Third Bike

 I wasn't looking for a third bike but a 1985 K75C was on sale locally in rural New South Wales so I went and had a look. It had only 48,000km on the clock, was in good original condition and at a good price, so I purchased it. I'm currently working through a series of maintenance jobs like replacing the coolant and brake lines: the bike is unfamiliar after nearly 40 years maintaining airheads but some things are the same. 

There's an interesting piece on the K75 by FortNine, he describes the engine as being easily capable of doign a million miles. Also, there were a couple of episodes of the Airhead 247 podcast devoted to the K75, it's available on Soundcloud, also apple and spotify. 

Starter Motor

 On a ride recently my bike started unreliably: there was a "click" from under the tank but no life from the starter motor. In each case I was able to get the bike started after a few attempts and moving it around a bit. I wasn't sure if the problem was the relay or motor itself, but neither has been serviced, ever, so I figured I'd replace both.

I purchased an Arrowhead starter for AUD219. This was less than twice the cost of overhaul parts for the original BOSCH starter. 

Shiny new Arrowhead starter installed.

Replacement was straightforward except for a couple of points. 

• There are two hex head bolts holding the starter in place. The one on the left side of the bike could be turned using a ring spanner, but the housing wouldn't allow this on the right. I had a socket that fitted, but to get access for this I needed to remove the airbox and battery, which was a nuisance. When reassembling it I used an allen key bolt, so this should be avoided next time. 
• There is a bracket on the leading edge of the starter under the timing chain cover. It has 3 bolts, two on the starter and one on the engine. One of the bolts on the starter is impossible to get off while the starter is in place, but the lower bolt, screwing the bracket to the engine, can be accessed using a 10mm socket from the front. 
• The relay I purchased had 4 connections and is appropriate for other functions on airheads, but not necessary on my bike. The correct relay has 5 connections. 
• Care needs to be taken removing the relay with a screwdriver because one of the connections is always live, and so can spark. 
• The crankcase breather hose was perished, clearly visible in the pic, and was replaced. 

LHS Spanner Access

After this was done with the original starter relay in place the bike didn't start, so I swapped in the relay from the other bike and it started sweetly, no problems. So, the problem from the beginning was the relay, not the starter itself. 

Shiny new Arrowhead starter installed.

Second Bike

 In September 2019 I purchased a second R65LS, broadly identical to the first: both red, both with Brembo brakes, both with stainless exhausts, but 1984 rather than 1983 and only 135,000km on the clock. It looked like a good deal, purchased from the mechanic who had maintained it for the last 20 years. It arrived on the back of a truck looking as good as it had in the pictures. 1983 on left, 1984 on right. 

When I went to get it registered the problems started, and they have only recently been properly ironed out. 

First problem was that it wouldn't rev above 4,000 rpm. There were lots of little problems with the carbs, each time I'd reassemble them and hope that the latest minor fix had resolved the problem, but eventually I did a full rebuild. It turned out that the seller's idea of "recently rebuilt carburettors" didn't involve replacing all the O rings or cleaning the main jet holder. Weirdly they had assembled one of the diaphragms rotated: it's surprising that the bike could be tuned at all. 

The image shows that the piston is rotated (the diaphragm is located correctly in the carb body, the problem is that it has been fitted to the piston rotated). 

Riding on the freeway a vibration was setup that suggested a failing wheel bearing, but when I pulled off the road the rear brake came on and locked in place. I'd noticed that the gearshift was in unusually good condition for such an old bike, it had been replaced and somehow part of the original had fallen into the housing of the rear brake pedal, jamming it on. 

Always find the bit you drop!

The engine note changed and then the exhaust flange nut on the LHS cylinder came loose: it had been held on only by one thread and a stack of grease. This was sleeved and rethreaded by an engineer. 

The pin put through the sleeve to the cylinder head is just visible. 

The carburettors were now running but difficult to balance. I had some holes in the header pipes welded over to fix this. 

Keeping two identical bikes is a bit odd, but there are lots of advantages. Obviously I can ride one while the other is off the road for maintenance. And I can swap components to troubleshoot. I have little experience maintaining bikes apart from airhead BMWs, and all my skills are easily transferred between the two LSs. 

I'm now to the point I expected to be a month after the purchase: two bikes, either of which I'd trust to go riding. 

Variations

BMW manufactured the R65LS from 1982 to 1984 in two colours, henna red and polaris silver, and two delivery markets, UK and US. There were a plethora of variations on these two themes some of which suggest that the bikes were completed from a spare parts bin.

Dashboard. Some bikes have "TURN" stamped in the centre of the green dashboard indicator lamps.

Decals. Usually the red bikes had a black and white decal and the silver bikes a blue decal. However, some red bikes had blue decals.

First Aid Kit The first aid kit was optional, but where fitted there was a red sticker on the LHS side cover indicating that it was under the seat. 

Fork Gaiters. The 1982 bikes had no gaiters. Subsequent bikes had a 14 rib gaiter. The current spare parts pairs a bulky 11 rib gaiter to this model, but the original is still listed for the R65GS and similar bikes. 

Front brake callipers. Most bikes had Brembo callipers, but some had ATE. Both had 36mm pistons. 

Front brake master cylinder.  The shop manual lists both 15mm and 16mm diameter. Both my bikes have 15mm. 

Fuel Tap. Most bikes have the delivery horizontal, but some bikes have the delivery straight down. I think that the latter fuel tap type is suited to tanks with a tap on both sides.

Ignition. US delivery bikes had the headlight always on, so the ignition had only 3 places not 5 as on other models. They also had a headlight relay setup so that the headlight would extinguish when the starter was being used, other bikes having no headlight relay.

Kick Starter. Some bikes had a kick starter. It seems that this was offered as an option on new bikes. 

Hazard lights. Some bikes had a hazard light switch in the centre of the dash.

Secondary Air System. Some US delivery bikes had hardware that reduced pollution by providing fresh air to the exhaust manifold. This system included a pipe from the airbox to the cylinder head, hoses from the vacuum port at the front of the carburettor to the airbox, and some valves inside the airbox.

Sidecovers. Most bikes have black side covers, but some are painted to match the tank colour.

Speedo. (Obviously) Kilometres for Europe and Australia, miles for UK and US.

Tappet Covers. Mostly unpainted (silver) but some bikes have black.

Wheels. These were painted white on red 1982 bikes and silver afterwards. All silver bikes had silver wheels. 

Do you know of any other variations?

Brake Lines

In March 2019 I replaced the original brake lines with Venhill braided lines from Motobins.

The original rubber lines were overdue for replacement. There were some irregularities (bumps) on the outside of the lines, and one of them released a bit of fluid when it was flexed.

Brake fluid on top one after flexing. Not also slight bulge in rubber casing. 

New, shiny lines. 

Needless to say the braking ability of the bike was substantially improved after this. 

Shorting Adaptor

The carburettors can be balanced by either using vacuum gauges or by alternately disabling one of the cylinders and tuning/adjusting the other. I did this for years by swapping the standard spark plug leads for car leads with exposed contacts. I could then disable a cylinder using a screwdriver to short the exposed metal around the plug to the cooling fins.

There are various shorting adaptors available on the internet for purchase, but I found that I could make one using a metal drawer handle. The standard threaded screw used for attaching these is roughly the same diameter and pitch as the thread at the top of spark plugs.

This is the drawer handle with a plug screwed in instead of the normal mounting screw.

With the posts unscrewed from the handle. The screw through the middle has had its head cut off.

Installed on the bike. The exposed metal allows shorting to the cooling fins.

16 January 2024: An update on this: I realised eventually that the thread is the standard M4, so some long nuts and bolts and couplers are all that is necessary:

Works BMW Flat Twin

The book Classic Motorcycle Engines has a chapter on the 1955 works BMW flat twin. I've uploaded it to:

https://drive.google.com/open?id=1gLaaD_xzHFQNXzSrnkPifBdrWnM_IWkg

The book was published 1986 and had detailed technical descriptions with historical context on 20 outstanding engines. In the case of the BMW chapter the engine under discussion dates from 1954, so the drawing and original discussion 1955, and the historical discussion dates 1980s. 

The technical description of the engines is incredibly dense, packing an almost unbelievable amount of information into each paragraph. I dipped into it tonight and I'm sure there was information that wasn't there yesterday. However, if you don't read it attentively you might miss things like the reference to the 500cc flat twin with desmodromic valve gear, unfortunately abandoned because of lack of funds. 

Full citation is "Classic Motor Cycle Engines: a new perspective on 20 outstanding designs", Vic Willoughby, 1986, Motor Racing Publications Ltd, Great Britain. 

Enjoy!