Topic: Adjusting tappets / valves

[HondanutRider]

Haven't seen this posted before.  My son gave me a good tip for making a simple tool that really makes adjusting the tappets on Honda engines - so much easier.  Using this tool, you can get a nice fine adjustment and then keep the tappet position in place while the nut is locked down.

What you need is a Robertson head screw.  (A Phillips won't do.  The Robertson slot is square like the tappet head.  Mr Robertson was a Canadian, eh!)  This screw head can fit nicely over the tappet and allow it to be adjusted as well as held in position when the locking nut is tightened.  I find a #3 head size (used with the black-handled driver) is a good fit.  A Marr connector is also useful to put over the screw end so that it can be easily gripped and turned.

Here are some photos of this neat tool that I made on my son's instruction.

[BobbyR]

Would you have a pic of the head on that screw?

[tbpmusic]

Brilliant !!!

I believe we call those screws "square drive" here in the US - available at any hardware store, or Lowes/Menards, etc.

bill2

[MCRider]

Brilliant !!!

I believe we call those screws "square drive" here in the US - available at any hardware store, or Lowes/Menards, etc.

bill2

The Robertson...driver and screw...http://en.wikipedia.org/wiki/Robertson_screwdriver

So there are different sizes, one needs the correct one. And BTW, a CB750 has slots not squares. 

[HondanutRider]

To: BobbyR

As you requested, here's a pic of Mr Robertson's head.  (I'll bet you could show us more of your lovely avitar, too.)

From: BobR (aka a "Honda nut Rider")

[BobbyR]

Thanks Bob. I Was all excited until I was just told I have slots. Very clever idea
nonetheless.

[HondanutRider]

"And BTW, a CB750 has slots not squares."  ...did not know that.  I guess that would make them easier to adjust than all the "smaller" Hondas that I have only had experience with.  With a slotted tappet head like on the CB750, I suppose you can just use a normal flat screwdriver.  The CB350F that I own has the square-headed tappets, as are all my other smaller Hondas - such as the SL100 head shown in one of my pictures.

I don't know about the CB450 motor, what with its torsion bar actuated valves. What about the other SOHC motors - the 500/550 and the 650 - are they square or slotted?  And, with bucket and shim arrangements, as on my GL1800, I don't think this tool will be of any use either.

But it works great on those square tappets.

[Steve F]

I've found that the slotted head is almost difficult to work with since the screwdriver won't fit tight in the slot and you get "backlash" while tightening the lock nut.  To get around this, I ground down an old small screwdriver to a wedge-like shape to fit the slot.  This way I don't have the backlash problem with the screwdriver in the slot.

[MCRider]

I've found that the slotted head is almost difficult to work with since the screwdriver won't fit tight in the slot and you get "backlash" while tightening the lock nut.  To get around this, I ground down an old small screwdriver to a wedge-like shape to fit the slot.  This way I don't have the backlash problem with the screwdriver in the slot.

That's a good idea. So thinking of that, it would also be good to grind the taper off the screwdriver tip so it fits real snug in the slot. Think I'll look for a sacrificial screwdriver.

[MCRider]

"And BTW, a CB750 has slots not squares."  ...did not know that.  I guess that would make them easier to adjust than all the "smaller" Hondas that I have only had experience with.  With a slotted tappet head like on the CB750, I suppose you can just use a normal flat screwdriver.  The CB350F that I own has the square-headed tappets, as are all my other smaller Hondas - such as the SL100 head shown in one of my pictures.

I don't know about the CB450 motor, what with its torsion bar actuated valves. What about the other SOHC motors - the 500/550 and the 650 - are they square or slotted?  And, with bucket and shim arrangements, as on my GL1800, I don't think this tool will be of any use either.

But it works great on those square tappets.

What are you working on, a 350/400?  The DOHC 450 is an odd duck, the adjusters are on the sides of the head, but they are lock nut over slotted adjuster.

I'll use your trick on my CB77.

[mr.brandon]

thank you for the tip.i am new and looking for a good tutorial on valve adjustment w/ plenty of pics for a 75' cb750. i have entire cover off.