Service Department
SERVICE DEPARTMENT
JOHN DUNN
WHAT'S IT ALL MEAN?
I was wondering if you could run an article on some of the main technical terms you use in your road tests. There must be a large body of readers who have no idea what a solenoid is or what it can do in a motorcycle (or car), and not everyone I know has a very helpful understanding of an alternator and how it differs from a generator. Until recently, I confused the words sleeve and bushing. No wonder I tended to pass over the description of engines which used both words.
Ordinary dictionaries don't always help. Mine starts its definition of bushing by saying it is a term used in electricity, which I suppose it is; but this is misleading, as I know now.
Just now I looked up the word magneto and found that this is a form of generator too. Are all generators magnetos? Perhaps an alternator is a magneto too — a magneto generator which sometimes puts out alternating current? You can tell by my questions how much I am able to appreciate your tests.
If I were a publisher of a semi-technical magazine, trying to increase circulation, I would be concerned if I thought some readers bought the magazine only to be told what product to buy. The reader who subscribes year after year to CYCLE WORLD is likely to be a person who reads your tests and needs to decide for himself what motorcycle he wants on the basis of what it is put together with. The motorcyclist who is not taught to care whether or not a part of his machine is supported by "three rollers and one ball bearing" (a phrase used in one of your tests) is likely to be a faddist who next year will leave motorcycling for something newer. No motorcycle, no CYCLE WORLD.
So it is in your interest to get your readers technically involved. Even if you published à mere glossary, this might encourage people to dig for more information than a definition can supply.
Your 1967 ROAD TEST ANNUAL tests two four-stroke twins under 600cc, a BMW of 593cc and a Honda 160. Could you test some four-stroke twins besides Honda between 300 and 500cc?
Robert Gunther Fort Collins, Colo.
Within the medium of this column I cannot include a complete explanation of all the technical terms related to the motorcycle and its components. However, I will explain some of the terms mentioned by you and, at a later date, produce an article on the subject.
(Continued on page 28)
A solenoid switch is an electrically operated switching device. It can be used for operating a valve in a gas or water line from a remote position. On a car or motorcycle, a solenoid switch is most commonly used in the starter circuit. If a solenoid switch were not used, it would be necessary to run the heavy starter cable up to the starting button on the handlebar. This is not practical, due to the large diameter of the cable required and the high current that the cable has to carry when the starter is operated. In practice, a short, heavy cable is used between the battery and the starter. A switch with heavy contacts (capable of handling the heavy current) is placed in the cable between the battery and the starter. This switch is operated by a solenoid switch. The current required to operate the solenoid is low; therefore, a small diameter wire can be used between the switch and the starter button that is on the handlebar. The word solenoid actually means, a helical coil of wire, which when electric current is passed through it, a magnetic field is produced. Therefore, when the starter button is pressed, this makes an electrical circuit through the solenoid coil; this then produces a magnetic field that pulls the heavy starter contacts together, making a circuit via the heavy starter cable between the battery and the starter motor.
A generator is a device that generates (produces) electricity. Depending on the type of device used, the electric current produced will be either AC (alternating current) or DC (direct current). An alternator generates alternating current and a dynamo generates direct current. Therefore, they can both be referred to as generators. A battery can only be charged by a source of direct current. It is necessary to convert alternating current into direct current before it can be accepted and stored in a battery. In an AC generating system, a rectifier is used to convert the current to DC for battery charging and storage. A high-tension coil (ignition coil) can be used with DC current stored in a battery or will work just as well when supplied with an AC current. A magneto is in actual fact an AC generator (alternator) which is supplying an h-t coil directly. Sometimes the h-t coil is an integral part of the magneto; alternatively, the h-t coil can be mounted in a remote location.
I would conclude this reply by stating that we do our very best to increase the technical knowledge of our readers through the medium of this column and by the many technical articles published. It is up to the individual regarding how much knowledge he can accumulate. If you or any other reader is serious. I would suggest that you purchase the book "Motorcyle Engineering," by Phil Irving, from our technical publications department.
(Continued on page 30)
TOO MANY NEUTRALS
My 1966 Honda 450 has a problem that is fairly common to the 450, according to a local Honda mechanic. The only trouble is he doesn't know what is wrong, as he has never tried to cure it.
This is my problem. Sometimes, when upshifting from first to second, it goes clear through second into a neutral between second and third. Also, sometimes when downshifting from third to second it goes right through into neutral. I'm hoping you can tell me why my 450 doesn't shift as flawlessly as the one CYCLE WORLD tested.
Christopher Moore West Orange, N. J.
I do not know of any official Honda cure for the shifting problem being experienced. All modern transmissions, including the Honda 450, are equipped with a positive stop change mechanism. When a gear is engaged, the change lever always returns to its starting position, ready for another gear to be engaged. Actuating the change lever rotates the shift drum through a certain number of degrees, which, in turn, moves the selector forks, the forks moving the gears to select the chosen gear. When the gear has been selected, the shift drum is held in position by means of a spring-loaded plunger (shift drum stop) which locates in the appropriate camplate notch. The camplate is attached to the end of the shift drum.
I have heard that several Honda 450 motorcycles suffer from a similar complaint to that described by you. It is my opinion that when the shift drum is rotated, it continues to turn further than intended due to its inertia. A stronger camplate plunger spring may provide the answer. To gain access to this spring it will be necessary to remove the right hand crank case cover and the clutch.
COMPRESSION RATIO
I am replacing the pistons (.020 oversize) in my Har ley FL 74. The pistons 1 have are 8-1/2:1 compression ratio and I am considering using two cylinder head gaskets on each cylinder (probably copper gaskets) in order to lower the compression ratio a little. Would you consider this good practice, and about how much could 1 expect this to lower the compression ratio?
Bill Lindsey Nogales, Ariz.
It is not good practice to employ two cylinder head gaskets, as this may promote a head leakage problem and also cause the cylinder head to distort. A compression ratio of 8.5:1 is not too high, even for street use. If you use a medium or premium grade of fuel, there will be no problem. However, if you still wish to decrease the compression ratio, this can be best achieved by placing a shim under the cylinder barrels. I could not tell you how much the compression ratio would be low(Continued on page 32)
ered without knowing the thickness of the head gaskets. It would be best that you assemble the engine with one gasket (only one cylinder would do fine), bring the piston to TDC on the firing stroke and then check the combustion chamber volume by pouring liquid from a calibrated jar into the combustion chamber through the spark plug hole.
Calculate the compression ratio by adding the combustion chamber volume to the swept volume of one cylinder, then divide the total by the combustion chamber volume. Example: Combustion chamber volume (80cc) plus swept volume (628cc), divided by chamber volume (80cc), equals the compression ratio (8.5). Adding a shim under the cylinder barrel will increase the chamber volume by 0.153 cubic centimeters for every 0.001 inch of the shim thickness. So, if you desired to lower the compression ratio to 7.5:1, it would be necessary to employ a shim 0.085 inch thick.
HI-OCTANE IN AN ANTIQUE
I am restoring a 1931 600cc ohc Ariel Square Four. Things are going smoothly, but I am bothered by one crucial question: What will the higher octane gas used today do to an engine built for use 35 years ago? Will this affect the heat range of the plug? (The manual recommends Lodge HI for high speed travel and I found a champion R-l when I disassembled.) And will there be need to raise the compression ratio to compensate for the higher octane? What plug would you suggest for this machine (which will see limited service as a transportation vehicle), and should the original 5.8:1 be raised, and how?
J. Updegraff Mountain View, Calif.
Considering the intended use, "limited service as a transportation vehicle," I would suggest that you retain the original low compression ratio. A regular grade of fuel will do very nicely. Use any of the following spark plugs to start with: KLG M60, Lodge HI, Bosch M 175 T 1, or Champion 13,6. If your choice of these tends to run on the hot side, choose one of the following: KLG M80, Lodge H3, Auto-Lite BT4, Bosch M 225 T 1, or Champion H-17 A.
SCREECH-HAWK
1 have a 1965 Honda 305 Superliawk and have just run into my first big problem with it. 1 was riding it one day when a loud screech came out of the right side of the engine and it cut off dead. 1 know it wasn't piston seizure, because the crank will still rotate, even though it does take a big kick. I had a Honda mechanic look at it and he said it was probably the bearing on the right side of the crankshaft and that just the bearing couldn't be replaced, but that the whole crankshaft would have to be. Is this a fact?
Martin Kelly
Columbus, Ohio
It would be difficult for anyone to diagnose the cause of the failure without visual inspection after dismantling the engine. From your comments, I would not rule out piston seizure. It is possible for the engine to completely lock up at the time when seizure occurs, then free or partially free off when the engine has cooled down.
It is unlikely that a ball or roller bearing with a steel cage would seize, even under conditions of complete failure. Bearings employing aluminum cages will quite often seize at the time of failure. Usually complete failure of a bearing with an aluminum cage will result in a permanently seized condition.
The big end and inner main bearings have aluminum cages on the Honda Super Hawk. To replace any of these it is necessary to dismantle the crankshaft; however, it may prove more economical to replace the complete crankshaft assembly. Many motorcycle repair shops do not have the necessary equipment required to rework and true crankshafts.
Only when the engine has been completely dismantled will you know the complete state of affairs.
DEER JOHN
1 am a 200 pound, 50-year-old school teacher who rode cycles 25 years ago and just started again when I found I needed a trail bike while deer hunting.
(Continued on page 34)
/ purchased a Honda Trail 90, 1966, 7 hp. I found it wouldn't climb as steeply as my pickup Ford. In fact, I had to push with my feet not unlike the first bicycle!
1 took off the big sprocket, 68 teeth, and found it would only make 35 mph on a level paved road, 7,000 feet altitude. After the 500 mile checkup, it would do 40. I have two questions:
First, I have heard one can get kits to give more power to Honda 90s, a stroker kit and/or a big bore kit. I don't know what a stroker kit is. Would these be a satisfactory answer?
Someone suggested putting on an 80tooth rear sprocket. This would be the cheapest alteration, and though 1 hate to cut down the road speed, I primarily bought it to climb and it won't. Just how much steeper would it climb?
Second, perhaps simply going to a more powerful trail bike of a different brand would be as cheap, but wouldn't the bike itself then be too heavy to hoist over logs in the trail, etc., and too big for tight corners? I suppose you'll go livid at the question, but could you please tell me the name and model of a trail bike that will carry fat me and a deer behind, up a good grade?
Being a teacher, with several gluttonous kids, I can't afford to keep trying different bikes!
Ronald Coke Los Alamos, N. M.
No matter what motorcycle you have, there will be approximately 25 percent decrease in performance when operating at an altitude of 7,000 feet, due to the lower barometric pressure and air density. It is therefore necessary to be certain that your engine is in first class condition and capable of working at its maximum efficiency under normal atmospheric conditions, before attempting to make performance comparisons and return for the higher altitude. The decrease in engine output is almost entirely due to the decreased quantity of air in the cylinder, which automatically lowers the compression pressure and reduces the amount of available oxygen, the latter being one of the important ingredients required to produce high combustion temperatures and pressures, which then result in high engine output.
All things being equal (ambient temperature, humidity), it will be necessary to rejet the carburetor to provide fuel in the correct ratio to the quantity of air being inhaled. An indication of carburetion can be obtained by making a plug check at the altitude in question.
It is possible to employ a much higher compression ratio at high altitudes, thereby regaining the loss in compression and combustion pressures. However, if the same (increased) ratio were employed at sea level, engine damage would almost certainly occur due to pre-ignition, and worse still, detonation.
Boring and stroking are both methods used for increasing the displacement (swept volume) of the engine. Bore (piston area) multiplied by stroke equals the cylinder displacement. The usual method employed to increase the stroke is to use a stepped crankpin. To have this work carried out it is necessary to dismantle the engine, remove the crankshaft assembly and forward it to a company specializing in this kind of work. Boring is the simplest way of increasing the displacement, providing that it is not carried too far, the limit being determined by the cylinder wall thickness.
The larger rear wheel sprocket (80 teeth) will provide more torque at the rear wheel, naturally improving the climbing ability of the machine.
If I were in your shoes, Ron, I would be inclined to keep the CT 200 and carry out the following modifications:
1. Increase the displacement by employing a "big-bore" kit.
2. Increase the compression ratio to 10:1.
3. Check the mechanical condition of the engine and have a valve job carried out.
4. Retain the 68-tooth sprocket, employing the 80 tooth if absolutely necessary.
If this work is carefully carried out I am sure that the machine will do all that you require. M
