The Service Department
THE SERVICE DEPARTMENT
JODY NICHOLAS
750 CHAIN PROBLEM
Perhaps you have an explanation for a problem that seems to be happening quite regularly in my area: namely, broken rear chains on the Honda 750 Four. I haven't experienced the problem yet, having ridden my Four for one year now (5000 miles), but I wonder when it will happen.
It seems that several things happen. Sometimçs the master link spring dip breaks, or the master link pins get loose and wobble in the side plate, or rollers crack off, and soon the chain lets go. What I don’t understand is why ad this chain trouble, (¡ranted, more horsepower is available to anyone wanting a big bike, but there are other big bikes also with close to the Honda's power. Harley 74 riders seem to run their chains for thousands of miles, yet don't seem to have any chain problems, and a 74 is heavier. / have heard of using the 74 chain on the Honda 750, but these pop faster than the original, / understand. How about the Tridents, Rocket Threes, Norton Commandos, Kawasaki Threes, Harley Sportsters all high performance bikes. Do they shed their chains regularly 7
Some of the ideas I've heard are that the rpms are too high and too quick, that the engine sprocket is too small for the rpms it is turning, that the chain is not heat treated, and that the chain oiler is shut off. How good is engine oil as compared to, say, TriCor chain lube? / use 'TriCor, and so far, so good.
/low did Honda harness the power at Daytona7 How do the super grand prix bikes such as the MV Agusta, Yamaha, Honda, Rene Hi. etc., keep their chains on for the Isle of Man race and the like. Surely the Isle of Man race with its bridge jumps and rough pavement puts a Jantastic strain on the drive chain, yet they seemed to stay on.
As you can tell this has me puzzled, especially when / haven’t heard a concrete explanation. Although / try my best to keep my chain in good order, I still wonder. / don't lose chains on my com pe ti i ion bikes: / surely don't expect to lose the chain on my road bike.
CYCTH WORLD has always been the bible and dictionary in the motorcycle world. I hope you can solve this problem or give some good ideas on it. Almost all of the powerful racing machines you mentioned use the Reynolds racing chain which is manufactured in England. This chain is singular in that it is hand assembled and riveted and is pre-stretched. Not only is it very, very expensive, but it is in very short supply and is sold to racing machine owners almost exclusively.
Keep up the fantastic job of keeping the motorcycle world informed.
David Olson Rockford, III.
The rear drive chain is the biggest problem on the Honda CB750 motorcycles, and both Honda in Japan and American Honda are working on ways to alleviate this flaw.
The main culprit seems to be the countershaft sprocket, which is currently 16 teeth. Later models will be introduced with 18-tooth sprockets, and there are 17-tooth sprockets on machines now which are available from dealers.
A chain that has to change direction rapidly, as must be done if it is wrapped around a small diameter sprocket, generates a lot of heat which, coupled with the CB750’s considerable horsepower and torque, is quite vulnerable and must be kept in perfect condition to preclude premature failure.
American Honda has been running a squad of CB750s around the Southern California area for several months, testing all the chains commercially available. They have arrived at a number of interesting conclusions. First, they have found that the original equipment chain, if kept properly cleaned and lubricated, lasts longer than any chain available, with the exception of the American-made Whitney chain. American Honda is offering this chain through its dealer network as a replacement unit because the Japanese manufacturer of the standard chain is unable to meet the demand for Honda’s and other Japanese manufacturers’ requirements.
Any number of things can happen to cause a chain to fail. The most common of these are lack of lubrication, overheating and dirt. When dirt mixes with oil, the resulting compound is somewhat akin to a valve grinding compound and hastens chain wear. Keeping your chain clean and well lubricated is of primary importance, as is keeping it correctly adjusted. When you remove your chain to clean it, inspect the master link carefully, and if it appears unduly worn or the pins are loose in the fixed plate, replace it with a new one. A good idea to prevent the spring clip from coming off is to make a tab lock from thin, brass shim stock. Insert this tab lock, which should be roughly 1/8 by 1/2 in., in between the spring clip and the outside plate, and bend it over the outside of the spring clip. If the chain begins to shed its rollers, it has been in service too long.
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With today’s higher speeds and heavier, more powerful motorcycles, chain life is a problem with almost all the larger hikes. Only with conscientious service can a chain lie expected to give reliable service.
FLAKY CAMS
My problem concerns my Honda CB 450, which has about 9000 miles indicated on the odometer. / recently noticed pitting (0.0 ! 0-0.015 in. deep by 1/8 in. in diameter) at the high point of the right cylinder exhaust cam.
/ have performed all maintenance requirements and have always used a good grade oj oil. Mv machine is ridden normally, with some turnpike and some hack road driving.
Is this a problem common to the earlier model CB450s? Is it a design problem, i.c., insufficient lubrication or soft spots in the cam ' Is it possible to correct the problem without major modifications'*
Robert Bruce Middle drove, N. Y.
Problems such as yours occur in the Honda CB/CL 450 models and are caused by an insufficient layer of Stellite facing on the cam lobes. Stellite is the trademark for a hard facing material composed of 75 to 90 percent cobalt and 10 to 15 percent chromium, with or without small amounts of other materials. It is used for cutting tools and other wear-resistant suri aces, such as camshafts and cam followers.
Since camshaft lubrication of these Honda models is more than adequate, the only way to reduce this wear is to use a good grade ot single-weight, highdetergent racing oil ot the correct viscosity rating for the outside temperature. Warming your machine up by riding slowly for the tirst tew miles alter starting from cold will help prolong the life of all components in the engine which are lubricated by engine oil.
Replacement camshafts are available at a reasonable price from your Honda dealer, and, with reasonable care in warming up your machine, they should last a long time. If the problem really disturbs you. it might be a good idea to write to a camshaft specialist in your area ( Ravesi Cams in the Boston area) and cheek into the possibilities ot having your camshafts reground to stock speeifieations and re-hardfaced.
