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Old 11-07-2012, 05:02 PM   #1925
DFH
270 deg crank
 
Joined: Nov 2008
Location: Adelaide, South Australia
Oddometer: 213
Quote:
Originally Posted by gtbensley View Post
Thank you for the response.

The wobble is there when he rides with both hands on the bars, it can be while he accelerates, holds a steady speed or starts to slow. Yes there is a lot of crap on the bike and that's what I figured was causing it initially. We removed all the gear though and it's still there.

We have already set the tire pressure to what you suggest as we'll as looking for flat spots on the tire. Sag is all the way up.....but there is still probably more like 42mm of sag.

Lose head bearing maybe? What about raising the foks 1-2mm to see if that changes anything? We will be in San Diego until Friday morning and hope to solve it by then.
By flat spots on the rear tyre I mean the centre of the tyre worn down flattening the profile rather than flat spots as if the tyre had been locked & skidding. Should be easy to spot. I assume that the bike has the Shinko 009's fitted front front & rear at the same time. Mismatched tyres, especially at different points of their wear life can cause these kinds of problems all by themselves.

The normal wear pattern for tyres as they age, especially with lots of slab miles is for the rear tyre to flatten off in the middle of the tread & for the front to become more pointed. The rear wear is obvious, the bike is pushed along by the engine through the rear tyre contact patch. Do some miles heavily loaded & even constant, moderate cruising speeds can wear a tyre out surprisingly quickly. The front tyre wears to a point because it does not do much work until the brakes are applied, then the tyre contact patch is mashed into the road. It is designed to flatten out at the contact point to give more grip under brakes & this flattening out wears the outside edges of the contact point much more than the centre. If a bike, as rough rule of thumb, can go from 100mph to zero in half the time it can go from zero to 100 then you can get an idea of the forces involved.

So I would consider replacing both tyres as a set before stripping the bike down & changing steering head bearings, especially as its such a labour intensive job. On the upside actually checking the steering head bearings is dead simple & should be your first step. Lob the VFR up on its centre stand (leave the luggage on so the front wheel is off the ground) and check the bearings. Turn the bars left to right, by fingertip force only. The bars should turn with a little resistance, not flop from lock to lock (bearings too loose) & without a notchy feel, especially just off centre (bearings worn & damaged, replace). Next step kneel down and grasp the bottom of the forks from the front & pull back & forward firmly (any clunking? bearings too loose). To tighten the steering head bearings leave the bike on the centre-stand. Loosen the top triple clamp allen bolts & handlebar clamps bolts on the fork tube. Loosen & back off the chromed centre bolt on the top triple clamp & slide up the triple clamp up the steering stem. Lift clear the locking washer (with tabs) & using a drift loosen the castellated locking nut. Using the drift tighten in small steps the lower castellated nut, testing the tension as described above. Once you are satisfied with the bearing tension tighten down the locking nut (lining up the notches so you can refit the locking washer tabs in the notches) using the drift, but being cautious not to tighten the lower nut in the process. Slide down the triple clamp & tighten down the centre nut firmly, then finally tighten the allen bolts clamping the fork tubes followed by the handlebar clamps.

It is my opinion (from 15,000km away I admit) that as the bike clearly changed from being OK to being a wobbly mess during the trip that something has changed in a more marked way than the gradual change that comes with stuffed head bearings. Now that you have checked their tension what next?

You have eliminated the weight of the touring luggage so cross that off my list.

Replace the tyres as a set with stock-sized quality sport-touring rubber... Tyres have a dramatic effect on the riding experience & you are touring for the fun of it so don't cheap out here.

If the wobble is still present after re-tensioning the steering head bearings & replacing the rubber then the next cab off the rank is the rear suspension. If the sag with rider & luggage with max pre-load is 42mm then the rear spring is too soft. I'll assume that with the preload at max you have adjusted the rebound damping to max as well to help control the spring. It is possible that the shock has lost its damping through aged seals, even if oil leaks are not apparent the shock could have well lost its damping due to it suddenly loosing gas pressure.

I would'nt raise the forks up in the triple clamps as what you are doing there is experimenting on ways of disguising the symptoms of a problem, not a cure.

Have fun

DFH
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270 deg crank
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