DSS sell the later oil restrictor for not much.
https://www.davidsilverspares.co.uk/CB750K6-FOUR-1976/part_322069/But I fully understand the urge to buy those parts. Hopefully a package deal since seller does not need to sell each part ony by one with shipping and eventual people claiming not getting the part, contacting eBay and PayPal.
I have a similar dilemma here when my local shop's mechanical guy will retire within 6 months. There is no other close that can restore CB750 heads and rebore cylinders as he can that has done this since middle of the 70's. Street bikes, racing and dragbikes.
Guys that can bore 45 minutes away by car instead of 5 minutes and charge +40% more.
I have let him rebore some cylinders lately. 836, 849cc with new or almost new pistons for future use.
- 890 cylinder to be done early next year for another engine build. Install sleeves and bore.
- Restore my ported 5mm stemmed head. (New guides on most ex, machine deeply sunken head nut marks etc. For the 890 build using 12.5:1 JE pistons that will like DP315 cam and chamber size of 24.4cc.
This engine will most likely enter my 3rd CB750, also a K2 1975 frame and registration.
- He is currently porting an old scrappy 392 head I have, time to restore with 33.5/28.5mm valves.
I told him to make more power than the head he recently restored, ported and decked that gave 101whp on dyno 2 months ago.
![Wink ;)](http://forums.sohc4.net/Smileys/default/wink.gif)
- Upon that another bore, K1 cylinder I have bought Cruzinimage 61.5mm K7 pistons for.
(Like my K2 1975 got earlier this year, but K6 cyl and restored K6 head)
- A rather fresh K1 head in need of new guides. (New valves in my garage). Can be used on a K1 bottom end I have.
Lots of investments to be done this winter while still possible for the old parts I have gathered in my garage during the years.
Sometimes it is a must to invest in things not really needed now, but for future years while still possible.