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[Peter Jones 20Participant @peterjones20]

This will be far to late for OP but anyone else looking for information may find it useful?

I worked in Honda dealers in late 70's, find the general information manual online, it fills in 'gaps' in factory service manuals. I've seen a lot of complaints about service manual not giving full details. It's because they were written for dealer staff, not someone with little experience or training

Japanese screws are JIS, correct screwdriver fits and doesn't bugger up the 'cross' (JIS = Japanese Industry Standard)

Google it for more information. It's been around since 1966 or so (previously there were different metric standards for threads, fit, etc) DIN may use same thread form but bolt head sizes are different

Honda use standard diameters but fine thread versions.

Finer pitch gives a larger core diameter plus ability to apply more torque

Usual pitches are 0.8mm, 1.0mm, 1.25 and 1.50mm irrespective of the diameter. (24×1.0 is actually quite common on steering stem as is 14×1 and 16×1 on crank ends)

1mm pitch is most common on 6mm and 7mm bolts but can be 'anywhere' (Honda normally use 7mm chain adjuster bolts on >250cc)

1.25mm pitch most common on 8 and 10mm engine bolts and clamp bolts (8mm standard ISO size)

1.50mm -, usually axle bolts

The only thread I found incredibly surprising was on spoked wheels where Honda were using 1/8" WHITWORTH until at least the late 1970's (Harley Davidson were using 3 or 4mm metric at the time,)

Comstar wheels were designed to flex but the rivets at rim will loosen over time (hell, they came loose while some bikes were still under guarantee)

A metric thread pitch gauge will be useful, I've had some since early 70's and haven't bought any new since early 80's

On a machining site I wouldn't have thought anyone wouldn't know how to measure any thread they saw?

[Peter Jones 20Participant @peterjones20]

Posted by Howard Lewis on 01/07/2020 10:34:55:

To retain aftermarket exclusivity some manufacturers used really odd fixings. The governor shaft on the Bosch EPVE was retained by three sided fixings (Guess what was the only place you could buy a socket to fit? )

I came out of a meeting with a potential fastener supplier, having just said "Nothing special, we don't want five sided heads" to find a Japanese cartridge type injection pump with five sided heads!

Presumably all in the name of tamperproofing; or exclusivity?

Howard

A large part of the reasoning is fines manufacturers have gotten from EPA and CARB in the USA (California Air resource Board)

A few years ago, Yamaha were fined around $23,000,000 for selling bikes in California that had been converted to California spec from 47 state models. They had not been imported as Cali spec and even though met all the standards required still resulted in massive fines and court costs.

The 'standard' fine for modifying a vehicle fuel system was around $10,000 per vehicle if done by a dealer and $5,000 per offence if done by an individual.

Honda went so far as to make not just sealed units but non adjustable units.

EPA did a lot of good things even though most 'petrol heads' hate them, we wouldn't have the high performance fuel efficient vehicles if it wasn't for EPA regulations.

CARB on the other hand, seems to be a beaurocracy designed to find fault and extort the maximum amount of money from people

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