SOHC.co.uk Forums > CB750

Handling

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leonardo269:
Hi Steve,

 I checked the swinging arm, no problem. From the frequency of the wobble I would say that it has to be the front wheel or tyre on my bike.

Jacking the bike up and spinning the front wheel, I have observed an uneveness in the contact edge of the tyre that varies by about 1cm per revolution. (probably the last owners emergency stop!):woohoo:

My therory is that this flat on the tyre is probably causing the forks to continaully bob up and down and becasue of the damping effect,  compress the travel of the forks so that when I pass over a bump in the road they bottom out.

I have a spare (rusty) front wheel & (just about legal) tyre that might be worth swapping over just to test the point.

Cheers,

Ray

shifty_steve:
Hi Ray, yeah I cant say I have noticed that much travel from front wheel or tyre, I had both new tyres fitted, rode 5 or 600 miles then realized the garage had fitted them wrong direction....very dangerous..so I ain't the most observant peg in the tin, made sure they are correct now though. This weekend I am determined to get to the cause, keep us up to date, fingers crossed with your test.

Steve

Ps; I did'nt think to ask but did you have this problem prior to forks refurb??

leonardo269:
Hi Steve,
             I dunno, the bike was a rusty (and dangerous) bag of spanners when I got it. I never dared to take it out on the road. The steering head bearings were that notched you would have had to turn in 5 degree installments.

To top it all the brakes were shot and the forks were lubricated with 1/2 a pint of mud per side.

I honestly dont know how someone can do that to a motorbike.

Much better now, even with the slight wobble.:lol:

Regards,

Ray

leonardo269:
OK - time for a bit of an update. I replaced the front wheel and tyre for a spare one that I had knocking about and it seems a bit better, although there is a fair amount of bobbing about from the front forks that indicates that the dampers are not working very well. (bearing in mind that I replaced the piston rings when the forks were rebuilt.

My local bike shop gave be SAE10W fork oil, but the Haynes manual specifies SAE10W-30. From the information I can determine the two figures relate to the viscosity of the oil in \"cold\" and \"at working temperatures\". with 30 being thicker than 10. This all seems to relate to oil that is going inside the engine, rather than inside the fork leg, so it is not completely clear.

The question is:- Is my existing oil too thin and could this be a reason for the lack of damping? Is it worth trying a SAE30 oil to see if this improves matters?

I have to do something this is ruining the riding experience at the moment.

Cheers,

Ray

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