The Service Department
THE SERVICE DEPARTMENT
GARY BRAY
DUAL CARB DREAM
I own a Honda Dream 305 and would like to know if there is some way to put a new Honda Super Hawk cylinder block on to give me a dual carb setup. if so, how much of a difference would it make? Also if I put in Super Hawk pistons and Triumph Tiger Cub valve springs would it greatly improve my performance at the drag strip quarter-mile run? What modi fications would you recommend for this type of racing?
Sam Jones Co/urn bus, Miss.
The Super Hawk cylinder head will bolt on the 305 Dream without any problem. Make sure that all oil passages in the head and cylinder line up properly, both feed and drains, as not all heads are drilled in the same places. The Super Hawk pistons will also fit without problems. Webco Inc., sells special valve spring kits, and cams that will give very good results. Of course there are 350cc kits (Webco & Precision Machine) that also help. The amount of money you can spend on your machine
will tell you how much you can do, as the list of speed accessories for the Honda 305 is almost endless.
SAY, UNCLE
Could you tell me what harm will come to a Yamaha Omaha Trailmaster 80cc with a YDS-2 spark plug in. The plug be came fouled and all we had were a couple of plugs in the YDS-2. I say get a proper plug, my uncle says it won't hurt. Also, my cousin has an identical trail bike only it is a year newer. Both have about tile same miles on, but his has a coil up where the ignition key is and has more pep. Il/hat gives?
Steven Bukosky Milwaukee, Wisc.
Both the YDS-2 and the 80 Trailmaster use NGK B7HZ (or equivalent) spark plugs; therefore interchanging would not hurt in the least. It is always a good idea to have the proper spark plug, which you should be able to get at your nearest Yamaha dealer. It would also be a wise investment to buy an extra spark plug to keep with the machine along with a plug wrench in case you should have this problem when you’re away from home.
The reason for the change in coil location is that there had been some trouble in the past with the plastic coating on the secondary coil cracking because of overheating. This was remedied by taking the secondary coil out of the magneto and mounting it on the frame where the passing air would keep it cool. Other than coil location your engine and your cousin’s are the same. If both are in good condition mechanically and in good tune, there shouldn’t be too much difference in performance. But bear in mind it would be very unusual for any two machines to be identical in every way.
(Continued on page 32)
RATTLE, KNOCK, CLICK
I have what may be a unique Honda as far as mechanical difficulty is concerned. Case in point, there is a distinct “rattling” coming from the left side of my CA-95 (150cc) engine, a “knock” which occurs only at a slow idle (600 rpm). This manifestation is defectible with clutch in or out, at a stop or moving 600-1000 rpm, and it even “clicks” when the engine is off and 1 turn it over manually.
To add to the complexity of the situation, on some days only the faintest trace is audible and on others it is extreme, and for no apparent reason (temperature, oil level, method of starting — kick or electric) and to compound the paradox the bike leaks oil from the transmission area during the time of the noise and not a drop when the engine is running smooth. Now you can imagine the looks I get when I tell the boys at Honda of my distress. Oh, and one more thing 1 almost forgot. When at idle during times of the disturbance, if 1 tip the machine 45° to the left the noise vanishes temporarily (along with normal cam-chain whine), but soon returns. Please help me, none of my four neighborhood shops will touch it for under $75.00, and that’s minimum for exploratory work only!!! Have you ever heard of anything like it before, please let me know.
Geoff Giles Bloom field, Mich.
Your problem isn’t as unique as you may think. This is quite common with the CA-95, when they are subjected to prolonged high speed. When the engine gets very hot the pistons do not get the proper amount of oil, which causes the piston skirt to collapse slightly. This causes a very distinct rattling sound; usually the problem starts to occur on the left side. The cure is to have the cylinders bored out to the next oversize and fit new pistons.
IT’S POSSIBLE, BUT . . .
From what I’ve heard it’s possible to bore out a Honda 55 to take a Honda 125cc piston. Is this true? If so could you tell me what the part number is and the size of the piston, and the closest place to buy one. Thank you.
Malcolm McDonald
Kodiak, Alaska
It is possible to install a 125 piston in the Honda 55, but it certainly isn’t recommended as it makes the engine extremely unreliable. The fact that Honda designed a completely new engine, rather than boring the old one when they wanted something bigger, shows their feelings on this matter are the same as ours. But all the required parts are available through your nearest Honda dealer.
(Continued on page 34)
TUNED EXHAUST
Do you know offhand the dimensions for a tuned exhaust expansion chamber for the Yamaha YDS-2? 1 don’t want it tuned for out and out competition, but rather a combination tune for both high speed scrambles and road work where the engine is usually turning about 7,000-8,000 rpm. Any information you can give me would be greatly appreciated.
Nelson Stoll
San Francisco, Calif.
Tuned pipes for the Yamaha Ascot Scrambler are available through any Yamaha dealer, or if you prefer to build your own from scratch, the article by Gordon Jennings (CW, Nov. ’64) will be very helpful. But bear in mind that expansion chambers are for racing and not intended for street use. They work hand in hand with other parts (heads, barrels, etc.) to give maximum performance and work best where used as a combination. Then there's the noise problem. When you mention road work, I assume you mean street riding, and a Yamaha with tuned pipes turning 8,000 rpm down Grant Avenue would be about as inconspicuous as Lady Godiva on a giraffe. The only solution is to buy or make a set of tuned pipes for scrambling and use the standard exhaust system for the street.
NUTS AND BOLTS
1 was talking to a man who owns an English sports car the other day and he told me that his MG-A was built with nuts and bolts that would fit American wrenches. Is this true?
My BSA motorcycle has Whitworth nuts and bolts, of course. Does it seem likely that the English will ever export motorcycles to the U.S. with American Standard size nuts and bolts? The Japanese D at sun
cars and trucks have most of their hardware conform to the American Standard sizes (nuts, bolts, threads, grease fittings, etc.).
The fact that everything on the English motorcycles is a special size and can only be found in the dealer’s shop must be very profitable to the English manufacturers.
Tom Hanson
Albuquerque, New Mexico
It is true that a so-called unified nut and bolt size is used on English automobiles, allowing the use of American wrenches. This practice was begun in 1956; however, some engine components (carburetors and such) still use Whitworth size nuts and bolts. Both American and Whitworth wrenches are needed if any great degree of work is attempted.
Whether English motorcycles will in the future be assembled with other than Whitworth size bolts is anybody’s guess. I imagine if and when a change is made it will be to the metric system, Metric size nuts and bolts are used on the majority of motorcycles manufactured in the world today. At present there are three basic bolt size categories: Metric, American and Whitworth. While the metric system is completely unrelated to either the American or Whitworth sizes, slight variations in size do exist between metric nuts and bolts used in different countries.
In other words, there is not the unity of size in this system we have been led to believe. American and Whitworth bolts both use the inch scale. The major difference between these bolt types is thread pitch, thread shape and, naturally, size of the bolt hex. The cost involved in making any changes in production that require re-tooling is anything but cheap. Evidently the motorcycle manufacturers feel that a change of this nature would cost too much. As far as salesmanship is concerned, the English manufacturers can’t fill the demand for their motorcycles now, so a change of this nature does seem unlikely.
The sea voyage that spare parts must endure in shipping does have a tendency to swell price tags about three times their normal size.
NOT SATISFIED
After reading your nice write-up about the Yamaha 305 in the June issue 1 decided to get one. I bought the first one to come to this area. I haven’t been too well satisfied with it because the service is not so good. The dealer does not know how to tune it and also the clutch is noisy and grabs.
1 live 18 miles from this dealer and about 35 miles from the next reputable dealer. So you see if 1 have to take time off from work to go there, it makes it quite expensive. The owner’s manual that comes with the machine does not tell you much. 1 have learned to tune the engine pretty well, synchronizing the points and carburetors, but the clutch chatters and lets out a squawk when released under load.
J. E. Jensen
Napa, California
Dealer service is, at times, poor. An unfortunate situation to be sure, and one not limited to the motorcycle industry alone. When this problem arises the owner can complain to either tHe distributor or manufacturer. The manufacturer will usually make an attempt to reconcile difficulty between the customer and dealer if the complaint seems well founded.
The only other alternative; the owner has to do his own work. This does require access to a shop manual and in most cases some special tools. A shop manual for your Yamaha may be available by writing Yamaha International Corp., P.O. Box 54540, Los Angeles, California 90054.
Clutch noise and rough operation are common problems encountered on most Yamahas which have acquired some mileage. Clutch design is the cause of the difficulty, and it is doubtful that a permanent cure can be achieved without a design change.
Replacement of the clutch throwout bearing (part #B-16007) will result in quieter and smoother clutch operation, at least for a while. It’s a shame that a powerplant as fine as the Yamaha has to be burdened with such a poorly engineered clutch.
