Topic: 1981 CB650 Custom Front Forks

[pmanning]

My son wrecked his '81 650 about a month ago bending both fork tubes and breaking the axle bore on the right fork leg.  He bought what he thought was a replacement front end off ebay but when we tried to fit it up today we discovered a major difference. His original fork tubes were 35 mm whereas the used ones he bought are 37 mm.  Before the wreck he'd also bought a fancy billet aluminum top triple tree clamp that he wants to reuse.  My hope is that we can get the tube bores on the clamps machined to accept the larger tubes.  The worry side of me wonders if that will leave sufficient metal in the clamps to provide adequate strength.  I'd like to know if anyone has tried this and I'd welcome any thoughts.

[mrfish2]

I've got a set of forks from an '82 650 nighthawk if you'd rather have another set instead of messing with all the machine work required to make your new forks fit.

[grcamna2]

2mm doesn't sound like that much to remove from those strong triples;what does your custom top triple look like? pics ?

[754]

That means 40 thou off each side, should be OK, But is the SPACING and OFFSET the same on the other fork, good chance its different.
 I cant see a 650 fork being real pricy..

[cb650]

They probably sent you 82 nitehawk forks that are bigger.    There are 3 diff sizes on the sohc4 650's and spacing.

[pmanning]

We got the bottom triple tree with the used forks but not the top clamp.  The spacing is different on the on the bottom clamp of the replacement forks we bought compared to the original geometry on the '81.

The billet aluminum top clamp that we want to reuse is a Dime City Cycle product; http://www.dimecitycycles.com/vintage-cafe-racer-caferacer-bobber-brat-chopper-custom-motorcycle-steering-parts-billet-aluminum-cb650-top-triple-tree-12-2147.html.

There is a very good machine shop locally that I trust to do the work.  My only concern is that the somewhat thinned clamps will be sufficiently strong.

[754]

 That is a bit thin, but the top gets less force into it,
 BUT..... if any of your dimensions, like width are different, you are screwed......

[grcamna2]

That is a bit thin, but the top gets less force into it,
 BUT..... if any of your dimensions, like width are different, you are screwed......

That billet top triple is thin and already 'bare to the bone' in those areas,I wouldn't bore that one out,get a matching oem Honda top triple for what you already have.

[mrfish2]

They probably sent you 82 nitehawk forks that are bigger.    There are 3 diff sizes on the sohc4 650's and spacing.

Interesting, I didn't know that. Guess he doesn't need mine then!

[SOHC4 Cafe Racer Fan]

I think the later nighthawk fork are 37mm and might have different spacing and offset. 

It sounds like it would be easier to just find another front if you are set on using the DCC top triple. 

[pmanning]

Thanks all for the input.  I think we will put aside the option of machining the clamps to accept the larger tubes.

So we are now in the market for an '81 front end if anyone has one available and we have and '82 Nighthawk front with legs, tubes and bottom triple tree if anyone is interested.

[SOHC4 Cafe Racer Fan]

I have one but it is 400 miles away in cold storage.  I kept the chassis rolling to make it easier to move around.

[SOHC4 Cafe Racer Fan]

Try member tomwitt 
He frequently parts out 650s.

[Flatlander80]

I have a set of forks off a 1980 CB 650 Custom. They are from a parts bike, but that bike was running a few years ago. If you're interested, PM me.


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[74cb750]

I also have a set of forks, air controled?
 see here:
http://www185.pair.com/canukvt/hon/

and

http://www185.pair.com/canukvt/hon/1983_cb650sc/

remember, there is often a lot of difference amoung the CB650c/CB650SC/CB650

make sure you measure and have the seller verify all dimentions you can....just saying.
michel