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Engine case bolt protective coating '86 -'89 VFR


Skipper

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My VFR 750 engine is looking good with a fresh coat of paint in two colors BUT I need to do something with all the cover bolts.

Knowing that paint normally will come off with a few applications of a socket whilst screwing them in or out, I wondered if anyone knows what the original coating system was and if it is available today? Where the bolt stem is inside the engine, the coating looks like new but weather and age have caused the exposed surface to deteriorate to a point that it needs a "fix".
I am somewhat color blind (like a good percentage of males) but the color looks a brown rather than black and I wondered if it is one of those fancy "military type" coatings, used on all sorts of Millspec equipment?
Before this coating the bolts may even have been CAD plated, not sure though I do not want the "Bling" factor of bright shiny bolt heads anyway.
There is also an argument that electroplating multiple times has an adverse effect on strength due to build up of hydrogen embrittlement.

Any help would be appreciated 🙂
 

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Pretty certain they’re black zinc plated. There are silver, yellow, and green colors, too. You might find a home kit or will need a zinc plating company, otherwise. 

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That’s what I used, satin finish Ti on all the visible engine bolts, they look OEM 

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Excuse my ignorance but are you saying you can buy black satin finished titanium bolts with the same small head as used on the original engine?

Sounds expensive for a complete cover bolt set?

Surely I must be getting the wrong message

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I had a lot of store credit to use before it expired …yes they were expensive 

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3 hours ago, Skipper said:

Excuse my ignorance but are you saying you can buy black satin finished titanium bolts with the same small head as used on the original engine?

Sounds expensive for a complete cover bolt set?

Surely I must be getting the wrong message

 

Think you have it correct - Ti bolts are available to replace OEM, same shank, shoulder,pre-drilled for safety wire, etc. Now your bike is 30+ years old so you might have to search by part # rather than simply buy a kit and, yes, they are expensive. Check it out - https://www.probolt-usa.com/

 

If you go down this road make sure to use a little anti-seize on the bolts

 

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My budget will not streeeeeeetch that far, I'm still looking to find the answer to my original question:

What was the original coating on the cover bolts of  an '89 VFR please

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A quick and simple way to get the bolt heads black is Kurust or similar 

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Thanks Thumbs for the suggestion, however it is not the pre-treatment I seek but the actual finish I am trying to replicate

Alternately a good durable finish that will not chip off with applying a socket on it to remove or re-fit.

The most common solution is "get the bolts re- zinc plated" (if that was their original coating) which I do wonder about but it is hard to find plating in the color brown

My own research tells me that any plating process will cause a lesser of greater degree of Hydrogen embrittlement (look it up on the net)

This would seem un-avoidable except that dependent on the particular prosses more (or less) damage is caused - but there will always be some damage

Solutions such as cleaning the bolts completely by hand prior to delivery for electroplating (most damage occurs during the longer immersion during cleaning - apparently?)

 

And all this still does not explain the brown / bronze color on the original bolts that I would like to replicate

I may yet end up buffing the heads clean, and applying an etch primer plus a good top coat in the appropriate color and hope for the best?

Please keep coming with ideas, I appreciate your input, kind regards to all

 

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Go buy new bolts from Honda. They’re black; not brown. That’s what age, sunlight, and cleaner/chemicals do to the finishes. 

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Turning brown with age and wear may be black-zinc coating over chromate. Or nitrided. Neither of which is something you can do at home.

 

There are black oxide kits you can DYI, but it's not very corrosion resistant and you'll see rust forming quickly. There are also rust-converter type surface-prep products that leave mildly-protective phosphate coating that needs to be painted. But no painted bolts will withstand tool marks.

 

Best to just get new bolts from Honda.

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Thanks Danno, appreciate your feedback. Yes, I am thinking along the same lines having closely checked all the bolts, there seems some variance in the shade of brown, some being more towards black even to my color blind eyes so black it is (as Ducnut said from the start) and nobody has claimed different. They are zinc plated under the color.
So it comes down to three options: buy all new bolts, re-plate the originals in black zinc with increased embrittlement or paint the heads of these suckers black

 

I want to thank all for their contribution to this discussion, I think I have made a choice but to each their own, I'm sure there will be as many disagree  with me as find my choice acceptable so I will not create controversy by disclosing what I will do. Suffice it to say I am retired and need to conserve my pennies in these troubled times, a condition I am sure that I am not alone in 😊

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