Engine Pan Screws

[Wayne]

I'm going through all of the engine pan screws for 576 and some are in tough shape. Deep pitting, rust on heads etc.

In my manual it says that the "Cross Screws" will have a 'Semi - spherical embossment. (mine don't, they are smooth)

I see replacement Honda parts have what appears to be a little "X" or a "+" on them.

I don't see anything on the individual screws Yamiya offers. The only difference I see are that the threads go right to the head of the screws. I can't tell from the image in this kit if these would be a good replacement screw. Has anyone used these screws/kit as a suitable replacement for pan screws? Thanks!

http://www.yamiya750.com/index.php?main_page=product_info&cPath=21_49&products_id=126

[Steve Swan]

i don't know anything about Yamiya screws.  i would hazard a guess they are maybe from Honda. 

I've always ordered new screws from Honda.

I believe you are referring to what we Yanks call Phillpips head screws; for the cam cover ?

FWIW, Japanese screw heads are actually JIS, i recently bought a set of JIS head screwdrivers from Vessel and the fit is 100% tight and secure, the tip of the JIS screwdriver locks into the head of the screw.  Phillips screwdriver heads are actually designed to "cam out" to prevent over-tightening and are a sloppy fit in a JIS head screw.

[1941wld]

The new screw that come fron Honda have the + or x on them these days. The old original Honda screws have center punch mark on them. For that perfect restoration, I would not use the new screws with the + on them.

Now if you are talking about the cap screws, I've purchased a set of #8's from Yamiya and they are spot on. The different sizes have little different shades of cad plated, some a bright silver some a slight yellow bright silver.

[Wayne]

Thanks. I actually do have a JIS screw tip for my driver. Nice tight fit. Actually locks in there much like the "posi-driver" screws that GM came out with years back. A LOT of Phillips screws heads were stripped out on GM cars until people realized they had a slightly different head! :/

OK, back to topic. The screws I'm talking about are indeed all of the cover screws. Cam, Dynamo cover etc. etc. The parts manual refers to them as "Scew, pan 6 x **"

So here is a shot of one of my good pan screws. As you can see, there is no marking on the head.



This is a replacement Honda screw. Note the little "x"



The YAMIYA pan screws say they are manufactured by YAMIYA.

Here is a YAMIYA screw. I can't tell if it's embossed or if that mark is a reflection. It appears to be embossed.



This is the information in the service manual I was referring to:

[Wayne]

If Conrad is saying the "original" screws have a punch mark vs a cross, yet non of the screws on 576 have any type mark on them do we have another "distinction"??

[Steve Swan]

I was able to use the majority of original 'Phillips' screws that came with 4363, they have no markings.  i have seen both types of markings; "x" and "."

I would hazard a guess, the "." marked screws came after the unmarked screw heads.  The "x" marked heads were after the "." marked heads.

[Wayne]

That was my thinking as well Steve. Wonder when they started stamping them? After sandcast run?? Anyway, I guess I'll be counting screws and the search is on for some good replacements. I think I'll email YAMIYA just to clarify what they have.

[Steve Swan]

let us know what you find w/ the Yamiya screws.

[Wayne]

Well, good news. He didn't mention the individual screws that YAMIYA sell however the screws in the engine kit:
http://www.yamiya750.com/index.php?main_page=product_info&cPath=21_49&products_id=126

do not have a "punch" or "x" with the exception of the P55x25.

From set:


and the P55x25:



Might be the way to go!

[1941wld]

Yes, Steve is correct. The early screws had no mark, next came the punch and now Honda has the +. I's say some where in the earley 70's the punch marked screw was introduced. My 1965 and 66 CL77s and CB77s have unmarked screws.

Off subject a little my 1966 CL77 scramber restoration uses 10mm bolts with 17mm hex and 8mm bolts with 14mm hex (all bolts on these bikes have no marks on the heads/hex. Honda changed the use of these bolts on the 1969 CB750 production using the #8 marking on bolts and reducing the hex size. Honda has never used a 13mm hex on any of there vintage bikes (unknown on new ones).

[Steve Swan]

i'm currently working on a 78 CB550 that has 'punch' marked Phillips screws.

[gary]

Hi Wayne, i have the screws from 786 and they have no marks at all.

[gary]

The screws on 786 are all good shape what should i do to them before reinstalling them. They buff up good. or should i re zinc them?  thanks  gary

[kmb69]

Conrad's post jogged my memory a little. I want to say it was in that time frame when Honda was switching standards from JIS hex head sizes and thread pitches to ISO. The "dots" or punches on the screw heads meant they still had JIS crosses.

The pitch change was never an issue on the 6mm x 1mm pitch fasteners as they were the same in JIS and ISO. Some of the smaller and larger sizes were affected by the change in thread pitch and hex sizes. Didn't look up the details but I'm pretty sure.

I also seem to recall a Honda Service Bulletin about this but I cannot find it.

[Marcello Tha]

Change in Thread Pitch -- The standard thread pitches for all bolts. nuts. and screws in the 3 mm. 4 mm. 5 mm and 12 mm sizes are changed as indicated below: ...

www.honda50.com/partslists/z50A-shop.pdf‎