Service

SERVICE

Six-cylinder stumble

JOE MINTON

I have a 1979 Honda CBX which has been in storage for the past 10 years. Recently, I tried to start it, and ran into problems. The engine fired up fine, but died when the choke was let off. I found the engine would run only if I kept the throttle one-third to one-half open.

To make a long story short, I dropped the engine, removed the carburetor assembly and cleaned the primary and secondary air jets. This did not fix the problem. The engine refused to idle or run at slow rpm. Could the idle jets be plugged? I did not clean these out because they are so small. If this is the problem, can they be cleaned without taking the carburetor completely apart? I would certainly appreciate any help in this matter. My wife is about ready to throw me and my motor-

cycle out on the curb for the trash collector.

William J. Ringle Dayton, Ohio

Your CBX's idle jets are almost

certainly plugged. Anytime a motorcycle is stored for more than a couple of weeks, the gas should be drained from the float bowls. And, if there is any doubt about the seal of the petcock, the fuel line should also be dis connected from the tank.

Gasoline deteriorates quickly, and the goo that results can completely plug the very small-diameter (.015inch or so) idle jets in most carburetors. Any engine has trouble running with clogged idle jets, and the problem becomes worse as the number of cylinders and carburetors increase.

Ás you state, the idle jets in your CBX are very small and difficult to clean. I know of no chemical that will unplug them while they are still in the carbs. The most certain cure is to simply replace them with new ones. I might try cleaning them if they were easier to get to than they are on the CBX, which, as you know, requires nearly complete engine removal to gain access to the insides of the carburetors. Compared to possibly doing that chore twice, the $30 or so for new jets looks like a bargain to me.

A clipped Wing

I own a 1978 Honda Gold Wing. Each of the last three years, my dealer has had to replace the right head gasket. Now just two weeks after the latest gasket was installed, I’m again having problems. I called American Honda and was told by Customer Service to try another dealer, or that I should ask my present dealer to call and ask for technical advice. I thought Ed write to you instead.

Philip J. Thalman

Miami, Florida

A blown Gold Wing head gasket is a rare event. Chances are you have a cylinder, cylinder head or both that are not adequately flat and parallel to one another. These parts must fit together very closely and evenly, otherwise the head gasket will not be uniformly clamped and will eventually fail. Once a head gasket begins to leak, local overheating will quickly follow. And overheating an all-aluminum engine like the Gold Wing's will probably warp both the head and cylinder. Making one flat again is not enough. You should have the sealing faces of both the cylinder and cylinder head checked for flatness.

One of the shop order copies you sent me makes reference to a labor charge titled “Sublet head-$45, " which would seem to indicate that your Honda shop sent the cylinder head out to be machined flat by an automotive machine shop. But was the cylinder also checked for flatness? In any case, I would choose another shop to do further work. Your present dealer's service department has obviously reached the end of its diagnostic resources.

More speed needed

I just finished reading an article on the 1990 Honda CBR600. I own a 1988 Hurricane 600 that I race and ride on the street. Eve installed a Dynojet carb kit, a K&N filter, a Factory shift kit, an Ontario exhaust system, and mounted some good tires.

What Em wondering is, would it be worth it to buy 1990 CBR carbs, with their increased throat diameter (from 29.3 to 30.4 millimeters)? What kind of performance gain could I expect?

Mike Rudella Cedar-Knolls, New Jersey

It almost certainly would not be worth the time, trouble or expense. While the later carbs do have seven percent more throat area, that is no guarantee that you will see a similar improvement in power. There are a number of factors that, together, determine power output. Carburetor throat size is merely one of them.

Without knowing the airflow capabilities of your engine's intake and exhaust ports, I cannot tell you whether or not the larger carbs even have the potential to increase power.

A substantial power gain with an engine as highly developed as the Honda 600 will be hard-won indeed. While we can often improve engine performance with aftermarket exhausts, cams, jetting kits and air filters, such gains are only possible because the stock engine was limited by the manufacturing necessity of meeting noise and emissions regulations.

You 've done about all you can with bolt-on parts. From here, you will need a dyno, air-flow bench, access to cams, carbs and one-off exhausts. You will also need to have the skills to use them, interpret results, make changes—in short,you'll have to be capable of beating Honda at its own game. fsl