A change of di­rec­tion

With the IT465 on hol­i­day, some at­ten­tion is paid to the rest of the ed­i­tor’s ma­chines.

Classic Dirtbike - - Contents - Words and pics: Tim Britton

With the IT465 pro­ject hav­ing a break, the ed­i­tor has a chance to do a bit of work on his own bikes.

Due to one thing and an­other crop­ping up at var­i­ous times, my own col­lec­tion of dirt bikes has been ne­glected a lit­tle re­cently. Like most en­thu­si­asts I’ve a few bikes in the shed and they’re there for rea­sons which will be fa­mil­iar to a lot of read­ers. Long­est stand­ing mem­ber of what has been re­ferred to as ‘my fleet’ is the 250 Bultaco Sherpa T I’ve had from new and it was the sub­ject of a re­build se­ries it­self 20 or more is­sues back. The new­est ma­chine – as in new to me not ‘new’ new – is a TY250 Mono Yamaha, sim­i­lar to the one I had in the Eight­ies and in be­tween there are a scat­ter­ing of Bri­tish and Euro­pean ma­chines with one thing in com­mon… they all need a bit of span­ner­ing. Prob­lems I’m fac­ing in­clude grum­bling

main bear­ings, leak­ing fork seals, worn gearchange shaft splines and a clutch need­ing strong hands to op­er­ate the lever. Ac­tu­ally this last one is also the tech fea­ture here and in­volved the help of some­one with more engi­neer­ing abil­ity than me to do the ma­chin­ing. With­out spoil­ing the sur­prise of the tech fea­ture too much, it in­volves a Can-am clutch mod­i­fi­ca­tion aimed at giv­ing the ed­i­tor’s clutch hand an easier time of it in en­duros.

The thing is, while a bike is apart there al­ways seems to be other tasks to at­tend to. For quite a while the pri­mary case on the Ro­tax en­gine fit­ted to my Can-am en­duro bike has leaked oil at an alarm­ing rate and this as­pect has been ig­nored rather longer than it should have been; in my de­fence the case has been on and off a lot, mak­ing sure the stan­dard clutch ac­tu­a­tor was lu­bri­cated prop­erly so it could per­form at its best.

I was just about to give up hope when sev­eral sug­ges­tions for mods were put my way, one ac­tu­ally in­cluded the bits to do the job…

With this task com­pleted I turned my at­ten­tion to stem­ming the flow of oil out of the case. Ro­tax’s disc valve two-stroke en­gine is a fairly well known unit and comes in a num­ber of spec­i­fi­ca­tions, de­pend­ing on the in­tended use, but it can be grouped into two main types, these be­ing auto lube and pre-mix. In the for­mer, the pri­mary case has a sep­a­rate com­part­ment in it which houses an oil pump fed from an ex­ter­nal oil reser­voir – in the case of my ex-mil­i­tary Can-am this reser­voir forms the top tube of the frame – while en­gines us­ing pre-mix of­ten have a dif­fer­ent case with no oil pump and the two stroke oil is mixed in with the fuel. Now, I was ad­vised by no less an author­ity than Jeff Smith, who ac­tu­ally de­signed the bikes for Can-am, to re­tain the auto lube fa­cil­ity on an en­duro bike, so I did. The way most of us flat­ten the mat­ing faces of a case is by rub­bing the case on an old mir­ror which has had some grind­ing paste spread on it and lubed by a squirt of light oil. All you do then is lay the face to be flat­tened on the mir­ror, in the gloop and swirl the case round while ap­ply­ing light pres­sure. It’s noisy, dirty and bor­ing, but works. The prob­lem with a Ro­tax case is the auto lube sys­tem pumps oil through pas­sages drilled in the case and it is al­most a dead cert grind­ing paste would find its way into the drillings and if not cleaned out would hap­pily de­stroy the big end bear­ing when fit­ted to the bike. So what, I hear you say, wash out the drillings... It isn’t quite that easy as the oil

pump feeds, in the form of two brass tubes, are pressed into the holes too and have re­stric­tor valves in­side – a spring and a tiny ball bear­ing. Still, a method of clean­ing the drillings was ar­rived at and in­volved squirt­ing light oil down the feed tube so the gloop was pushed out. A fur­ther re­fine­ment was to put some grease over the end of the drilling to stop any grind­ing paste go­ing in there in the first place.

I did try squirt­ing con­tact cleaner down the tube but the re­stric­tor valve was too much for the pres­surised liq­uid and I man­aged to squirt it ev­ery­where. In the end I used a pump ac­tion oil can. Just got to re­assem­ble the oil pump into the cas­ing then ap­ply a light smear of in­stant gas­ket, re­fit the case and then I can put the Can-am to the bot­tom of the list…

Next on the work bench is likely to be my BSA B40, which man­aged to shed its gear lever dur­ing the Pre-65 Scot­tish Two Day Trial. The splines on the shaft are worn to the point of non-ex­is­tence. Luck­ily, there is a re­place­ment part avail­able which means the gear se­lec­tor can be saved as the shaft only can be re­placed rather than the whole part. It does of course re­quire a strip down of the tim­ing side of the en­gine to ac­cess the in­ter­nals, but at least with a B40 this can be done with­out tak­ing the en­gine out of the frame. No doubt when the case is off there will be other is­sues to sort too, such is life with a 50-year-old mo­tor­cy­cle. The Beezer does need some work else­where too, on the cy­cle parts or brakes but they are sort of ac­cept­able and work well enough to pass the MOT test, but first wa­ter splash and they’re his­tory. Prob­a­bly the eas­i­est job to do will be the fork seals on the TY and to be hon­est the new seals are in the spares box but find­ing five min­utes to do the job has proved awk­ward lately. The big­gest job fac­ing me is re­plac­ing the main bear­ings in my 250 Bultaco en­gine. The bike was re­built in 1988 for the Scot­tish Six Days Trial and in­ter­nally at least has

re­mained largely un­touched since that day as the re­build se­ries fo­cussed on the cy­cle parts. It’s been rum­bling for a while and a re­cent out­ing at In­ver­ness DMC’S High­land Clas­sic at Alvie and the fol­low­ing week­end’s Bultaco Nostal­gia trial in Cum­bria are pretty much it un­til I change the bear­ings. Yes, it still starts and runs quite well too but there’s al­ways the dan­ger of do­ing other dam­age and in any case it’s not ‘right’ and that isn’t the way things should be done.

Thanks to the age and use the Bulto has been through there are other prob­lems to con­tend with, gear chang­ing has be­come dif­fi­cult when the en­gine is warm. Chang­ing the oil and clean­ing the clutch plates didn’t solve the prob­lem and a bit of re­search – or, more ac­cu­rately phon­ing Dave Ren­ham up and ask­ing – gave me a few ar­eas to check when strip­ping the en­gine. So hope­fully all will be well with my Bulto soon.

There is a dan­ger when sev­eral bikes need at­ten­tion that sev­eral bikes are stripped down and I won’t be the only one who has ever been caught out with every bike they own in bits. Thank­fully, I’ve man­aged to avoid that sce­nario lately but it has hap­pened in the past and if your work­shop is large and can have a ded­i­cated work area for each bike then it’s not so bad but, if like me, you’ve to haul ev­ery­thing out in or­der to ac­cess a work area then it is best to keep things as rolling chas­sis at least. Such is the case with my Can-am and with the case off at least I can still wheel the bike in and out of the work­shop. Luck­ily, I do have some or­ganic shelv­ing which has been added to as time has pro­gressed so I am able to ded­i­cate an area for sub-as­sem­blies at least.

Hav­ing too many bikes in bits at one time means more chance of things be­ing lost, mis­placed or just for­get­ting how they go back to­gether. Nat­u­rally jobs such as the fork seals are prob­a­bly an hour from open­ing the shed door to putting oil in the fork leg, but the clutch case has needed some ma­chin­ing and some fet­tling to get it right, plus the flat­ten­ing so it’s been apart for a while. Now it’s go­ing back to­gether I’ll have to re­fer to the pics I took of it be­ing stripped apart so I can re­mem­ber where ev­ery­thing goes.

Once the clutch is in place again it will be time to look at other bits of the bike, such as the lights. One of the reg­u­la­tions for an en­duro re­quires a mo­tor­cy­cle to have lights fit­ted and in or­der to pass this re­quire­ment I jury-rigged some in place. These madeup lights were the bro­ken front one from Pro­ject IT – the mount­ing ears had bro­ken off – which, with some gen­tle scrap­ing and sand­ing, slipped in­side the Presto Petty front num­ber board/light­ing unit. The rear one was one of sev­eral orig­i­nal mil­i­tary Can-am units I have and is a truly mas­sive af­fair. It lasted one lap of the last en­duro I did and its demise was writ­ten about in my col­umn a cou­ple of is­sues ago. How­ever, some­thing bet­ter is needed and while the front light fits and will work okay, a unit slightly more sleek than the orig­i­nal one, the size of a bun­ga­low, will be sourced.

All the giz­mos for sort­ing lights are in place and long-time read­ers will re­mem­ber our prize bike was wired up by Ferret from Ferret’s Cus­tom Elec­trick­ery who had the in­struc­tion to ‘…pro­vide a white light at the front, a red light at the rear, the front one has to dip and rear one needs a brake light too, both have to work even if I drop the bike in a river…’ “any­thing else?” joked Ferret. ‘oh, yes, a horn would be use­ful too and I don’t want a bat­tery on the bike.’

This in­struc­tion is pretty much what I want for my own bike too, but this time I shall at­tempt the dark and mys­te­ri­ous world of mo­tor­cy­cle electrics with wires and con­nec­tors and stuff. I know elec­tri­cians will be shak­ing their heads and col­lec­tively sigh­ing ‘but it’s easy’ which is what all trades­men say about their skill – I’m as guilty as any­one when it comes to wood­work­ing things – but don’t for­get not ev­ery­one will have had the ben­e­fit of work­ing with oth­ers as they learn such skills.

All that’s needed now is to give the work­shop a quick clean as it’s not good prac­tice to have en­gines apart in dirty con­di­tions and it is amaz­ing how soon dirt can ac­cu­mu­late in an av­er­age work­shop. A ‘clean room’ for en­gine as­sem­bly is an ideal few of us have space to ded­i­cate to, so a sweep of the bench, make sure noth­ing can drop down from the ceil­ing and all should be well... )

Right: Once the re­turn spring was fit­ted, all the case needed was a light smear of in­stant gas­ket… a re­ally light smear. Se­ri­ously, I once saw an en­gine where the owner had, in­amis­guided at­tempt to ste­moil leaks, used al­most a full tube of the stuff....

While the clutch was be­ing done we did a few other things too as for some rea­son the oil was de­ter­mined to leak past the case. The pump was re­fit­ted quickly enough and the oil pipes can only go back one way, I still used my pic for ref­er­ence though. It...

The two brass tubes are for the oil feed to the big end and the mix­ture.

Next task is the Beezer gear shaft… no won­der a gear lever won’t stay on. And the task af­ter that is for the Yam’s fork seals. A fid­dly job, but hey… Just the oil feed and the pump ca­ble to at­tach.

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