The Service Department

THE SERVICE DEPARTMENT

GARY BRAY

GEAR GRIND

I have a 1961 Matchless Typhoon and a gearbox problem. When going into low gear, and with each shift up to 4th, there is a slight grinding of the gears. I have adjusted the clutch and push rod according to the book. When disengaging the clutch and pushing the kick starter through, there is no drag. I have also disassembled the gearbox completely and looked over each part. Everything looks almost new as the gearbox has only about 4000 miles on it. The steel clutch plates have a very slight bend to them when laid on a plate of glass, however. This grinding seemed to start after I put in a new kick starter spring. Russell Steinsiek San Diego, Calif.

It sounds very much like a slight clutch drag has caused warpage of the steel plates. These plates tend to warp if there has been any slippage. The fact that you changed the kick starter spring would indicate you possibly didn't get the same cable and push rod adjustment when you replaced the outer gearbox cover.

With the steel plates slightly warped you may have to use closer adjustments than normal. Sometimes a lighter oil than is called for in the primary chain case will help a dragging clutch. I would make sure to check the primary and rear chains for tension; if either chain is too tight this might also cause the clutch to drag.

I doubt if the gearbox itself is at fault, but if for any reason the layshaft has lost its end play, this, too, could produce these symptoms. If nothing else helps, then try replacing the steel plates.

HONDA WOBBLE

I get a front end wobble from my Honda scrambler when running at speed on a loose surface. On one occasion this became violent enough to approach disaster. Is there a cure other than keeping the speed down to where the oscillation is slow enough to be controlled by the rider's reactions? The dealer says they all act that way under these conditions. The hydraulic damper helps some but the effect is still there. William S. Woodman Phoenix, Arizona

I have encountered this problem in the past, particularly with the old Triumph Trophy. This machine had quite a bit of trail and a short wheelbase which made it somewhat tricky on loose surfaces.

One thing that may help you is to move your weight as far back over the rear wheel as possible. This tends to make the front end lighter and gives a lighter touch on the handlebars.

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Strange as it sounds, the installation of a knobby tire on the front wheel may also help the situation. And, here in California, most of the desert riders remove the hydraulic damper. Head angle and trail can of course be changed but both are expensive procedures and require competent workmanship.

SURFACE AREA

What effect do lightening holes in the cylinder head have on cylinder temperatures? Some say that the holes aid in cooling because of better air circulation around the head, while others say you have to have surface area so the heat can radiate outwards. Also, what do you think of lightening holes in general? Are they worth the trouble? Surface Area San Jose, Calif.

There were some tests made in Europe a few years ago concerning engine temperature but they dealt with colored and plain metal cylinder heads and cylinders. It was found that a dark colored cylinder and head operated about 10% cooler than ones that were plain aluminum or silver.

No one to my knowledge has tried to determine whether holes or lack of them have any effect on engine temperature. In my opinion, drilling holes in the cylinder and cylinder head would certainly not help in cooling. The Manx Norton, Matchless G-50 and BSA Gold Star, for example, have massive fin areas. This allows the engine to operate at long periods with a low cylinder head temperature. Since the idea is to have a large area over which to dissipate heat, then it would follow that drilling holes just reduces that area.

Regarding the value of drilling holes as a means of reducing the machine's weight, I would say that it more or less depends on how far the individual wants to go in preparing the machine. Once the nonessentials are removed, weight reduction-becomes more difficult. I feel that in most cases if a given part cannot be made or replaced with a lighter material, then drilling may have some merit, but anyone contemplating this should give serious thought to each part to be drilled. It is far more desirable to have a heavier machine that finishes a race than an ultralight job sitting in the pits.

LET'S DRAG

I own a Honda Super Hawk and plan to drag race it this summer. Can you tell me the best size of sprocket for this type of racing? A. P. Badeaux Jr. New Orleans, Louisiana

I suggest you start with a 33-tooth rear sprocket for quarter-mile drag racing. You may have to go one or two teeth either way, depending upon the tune of your machine. The gearing may also vary from strip to strip so, in the long run, best results will be obtained through experimentation.

PLUG BURN

I have a Honda 150 and it burns spark plugs like mad. Are there any American plugs manufactured that will fit it and also the Honda 250 scrambler? Joe Ochos Lindsay, California

I don't think your problem lies with the brand of spark plug; it sounds more like the plug is too hot. Also, your carburetor may be set too lean. Since weak condensers will in some cases cause plug burn, the ignition timing on your machine should be checked as well.

Champion does make plugs for Honda but to my knowledge they have not been too successful. The D8H NGK plug is recommended for your machine but you may find the D9H more suitable for your type of riding. The Honda 250 Scrambler also uses the D8H and D9H.

HEAD CHANGE

I own a 1957 BSA 650cc twin. The engine is slightly modified, having a thick base cylinder and, I believe, a late model cylinder head. I would like to further modify the engine by adding a second carburetor. Rather than adding a second carburetor by means of a special manifold, is there available a head designed for two carburetors which might fit my machine? Would the dual carb head for the 1964 BSA twin fit my machine? Lex Passmen Princeton, New Jersey

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The 1964 BSA cylinder head is not adaptable to earlier BSAs. In order to install dual carbs on your machine with a minimum amount of trouble you can replace your present cylinder head with a head from a 1955 Road Rocket. I believe this cylinder head is the only one BSA ever manufactured for 650cc twins with a removable manifold.

A special manifold is required for this installation. In dual carburetor installations for drag and T.T. machines, the existing manifold has been cut off and new holes cut into the cylinder by means of a milling machine. Spigots are then machined up and welded in place; the final operation is to blend and smooth the ports.

WHAT SHALL I BUY?

I'm a cycle fan but I don't have a cycle. I am looking into a BSA Royal Star 500c for touring and was wondering if your magazine could aid me in my decision. If you feel there is a better machine that is as good looking as the BSA I will look into it. John J. Redmond Casa Grande, Ariz.

There are any number of good 500cc twins on the market' today; to say that one is better than another is difficult at best. Your possible choice of the BSA Royal Star is a very good one. Of course, parts availability and service in your locale should be taken into consideration when buying any make of machine. I cannot in all honesty claim that one machine is better than another; buying a motorcycle is strictly a matter of personal choice.

TT SPECIAL FOR THE STREET?

I am thinking of buying a Triumph Bonneville TT Special and setting it up with equipment for street use. I have heard rumors of them blowing up when used as such. Is this true and do you recommend my doing so? Doug Miller Stockton, Calif.

Since the Triumph Bonneville TT Special is set up as a racing machine it naturally won't run as many miles as a stock machine before overhaul. However, there is no reason that it should "blow up" simply because you bolt on a headlight and mufflers.

I certainly would not recommend using this machine for street riding. It has a very high compression ratio which does not take kindly to slogging around town. Also it seems a waste of money to go this route. Why not a regular Bonneville instead?

(EDITOR'S NOTE: We have had several requests regarding metric dial gauges for Yamahas. Readers can write directly to Yamaha International Corp., 1224 So. San Pedro St., Los Angeles 15, California for information on purchasing them.)