King of the IT crowd

Put two off- road­ers to­gether and the first ques­tion from ei­ther is gen­er­ally “What’ve you got on the go at the mo­ment?” This is of­ten fol­lowed by “You’re do­ing a WHAT!?” Oc­ca­sion­ally it is “Oh, one of those…” but more of­ten it’s “You must be mad”. You ch

Classic Dirtbike - - Contents -

Assem­bly pro­gresses as a prob­lem is solved and more in­for­ma­tion comes the edi­tor’s way.

To be hon­est I thought I’d be rid­ing this IT465 by now but hey ho, that’s the way things go some­times and un­like our last few pro­ject bikes where spares have been plen­ti­ful, the IT range has gaps in it. Okay, peo­ple are work­ing to fill these gaps but it can still be a long process to source bits but there were enough bits to make a rolling chas­sis for the In­ter­na­tional Dirt Bike Show stand. The IT pro­moted quite a bit of in­ter­est on our stand and a few peo­ple did say they’d got bits and pieces left over from their own re­builds, in­clud­ing a lad who reck­oned to have a re­place­ment lower front curve for the ex­haust pipe. If you’re read­ing this… still in­ter­ested in the pipe…

One of the bits tak­ing for­ever to source was the small bear­ing on the end of the se­lec­tor drum. In the bear­ing world that one doesn’t have a par­tic­u­larly hard life, un­like a wheel bear­ing, which spins when­ever the wheel moves, this se­lec­tor bear­ing has to move when the gear pedal is pressed and, as such, is not noted for wear­ing out. But our en­gine has suf­fered a bit through lack of main­te­nance and the… well I was go­ing to call it oil but that would be stretch­ing it a bit… sludge in the gear­box cas­ing had done its worst and even when still on the shaft, the poor bear­ing felt rough. Once off the shaft and rinsed through in the parts washer to get all the crud out it didn’t feel any bet­ter, even soak­ing it in oil didn’t mask the rough­ness and I stopped kid­ding my­self that it could be reused. I had to con­vince Nick Scott at Mo­to­duro that this bear­ing was worn out… he thought I was jok­ing “…but it never wears out?” Ours has…

Once the bear­ings were all in the work­shop I could lay the cases out, warm them through and drop the bear­ings in place. Once upon a time a gas blow torch would have been used to heat the cases up but these days a hot air gun is a safer op­tion, even if it may take a lit­tle longer to work. The old test method of once spit bounces off the metal be­ing heated is still a good in­di­ca­tor of when the cases are hot enough. Once up to tem­per­a­ture and with the bear­ing still cold it will be an easy job to press it into the hole with­out re­sort­ing to any ham­mers and drifts. Once the bear­ings are in, leave the cases to cool, though I sus­pect in a pro­fes­sional work­shop things might be a lit­tle dif­fer­ent, as they have to earn a living re­build­ing things, whereas I’m do­ing it in an am­a­teur way.

While the cases cooled I laid out the gears and se­lec­tor drum and re­ferred to the man­ual and the strip­down pics to see where ev­ery­thing went. The cogs on these shafts are held in place by a se­ries of cir­clips and it could be easy to lose the se­quence they’re on their shafts so I took plenty of pics and re­ferred to them as the cogs went back on. A vis­ual in­spec­tion of the cogs and shafts showed they were okay, no chipped teeth or any­thing like that and once through the parts washer they were rinsed and dried, then oiled and were ready to go back into the case. Most mo­tor­cy­cle en­gines have a par­tic­u­lar assem­bly method sug­gested by their maker and it makes sense to fol­low this, as life will be eas­ier. In the case of the IT465 the right-hand case is laid flat and all shafts and the crank are in­serted into it, then the left-hand case is fed over the top.

The im­age in the of­fi­cial Yamaha man­ual for the IT465 shows a scrupu­lously clean work area and an en­gi­neer in pris­tine clothes work­ing on a sup­port jig spe­cially made for the job. In our work­shop the bench was swept clean, then a rag soaked in oil was wiped over the sur­face to pick up all the other bits and pieces of muck be­fore a slightly more or­ganic sup­port jig was used to lift the case face off the bench top. The crank end would hit the work­top oth­er­wise. For our en­gine I used some 100 x 50 dressed soft­wood and drilled a cou­ple of holes for some round bar to go in, which stopped the case drop­ping off the sup­port. To cut the dust I wiped the wood with the oily rag again and assem­bly was rel­a­tively sim­ple. I did have to use a puller to make sure the crank­shaft went in the main bear­ing fully but it all went smoothly and the mat­ing faces of the case had a light smear – and I mean a ‘light’ smear – of gas­ket ce­ment.

It is a nar­row mar­gin be­tween enough ce­ment to seal and too much so it squirts out. I once was asked to have a look at an en­gine that had stopped work­ing and the an­swer was ob­vi­ous as soon as I saw it… se­ri­ously this en­gine had or­ange gas­ket goo com­ing out of ev­ery­where and looked as if it had been la­dled on with a trowel. Early in my days of do­ing my own main­te­nance I was qui­etly told noth­ing beats a flat mat­ing face and the light­est smear of in­stant gas­ket for seal­ing. What a lot of peo­ple seem to miss is if the goo squirts out and is vis­i­ble on the out­side, then it will do the same to the inside, which can get in oil ways.

Just be­cause it came off that way doesn’t mean it was right. The swing­ing arm on the 1981 IT is taken from the pre­vi­ous year’s YZ and is a strong but light con­struc­tion with steel bushes, stops and bear­ings pressed in. To fit to the frame the swing­ing arm ears go ei­ther side of the en­gine and there are tubes that clamp up when the spin­dle passes through them, while the frame and en­gine and face bear­ings pro­vide a mea­sure of cen­tral­i­sa­tion. At least that’s the the­ory but try as I might there was no way the assem­bly would go back in as it was when it was stripped out. I couldn’t fig­ure out what was wrong. I had pic­tures of the way it was when we got the bike, but not only could I not get the new bear­ings to go in, the old ones didn’t go in ei­ther, yet there they were in the pics. In the end, just for dis­play at the show, I didn’t bother with the face bear­ings and ac­tu­ally de­ter­mined some­thing was wrong with the orig­i­nal assem­bly.

It was only when I got an orig­i­nal schematic draw­ing of the assem­bly that

things be­came clear. Who­ever had been re­spon­si­ble for main­tain­ing the bike in the past had man­aged to get the face bear­ings be­tween the swing­ing arm and en­gine… this must have taken an aw­ful lot of force and prob­a­bly some kind of jack to spread the frame enough so the bear­ings would go in.

With a draw­ing avail­able and all the bits laid out on the work­bench it was ob­vi­ous there were a cou­ple of bits miss­ing from the orig­i­nal set-up. Al­ready pur­chased was a bear­ing kit that has the nee­dle roller bear­ings, new shafts and the ny­lon bushes, plus the seals that go on ei­ther end. Miss­ing were the steel bear­ing cov­ers, which are also part of the dis­tance pieces. Thank­fully, Mo­to­duro stocks them and it also does new bot­tom mount bushes in stain­less steel and snail cam stops in the same stuff. With the new parts look­ing all smart and non-rusty, the ac­tual swing­ing arm it­self looked sec­ond­hand and could do with a clean-up. The orig­i­nal lac­quer finish had been worn away and there was some cor­ro­sion un­der the bits that re­mained. A while ago I found the ac­qua blast­ing finish to be more than ac­cept­able as a fi­nal treat­ment to al­loy, it gives a satin finish and is eas­ily main­tained. Sort of lo­cal­ish to us is the Aqua Blast Cen­ter at Don­caster and its cab­i­net will hap­pily ac­cept some­thing the size of the swing­ing arm.

Once cleaned and back in the CDB shed it didn’t take long to press the bear­ings, bushes and stops back in and now the swing­ing arm looks good.

With the schematic di­a­gram on hand to show the se­quence of parts, all should be well with assem­bly. 

n to rit B m Ti : cs pi d an ds or W

Gea rbox shafts and cogs seem in good or­der. Cleaned, in­spected and lightly lubed ready for fit­ting. A parts washer is some­thing we all should have

in the work­shop. As­sem­bled for Stoneleigh The old cases with the new bear­ings, so I know where they go in the new cases.

Thanks to a lad in the USA these cases are in prime con­di­tion.

… and it’s start­ing to look more en­giney.

These days a hot air gun is safer than a blow-torch.

… like this then the bar­rel to slip over…

Pis­ton to go on next…

Now we’re get­ting some­where, cases to­gether and yes, the gears work.

A sup­port jig doesn’t have to be elab­o­rate, just as long as it works.

... which was a good job re­ally as it was wrong. This is the cor­rect se­quence.

The swing­ing arm be­fore be­ing taken to Aqua Blast Cen­ter with all the parts laid out.

Try as I might, I could not get the new bear­ings to go back in this lo­ca­tion…

The cab­i­net at Aqua Blast Cen­ter can eas­ily cope with our swing­ing arm.

Newspapers in English

Newspapers from UK

© PressReader. All rights reserved.