to scrape away at the in­side and have tried a num­ber of things over the years. ou can use gravel, prefer­ably with sharp edges, but that has the dis­ad­van­tage that it is uite hard to get out again. This is be­cause you will gen­er­ally nd a lip around the bot­tom of the ller which seems to be sci­en­tiae cally de­signed to make it harder, but by shak­ing the tank it does come out even­tu­ally. pro­gressed to us­ing a hand­ful of ran­dom nuts, bolts and wash­ers which worked okay and had the ad­van­tage that it was eas­ier to re­move them us­ing a mag­net on a stick' pickup de­vice (Photo 6). Best of all though is a steel chain which works well and is easy to re­move (Photo ). With the clean­ing uid and scrap­ing ar­range­ment in the tank, just keep on mov­ing it around ev­ery way you can un­til you are thor­oughly fed up with it. f you ll the tank right up you will dis­cover that 15 litres of wa­ter make it sur­pris­ingly heavy and you will re­mem­ber not to ll it up so much next time. Af­ter tip­ping out the con­tents (you have only used house­hold clean­ers so it will be okay to pour down the drain), use plenty of wa­ter to rinse it out sev­eral times and you will prob­a­bly see uite a bit of rust be­ing ushed out. Next time we shall look at a more di­fae cult case and move on to ap­ply­ing the new coat­ing.

Mark’s back on the chain gang. It does the trick...

3 Messy, but needs to seal!

Mag­net on stick works!

2 Tap mount­ing was cleaned.

5 Bung the bung in the tank hole!

1 Re­pairs needed on fuel tap.

4 Our Mark swears by this stuff.

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