The Service Dept

THE SERVICE DEPT

JODY NICHOLAS

HONDA DWELL

I would like to know the proper dwell setting for a 1970 750 Honda.

I have a regular dwell tach for a car. I have settings for four, six, and eight cylinders. What would be the setting for a Honda on this dwell meter?

When I set my point gap at 0.014 the meter reads 27½ on the eight-cylinder scale. On the six-cylinder scale it reads 37½ and on the four-cylinder scale it reads 57½.

I understand the correct dwell for this machine is 98. This dwell meter does not read that high.

Paul E. Teel Melbourne, Fla.

Using the 4-cylinder scale on your automotive tachometer, you should obtain a dwell indication of between 95 and 98. Ideally, you should have a dwell meter with a two-cylinder scale because each of the two sets of points in a Honda CB750 fires two spark plugs. Either that, or get a dwell meter that reads at least high enough to get a reading of 95-98 on the 4-cylinder scale.

This dwell figure of 95-98 was figured out by the personnel at the service

department at American Honda Motor Co. in Los Angeles by setting the contact point gap at the specified 0.035mm (0.014 in.) and verifying this with the aid of a dial indicator on the points themselves. Then they started the machine and obtained the dwell figure of 95-98 on the 4-cylinder scale.

Dwell, incidentally, as used regarding ignition systems, is merely the number of degrees of point cam rotation that the points remain closed. The reason the reading is as high as 95-98 on the 4-cylinder scale is because there are two sets of points each firing two cylinders.

If your dwell tachometer does read higher than, say, 60 and your Honda doesn’t peg the meter, it’s out of whack.

TRIUMPH FOR THE DIRT

I am planning to buy a used Triumph Bonneville, which I will set up for dirt. I am going to put on a single carb. I cannot afford the single carb head. I believe that on the 500 Triumph single carb model, there is a 2-carb head with a manifold for one carb. Would this manifold fit on the 650? If not, does anyone make a manifold such as the one I need?

What type carb would be best for this-one of the stock Amáis, a Kendick pumper carb, or a Yamaha XS-2 type carb? I need good low end response, but I am not sure if a carb small enough for this would have enough draft for upper rpm.

Also, in the ignition department, I was planning to put in a battery eliminator and a CD ignition, but a friend told me that if I was ripping out everything electrical but the spark plugs, I could take the hot wire from the alternator right to the coil (points?—I don't know much about ignition). Is this true? What would be the simplest

way to wire it? I may decide to keep the headlight for night riding—could this be done, keeping in mind that I am taking out the electrics?

Charles Ford Watchung, New Jersey

Short of buying a single carburetor cylinder head for your Bonneville, you have only one alternative: have a ma chine shop build you a manifold to accept one carburetor. The Bonnevilles have used the Triumph “splayed port” cylinder head for years, which is a high performance item. They simply weren’t designed for single carburetor application.

A TR-6 Triumph with a single carburetor cylinder head is easily adapted to fitting twin carburetors with the aid of accessory manifolds available from a number of sources. The inlet ports are parallel to each other instead of being angled outward and away from each other like a Bonneville head.

The simplest method of carbureting your special would be to use one of the 30mm Amal standard carburetors from the Bonneville and replace the 0.106 needle jet with a 0.107 and substitute the No. 2Vz throttle valve (slide) with a No. 3 slide. You will have to experiment around with the main jet size, but the standard size for a TR-6 Triumph is listed as a 230.

A battery eliminator is fine and dandy if New Jersey doesn’t require that the lights remain illuminated for a time after shutting down the engine. The stock Lucas ignition system works well if all components are in good condition. My suggestion is to use as many of the standard components as possible and avoid possible future problem areas with something you’re not familiar with.