My 1989 Vmax Outfit has a braking problem.
The front end is an Earles fork layout fitted with standard Vmax rear shocks and early model single piston calipers.
Whenever the thing shakes its head, the pistons are forced up into the calipers and the brakes require one or two pumps to get them working again. Overcooking it into a left-hander can be interesting. (The chair is mounted on the left)
The problem occurs even when the bike has not had a headshake - just go through a corner at modest speed, and the brakes are spongy.
The brakes have been bled, and the front bearings replaced.
The steering damper is adequate but not great. The steering head has had the Furbur fix. I don't believe the death wobble effect is the real problem.
Images here: http://dropbears.com/gallery/yamaha_vmax/
Suggestions welcome. Preferably ones on how to fix it.
Nice looking outfit! Perhaps a rebuild on the brake calipers may help also seems to me the LL maybe undersprung try better shocks with stronger springs.
The problem is to much play in the front wheel bearings.
Jay G
DMC sidecars
What is happening is that when you turn, the rotors are pushing the pistons back in. To make this problem go away the rotors must not push the pistons back in on turns. We have seen this before when wheels for motorcycle use have been used on the sidecar. If your wheel has tapered bearings you can either remove the sleeve between the bearings and adjust the pre load or machine the spacer down a bit, you must use caution when doing this in order to make sure that when the bearings heat up a bit and expand that they do not end up to tight.
Another possibility is that as this is not a stock front end, there may be play between the axle and the bearings if the original axle was not used this is very likely. The axle moving in the swing arm could also do this. Or if the swing arm on the leading link front end is not robust enough it could also be causing this. It does not take much movement at all to cause this as a little movement at the axle is a lot of movement at the end of the rotor. One thing that can help cover up the problem but is not a fix is to install 2lb residual pressure check valves in the brake lines.
Jay G
DMC sidecars
www.dmcsidecars.com
Bearings are conventional roller 6303 2RS - tapered roller bearings would be preferable, but quite a bit of work to fit them. Axle appears to be standard Yamaha - I didn't check the clearance fit in the bearings when I had it apart last night but not likely that's the cause. Best bet is the swing arm - I'll have a look at that today.
When I put a dial guage on the discs, move the steering onto the stop and then apply pressure to the side of the wheel, there is a lot of movement at the guage which shows that this is definitely the problem area.
Many thanks for your suggestions.
