SPORT TOURING - TRANSMISSION PROBLEMS

Sport Touring Corner

By Norm Kern, MSTA Editor / ReasonsToRide.com Contributor

Transmission Problems, and Why They Are Always With Second Gear

“Should I buy heated grips or heated

The sport touring world is buzzing right now with news of a transmission recall for Yamaha FJR models from 2016 onward. According to NHTSA, there have been two reports of second gear failure in the USA, although there are additional instances in other countries and the recall is worldwide. This is a major repair, as it involves replacing both shafts and all the gears in the transmission. (See the sidebar for details on the Yamaha FJR recall.)

Since the recall includes my FJR, many have asked me what the problem is, and especially WHY it occurs. It turns out that lots of bikes have similar problems and large sport touring models are among the most vulnerable. Let's begin with how motorcycle transmissions work.

Motorcycle transmissions have two shafts

The clutch shaft is connected to the engine through the clutch. It has a gear for each transmission "speed" that meshes with a mating gear on the output shaft. One gear of each pair has "dogs" on the side that can be engaged to lock a gear to its shaft or let it spin freely. The shift lever operates a cam that moves the shifting forks to engage and disengage the dogs on the gears. One set of dogs must disengage before another engages to avoid locking the shafts.

Shifting from one gear to another

As we accelerate, engine RPM increases and we want to shift to a higher gear to drop engine revs down to a reasonable range. Shifting gears changes the gear ratio between the clutch and output shafts, so one or both of them must immediately change RPM. Since the output shaft has the momentum of the bike's rear wheel and drive train connected to it, its RPM stays nearly constant during the shift. Therefore the clutch shaft must suddenly drop RPM on an upshift.

If the clutch is disengaged before shifting, it's just the clutch shaft itself and some of its gears that have to slow down. That reduces, but does not eliminate the shock force on the gears and dogs. Reducing throttle during upshifting slows the crankshaft but has no effect on the clutch shaft, as it is disengaged by the clutch- it only affects stress on the dogs and gears when the clutch is released. Remember, the moment the gear ratio changes is always the moment of greatest stress.

Why are most transmission problems related to second gear?

Look at the chart, which shows the drop in clutch shaft RPM when upshifting between gears on an FJR. By far, the greatest RPM drop is between first and second gear. That's where the most stress occurs. Another factor in second gear damage is the neutral detent between first and second gear, which makes it easier to miss the 1-2 shift by not getting the transmission all the way into second. When this happens, the clutch may be released and power applied, only to find the transmission is in neutral. A quick stab at the shift lever can engage second while under power with the clutch already released- a recipe for disaster.

Look again at the chart. The drop in RPM between shifts is proportional to the engine RPM at the shift point, so the greater the RPM, the more stress on the transmission gears and dogs.

What about first gear?

Isn't first gear just as vulnerable as second, since it's on other side of the big ratio change? No. First gear is only engaged when stopped or going slow just before a stop, so it rarely gets damaged.

Fortunately, Avoiding transmission problems is simple These four tips work with all manual transmission bikes.

1. Avoid revving the engine up to the redline in first gear before shifting to second.

2. Always use the clutch when shifting from first to second. Southwest Ohio Breakfast, 9AM, March 20 Village Family Restaurant 144 S. Main St. Waynesville, OH 45068

Central Ohio Breakfast, 8AM, April 4 Portside Cafe 6515 S High St Lockbourne, OH 43137

3. If you miss a shift, pull in the clutch and don't release it until you've positively engaged a gear.

4. If you want to use a quickshifter, at least use the clutch for the shift from first to second. How Yamaha is Handling the Recall

When Yamaha developed a fix and decided to do the recall, they created a training video to show technicians critical points on how to do the job. They had the new parts manufactured and created an amazing recall kit, including special tools, transmission cluster, crankcase bolts, orings, gaskets, tie straps, factory sealer, oil filter, engine oil, coolant, etc. 2103-03.jpg

Transmission repair on an FJR is a major job- 2103-04.jpg bodywork must be removed, coolant drained, exhaust etc. removed. 2103-05.jpg Engine is removed from the frame and clutch and lower crankcase disassembled. 2103-06.jpg Both transmission shafts and all gears are replaced, everything reassembled. Start to finish is about 14 hours of labor.

The recall is at no charge to the customer, in or out of warranty. I took advantage of the recall to get some major long-term maintenance done. Most of the normal cost of these service operations is in the removal of bodywork, exhaust, coolant etc. Since they already have these parts removed for the recall work, I was able to get the additional work done at a fraction of the normal cost.

Clinton County Motorsports, in Wilmington, OH, ordered the parts kit and scheduled my recall work in mid February. The weather didn't cooperate, so I had them come and pick up the bike. The driver arrived right on time and the cost was very reasonable. In just three days the work was complete, but the weather was so bad they had to wait to test it. I didn't mind the delay- if the weather's that bad, I'm not riding anyway!