Got my 1973 CB500 running with working clutch and brakes for the first time last weekend and as I hopped on for my first test ride I found that first gear would "slip" in and out under load even when cruising at 5mph, causing severe lurching. It happened frequently and the problem subsided after shifting into second. Also I was unable to shift above second. I have avoided basically everything transmission related on the bike in a prayer that it work but it is obvious now that it doesn't (bummer). After diving into the forums I have narrowed my problem down to 2 things (and potentially a third). For ease I will list below.
1. Worn gear forks:
I have split the engine case apart and pulled the three gear forks to attempt a "hardfacing" and sanding to reduce freeplay for the dogs as they slide with the forks. The thing is, I have measured them and only one is out of the listed serviceable limit in the manual and the wear is progressive down the fork (the tips still measure manufactured thickness). They are not bent - measured using the level on my iphone - and it seems that such a small amount of wear having such a profound impact on the ability of the forks to hold the gears in place seems wrong when everything is fixed to shafts and has very little freedom to wiggle except along the direction of the shaft. This makes me think my bike as symptom 3 below and that I don't need to attempt a repair of the forks. Any advice would be helpful!
2. Sliding Shift Drum:
I have seen multiple places in the forum talk about a slight slide of the shifting drum and how it can be a culprit of loss of gears and various other things. When I removed the clutch side cover and watched the ratcheting mechanism and drum face operate when changing gears via the pedal when going 2-3 the drum would shift "out" slightly. The action on the pedal seemed to feel as though it properly moved the forks, but there was no locking click and the runner that locks on the pins in the ratcheting mechanism would run off the drum. As I said before I have seen mentions around of this issue being a thing, if someone could offer insight as to the cause and maybe a solution that would be very helpful! I tried tightening the screw on top of the case that hold the drum in place.
3. Worn gear dogs:
I am away from the motorcycle now and wont be able to check on the conditions of the dogs themselves for another week or 2. I fear they are most likely the true culprit of the "slipping" due to what i feel like is not terrible wearing on the gear forks. I will check either way but for piece of mind, I have included photos of the gear forks and am interesting in any person with experience's opinion on if the wearing is severe enough to cause these issues alone.
