Low Head Allen Bolts

[Mick Taylor]

Tinkering with my Classic today, I removed the upper and lower steering yoke clamp bolts.

They are a bit of an oddity; the cap head of the bolt has a reduced height......(low head) about half the height of a typical Allen head, and underneath this reduced height head in each case is an aluminium spacer, I didn't measure it, but maybe 2.5mm thick.

Added to that......my eyes might be playing tricks on me, they're not brilliant at close up....but the seat where the spacer sits doesn't look square but slightly tapered..but I could be wrong.

The parts book just shows Allen bolts, no mention of special features or spacers......they appear to be original in so far as they were manufactured as low head bolts......and the upper pair take a smaller Allen key than the lower pair despite having the same thread which suggests a reduced torque.

Anyone know what the purpose of these spacers might be?

Mick.

[Richard Negus]

The wonders of Italian logic! I never worked that one out either, and always replaced them with standard stainless bolts as a matter of course.
Just checked the Classic here; lower bolts are low head 10mm, 8mm recess, marked 10.9 grade, with aluminium washer.
The uppers are full head 10mm, 7 mm (seven!) recess, marked 8.8 grade, no washer.
The only other application of a 7mm recess I ever met was also Italian - the head bolts of a Lambretta sc##ter.

[Mick Taylor]

Thank you for that Richard.........as it happens I was planning on replacing them with stainless and getting all the originals bright zinc plated as soon as I have enough to justify a trip to the platers.

I assumed (which is always fatal) that the smaller hex in the upper bolts might relate to reduced torque....or not

In short ........ no known reason for it ......it's weird, but that is good enough for me, many thanks.

Mick.

[johnbirchjar]

All four bolts on my Classic are exactly the same,and I have owned the bike from new ,J.B.

[Mick Taylor]

You would imagine there must be a reason, surely they wouldn't go to the trouble of using specific (odd) bolts with alloy spacers without a good reason, .........would they?

That was what stopped me from just replacing them, in case I'd missed the bleedin' obvious......I think I'll turn the heads down on some stainless bolts and use those with the original alloy spacers......

Mick.

[johnbirchjar]

Do IP2's have odd bolts and spacers?'cos I have always been under the impression that Classics were(more or less) naked IP2's ,J.B.

[Mick Taylor]

There are a few odd threads in the mix too......the vast majority of threaded parts on the Classic appear to be metric ......... but there are a number of parts where a UNF thread is shown. The rear torque arm, for instance, has a UNF threaded bolt at the front end and a metric one at the other end

Mick.