Topic: Broken triple clamp cb 750

[aminemed]

Hi all

Just discovered that my cab 750 K2 upper triple clamp is broken (see picture). Can I weld it ? Or drive with it for a short time until I find another one.

What is pissing me off is that the D washer was there and that I just fitted this upper tree 2 months ago

[pjlogue]

I would replace it.  Triple clamps are readily available on fleabay.  You could probably gently  ride it like that but I would not.  Unexpected pot hole or other heavy stress situation and who knows what would happen.  Just not worth the risk.  It would be like driving a car with a broken steering knuckle. 

-P.

[70CB750]

I rode Dorothy for a while before i found the top bracket was broken. Get a new one, once you know about it, riding is not the same.

[rotortiller]

Can I weld it ?

Yes it can be welded and is done often enough. I had one on a Kawasaki H1B that snapped several years ago that is welded as I could not find a replacement. You need a good welder/machinist and understand why it snapped  (lack of spacer washer etc). Again, you need a professional welder with something like this. Lots of structural stuff is welded and common place.

[ekpent]

  Looks like since yours is machined custom and does not use the stock gauge clusters etc. that you could fit a later model 73-76 top triple which are way cheaper then the 1972 "unicorn" clamp and much more plentiful.

[aminemed]

Any idea on why it broke ? D washer was properly fitted.

I'm gonna look for a new one, i understand that welding it is not a wise idea

[Don R]

 One of my bikes has aftermarket tubes, I can only assume they are bigger OD, I have D washers but they don't close up tight without breaking the top tree. consider making thicker washers and pay attention to the torque on the bolts.

[ekpent]

Any idea on why it broke ? D washer was properly fitted.

I'm gonna look for a new one, i understand that welding it is not a wise idea

Who knows after all these years but maybe when you remove it and do an autopsy you will see an air bubble or casting flaw. Maybe that machining you had done  when metal was removed increased the stress load a little bit.  Since its a cafe racer maybe you drive to fast and hard 

[cooldrum]

My upper triple cracked in two places (right fork tube side on K4) with D washers in place.  May have been over torqued a bit.  So be aware of torque values.  I posted in "wanted section" for a replacement and a forum member had a spare for me.  I wasn't going the welded route for safety reasons. 

[Stev-o]

I'm gonna look for a new one, i understand that welding it is not a wise idea

I have a spare modified [cut] triple top from an early K...

[754]

They are not cast i bet.. forged they should be..
 Otherwise they would all be broken by now..

[tlbranth]

Any idea on why it broke ? D washer was properly fitted.

I'm gonna look for a new one, i understand that welding it is not a wise idea

Let me throw out an opinion that'll run contrary to popular dogma.

The store-bought d-rings are a waste of money.
The lower clamp can be cinched down tight because it's steel. This keeps the forks from moving vertically and helps some from horizontal movement.
The uppers don't need to be bolted down tight. They're there to prevent horizontal fork movement and snug will do it. Make your own d-rings from washers. Try different thicknesses and sand down where necessary so you can tighten the bolts with just a snug fit on the fork. More stress on the clamp  adds nothing to fork stability.

My opinion. Flame away.

[jaytee-nz]

I agree - why else would Mr Honda make the upper clamp out of crappy alloy (and it is s*&t if you have ever tried welding one) and the bottom one out of steel ?

[754]

Look at a Beemer top clamp from the 80,s....
Always wondered how much does this hold from twisting..