Monthly Archives: March 2020

A Strip of the Old Bike 4

While I’m working on the old girl I’ll take the chance and make a couple of upgrades.

The first is the rear brake pull rod. The current rod is original to the frame and is over 50 years old. The adjuster nut is beginning to jump the thread so I’ll make up and fit a new rod while I have the chance, it’s been intended for a while so the materials are to hand, a clevis and a length of 6mm rod.

First step was to thread the end of the rod to take the clevis, with this in place the rod was cut to the same length as the old one and the free end threaded to match the old.

Next is the adjuster nut. The original is a brass wing nut so you don’t need tools to adjust it. The idea is good but proximity of the silencer makes it awkward so a new one made from a bit of brass hexagon rod is indicated. This can be adjusted using a deep socket and extension bar or an old-fashioned box spanner (tube spanner for those in the colonies).

Manufacture is simply just a case of drill and tap it 6mm, turn part of the length down to about 10mm diameter and cut to length. A bit of work with a file to shape the end to a saddle for on the lever roller and that’s it.

The other is the link in the gear-change train.

The original link here is a length of steel rod with a 90º bend at either end.

I’ve always found that this puts the lever a bit too high and have been meaning to change it for long enough. I’m doing it sophisticated like though, using a pair of rose joints and a threaded bar.

I’m being really posh though and having the rose joints left and right hand threaded so the final position of the pedal can be easily trimmed to suit, just means I need to get a left-handed 6mm die up from Tracy Tools.

The bike’s gear levers each have a 5mm clearance hole for the original rod while the rose joint mounting studs are 6mm thread. Tapping size for 6mm however is 5mm so rather than just open them out a bit I’ll run a 6mm tap through the levers, screw the rose joints into place and fit a lock nut as a “belt and braces” to secure them in place. I could have just done this using clevis joints on the rod ends but the rose joints are a neater answer.

I’m now nearly at the point where I can start the re-assembly, there’s just the rear swinging fork to repaint. Once that’s done I’ll refit it temporarily and take the opportunity to properly centre the rear mudguard.

At the moment it has been done by eye, the original position needed altering due to having a car tyre fitted at the rear end.

Normally on a BMW the wheel runs biased towards the right side of the swing fork. This allows space to remove the wheel so, while the wheel may be centred in the frame, the swing fork is not.

Using the wider car tyre meant that the wheel had to be shifted over a bit as the right side of the tyre was fouling on the swing fork so the mudguard was no longer centred on the wheel and had to be moved over as well.

While the guard was moved across a bit it was not quite enough as at full bump the left side of the tyre rubs a bit on the inside of the guard. It only happens on full bump though so I’ve been living with it but I’ll take the chance of fixing it while I have it, if I shift it by 10mm that should do it but any more and I’ll foul the other side.

A downside of using the fatter tyre is that to take the wheel out now means that I have to remove the final drive as well, but this is more than compensated for by the increased tyre life.

I’ve already checked the tyre against the rear mudguard and there is clearance, but not much so a future project will be to make up a wider guard.

UPDATE

I’ve just refitted the mudguard to measure up to find that the problem was not that I had not moved it far enough over the first time, the top of the guard was centred on the tyre.

The problem was that I had not moved the bottom front mount over as well, the front of the guard was still on the original mounting so the guard was twisted!.

All that was needed was to reposition the front mount and the job was done!.

A Strip of the Old Bike 3

Well that was the plan, but with the rear end stripped away there’s so much weight on the front wheel that it’s difficult to raise it off the ground when wheeling the bike on the dolly so manoeuvering it around is awkward.

Answer is to make up a “skate” for under the front wheel using some old castors, which has the added advantage of bringing the bike back to nearer level.

First try with the skate under the front wheel resulted in the wheel turning as the bike was moved forward and coming off the skate but a lashing round the front brake lever sorted this out, and I put a pair of eyes onto the skate and another lashing through these and the front wheel kept the skate in place.

Final piece of the strip was to take out the gearbox, this was strictly speaking not really needed but I’ll take the chance while I have it and clean off and lubricate the clutch splines.

Now I’ve the decks cleared it’s just a case of set to with a wire brush in the angle grinder and clear the sub-frame to bare metal.

As paint does not hold well if there’s any trace of oil on the bare metal it needs swabbed of with a non-oily solvent before it is coated, I’m using “Panel Wipe” which seems to be naptha based, wipes down well and dries quickly.

First coat is an etching primer, to “bite” onto the metal, followed by a couple of coats of a high build primer to level things off and this is allowed to dry thoroughly before the top coat is applied .

I decided to work on one side at a time so the nearside of the rear sub-frame was attacke with the wire brush and taken back to bare metal. Using a brush in the angle grinder is very effective for this but the downside is that the brush tends to shed bristles so a faceshield is a MUST when doing this, you also find that the shed bristles will snag into clothing and jag into you later on!.

Once it was cleaned down I then wiped it over with Panel Wipe and then applied the etch primer.

What I’m using is a rattle-can etch-primer filler from the local car-body shop, it does the job well but the downside is that you need to shake the can vigorously for two minutes after the ball starts to rattle, this is one of those occasions when time d-r-a-g-s on!!.

The job was then left overnight to dry out thoroughly, I’m not in a mad rush here after all.

Next day I went into the garage and was met with a strong smell of petrol. Initial thought was that I’d left a fuel tap turned on but investigation showed fuel wet along a tank seam and a s-l-o-w drip from it, bloody ethanol fuel finding a weak point on a seam!.

So I drained off the tank and reviewed the options.

These are:-

1 – Get a “new” tank.

2 – Use a tank sealant.

3 – Farm the job out.

Well, taking them in order.

Option 1. A replacement tank from Motorworks will cost around £300 and it will need modifying to fit on my bike.

The bike is a “convert”, an Earles fork frame fitted with a later and more powerful engine/gearbox unit. Why do this? Answer is that the Earles fork frame was built with sidecar use in view while the later one is not and a “convert gives the best of both worlds for sidecar use. However the tank moutings are not compatible so a new bottom will need to be put into the tank to match with the older frame. Option 1 goes out the window!

Option 2. The tank already has a sealant in, one that has failed. The existing sealant was put in back in 1986 when the tank was modified originally and it has succumbed to the attack of the ethanol added to modern ersatz petrol so this will need to be stripped out before any new sealant can be used.

On to the ‘net to find out options here and find various options most of which will not work because of the design of the tank itself.

On the net however I find reference to a firm only 20 miles away so I decide to investigate further and decide on Option 3.

They will bake the tank to clear it of fumes, cut it open, blast clean it inside and out, repair any “imperfections”, close it up again and buff out the welds. Then they will internally seal the tank and prime the outside.

As a bonus, the tank is an ex-police one with the radio box in the tank. They are going to remove that to open the tank for blasting but instead of replacing it they will patch where it was, giving me a bit more tank capacity and the possibility of using a standard tank cover and tank bag.

It’s going to cost around the same as getting another tank would, before paying out to have it altered

but it will in effect be a new tank, I’ll need to paint it, but that was on the schedule anyway.

A Strip of the Old Bike 2

With the body out of the way it’s easy to get to the sidecar’s mount points.

There are 4 of these, the two upper being clevis joints and the two lower are ball and socket clamps.

Once the top braces are removed the chassis will try to fold up towards the bike so first thing is to put the bike onto its centre stand for the first time in years.

I’m making all this sound easy, well there’s none of it particularly difficult but when you’re working on your own and have to manhandle the bike around it raises problems.

To make moving the bike around easier I’ve got one of those wheeled platform dollies that go under the centre stand so the bike can be moved around in any direction, I’ve just to get it under the stand, a pig of a job because the bike is on smaller diameter wheels than when it was a solo and so it’s not only a higher lift to get it onto the stand but the roll-on action only comes into effect once the rear wheel is around 2 inches clear of the ground, before that it’s a deadweight lift.

I’ve come up with a cunning plan to help with this.

I put a length of 2 x 4 timber on the ground behind the rear wheel with another length on top of it but stepped back so there were two 2 inch steps.

I then backed the bike back onto these and then I could lower the stand.

Unfortunately while there was enough height to lower the stand it wasn’t enough to slide the dolly under.

So it was a case of moving one of the 2 x 4’s to between the bike and sidecar, digging out the scissor jack from the sidecar boot and using that under the rear sidecar mount and at maximum lift I just managed to slide the dolly under the legs of the stand.

It’s now standing on the front wheel, the sidecar wheel and canted onto one leg of the stand but once the top brace fittings are removed it drops over onto both legs of the stand.

Both lower mounts have a drawbar to close the socket jaws onto the ball so it’s loosen this off, and then it’s twelve full turns to get the jaws wide enough to clear the balls before the chassis can be lifted away.

Well that’s assuming the jaws will open, one pair wouldn’t until given some “percussive maintenance” with a 2lb hammer!

Now, the aim of this job is to repaint the rear sub-frame so what’s in the way?.

First of these is the silencers, so off they come, they’re stainless steel, bought back in the late 1970’s and all they need is a clean and buff up, well worth the money they cost!.

Next off is the rear wheel.

When I took the rear wheel out I noticed that the tyre tread was down to just above the wear bars, so that means I’ll need a new rear tyre while I’m at it. This raises a neat point though.

The rear tyre is a 15 inch car type so it’s wear bars are set for car use, but the wear bars on a bike tyre are set lower, 1.6mm for a car but at only 1.0mm for a bike. I’ve no desire to try to argue the point with either the police or the insurance however so there’s a new tyre on the list now.

I’m going to go the whole hog here and remove the rear swinging fork as well, Think Big!.

To do this means splitting the shaft at the gearbox coupling, just undo the rubber boot and undo four twelve-point headed bolts and that’s done.

But first the rear mudguard has to come off , only hassle here is the electrical connections, I’ll look to improving these while I’m at it, while BMW themselves used a choccy block connector on the /2 models that this combo is based on, I’m going to change it to a multi-connector and tidy up the wiring.

Then you undo the suspension units, unscrew the pivot bolts and the whole thing lifts away.

All that’s left to do now is remove the seat and tank so they don’t get damaged and I’m ready to start stripping off what’s left of the old paint, a wire brush in the angle-grinder will make short work of that!