Service

SERVICE

JOE MINTON

Stumbling, bumbling Venture Royale

My 1983 Yamaha Venture Royale starts with extreme difficulty, bogs when the engine is cold, hesitates when accelerating and has a flat spot at about 55 mph. To date, I have taken the bike to three dealers. They have adjusted and synchronized the carburetors, put new ends on the sparkplug wires—maybe even changed the air in the tires, for all I know. I’ve lost time, bike use and $150, but I haven’t lost the problem! Do you have any suggestions?

George Adams

Eagle River, Wisconsin

It is likely that your carburetors' idle jets (also known as slow jets or pilot jets) are clogged with deteriorated fuel. Cleaning the jets or replacing them should take care of the problem. Because you live in Wisconsin, I presume you store your Venture for at least a couple of months each winter. Your Yamaha's owner’s manual has a section covering recommended storage procedures starting on page 143. The first of these recommendations is to drain the tank, fuel lines and carbs if the

bike is going to be sitting for more than 60 days. I recommend that the carburetor float bowls be drained if a bike is to be stored for more than 30 days. As you’ve found out, time spent properly preparing a bike for winter storage can pay dividends when riding season rolls around in the spring.

Pain in the gas

My question concerns unleaded fuel, as I’ve been told that leaded fuel will no longer be available in my state. What’s going to happen to engines in old bikes still on the road?

My 650 Yamaha Twin is 18 years old and isn’t worth doing an expensive conversion on the valves to make it unleaded compatible.

Cecil Sutton

Pioneer, California

Lead-free gasoline has not proved itself to he the problem we feared it might become. Most motorcycle engines have steel valve seats that do not wear much in the absence of leaded gasoline. Many of Detroit's old car engines had valve seats simply cut into iron head castings, and these would wear rapidly when run with unleaded fuel. Your Yamaha has tough valves and valve seats. I doubt that you will have a serious valvewear problem.

Knock-knock joke

I own a 1982 Honda CM450 Custom with 10,500 miles. My problem is a constant knocking from the cylinder-head area. I’ve adjusted the cam chain, the balancer chain and the valves, but the noise persists. One mechanic told me, “Just ride it,” another wants megabucks to tear the bike apart. Is this type of noise common to older Hondas?

Michael Latrella

Blackwood, New Jersey

In my years of diagnosing engine problems, I have run up against some pretty odd noise sources. There was the loose cylinder sleeve that only rattled when the engine was thoroughly warmed; the piston that lightly tapped an incorrectly manufactured head gasket; the cam lobe that was ground onto the cam backwards. The problem with unusual noises in the valve gear is that there can be as many possible sources as there are parts in the area. Rough cam lobes, battered valve-lash screws and other parts that go thump against their neighbors are all possible noise generators. I would start by inspecting the valve gear. Your

CM450’s valves are operated by rocker arms coming off a single overhead camshaft. The contact pad, or shoe, of the rocker arm is chrome plated for wear resistance. It is common for this plating to become damaged and for the pad to wear significantly. It will then make noise yet not interfere with engine operation. If worn, the rocker arm should be replaced (maybe the cam, too).

Also check the tips of the valve-lash screws. If they (or the valve tips) are pitted, they will make noise.

The wobble that wasn’t

I own a 1989 Honda CBR600 that has a pretty bad wobble in the front end at 55-65 mph when I let go of the handlebars. The bike has been checked out by two shops. Both claim everything is straight. What could my problem be and how can I fix it?

Spc. Kevin Heuring

U.S. Army, Saudi Arabia

More than likely, you don't have a “pretty bad” wobble. What you're experiencing is a consequence of a design decision. Honda's engineers could have chosen to eliminate the minor wobble you have at 55-65 mph, but they would have strongly increased the likelihood of a genuine, lock-to-lock, terminal wobble above 80 mph.

The front end of most motorcycles has a tendency to oscillate about the steering-head bearings. The tire provides the damping required to prevent runaway wobble. The forces responsible for front-end wobble increase with speed, and it is a highspeed wobble that is the most dangerous. Steering geometry that will better damp high-speed wobble may allow the front end to oscillate moderately at lower speeds.

It is very unlikely that you will have a serious wobble problem as long as your CBR in is good mechanical condition-properly adjusted steering-head bearings, the correct tires for your bike set at recommended tire pressures, properly functioning suspension components and no heavy objects hanging off the back of the bike. It would also help if you kept your hands on the bars, where they belong. E3