cylinder head stud threads

[IanA]

Me again - Sorry.
Despite having 3 part engines to amass 2 working engines from i have only 2 head stud bolts. These are 230mm in length and so different to the bigger engines and are only 8mm diameter vs 10mm i believe. Having unscrewed them from the cases, i am on the hunt for replacements but am being stumped by the threads. Using metric thread pitch gauges i cannot get a match and whilst illogical am now assuming they are imperial but dont have any imperial thread pitch gauges. I know that the footrest bolts from memory have an imperial pitch.
The crankcase end is a finer pitch than the head end. i can buy high tensile metric studding, so worst case could tap out holes and helicoil to M10 and use high tensile M10 studding but seems a shame.
Any wise words out there?

[ducwiz]

Hi,

I'm not a specialist for the 160 (I suppose your bike is one), but I have two spares catalogs available. The italian type lists not a stud but a bolt/screw M8x209, and same can be found in the spanish catalog. I have never seen cylinder head studs on a Ducati single.
Have you checked the threads in your engine cases - are they M8 or also different? You can use a std. M8 screw to check this.

cheers Hans

[IanA]

Thanks Hans. You raise several good points, in fairness i have been lazy and didn't assembly the barrel and head and see if the studs were proud and therefore overlength, i will check both the thread with an M8 and the length in the morning, too damn cold now. My concern was that the stud seemed to fit one of the other engines but as all from one previous owner perhaps the mod was done across all 3 engines. the 209mm length will be most valuable - Thank you.
I have found some over length helicoils which are approx 25mm long and so would go to the base of the crankcase holes, if i need to go that rote to get back to metric threads.

[PhilR]

Ian, 160 manual shows 8MA x 209. I buy bolts and screws from ACCU.co.uk and they list M8 x 210 in stainless. Hope this helps.

[IanA]

Thanks Phil, good contact, just need to resolve what thread they are now, hopefully just crap thread pitch gauges but usually ok. allowing the temp to rise before i venture out, -8oC today

[IanA]

Investigations show that one engine has been modified and the thread is actually 5/16th, luckily the other 2 engines are M8, so will order up some high tensile stud and weld on nuts to make my own bolts.

[ranton_rambler]

Or just put nuts on top, as Brian has done. Only disadvantages is that you can’t take the head off with the motor in the frame.
Ian