Vacuum screws

[Oddjob]

Honda have been in business far longer than 20 years AND they are Japanese so I'm sure they know what the standard JIS thread pitch is, please note what Honda said. All screws and bolts fitted to the 750 (which clearly means all bikes after as well) are to ISO standard thread pitches not JIS. So they've clearly made JIS screws and bolts with the head of the JIS standard BUT they threaded them to ISO standards not to the more normal for Japan, JIS standard. As the ISO standard for M5 is 0.8mm that means all M5 bolts and screws are 0.8 and not the JIS standard of 0.9.

So your statement was wrong, whilst correct in saying the screw is 0.8, the part about JIS standard pitch is not.

As you're so keen to point out other peoples mistakes I thought I'd point out one of yours, fairs fair.

[Trigger]

So you are saying that all the M5 threads on all the SOHC's from 1969 have a pitch of 0.9  And i have been fitting the wrong pitch JIS bolts and screws all these years and forcing the JIS bolts and screws to damage the threads but, 0.8 screws bolts fit perfectly  Just tried to get a M5 with a 0.9 screw in to a head light rim for a SOHC and guess what, it doesn't fit.

And the member Pauarc has already stated that he has checked his sync port screws and his are 0.8, though the CB750K sync port screws are not the same as any other SOHC sync port screws but, only members with CB750's will know this.

Some member have experience and some members just believe what they have read   

[Laverdaroo]

MASSIVE  yawn!

All very boring now, anybody want to talk motorbikes instead of who’s got the smallest Willy?

Like a pair of lasses!


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[Oddjob]

I've got the smallest willy, problem solved

As for Graham.

Do you really not read what's been posted? or are you being deliberately obtuse?

Whenever it's shown you're wrong you start throwing toys out of the pram and invent stuff to support your failed arguments. You got it wrong, just admit it and move on. I do.

[McCabe-Thiele (Ted)]

This JIS pitch conversation is weird, it appears that Paurec says the pitch is 0.8 he has checked with a gauge & posted a chart, Graham has sold millions states the pitch is 0.8, Ken says they are 0.8.

So what was the point of trying to get a M5 0.9 pitch screw in a headlight rim to prove its 0.8 I'm lost in semantics here.

[Laverdaroo]

Loz did say that Ken


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[Laverdaroo]

Don’t be Ted, just yawn, tut and roll your eyes like the rest of us!


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[Laverdaroo]

Nearly forgot……….


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[Trigger]

I know I am not wrong. I went to Honda technical collage in Japan, where I was taught that the JIS bolts and screw thread changed in 1966 to 1967.
The question was about a CB750 and the 750 was not made in !966/67 

[Oddjob]

Paul posted a picture of a Honda bulletin which says that motorcycles like the CB750 were fitted with what are essentially a mixture of both ISO and JIS standards Ted. In order to try and avoid stripping threads Honda decided to keep the look of the JIS screw and bolt BUT they threaded them to the ISO standard and not the JIS standard. The JIS standard for an M5 screw or bolt is 0.9mm, whereas the ISO standard is 0.8mm.

Graham in his usual, I know everything manner, incorrectly said the JIS standard is 0.8mm and the Honda bulletin clearly shows he's wrong. Now for some reason he can't read bulletins any longer and when he does he clearly misreads them, or as is more likely, he pretends to misread them and continues to argue a losing point.

So to clarify, all bolts and screws fitted to bikes like the 750 are threaded to ISO standards not JIS standards, the shape of the head is irrelevant, as it's the thread pitch that counts not what it looks like.

Roo, 

[McCabe-Thiele (Ted)]

Ah but did they still put a dot on the head of the screw as I understand it they do not need it anymore to indicate a JIS head?

To clarify my status I must have bought probably 10 JIS screws in the last two years - does this make me credible though?

[Oddjob]

I know I am not wrong. I went to Honda technical collage in Japan, where I was taught that the JIS bolts and screw thread changed in 1966 to 1967.
The question was about a CB750 and the 750 was not made in !966/67 

You seem to ignore the fact that IF that were the case Honda would have had no reason to post a bulletin stating the thread pitch problem.

Oddly on all my Honda courses not a single mention of JIS was made. They just assumed we all knew what it was and what it meant.

And yes Ted, they still made them look like JIS screws and bolts, I suppose that was the point of the bulletin, to point out that they were not JIS thread pitched. The dot was to show the recess was made for a JIS screwdriver for example and not a Phillips screwdriver 

[Laverdaroo]

Paul posted a picture of a Honda bulletin which says that motorcycles like the CB750 were fitted with what are essentially a mixture of both ISO and JIS standards Ted. In order to try and avoid stripping threads Honda decided to keep the look of the JIS screw and bolt BUT they threaded them to the ISO standard and not the JIS standard. The JIS standard for an M5 screw or bolt is 0.9mm, whereas the ISO standard is 0.8mm.

Graham in his usual, I know everything manner, incorrectly said the JIS standard is 0.8mm and the Honda bulletin clearly shows he's wrong. Now for some reason he can't read bulletins any longer and when he does he clearly misreads them, or as is more likely, he pretends to misread them and continues to argue a losing point.

So to clarify, all bolts and screws fitted to bikes like the 750 are threaded to ISO standards not JIS standards, the shape of the head is irrelevant, as it's the thread pitch that counts not what it looks like.

Roo, 

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[Trigger]

Paul posted a picture of a Honda bulletin which says that motorcycles like the CB750 were fitted with what are essentially a mixture of both ISO and JIS standards Ted. In order to try and avoid stripping threads Honda decided to keep the look of the JIS screw and bolt BUT they threaded them to the ISO standard and not the JIS standard. The JIS standard for an M5 screw or bolt is 0.9mm, whereas the ISO standard is 0.8mm.

Graham in his usual, I know everything manner, incorrectly said the JIS standard is 0.8mm and the Honda bulletin clearly shows he's wrong. Now for some reason he can't read bulletins any longer and when he does he clearly misreads them, or as is more likely, he pretends to misread them and continues to argue a losing point.

So to clarify, all bolts and screws fitted to bikes like the 750 are threaded to ISO standards not JIS standards, the shape of the head is irrelevant, as it's the thread pitch that counts not what it looks like.

Roo, 

The whole post is about a CB750 and CB750 have JIS post 1967 M5 with a 0.8 pitch thread which are Japanese Industrial Standard after the change over in 1967. It was not about JIS pre 1967 which are M5 with a 0.9 pitch thread.
Both are classed as JIS. It is just pre and post pitch size.

[Trigger]

Does anyone know what size the vacuum screw on carb on cb750k are  like to change them they are a bit damaged

M5 with a 5mm thread 

Not entirely correct that….

Surely if it’s an M5 bolt, it’s telling you it’s 5mm, the pitch of the thread is what your after in that question in which case it’s only one of two options .08 or .09, that’s all it can be. Not in the workshop so can’t check but if you have a tap and Dye set use your thread gauge and find the matching pitch in that particular screw. Simples




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 I would like to remind that only one option for the SOHC bikes which this thread was about and to say that it is one of two options is incorrect