Post by: Pauarc on August 31, 2023, 04:05:50 PM
Post by: Trigger on August 31, 2023, 05:42:13 PM
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 ;)
Post by: Pauarc on August 31, 2023, 07:22:29 PM
Post by: Trigger on September 01, 2023, 08:36:22 AM
Thanks Trigger
You can use brass cheesehead screws but, hard to find in a 5mm thread length so you have to cut them down. The sealing alloy washers are 4.9mm which bloody expensive for a sealing washer ;)
Post by: sprinta on September 01, 2023, 09:55:35 AM
https://www.ebay.co.uk/itm/134331731567
Post by: Laverdaroo on September 02, 2023, 10:08:13 AM
Not entirely correct that….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 ;)
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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Post by: Matt_Harrington on September 02, 2023, 10:29:12 AM
Post by: Trigger on September 02, 2023, 10:33:36 AM
Not entirely correct that….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 ;)
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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The Question was: What size the vacuum screw; and the bolt is M5 with a 5mm thread length. He never asked the pitch but, it is JIS standard 0.8 ;)
Post by: Oddjob on September 02, 2023, 03:05:39 PM
Post by: Trigger on September 02, 2023, 05:48:24 PM
Post by: Pauarc on September 04, 2023, 08:21:27 AM
Post by: Matt_Harrington on September 04, 2023, 09:19:56 AM
Post by: Laverdaroo on September 04, 2023, 10:35:52 AM
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Post by: Oddjob on September 04, 2023, 02:27:19 PM
He never asked the pitch but, it is JIS standard 0.8 ;)
According to that chart from Honda that information would appear to be wrong, ISO is standard at 0.8, JIS standard would be 0.9. ;)
Post by: Trigger on September 04, 2023, 02:52:41 PM
[attachimg=1]
Hard to get a good picture
[attachimg=2]
Post by: Oddjob on September 04, 2023, 06:30:53 PM
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.
Post by: Trigger on September 04, 2023, 07:02:28 PM
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 ;)
Post by: Laverdaroo on September 04, 2023, 07:30:53 PM
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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Post by: Oddjob on September 04, 2023, 07:33:56 PM
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.
Post by: McCabe-Thiele (Ted) on September 04, 2023, 07:48:11 PM
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.
Post by: Laverdaroo on September 04, 2023, 07:49:03 PM
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Post by: Laverdaroo on September 04, 2023, 07:50:15 PM
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Post by: Laverdaroo on September 04, 2023, 07:50:30 PM
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Post by: Trigger on September 04, 2023, 07:54:42 PM
The question was about a CB750 and the 750 was not made in !966/67 ;)
Post by: Oddjob on September 04, 2023, 08:01:07 PM
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, ;)
Post by: McCabe-Thiele (Ted) on September 04, 2023, 08:05:30 PM
To clarify my status I must have bought probably 10 JIS screws in the last two years - does this make me credible though?
Post by: Oddjob on September 04, 2023, 08:10:09 PM
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
Post by: Laverdaroo on September 04, 2023, 08:50:15 PM
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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Post by: Trigger on September 04, 2023, 11:18:22 PM
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.
Post by: Trigger on September 04, 2023, 11:25:06 PM
Not entirely correct that….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 ;)
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 ;)
Post by: Laverdaroo on September 04, 2023, 11:32:54 PM
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Post by: McCabe-Thiele (Ted) on September 04, 2023, 11:38:45 PM
Post by: AshimotoK0 on September 05, 2023, 01:46:44 AM
[attachimg=1][attachimg=2]
Post by: Oddjob on September 05, 2023, 05:46:28 AM
Not entirely correct that….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 ;)
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 ;)
No, that's not what you said.
You clearly stated that the standard JIS thread was 0.8, not the modified standard thread, which is 0.8. There are STILL 2 JIS standards, the old and the new, the fact it's a 750 we are talking about is irrelevant. It's very interesting that Honda did take the trouble to clarify the situation even 2 years after changing.
As for the Honda college, you are really trying to say they were discussing JIS over 10 years after changing the standard? Plus back then you'd have needed to be fluent in Japanese to attend and that's a language notoriously difficult to master never mind talking technical Japanese.
Post by: Trigger on September 05, 2023, 06:18:19 AM
Roo contradicted my answer with the wrong information about a M5 pitch screw for a 750 and any other SOHC's.
Ken jumped on the band wagon with his little team to confuse the thread and the correct answer.
They spoke very good English in 1992 in Japan as they do today. And yes they teach you a lot about JIS in the engineering collage and do teach you about changes in Honda parts and engineering practices ;)
Post by: Laverdaroo on September 05, 2023, 07:07:34 AM
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Post by: McCabe-Thiele (Ted) on September 05, 2023, 10:28:31 AM
We are aware that many members here have vast experience on old Hondas without all this theoretical bickering over a thread pitch.
If I want 500 advice my first port of call in reverse alphabetical order is is Ken or Bryan.
If I had a 750 it would be Graham.
Lots of folks here know about the 400's.
Time for a truce eh lads or just agree to disagree.
Members make their own choices about whose advice to take.
Post by: Matt_Harrington on September 05, 2023, 10:42:50 AM
Post by: oldchuffer on September 05, 2023, 12:24:26 PM
Post by: Oddjob on September 05, 2023, 01:45:10 PM
Post by: SteveD CB500K0 on September 05, 2023, 03:15:02 PM
Any more and I’ll delete the whole thread.
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Post by: Oddjob on September 05, 2023, 03:33:14 PM
Personally I'd say delete the thread. No knowledge will be lost and the back and too doesn't make the forum look good. Maybe for the best to put this to bed.
Post by: Laverdaroo on September 05, 2023, 05:22:07 PM
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Post by: McCabe-Thiele (Ted) on September 05, 2023, 07:32:32 PM
Post by: Trigger on September 05, 2023, 11:46:55 PM
I always use this Service Bulletin as a reference for threads Honda used pre and post 1967, as I have early 60's bikes and post '67 ones too.
(Attachment Link) (Attachment Link)
Cheers for posting it Ash, i could not find it yesterday mate