The Service Department
THE SERVICE DEPARTMENT
GRAY BRAY
JOHN DUNN
Due to the tremendous volume of Service Dept. mail, we are unable to reply to individual letters. We shall continue to answer as many as space permits in this column.
I DON'T KNOW
I am considering building a two-stroke wet sump lubricated engine. Instead of a fuel-oil-air mixture going into the crankcase before being sucked into the cylinder where it is compressed and ignited, a fuel-air mixture would be sucked directly into the cylinder on the down stroke of the piston.
For proper lubrication, an oil ring should be added on the piston below the two compression rings, as on most fourstroke engines, and perhaps a splasher could be added to the lower part of the connecting rod. I am wondering if such an engine would work properly and if so, why no one has built such an engine yet.
John Ciar no Tucson, Arizona
Combining various features of the fourcycle and two-cycle engine certainly does not seem possible. On the other hand, today’s impossibilities many times become tomorrow’s realities. Are you sure you’re not trying to put someone on, John?
NOT SATISFIED
After reading your nice write-up about the Yamaha 305 in the June issue I decided to get one. 1 bought the first one to come to this area. I haven’t been too weil 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.
I live 18 miles from this dealer and about 35 miles from the next reputable dealer. So you see if I 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, hut 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 manu facturer. The manufacturer will usually make an attempt to reconcile difficulty between the customer and dealer if the complaint seems well founded.
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The only other alternative the owner has to do his own work. This does re quire 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.
common problems encountered on most Yamahas which have acquired some mile age. Clutch design is the cause of the diffi culty, 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 engineer ed clutch.
NUTS AND BOLTS
I 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 motor cycles to the U.S. with American Standard size nuts and bolts? The Japanese Datsun cars and trucks have most of their hard ware 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 -A lbuquerque, New Mexico
It is true that a so-called unified nut am bolt size is used on English automobiles allowing the use of American wrenches This practice was begun in 1956; how ever, some engine components (carbure tors and such) still use Whitworth siz~ nuts and bolts. Both American and Whit worth wrenches are needed if any grea 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 to day. At present there are three basic bolt size categories: Metric, American and Whitworth. While the metric system is completely unrelated to either the Ameri can 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.
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The sea voyage that spart parts must endure in shipping does have a tendency to swell price tags about three times their normal size.
OH, WHERE?
1 have just acquired a 500cc Sunbeam motorcycle (shaft drive, overhead cam, etc.) for which 1 do not know where to get parts. It needs gaskets and rings in a bad way. All four rings are completely frozen in the pistons. Any help would be appreciated.
Aubrey Sanders 1715 Wimbley Kennett, Missouri
The Sunbeam motorcycle was at the time of its manufacture a BSA product. Spare parts and service were available through most BSA dealers, though lack of popularity of this model did make dealers rather hesitant to stock any great amount
of parts. Undoubtedly some spare pieces do exist somewhere in this country for the Sunbeam. Since locating parts by corresponding with various BSA dealers would be quite time consuming, I therefore suggest you try contacting BSA Eastern, 639 Passaic Avenue, Nutley, New Jersey. We are also including your complete address in the event that a BSA dealer in your part of the country is able to supply the necessary pieces.
AJAY DEFINITION
7 recently obtained a 1953 AJS 500cc single. 1 rode the bike for one week to work, did not go over 60 mph, and the engine started knocking. 1 pulled the engine down and found the wrist pin bushing beaten out; also the piston and cylinder are ruined. What would cause this? What does AJS mean?
1 plan to rebuild this motor and will appreciate any help you can provide me with.
Tommy G. Sty ron Morehead City, No. Carolina
It is quite possible that your engine was in poor mechanical condition when purchased by you and when pressed into service again it just quit.
After such serious damage it is essential that the engine be completely dismantled and inspected for wear. I suggest that you obtain a workshop manual for this model which will give all the standard dimensions and wear limits. Before installing the
rebuilt engine, first remove and thoroughly clean out the oil tank and oil lines. Also fit a new oil filter element in the oil tank.
The name AJS stands for A. J. Stephens who was the original manufacturer of the machine. It is now manufactured by Associated Motor Cycles (A.M.C.) along with the Matchless, Norton, James and Francis Barnett.
TWO-STROKE TANGLE
7 bought a 1954 (200cc) Zundapp Norma. The engine doesn’t use any gaskets and it has oil leaks. I’m using the heaviest oil 1 can get now but it still leaks! Is this normal for the Zundapp? Is it possible to use a light grease instead of oil? Also, it has a rigid frame. By modification I think 1 can put shocks in. Do you think it is possible? Is there any frame I could buy for a frame swap that would fit the engine without too much work? Or any frame made for this purpose?
1 know the engine is only about 9 lip; is there any way to squeeze any more power out of it? Top speed is about 63 mph. Any way to increase it? Is a high compression head possible?
Dave Craft Minneapolis, Minn.
The only way to effect a cure for the oil leak problems you have encountered is to dismantle and rebuild the engine. Clean all mating surfaces, making sure they are free from burrs, etc. Use a good non-setting gasket cement when reassembling. It would also be advisable to renew all the oil seals, crankshaft main bearing seals, gearbox output shaft seal and gear change shaft seal. The use of grease as a lubricant would only lead to premature transmission failure.
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Yes, it would be possible to fit rear suspension but this would entail extensive modification and would prove very expensive.
Tuning a two-cycle engine for an increase in power output is a very involved and complicated procedure requiring a great deal of knowledge and experience with the unit in question.
An increase in BMEP (Brake Mean Effective Pressure) will be achieved by a slight increase in compression ratio. With your engine I would not go over 8.5 to 1 for normal street use. This can be obtained by machining some thickness from the cylinder head.
PIPE TUNING
1 own a 1956 Ariel Red Hunter 350cc with a dual exhaust head. 1 run no mufflers and would like to know what is the correct length of pipes that should be used for a tuned exhaust. At present I am running 23 inches on each pipe. Also for running “alky” what size carburetor would you recommend.
Lee Everett Santa Ana, Calif.
To advise what length of exhaust pipe would be the most effective on your machine, it would first be necessary to know what cam you are using, together with timing details and a valve lift diagram. I would think that the length you are using at the moment is too short and would not become effective within the usable engine speed ranges. I suggest you try a 40-inch exhaust pipe.
Gordon Jennings wrote a first class article on the design and function of the two-cycle engine exhaust system in the CYCLE WORLD Technical Manual, and if you are interested in this subject I strongly suggest you obtain the book. The two-cycle system is more complex and cannot be directly related to the requirements of the four-cycle engine,-but an understanding of what’s happening in the pipe can be obtained from this article.
Carburetor size is mainly related to port valve size and, providing your engine has not been modified in this respect, I would suggest that you stick with the standard instrument. The main point to watch is that the fuel lines and carburetor passages are of adequate size. The internal bore should not be less than VA " or fuel starvation is likely to occur.
WHY?
ƒ have a 1955 Ariel Scrambler 500cc and would like to know what kind of engine could be fitted to this frame with the least complications. Also would you have any idea about the cost?
Bryce H. Campbell Moscow, Idaho
It would be possible to install almost any of the big English single-cylinder engines in your Ariel Scrambler. New front engine plates would have to be made. It may be possible to rework the rear ones. Primary chain alignment will require attention and may necessitate off-setting the engine in some instances. One of the most difficult jobs is usually encountered when trying to adapt a satisfactory primary drive case.
But why go to all this trouble when any of the Ariel singles can be fitted? They were a first class engine and very suitable for competition purposes.
FAIRING FACTS
Generally speaking, do the current crop of touring fairings now available help or hinder the cooling problems of verticalengined machines?
Raymond L. Sine Boston, Mass.
It is generally considered that most fairings assist cooling when the machine is traveling at speed. However, cooling is adversely affected when the machine is stationary, as in heavy traffic, due to poor air circulation. Usually the fairing does not have an adverse effect on engine life and does not normally cause any distress.
MORE REVS NEEDED
7 recently purchased a Honda 305 Super Hawk with a 350 conversion kit. It runs fine up to 6000 rpm, but above that point it will sometimes start sputtering. I can never use full throtle because it won’t catch. It sounds as though it’s flooding out. Also, the carbon is very moist. It could be due to the fact that the pistons and rings are new, but I’ve got to have more revs to shut down my friend’s Parkinsonconverted James.
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Dave Monroe Claremont, Calif.
As you point out, the trouble being experienced with your Honda 305 Hawk could be caused by carburetion problems, and I suggest that you check the float chamber fuel level as described in the Honda workshop manual. Check that there is no restriction to the power air jets, and, if fitted, also check that the air cleaner elements are not clogged with dirt as both these faults could give similar symptoms.
This model was prone to valve float, normally limiting maximum engine speed to approximately 8000 rpm. The indications are quite similar to those described by you. It is possible that the valve springs in your engine need replacing or that they were incorrectly set when the 350 conversion was installed. We strongly suggest that you do a good valve job and fit new springs, preferably a set of the high frequency variety, as sold by Webco.
Ignition timing is also critical on this model and should be checked very carefully. It is most important that both sets of points are accurately timed to give good all-around performance. Standard static timing is 5° BTC.
PICKING A PIPE
ƒ have a 1962 CZ 175cc and was wondering where to find out where to get a tuned exhaust made. 1 use it just for trailing, as it doesn’t have the power to put on the track to race. Could you tell me if you think aviation gas would help but not hurt the engine if 1 use a 4-1 mix?
Roland R. Edwards San Jose, Calif.
I would say that having a tuned exhaust system made for your machine would be the least of your problems. Designing a system to suit your intended use would be the hardest task.
I strongly suggest you purchase the CYCLE WORLD Technical Manual by Gordon Jennings covering the design and function of the two-cycle exhaust system. If the machine is used solely for trailing, the original system should prove quite satisfactory, since it was designed to operate with reasonable efficiency over a wide speed range.
It is not necessary for you to use aviation gasoline in your machine. Any premium grade would do nicely. I would follow the manufacturer’s advice regarding the grade of oil used, also their recommended gas-oil mixture ratio. This data will be given in the machine instruction book. Most two-strokes use a 16:1 mix.
