In order to enhance the possibility of any logic or enlightenment shining through in the test of our Mk VIII 360 Pursang it would first be helpful to recognize two postulates. Namely: the Bultaco Ms. VIII 360 Pursang could be the quickest production 500 class machine currently available, and there may be a half-dozen riders in our whole wide country who can make full use of any 500 class machine. With that in mind we may assume that a 500 class machine might be judged, to some extent by how easily its potential may be tapped and then how it lends itself to teaching the rider to use more and more of that potential
Those are two distinct categories also. Example: it will be easier for a Novice rider to climb on a 400 Maico or CZ and go fast than on the Pursang……First time. But the Bultaco may end up teaching a Novice more in the long run.
Why? VIII Mk’s of evolution have caused the Pursang to become a highly refined machine. Naturally, is it becomes more and more polished, its purposes become more closely defined.
Power and handling are wade to compliment each other and to point towards a single purpose: quickness. If you follow the European/Ross Darnell school of motocross logic, you know that speed is not necessarily quickness. But quickness is definitely called winning.
Over the past three years the Pursang manners have been narrowed and pointed with startling single-mindedness towards quickness.
Not long ago the 500 class Bultaco was actually a 326 which caked and squeezed out more than competitive horsepower. It was fast a little pipey and id ]cast loved to be kept at full-song. You rode one with the throttle and an amazingly predictable skidding rear end. No mistake. it was fun to ride and for the very quick a more than pleasing mount. Today the 500 class Pursang displaces 363cc and uses them very differently. It is a torquey motor, producing as much, if not more instantaneous acceleration than any 500 class machine. You can wind it up or shift it early and it will get there in about the same short period of time. To have both torque and speed is becoming the advantage of Spanish machinery.
Though the frame is not significantly different, the handling changes a disproportionate amount due to the new motor characteristics and the L.T.R. suspension. The Pursang has become a bike that works by weight transfer. Stand on the front wheel coming into corners with 8 inches of excellent Betor fork and ride out on the rear with 6 1/2 inches of rear wheel travel. The front wheel almost knifes through corners. The bike is on and off berms in an instant. It has become quick in preference to just fast and that’s what’s happening.
If you want to learn to be quick or if you already are and want a fine compliment to your skills, then Mk. VIII is neatly designed to fit your needs. Extensive rear wheel travel evolution has accentuated the Pursang’s insistence upon quick and precise turning. Unlike a Maico or CZ, the Bul is reluctant to bend slowly and smoothly into a turn. Squaring corners is much easier and is a more effective use of the machine’s capabilities.
Because a well-squared corner happens much more quickly than a rounded off one, more precision is required of the rider. Each little motion that comprises the turning of a motorcycle must happen a bit more quickly and accurately. It may make you feel like a humbling font for awhile, but when you refine your reactions you and the motorcycle will be graced with great quickness.
Such is the mystique of a Bultaco. You learn what the motorcycle requires, teach yourself to provide it and you get a harmonious team. It’s a little like having a very competent teacher with you at all times reminding you of your mistakes. Frustrating at first, but ultimately rewarding. The Mk. VIII is a demanding teacher.
You must learn to use the brakes, especially the front brake. Approach to a corner is critical to get the most of the turning capabilities you must load the front wheel heavily with the front brake. Without that load, turning will be uncertain and the front wheel may wash out.
You must learn to load the outside peg and cut the corner cleanly with a single movement of the bars. At first it may be difficult to learn that turning is actually easier than you may think not so much yanking and tugging is actually necessary. In time the right amount will seem natural.
You must learn to make a decisive move to power-on and accomplish a smooth transfer of weight to the rear wheel. When you do, the torque of the 360 motor will combine with the L.T.R. to drive you off a corner more quickly than any. The Pursang’s power is both hard and controllable at the same time. It is very predictable but incredibly strong. Simply because the motor drives so hard from low revs it tends to beat most any 500 class machine from one corner to the next. It may not have more actual power, but it is quicker.
Your throttle control will improve because the 360 responds immediately and significantly to any right hand movement. Just a little twitch in the air will set up the bike’s attitude for landing. If you indiscriminately crack the throttle you can wheelie over backwards in a hurry. The 360 Pursang is a sure cure for sloppiness.
If you do learn to get along with the Mk. VIII’s attitudes about motocross – spend some time riding it and thinking about what is happening you’ll end up finding most other bikes very easy to ride, but maybe just a bit unresponsive. It’s the reason you find Bultaco freaks, they’re spoiled for others.
Likewise, a few years ago Bultaco gained an ill-deserved reputation for lack of reliability because too many people didn’t understand the concepts on which the motorcycle was constructed. No Bultaco owner will tell you that you can ride a Bultaco and ignore it. Maintenance is part of the responsibility of having it around. You must learn which parts to keep an eye on, what to clean and how to adjust. Once well attuned there should be no surprises and consequently few DNF’s.
A few things about the Mk. VIII that we figured out while it was around or stole from other Bul owners:
WHEELS: Ridgeless Akronts seem to vary in hardness but should last indefinitely if they aren’t beaten with rocks.
Some of the extra-hard ones will crack rather than bend so keep an open eye. Spokes are very strong, suitable for re-use if you change to a Sun or DID rim. The narrow Akront works well with a 3.00 front tire (shapes the tread well) but doesn’t make full use of a 3.50,
Keep the inside of your hubs clean (i.e., inspect them after each muddy race or every other dusty one) and sand off any high spots that appear on the shoes. Maintain them thusly and you will have some of the best brakes around. Don’t over grease the wheel bearings as it can seep into the hub.Wheel bearing grease lasts quite some time.
Of course. keep your spokes tight, our test bike didn’t tend to loosen much at all. Some seem to more than others, probably due to rim hardness variation.
SUSPENSION: After a half-dozen or so races the fork springs will begin to sack. They should be replaced with S&W 20-pound/18-inch items. If you attempt to use more than about 15 weight fork oil without modifying the damping rods. your forks will hydraulic lock. 160cc of Bel-Ray 10 and 60cc of Bel-Ray 20 mixed together works well for 150- to 180-pound persons. Standard fork seats will go well as long as you don’t over-fill the forks.
New forks also have the caps described in the Betor fork article in June DR. Nevertheless, you may experience some oil blowing out the top. Keep the inside of the cap nuts clean and squirt a little WD40 in occasionally and they should work fine.
Telesco shocks will work okay for maybe a half-dozen races, but you will probably like them better with 120 pound springs rather than the 130s they come with, Eventually they will lose damping and repairing them will be frustrating. They are just a bit too fragile and have too little capacity for the highly stressed L.T.R. Most important: be sure that the nut that locks the top eye to the shaft stays tight if it comes loose you may find yourself with one shock at some inopportune time. If you tighten it too tight you can strip the threads. All the pieces in the Telescos are touchy enough that we recommend that you use them til they go away and then discard them. As of this writing, the only shocks we’ve used that work with consistency are Works Performance shocks described in DR Recommends.
FRAME: We are aware of no frame problems other than potential swingarm bending if a shock seizes or some similar calamity. Still, an additional gusset along the inside shock mount wouldn’t hurt just in case a shock does take a break.
In the Frontera article this month you can find info on a chain tensioner set-up which helps solve the problem of necessary chain slack for L.T.R. Without a tensioner, adjust your chain so that if pulled tight from the bottom it reaches to about 11/2 inches from the swingarm.
Steering head bearings are tapered rollers which hold grease extremely well and don’t let the steering head get loose. Little problem there.
MOTOR: The newest 360 revs a bit higher than the ’74s by using a shorter expansion chamber but still remains easily within the crankshaft’s rev tolerance. The Astro revs to 10,500 rpm on the same crank with reasonable reliability. A problem of yore seemingly gone.
Biggest motor maintenance item will be the clutch springs. Initially, they should be adjusted 21/2 turns out from coil bind, but after a few months they will begin to sack, They may be adjusted in to just before coil bind to reinforce engagement but then will have to be replaced.
In order to adjust the clutch correctly all the plates must be running parallel. Just because the screws are adjusted out the same amount does not mean that the plates are parallel. Pull the clutch in slightly (so all the plates rotate but skid against each other) and spin the motor with the kick starter. Adjust the screws so there is no wobble. Then adjust free play with the nut and screw on the end of the clutch (accessible through the nylon plug in the clutch case). Adjust to the point of tension and then back off just a lad. If you remove the clutch plates, be sure to put the drive plates in so they say TJ and the driven with sharp edge in. Now your clutch should work fine.
Replace the Dural shift lever with a steel one which can be fashioned from an old brake arm (same splines). The aluminium one flexes way too much. Or, you can go back to right side shifting by flopping the rear wheel and welding on a tab for a backing plate brace. Old brake and shift levers will[ bolt on to the newest frames. If you still have any shifting problems make sure the shift drum detent spring hasn’t gotten sleepy. That’s accessible through a plug in the back of the case. (0h, those Spanish springs!)
Bel-Ray Racing gear oil works well in the transmission but Bel-Ray primary oil is so slippery it seems to help the clutch slip. We mixed 150cc BelRay 30 and 150cc of premium 1OW30 motor oil. Works nicely.
Replace your pipe mounting springs every couple of races since the heat tends to take away their temper. Also, it’s a good idea to reinforce both the bottom and rear pipe mounts. If you don’t crash they will be fine, but if you do they may begin to stress-crack.
Only top-end problem we have experienced from running Bel-Ray MC-1 too rich (50:1). The rings got gummy from over-lubrication. 60:1 is the latest Bel-Ray official recommendation and we have been running that way for a month now with noticeable power improvement.
Make sure the top motor brace stays tight Extremely important!
Jet your square body Amal carefully as they seem to vary in their demands from bike to bike, altitude to altitude and climate to climate. Stock is close. Watch the rubber flange that mounts the carb to the manifold as they sometimes crack. Treatment with Armor-All seems to keep them healthy. Either a Champion N2G or Bosch Z60 1 seem to work well in the plug hole. Timing can be anywhere from about 2.6 to 3.0mm BTDC. At 3.0 jetting begins to become more critical.
TIRES: The 3.00×21 Pirelli seems to work poorly tinder a wide variety of conditions. We haven’t been able to find a condition yet where it does work. Replace it right away. The 4.50 rear Pirelli works okay in the mud, but not particularly well anywhere else. It’s probably worth wearing out. Oh, be sure to Loctite your rim screws on the left side of the bike or rotation will work them loose.
What you find out when you start doing these things to a Bul is that with a few exceptions, it is incredibly easy to work on. The pipe is a bit of a bitch to get off and the seat is miserable. Fortunately, there’s no reason to remove the seat. Now the pipe…. Anyway, after you get used to the things that have to be done you’ll find it easy and not time consuming.
But you better do them. If you do, you’ll have the confidence of knowing that your bike will perform well and finish. If you ignore it, your BuI will tend to get “old” fairly quickly. Even if you do screw-up, Bultaco will cover it for 60 days, parts and labor.
All of which is part of being an extremely competent, precise and demanding motocross machine. If you make contributions to its well-being and work studiously with it, you’ll find none better.
|Compression ratio .||10.5 1 (uncorrected)|
|Carburation||36mm square AMAL|
|Gear ratios (1)||2.66; l.95; 1.49; 1.22; 1.00|
|Primary drive||Double row chain, 2 375 1|
|Final drive||13146 (3.54)|
|Lubrication||Bel-Ray MCA 56:1|
|Warranty||60 days parts and labor|
|Wheelbase||54.5 – 56.0 inches|
|Ground clearance||9.0 inches|
|Peg height||14.0 inches|
|Seat height||34.5 inches|
|Running weight||208 pounds|
|Weight distribution||45.4% front/54.6% rear|
|Fuel capacity||1.8 gallons|
|Transmission capacity||2 pints|
|Throttle turn||80 degrees|
|Handlebar width||34.0 inches|
|Ignition timing||3.0mm B=|
|Forks||8.0 inch Baton|
|Shocks||6.5 inch RWT Telesco|
|Frame||Single downtube chrome molybdenum|
|Pegs||Folding, spring loaded, steel serrated|
|Hubs||Conical spray metal|
|Tires||Pirelli Motocross 3.00×21/4.50×18|
|Brakes||SLS cable front, rod rear|
|Sparking plug .||Bosch WM 260T|
|Number plates||3 plastic|
|Kill switch||Button left bar|
|Muffler||Not bad, not good, no arrester|