Topic: 1972 Honda CB750 Stripped Tachometer Screw

[Honda3]

There is always something.

Why do Previous Owners tighten and overtighten everything down like their effing lives depend on it?

Went to change the tachometer seal and noticed the screw that bolts in the tachometer (in the head) is stripped.

Any ideas on how to get it out?

Super annoyed.

[minimo]

If it’s far gone...

Spiral Screw Extractor Set (5-Piece)
https://www.homedepot.com/p/205469301

This and a power drill, lubricant like Marvel’s Mystery Oil, and patience. Go slow.


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[Honda3]

If it’s far gone...

Spiral Screw Extractor Set (5-Piece)
https://www.homedepot.com/p/205469301

This and a power drill, lubricant like Marvel’s Mystery Oil, and patience. Go slow.


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Thanks. What if its not totally far gone?

[minimo]

You can try a larger bit size


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[Honda3]

You can try a larger bit size


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Im scared lol. Really dont want to mess up the head.

[minimo]

A picture or two would help here. Let’s see what you’re talking about


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[Honda3]

A picture or two would help here. Let’s see what you’re talking about


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In the AM. its nearly midnight here in NYC. What about a small vise grip?

[minimo]

Is that to suggest that a little bit of the screw is backed out? Those tach screws are typically an oval head so if you can get a set of Vise Grips on the sharp edge then sure, have at it.


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[Don R]

 If the screw head is ruined you need to replace it anyway. Craftsman did have some left hand drills with an easy out made on it. I just used one on some stripped shifter cover screws. They zipped right out.

[Don R]

https://www.sears.com/craftsman-drill-extractor/p-00952152000P?ef_id=CjwKCAjwm4rqBRBUEiwAwaWjjGr0U-iTDoXyEEMSRLvqN2tXeXcS6GtclM-jt1_lmQRGVM2gedpzaRoC3zsQAvD_BwE:G:s&s_kwcid=AL!8592!3!317853285778!!!g!761465361272!&sid=IDx01192011x000001x1651384318&utm_campaign=9021994&utm_group=62569197599-317853285778&utm_term=pla-761465361272&gclid=CjwKCAjwm4rqBRBUEiwAwaWjjGr0U-iTDoXyEEMSRLvqN2tXeXcS6GtclM-jt1_lmQRGVM2gedpzaRoC3zsQAvD_BwE

[jgger]

If it is the Phillips screw that is buggered up, take a flat punch and smash on the edge of the slots. This will "bend" the metal back into the hole where the tip of the screwdriver goes. Then using the tip for an impact driver (the kind you hit) tap the bit into the screw so it seats good then use the impact driver (again, the kind you hit) put some torque on it then smack the driver like you mean it. If you hit it with your purse it will just bugger it up again, then more drastic measures will be needed.

If it comes out the only thing you want to use the old screw for is to compare to the NEW one to be sure it is correct.

Very common issue when using Phillips drivers and not JIS. Back in the old days I used this method alot because nobody knew WTF a jis driver was...........including me!🙈🙉🙊

[jgger]

Don, I think Homer's De-pot sells a double ended one singular. Just have to remember to set the drill in reverse, then flip the bit and use the extractor end.

[Honda3]

If the head is ruined you need to replace it anyway. Craftsman did have some left hand drills with an easy out made on it. I just used one on some stripped shifter cover screws. They zipped right out.

Hi and thanks for your message....BUT, I didnt say the head is messed up. I said I dont WANT to mess it up while trying to remove the stripped screw.

There is nothing at all wrong with the head or the bike:

[jgger]

The head both of us are referring to is the head of the screw, not the engine head.

If the head of the screw is good then use the impact driver (the kind you hit) with the proper JIS bit and whack away.

[Honda3]

The head both of us are referring to is the head of the screw, not the engine head.

If the head of the screw is good then use the impact driver (the kind you hit) with the proper JIS bit and whack away.

Ah I see. Im going to see if a small vise can fit on the head first.

[Honda3]

The head both of us are referring to is the head of the screw, not the engine head.

If the head of the screw is good then use the impact driver (the kind you hit) with the proper JIS bit and whack away.

im also going to see if I can find the allen head version screw.

[jgger]

Yea, I kinda thought that was an Anna Rosanna Rosanna Danna moment😁

I thought that screw was a counter sink one. What were you going to clamp onto?

Pics would help a bunch.

[PeWe]

Screw only rotates, not coming up due to ruined threads?
Put a thin screwdriver under the had and press upwards while you unscrew the screw. It will enter the good threads and come out.
I think I fixed a thread like that with an  M6 tap. M6 screw next time.

[Honda3]

Screw only rotates, not coming up due to ruined threads?
Put a thin screwdriver under the had and press upwards while you unscrew the screw. It will enter the good threads and come out.
I think I fixed a thread like that with an  M6 tap. M6 screw next time.

No. That is not the case.

 The screw is not stripped and the threads are not ruined. Its screwed in tight and I cant unscrew it because the head is damaged.

[minimo]

Would still help to see a pic of it.

You can also try to carefully Dremel out a larger cross pattern to accommodate a larger bit and driver. Liberally apply PB Blaster into as close to the threaded part as you can. Localized heat with a micro torch might help too (though I’d be careful with heat if you want to maintain the rubber oil seal that’s on the tach drive - may need to replace that and the screw anyway)

[Don R]

 As posted, try a larger point screwdriver, usually I find the one that fits best and use the next bigger one, or get a set of jis screwdrivers that are intended for these screws.

[Honda3]

Would still help to see a pic of it.

You can also try to carefully Dremel out a larger cross pattern to accommodate a larger bit and driver. Liberally apply PB Blaster into as close to the threaded part as you can. Localized heat with a micro torch might help too (though I’d be careful with heat if you want to maintain the rubber oil seal that’s on the tach drive - may need to replace that and the screw anyway)

Thanks for your help. I will post a pic in just a bit. I have to do some work on my 73 CB500.

[Bankerdanny]

A hand held impact driver isn't going to damage the valve cover. It is very common for the various engine cover screws to have buggered up heads and be over tightened and a manual impact and a hammer will get out 99% of the screws.

It is highly unlikely (although not impossible) that you will actually damage the cover. You can use a regular claw hammer, it doesn't have to be a heavy sledge. Make sure that the impact is set to loosen the screw though, accidently tightening it with the impact could cause the cover to crack. Not the end of the world if the cover as a crack at that point should be repairable with something like J.B. Weld.

[maxheadflow]

The tach screw is a simple 5mm button head phillips .  My method for removing these is to use a punch sharpened to about a 60 degree point and a small ball peen.  Set the point on the side of the head and tap lightly until you got a reasonable divot.  Angle the punch to drive the screw counter clockwise. Keep tapping.  They usually come out first try but if punch only tears the divot, try again in another location.

[Honda3]

Thanks,

Devoted my attention to my CB500 today. Before and after:

[Ll_lis]

Just another tip to avoid damaging screws in the future. I’ve found these screwdrivers from harbor freight work really well on these engines especially for these seized ones. You can take a wrench or socket to the crack of it while holding the screw driver for leverage.

Link:  https://www.harborfreight.com/hand-tools/screwdrivers-nutdrivers/screwdrivers-screwdriver-sets/8-piece-bolstered-screwdriver-set-94899.html

[pjlogue]

If the threads of the screw are stripped and it will turn but won't back out use a set of diagonal cutters and gently pinch under the head of the screw to lift it as you turn it out. 

-P.

[Honda3]

The tach screw is a simple 5mm button head phillips .  My method for removing these is to use a punch sharpened to about a 60 degree point and a small ball peen.  Set the point on the side of the head and tap lightly until you got a reasonable divot.  Angle the punch to drive the screw counter clockwise. Keep tapping.  They usually come out first try but if punch only tears the divot, try again in another location.

thank you for this!

[evinrude7]

honda3 that .8 is the pitch.  soak the screw in the valve cover with some penetrant and put a set of vice grips on it and get it out of there.  also when you put the new one in it doesn't have to be outrageously tight.  it's just a retaining screw.