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Technical

The Cossack Owners Club offers technical advice that is in addition to that offered by the manufacturers, importers and the dealers.

We do not offer specific technical advice here, since a poorly executed modification can result in danger to the rider, the passengers and other road users. Advice is given to club members that includes advice on safety, but even so the user of the vehicle is always ultimately responsible for the safety of the vehicle being used. The Cossack Owners Club strives to ensure that any modification advised on will be safe and that the modifier is aware of the safety implications of the modifications and also any possible effect on new (or second hand) motorcycle warranty or increased wear on other parts.

We do offer a few ideas that may be useful advice on a varying amount of subjects.

Some might be new to you, but the tips are well used. I hope the some of you find them useful to help your servicing and riding pleasure.

The COC does not specifically support the fitment of lesser engines such as BMW, VW or Citroen, but may offer engineering advice to those in need. To ensure safety, the fitment of higher performance engines must be matched with an increase in performance of the brakes and tyres and also possibly other components such as forks and lights.

Cossack Owners Club Technical Advice

CLUTCHES

The holes in the floating plates elongated? - Results in excessive backlash in the transmission and rattles with clutch pulled in - drill 6 new holes of same diameter between the damaged holes. Use a good clutch plate as a template. Carefully clean up the new holes to give a good fit over the clutch pillars. This can be down many times before you run out of space!


GEARBOX OIL

Slow gear change? - Use 90 grade. This quietens the change and also quietens gear noise. Modern 'Light EP80' will absorb less power but will make slower changes. Do not use engine oil in the gear box; funnily enough it is designed for engines whereas gear oil is designed for gearboxes!


FINAL DRIVE (URALS)

Oil over brake shoes? - do not over fill. When it says 'level with the lower threads' make sure it is, and not nearly out of the top threads! There is a breather in the unit on the brake side, but it does depend on the seal and the retaining plate being assembled correctly to allow any expelled oil to run down the inside of the casing relatively out of harm's way.


With too much oil in the case then oil will be expelled from this breather, as the casing warms up then the air expands and forces any over-filled oil out, if filled to the correct level then only air should be expelled. If still a problem drill a breather hole in the filler nut and fit a short piece of copper brake pipe in it with a down turned end. (Dniepers already have a breather). Water ingress when fording deep rivers can be a problem through a breather - the cold water cools the casing; this cools the air that contracts thus pulling water into the case - tough! Military vehicles with deep water fording abilities have high mounted breathers for their transmission cases.


GENERATOR ALIGNMENT

Fed up of having to adjust the backlash every time you remove the generator? - mark the angular position of the generator with a permanent marker pen or scriber, before removing it. Align the marks on re-assembly.


GEAR CHANGING

Very crunched gear change is one less gear-change before the sliding rings and dog clutches wear out and drive is lost in that ratio and new parts are required £££££££££. Within reason, change up early and pause between coming out of the lower ratio and engaging the higher ratio - change down late and if time allows, slightly release the clutch between the ratios and blip the throttle to help synchronise the gear teeth speeds. (Dniepers - note that there is a second neutral notch on the cam plate between 3rd and 4th!, not on Urals). Problem caused by big clutch running at engine speed that needs to change speed at every gear ratio shift.


FUEL TAPS

Leaks through and out of them? - the tapered fuel taps do leak, but they can be adjusted to improve things. Often the levers are so loose that they rotate with vibration! Remove the nut and the lever. With a pair of needle nosed pliers (or make a special tool), screw the sunken 'nut' slightly further and reassemble. Do not over tighten of you will increase wear. Re-assemble, ensuring ON and RESERVE in same positions!


BRAKES

Worn or poor performing linings? - get professionally relined with Ferodo MZ41 material bonded on. This is the same material as used on classic cars such as Moggies that need all the braking they can get, it is high friction and high heat dissipation. The linings for Moggies are per-formed at 8inches, Ural and Dnieper brakes are 200mm = 7.87 inches which is close enough and use the same nominal liming thickness. Never try to rivet the linings yourself, if you do not know why not, then you must not do it! Badly riveted linings kill!


WHEEL BEARING ADJUSTMENT

Removed the locking ring with a 'C' spanner, but having difficulty in undoing the nut that preloads the bearings with the special tool? - Put the wheel back in the bike, before fully pushing home the axle, fit the special tool in between the dust disc and the offending nut. A little preload on the axle keeps the special tool in place, allowing the tool to be tapped around with a soft hammer with no chance of it coming out of the holes and causing damage! when loose, remove wheel and continue. 


MODIFYING CHROMED AIR INLET TUBES

Chromed air inlet tubes as fitted to the Dnieper MT9 and MT10-36 can be easily modified to fit the side-valve M72 and MT12 engines where the carbs sit closer to the crankcase. The length can be shortened and a new slot cut to refit the air restrictor lever. The standard rubber pipe or new ones cut from car water hoses can then be used to connect up.


WARPED CARBURETTOR FLANGES

These are the biggest source of air leaks causing weak mixture and poor running. Here is a method to get them flat cheaply (instead of paying £££ to get them machined), but it does leave many light scores that are not important, since sealing compound fills those. Strip the carb or stuff a cloth down the throat and tape a polythene bag over the complete carb leaving just the warped face exposed. Find a concrete paving slab; they are always pretty flat, certainly flat enough for our purposes. Wet the surface with water. Grip the carb in both hands, wear gloves to protect your knuckles. Press the carb flange onto the slab. Use a large 'figure of 8' motion to grind away the warpage. Check every few cycles for the effect. Adjust pressure to get a more even effect. Use on your work bench under surgical conditions if you do not want the neighbours to feel convinced you only deserve to run a Ural. I use this method, and others I have done it for are impressed with the results but never saw the method! PS wash the carb well afterwards!


SETTING UP YOUR OUTFIT

Set up your outfit on your concrete slab drive. Resist all temptations to have your oil stained concrete slabs replaced by nice red brick or tarmac. You can use the regular grid pattern of the slabs to set up the sidecar toe-in. Run the bike onto one of the line of joints, then place a 6 foot plank on bricks touching the sidecar tyre. You can then easily measure the toe in from the plank to any line in the slabs that is parallel to the line the bike is standing on.


RUBBER COUPLINGS

The rubber couplings on Urals and Dniepers on the swinging bikes have to absorb longitudinal motion of the rear chromed fork. On the original (BMW designed) plunger framed bikes, this coupling only acted as a pivot and shock absorber. The unwanted longitudinal motion of the rear forked coupling often punches its way through the rubber if the shaft cir-clip adjustment is incorrect. Lubricate the rubber with chain lube to minimise wear, it does not attack the rubber and does not get flung off.


UNLEADED PETROL

Modern unleaded petrol contains really nasty carcinogenic (causes cancer) substances like Benzine, that in laboratories has to be treated as a poison. Do not wash your hands in it, do not breath in the fumes, avoid washing dirt parts (of motorcycles!) in it - use proper hand cleaner and use a degreaser or paraffin to clean parts (paraffin is cheaper too). In the days long ago in the USA when petrol stations had forecourt attendants to fill up the customers' petrol tanks, many attendants developed skin cancer on their hands after the change from leaded fuel. (Remember the times when the petrol pump attendants in the old rural garages with slow pumps had to insist that the big American gas-guzzling 'yank tanks' had to turn their engines off whilst being filled, since the pumps could not keep up with the consumption at idle! - joke). Leaded Fuel.


Lead quantities put into the atmosphere from those of us who still use good old leaded fuel. (I am lucky that the garage in my village is one of the few that has the licence to sell leaded 4 Star.) All the vintage and classic car and motorcycle racing in one year only puts into the atmosphere the same amount of lead compounds as one flight of a light aircraft from London to Edinburgh running on high lead aviation fuel. The amount of lead shot that is shot over the land at living creatures in Europe by 'Sportsmen' was in 1996 was 30,000 tons - do not tell me that the use of trained hunting dogs is more environmentally friendly either!  


FITTING NON STANDARD CARBURETTORS 

Fitting carburettors from another motorcycle and getting the mixture correct through the whole range is a long difficult task. You will need a reliable method to measure mixture strength such as 'Color-Tune' or lots of experience of tuning carburettors successfully. Considering slide type carburettors - the mixture for the first 1/4 turn of the throttle is controlled by the idle jet size and air screw (screw air screw out to let in more air and weaken mixture), the mixture from about ? to 3/4 throttle is controlled by the needle position and profile (lower the needle to weaken mixture), the mixture from 3/4 to full is controlled by the main jet size.


The fuel level controlled by the float needle position affects the mixture differently at different throttle positions. The slide cutaway affects mainly low throttle openings. The little depression in the top of the needle jet contains the pool of fuel that is collected by the needle on sudden throttle opening to give enriched mixture on acceleration. All these effects are interrelated. So on a quiet weekend, try your hand and ear! just because a carburettor came off another 650cc twin does not mean it will able to be tuned to suit your Ural without jet and even needle modifications. Oh yes and also air cleaner and silencer condition will affect mixture at higher engine speeds irrespective of throttle opening! The matter of tuning the even more complicated constant depression or constant velocity carburettors can be in fact easier, although there are a whole different range of features that can be changed.


Do not rely on plug colour as an indication of mixture, it is a lot less reliable now that fuels contain no lead compounds and do you know if you have the right plug heat range before you start testing? This is not to say that you will not be able to get the engine running reasonably well, but poor fuel consumption, poor starting from hot or cold, hot running at speed, 'running on' after ignition turned off, holed pistons etc are all indications that more work is needed.


ALTERNATIVE BRAKE LINING MATERIAL FOR BRAKE SHOES

The drum brakes on the Soviet motorcycles do not tend to work as well as they should for their size. After you have done all the usual things to maximise their performance such as:

Lubricating the cables

Lubricating the pivots and cams

Ensuring all of brake shoe material is in contact with the drum

Skimming the drums to make sure they are round

Adjusting twin leading shoe brakes to ensure both shoes contact at the same time

Only then consider better brake lining material.

NB

The friction material suggested here is suitable for the motorcycles in question when used in the manner for which they were designed. If you intend to use the motorcycle at high speed, in competition, carrying or hauling loads higher than specified or for any other unusual purpose then for safety and product liability reasons you should either use the standard parts or take professional advice.
  

Any relining of brake shoes must be done by a professional shoe relining establishment to ensure that they are attached to give maximum safety and performance. The use of incorrect rivets and incorrect lining preparation will result in poor performance.
  

Do NOT chamfer the leading edge of the new lining. A sharp edge, particularly on a leading shoe, increases the performance of that shoe. A chamfered edge will stop the shoe grabbing.

Recommended lining material is Ferodo MZ41.


In the UK it is often used on cars such as the Morris Minor that have similar braking challenges. Lining material manufactured for 8 inch brake drums as on these cars will suit our brakes with a drum diameter of xxxmm.


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