[motorcyclistonline] - Why Do Similar Bikes Have Different Valve Adjustment Intervals

[Ninjette Newsbot]

Q. I have two bikes, a Triumph Bonneville and a Honda CB1100. The Triumph’s shop manual says to check the valve clearances every 12,000 miles, but the Honda’s says every 8,000. They both use shims to set the clearance, and they’re both low-revving air-cooled engines. So why the different adjustment intervals? A friend with a Honda Gold Wing says his valves don’t need to be checked until 32,000 miles. Is that because it’s water-cooled? I’ve read on Internet forums about riders who have never checked the valves, and their bikes run fine for thousands of miles. Is it really necessary to check them at all?

Joe Robie
Watsonville, CA

Got tech questions that need ANSWERS? Email us at*mcmail@bonniercorp.com.

A. Whether or not a bike is liquid-cooled has less to do with valve-check intervals than things like cam profile and lobe hardness, the kind of followers or buckets, valve weights, average rpm, and a host of other factors. Also, intended use, which is why Honda specifically built the Gold Wing for longer valve-check intervals, appreciating that owners tend to put a lot of miles on them.

Manufacturers test to determine valve-train wear and set inspection intervals to protect from a worst-case situation. Because they’re conservative, the vast majority of the time, inspections at the first couple of intervals reveal very little wear. Some engines wear tight—that is, the valve clearances decrease because the valve settles into the head faster than the material between the cam lobe and the follower wears. Some go the other way. The only way you know for sure which way your engine is going is to check it. It’s easy to get complacent when the first or second intervals reveal valves to be right on spec.

Ignore the forum chatter. The loudmouth who says you never have to check your valves won’t pay for repairs should something happen and won’t stand behind you when the dealer denies warranty coverage because you haven’t followed the manufacturer’s recommended maintenance schedule. Also, should you decide to sell your bike, you’ll have to find a similarly maintenance-averse buyer to accept the fact that you haven’t checked the valves. The odds are very slight that you’ll ever have valve train-related problems, but knowledge is far more useful than hearsay.

More tech questions and ANSWERS from the MC Garage HERE




Click here for full story...