HONDA CB750 K2

Mark Hay­cock fi­nally sorts his chain and sprock­ets!

Classic Motorcycle Mechanics - - CONTENTS -

We are now ready to fit the new chain to the CB750, and I shall take a look at a cou­ple of very rea­son­ably priced tools to fa­cil­i­tate this. First though, be­fore putting back the cover over the front sprocket, I did no­tice that the elec­tri­cal con­nec­tions in this area (Photo 1) were not in great con­di­tion as the in­su­la­tion must have shrunk af­ter be­ing heated by the en­gine for years, ex­pos­ing the con­duc­tors, so I wrapped them with ex­tra in­su­la­tion in the form of non-sticky plas­tic tape: best to sort this out now, rather than by the side of the road. The chain in the kit was sup­plied as be­ing the cor­rect size and length for the ap­pli­ca­tion so I was a lit­tle sur­prised to find that it was ac­tu­ally too long and so it would need to be short­ened to suit. Also I should point out that time has moved on and the old-fash­ioned spring link orig­i­nally used on CB750S (and ev­ery­thing else come to that) is now re­garded as in­se­cure and hence un­sat­is­fac­tory. The rec­om­mended way now is to use a riv­eted link and ev­ery­thing you need should be in­cluded within a kit such as this. In the past I sim­ply used an an­gle grinder to shorten chains and did the riv­et­ing for join­ing by hand and this worked okay, but I de­cided to ‘get with it’ and buy the proper equip­ment. What put me off be­fore was the price of the kit which I would rarely use, but things have changed and now you can ap­par­ently buy the tool you need for a ten­ner, in fact, here it is (Photo 2). Even I am not that stingy. Sounds re­mark­ably cheap, but does it work? I have seen a few re­views of this tool which were some­what less than glow­ing, but let us see. The first thing that struck me was that it came with no in­struc­tions what­so­ever, which strikes me as an odd omis­sion. Any­way, I knew what to do, so hav­ing checked how much chain I needed to re­move (Photo 3) I could dive straight in and push the rel­e­vant rivet through. Re­ally though, this was prob­a­bly ask­ing a bit much for a cheap lit­tle tool like this so to give it a bit of lee­way it is best to re­move the end of the rivet with an an­gle grinder as in Photo 4. I try to do grind­ing out­side if pos­si­ble as I feel that the abra­sive dust fly­ing ev­ery­where is best not com­bined with en­gine in­ter­nals from other projects. Be­cause the hold­ing han­dle for the tool was a bit fee­ble look­ing, the whole thing needed to be held in a vice and it was more con­ve­nient to use the Work­mate and here it is, part done (Photo 5). There are one or two points about what we see here. One re­viewer said that he had man­aged to bend the pin as it was in­serted to push out the rivet. This ten­dency to bend can be at least re­duced by grind­ing off the rivet as we saw but also by ar­rang­ing things to min­imise the ex­ten­sion of the pin,

es­pe­cially to start with. I have also seen com­plaints that the threads are a rather poor fit and that is quite true. This makes it dif­fi­cult to en­sure that the pin is in pre­cisely the right po­si­tion. I packed the threads with PTFE tape to tighten the fit but I don’t know if it made much dif­fer­ence re­ally. Fi­nally, note that the tight­en­ing to press out the rivet should be done us­ing the big­ger thread: the small one is just to po­si­tion the pin. The great news was that the pin did not bend and the tool worked per­fectly. I had some bits of chain left over which I kept just in case – well, you never know, do you? Now we come to join­ing the short­ened chain. DID are very par­tic­u­lar that the com­po­nents of the join­ing link should be well lu­bri­cated and they of course pro­vide the cor­rect grease as well as the four O-rings you need (Photo 6). And here is the join­ing link as­sem­bled, ready to be pressed to­gether (Photo 7). This is done us­ing these two plates (Photo 8) as the parts fit quite tightly. The dif­fi­culty here is that the side-plate needs to be pressed on far enough, but not too far so that it starts to bind and thus is reluc­tant to bend around the sprocket. You can as­sess the cor­rect po­si­tion by mea­sur­ing the chain width us­ing a caliper on an­other link and mak­ing the join­ing link the same. Then the O-rings (you did put all four of the O-rings in place, didn’t you?) are just be­ing lightly pressed and will seal with­out be­ing flat­tened. And you will end up with some­thing like this (Photo 9). Now we are ready to ex­pand the end of the rivet. In the CB750 man­ual Honda rec­om­mend us­ing a flat chisel-shaped punch to form a cross at the end, but the DID joint riv­ets and tool here are set up to use a pointed punch to open out the hol­low end in a cir­cu­lar form. The riv­ets I re­moved to split the chain were shaped like this (Photo 10) and you can see that they are ex­panded at the end by just a very small amount. It is safer to ex­pand the softer join­ing riv­ets by a lit­tle more than this; an in­crease of about 0.7mm in di­am­e­ter is okay. By ex­pand­ing the end by too much though, you are not mak­ing it even safer: quite the re­verse as the ex­panded part is then too thin and it is thus weaker.

Now the big test: is this cheap tool strong enough to ex­pand the rivet prop­erly? The at­tach­ments they give you are shown in Photo 11. My first thoughts were that the shap­ing tool was not formed cor­rectly to work and so it proved. Af­ter tight­en­ing the screw as much as I dared, the rivet had not changed. So I ground the end down to a more pointed shape as in Photo 12. Same re­sult, be­cause the tool was ap­par­ently softer than the rivet. The con­clu­sion must be that the com­plete tool as sup­plied is not ca­pa­ble of fit­ting a new chain (of this size, any­way) but to be fair it did okay at split­ting the old one so for less than a ten­ner it could be of some use. So the next step was to buy an even more ex­pen­sive chain tool and here it is (Photo 13), price £15. This is a much more sub­stan­tial-look­ing set-up and I had high hopes for it. Photo 14 shows it ready to use and you can see that (1) the han­dle is ac­tu­ally sub­stan­tial enough to grab hold of and (2) the part which ex­pands the rivet is a ball bear­ing, which of course is hard enough to do the job. It worked per­fectly, and Photo 15 shows the re­sult on the first rivet. I couldn’t com­plain about that (well, the chain hasn’t fallen off yet) and it was con­sid­er­ably cheaper than the gen­uine DID, or any other, pro­fes­sional tool. So is it worth spend­ing £100 or more for a sin­gle pro­fes­sional-stan­dard, one-task tool which is rarely used? Well, if you have any sense, prob­a­bly not. But pay­ing to get some­one else to do this work is now very ex­pen­sive. So why not have a go with some­thing cheaper which will do the job and is fine for oc­ca­sional use?

1 Elec­tri­cal con­nec­tions near sprocket hadn’t aged well.

2 Chain sort­ing tool for a ten­ner!

5

Work­mate more se­cure than tool’s ‘chain han­dler’.

6 O-rings go­ing in place.

8 Two plates push the join­ing link to­gether.

7 Chain ready to be pressed to­gether.

3 Check­ing to see how much chain is over.

4 An­gle-grind­ing the rivet.

9 This is what it should look like.

13 Voila: the £15 tool! Will this one work?

10 The riv­ets as seen when re­moved.

14 Much more sub­stan­tial!

15 At last! One to do!

11 At­tach­ments didn’t look right.

12 Nope, that didn’t work.

Newspapers in English

Newspapers from UK

© PressReader. All rights reserved.