Fixing the speed wobble problems 2

[TurbineGen]

In the last few years I've had issues with older 4 cylinder Japanese motorcycles becoming unstable above 75 mph. The years where this was the worst are between 1975-1984. Several of the bikes had ecessive play in the swing arms in the rear which needed to be ground down (namely the Honda cb650 and cb650 Custom models), but they still retained the speed wobble. I tried replacing the head bearings in some that had cut tracks in the bearing race and replaced them with roller bearings. Again they still had a speed wobble, but this pushed the speed up from 50 to 75 or so before the wobble came back.

I cannot for the life of me figure out how to correct this problem. I've tried everything I can think of and am coming up short. The only thing I can think is that maybe the forks are too small and are flexing at speed. All of the bikes that wobble appear to have smaller fork tubes and no fork brace. Would fitting these with fork braces help prevent this? I have been restoring classic bikes for some time now and this issue I can't seem to correct.

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If it is broken, fix it. If it isn't broken, I'll soon fix that.

 

[drwebb]

Do you run the Sport Demons with tubes? They made a world of improvement also in my GS500E but part may be due to the shop previously installing another brand with the wrong aspect ratio (too tall) on the front. I haven't heard of a disappointed customer yet.

 

[TurbineGen]

No tubes in any wheel unless it was a spoked wheel and required it. The Sport Demons and the Bridgestone Battlax have been great tires on the old bikes. They handle much better than the original tires for sure. I stay away from the cheaper tires and Dunlops. They don't handle nearly as well.

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If it is broken, fix it. If it isn't broken, I'll soon fix that.

 

[MALK]

TurbineGen, you must be thinking of old Dunlops, I can't fault the current pair I have on my modern sportsbike, in wet or dry. The modern tyres I have tried (Bridgestone, Michelin, Dunlop) seem to have very little to choose between them at my level of skill/daring

 

[TurbineGen]

New Dunlops in my opinion are even worse than the old ones. It seems they wear much faster than just about any other tire yet handling isn't improved. I'm also finding them way out of balance. Adding 100g weight to my wheel to balance a tire is unacceptable. I reject anything more than 50g. I rejected two tires (Dunlope Elite's) before accepting the third to go on my Honday GL1200 GoldWing. 4,000 miles later, it was square as can be. Thus I don't run them anymore. Your tire is the most critical part of the bike.

Of course, this is coming from a guy who is contemplating removing his center stands from three bikes to acheive a greater lean angle... I keep smakcing mine off the ground in turns and it scares the life out of me. I know old bikes weren't meant to handle like that, but then again, if they can be modified, then why not?

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If it is broken, fix it. If it isn't broken, I'll soon fix that.

 

[dgallup]

I've just about run off my second set of Dunlop Qualifiers and found them to be quite comparable to the Michelin Pilot Powers that came stock. Very similar grip, turn in & life, no balance problems. I have also tried the dual compound Pilot Powers and Pirelli Diablo Corsa III, both of which gave a little bit more grip at insane lean angles but less life. I only get 2200 miles at most from a rear, the Corsa III less than 1800. I have a set of BT016's waiting to go on next.

 

[evelrod]

So many bikes, so many tires...hard to remember them all. Perhaps it was just me...or, just maybe each bike had some secret pact with certain tire mfgrs?

Anyway, it seems many of my bikes liked one particular brand or another and would handle poorly with any other make. The old Yammer 650 would only do well on Michelin while the Beezer only liked Metzler. My KZ liked Dunlop but my GL1100 would only take the old Goodyear "run flat" tubeless. Those Goodyears really were 'run flat' as I made it home a couple times with nails in the rears. As long as I stayed under about 35, no harm-no foul. Too bad they quit selling them. Don't know why, they had good grip, they did not scare the crap outta me in the wet, they would do 6000 to 8000 on the rear...and...they were fairly cheap. They did have one drawback...a real bugger to mount an dismount. Oh well, that was ancient history.

Rod

 

[MALK]

I'm going to start a new thread, re tyre choice

 

[BrianPetersen]

dgallup, I did not like the BT016 tires when installed on my 2004 ZX10R. Grip was fine, and the life probably would have been fine, but I found that they gave heavy steering and made the bike want to stand up and resist cornering. I ended up taking the bike to the drag strip twice with those tires to finish them off because I hated the steering feel.

I have race take-off Dunlop Sportmax GPA Ntecs on it now, and they work fantastic on the back roads, but they're not going to last long.

Michelin Pilot Power has worked well on this bike in the past and I have a new set ready to go on.