Topic: Shimmy on deceleration

[callbr549]

Riding my newly acquired '72 CB750 I sometimes (not always) notice a slight shake or shimmy in the front end on deceleration, especially while turning. Any ideas?

[mystic_1]

Replace your steering head bearing with a set of All Balls tapered bearings.

mystic_1

[Kev Nemo]

Replace your steering head bearing with a set of All Balls tapered bearings.

mystic_1

EDIT: Sorry, my last post probably wasn't clear. What online sources carry All Balls for a 1978 750k-Bike Bandit, Dennis Kirk,etc?

[HondaMan]

Check for side-to-side looseness of the swingarm, and dimpled steering head ball bearings, and irregular chain with worn sprockets. All 3 of these can make this "speed wobble" show up. Oh, and worn tires, like a flat spot in the middle of the rear, especially.

Not to 'plug', but I rebuild those swingarms with lifetime parts. Honda's replacement parts are no longer correct for these bikes, and will yield very short life, with strong rusting tendencies (can't say why, just an observation from recent rebuilds.  ).

[chrislib]

Yup what they said, and Hondaman does outstanding work. I have one of his S/A rebuilds in my bike and it is verry nice.

[BobbyR]

While you are at it raise your tire pressure and see if it has an effect. The modern tires have softer sidewalls than the tires of 30 years ago.

[markjenn]

Just to be sure you don't fix something that isn't broken, most bikes have a bit of a wobble hands off when deceling through 35 mph or thereaabouts.  That speed is when you're at the resonant frequency of a fork front end.  If it only occurs in this circumstance and keeping hands on the bars damps it, I'd live with it.

- Mark

[mystic_1]

Replace your steering head bearing with a set of All Balls tapered bearings.

mystic_1

EDIT: Sorry, my last post probably wasn't clear. What online sources carry All Balls for a 1978 750k-Bike Bandit, Dennis Kirk,etc?

These are available in a number of places, I got my latest set off of Ebay.  Any shop that carries Parts Unlimited will be able to get them for you, too.

You want All Balls part number 22-1011 which is for CB750's from 69-78, plus many other models.

+1 on what Markjenn and the others are saying, however.  Steering bearings are a common source of this kind of shimmy but do check all points mentioned above for looseness.

Having said that, upgrading from the stock steering bearings is something I would do whether they were worn or not, but maybe that's just me.


mystic_1

[Kev Nemo]

...Having said that, upgrading from the stock steering bearings is something I would do whether they were worn or not, but maybe that's just me.


mystic_1

I'd heard that before-is the only improvement over stock the shimmy reduction?

[HondaMan]

...Having said that, upgrading from the stock steering bearings is something I would do whether they were worn or not, but maybe that's just me.


mystic_1

I'd heard that before-is the only improvement over stock the shimmy reduction?

It also improves steering performance and accuracy, and will immediately make the bike 'feel' smaller and lighter. As soon as you turn your first corner, it will pay for itself... 

[Kev Nemo]

...Having said that, upgrading from the stock steering bearings is something I would do whether they were worn or not, but maybe that's just me.


mystic_1

I'd heard that before-is the only improvement over stock the shimmy reduction?

It also improves steering performance and accuracy, and will immediately make the bike 'feel' smaller and lighter. As soon as you turn your first corner, it will pay for itself... 

awesome! I think a huge part of the 'cafe' feel is handling. I think the bearings are a good start.

[magnus72]

i would pull the front and see if it was balanced first.

[Steelo]

When I had a similar problem I found my spokes needed tightening - they were really sloppy when I had a good look - magic now!!!

[Kev Nemo]

When I had a similar problem I found my spokes needed tightening - they were really sloppy when I had a good look - magic now!!!

That's an easy check,too. Just go around the hub with either a smaller hammer or 'thump' the spokes with your fingers-if it 'rings' your good, if 'thuds', get to tightening!