TRAIL ZONE

ASK DR PHIL:

THE CASE OF THE WR450F's MISSED SHIFTS

Hi to all at TRAIL ZONE: Long-time listener, first-time caller. I am a pround owner of a Yamaha WR450F that I purchased new in August 2008. Prior to this I spent 10 years riding mountain bikes, but more about that later. I have recently completed a seven-day trail ride in the Victorian high country that covered 1,150km. Before the seven-day ride I replaced many parts including the gearshift. My original leaver lasted a whopping 5,200km and was very sloppy to say the least. I've grinded out the pinch-gap, resulting in very little (if any) improvment. It seems to me that the hard steel spline chews away the soft aluminium. This used to be a big problem with mountain bike cranks until the late 1990s, but now they use a star shape spline and works excellently. I have been reluctant to try the hammerhead lever as I fear the same thing will happen. My question would be that R&D can come up with a motor facing backwards, upside down etc, but they still use the same crappy spline? Any help would be greatly appreciated. I love all the IN THE ZONE DVDs and I always have a mag handy: you never know when you need a good read. Keep up the good work.

-- Matty Backpack via www.trailzone.com.au

Thanks for your email and feedback to TRAIL ZONE magazine on the WR450F gear shaft spline design, Matty. I’m sorry but I couldn’t disagree with you more, as I believe the design is very close to perfect. A couple of things need to be considered here, however: the reason your stock alloy gear lever crapped-out is because it slowly came loose, and you spotted this way too late. If kept tight, and rechecked after each ride, and especially after each get-off where the lever cops some strain, you’ll have no issues -- ever. The Yamaha spline is the same as most other popular bikes. It’s as fine as it is to allow for those very small height adjustments that we all need to make to suit our particular riding style and the height of our boots where they tuck under the gear lever. A more course spline would mean there would be way too much height movement after an adjustment. And in favour of a finer spline is the fact they have substantially more surface area to grip on and that will mean they stay tighter longer. Your Yamaha WR-F is one of the lightest 450cc enduro machines around, that’s just one of the reasons you love it so much, right? It’s light weight is down to a wealth of lightweight alloy components. If you wanted a gear lever or kickstarter that wouldn’t wear out when it came loose, think about a 1970s vintage British motorcycle -- they had cast steel gear and kick levers and a wealth of other strong but awfully heavy components. They were also slow and handled poorly. Now, here's a Dr Phil tip: Whenever you remove the gear lever, clean the spline shaft with an old tooth brush and spray clean it with a high-pressure spray pack of WD40 or contact cleaner; the same goes for the internal spline on the gear lever. There’s NO chance the gear lever will EVER stay tight if it’s tightened up with crap or dirt on the spline surface areas. Now, the only low-grade item on the WR-F gear lever is the bolt they use: it’s slightly stronger than a Paddle Pop stick. Purchase a high quality “grade 8” metric bolt from an engineering supplier, it will most likely be coloured black and have an “8” on the head or 6 or more lines on the bolt’s head, and use a small flat washer as well. Cut its length so ALL of the alloy thread is used when the bolt is tightened (the standard Yamaha bolt is always just too short and this helps rip out the alloy thread when things get sloppy). If you need to also replace your gear shaft due to too much wear, it’s a fairly inexpensive part and is fairly simple (and cheap) to install, with only the clutch pack needing to be removed (no costly crankcase splitting required). If you think you’re unhappy with the popular Yamaha spline shaft design, I can’t wait to hear what you’d think of the “tapered spline” design that KTM use.

-- Dr Phil, www.trailzone.com.au