Sorry for the lack of information and introduction. So it is a K2 1972 CB750 that was all original with 11,000 miles that sat for 30 years and I bought it as a covid lockdown project. I have modified the bike to be a sort of "hybrid cafe racer" but kept to the original design for the most part. It was clear that there was quite a bit of moisture that sat in the engine due to the rust internally on the valves and guides on the exhaust side but the engine did turn over easily. I wanted to complete the bike 'as-is' knowing the engine will need a rebuild but since the engine started right up after I cleaned the carbs and I unstuck the one valve on #3, I rode it until it became problematic. I would say I put on around 2000-3000 km since and rode it fairly aggressively without many issues.
Issues that were present: rising idle when the engine became hot, oil burning when the engine was hot, and I would say the engine was a little "buzzy" at high RPM but I don't have reference to sorted CB750's (and I'm led to believe they should be very smooth).
I have attached pictures of the bike and top end parts which all show nominal signs of wear and zero rust. There is a minor chip on one of the camshaft lobes as pictures but it is offset. I've attached a picture of the associated rocker as well showing its damage... I don't believe that would be the cause of the ticking, but I'm glad I have replacement parts.
The ticking sound developed after I put it away from sitting outside during the winter and it subsequently became more difficult to start and slight loss in response/power the following Spring. I double checked all clearances and they were fine. I did try to pinpoint the ticking sound using all the mentioned 'tricks' but failed to locate it other than it being in the vicinity of the middle of the engine and possibly towards the top end (this may explain why it could be the valve guides, especially on #3). Speaking of which, I cannot take a picture of the slight abrasion marks on #3 that I noticed as it needed to be pressed downwards by the cam to clearly show this.
Upgrades and new parts include: new cylinders modified and bored by CycleX to 836cc with JE domed Pistons, RC295 camshaft, M.R stage 3 ported head with oversize intake valves, titanium retainers, Kibblewhite valves, bronze guides, serdi valve job. On top of that, I have purchased refurbished guide pins and rockers by CycleX just to be safe and ready for the RC295 camshaft.
I have also gotten a new cam chain guide but I think I will keep the exiting chain as it looks to be in great condition with zero pitting and rust (I'd have to open the cases up anyhow to replace and I'd want to avoid that)
Lastly, I just wanted to add that the bores could easily be honed and cleaned up for reuse. There is corrosion but zero pitting and they are all smooth - I suppose the mileage I put on the bike may have certainly helped clean this up without problem. I decided to get refurbished head and cylinders because it was more cost effective buying it from the guys who were going to perform the work on the parts, rather than shipping it to them, waiting, and shipping it back (I'm located in Canada)
