Rebuilding a Ural 750 motor
Intro and background
I've always loved motorcycles.
Ever since I was a teenager I loved the sensation and emotional reaction of riding them. The feel of the wind, the rush from potential danger, and all the things associated with bikes.
Then the kids arrived.
Like any other new arrival, the birth of my daughter caused me to re-prioritize my life and interests. One of those was my motorcycling. Racing is out, and even opportunities for going out for long rides alone were few and far between.
However, I'd always thought that motorcycle sidecars were cool and I saw this as an opportunity to incorporate my new family into my interest. Just about everyone, from dogs to little kids all have a natural affinity for riding as "monkies" in the sidecar.
So I began researching and looking for a "rig" as motorcycles with attached sidecars are called. They aren't exactly common. I found the most interesting to be in the Ural, a Russian model of machines that have their nefarious origins prior to World War II. They are cool in a funky kind of way. Also pretty expensive. So it took a while before I found the right one, someone who happened to have the exact type I was looking for, a 2002 "Bavarian Classic" that looks like an old BMW.
Urals, being Russian, are not noted for their precision engineering. Its one the "charming" features of them. Some would call them crude. They have a tendency to vibrate excessively which destroys the gears and alternator. This one was exhibiting symptoms of one failing. So I went and got it even knowing it had a problem with its generator. Shortly there after, this happened:
Then Things Got a Little Odd
It got progressively louder and then silent as the abused timing gear (the chunks of gear wedged around the front timing compartment) finally failed, spreading fragments throughout the engine.
So, it meant an engine rebuild right off the bat.
Already a hanger queen...
Got the motor mostly torn down and so far pretty good. The cam shaft seemed to have survived the trauma, its still true. Boy those Russians can design it tough. Some of the bearing surfaces show minor scoring, more like streaking, but no gouges.
The alternator is toast however. The Russian alternator is so vulnerable to damage from the usually out-of-round generator gears (the root of the problem) and come apart so often that they are known as "grenades" amongst Ural owners. Notice the cracks all the way around the housing.
Many choose the low cost option of going to a "total-loss" electrical system, mounting a deep cycle battery to run the ignition and lighting system for several weeks and hundreds of miles. I did not like that option so decided to upgrade to what is currently used on new models, Japanese Denso alternators with an adapter fitting.
One re-builder's trick is to make sure you document with pictures and drawings of how things were assembled before you took them apart, and to put associated parts and fasteners into baggies and mark them with where they came from.
The Clutch flywheel can be difficult to remove from the end of the crankshaft. A gear puller and even heat may not be enough to get it to pull free. If not, most machine shops can do it for a nominal charge.
Once you have the clutch flywheel off, you can remove the rear seal/bearing plate and extract the crank. There is a trick to getting the crank out. You have to align the key slot at the 12 o'clock position and then start rotating the crank vertically, which folds the connecting rod arms in and the whole thing barely fits. Its quite remarkable to see and do.
Now that its all taken apart. You can begin to clean and prepare for the reassembly.
I used a 5 gallon steel tub filled with carburetor cleaning solvent as my cleaning tank, with a palm sander clamped to it to act as an improvised agitator, sorta- sonic cleaner. It helped remove some of the carbon build up but is not necessary.
You want to get it very clean, because besides looking better, you need to get all of the small metal fragments, grit, and other contaminants out of the parts before they go back together. Otherwise they can cause damage and lead you to have to do the whole thing over again.
You also need a nice place to work and to be able to lay out the parts where they won't be disturbed.
The Russian OEM gasket material is extremely stubborn, resistant to solvents, and hard to remove. You will need patience and elbow grease in equal measure to get it off. Most of the covers and mating surfaces can be sealed with high-temp RTV.
The only place you really need the paper gaskets are for the rear bearing plate, the oil pump, and the front breather seal. As a sealant/coating for the gaskets, I have found that a product called "Gasgacinch Gasket Sealer" available in most auto parts stores, and is much easier to clean up than the original "snot".
Once you have the crank replaced, which is the reverse of, and just as magical of a process as removal, you can start putting the rest of the components back together.
Above you can see the beautiful precision German made "Herzog" gears that replaced the old cast Russian gears. Also you can see the modern Denso alternator and its gear having the clearances or "lash" set with a dial gauge.
You don't actually need a dial gauge for this part. You can use a feeler gauge between meshing teeth to set the clearances. The alternator is mounted on an off-center boss, so that as you turn the alternator body on the crankcase it move away or closer to the big timing gear that turns it.
All in all a much better gear train than Urals came with until just recently.
Compared to other makes and types of vehicles, Urals are extremely simple and easy to work on. Almost fun.
Someone with even modest mechanical ability and tools (the original owners tool kit has almost everything needed for a complete rebuild), can handle it.
The Reason to Own a Sidecar
Some Useful Ural Links
- The Official Ural web site
New Models, Dealer locations, support, etc.
- The Soviet Steeds web forum
Where Ural owners can share info and cry into their Vodka about their balky machines.
- The MY URAL online Ural manual and mechnaical tutorial site.
Indispensable information and "how to" for the home Ural mechanic.