[Scramblr]

Hello, I am asking for help to troubleshoot an issue with shifting my 1975 CL360 with 6-speed transmission. It runs great and most of the time will upshift without issue. When accelerating in the upper rpm range, the shifter will not always engage the next higher gear. It will find a neutral state between gears and require another effort at the foot lever to pull up into the higher gear. When I shift at lower speeds I can shift without using the clutch.

I removed the side cover and clutch today to check the movement of the shifter arm. The printed manuals describe adjustment of the "overshift travel" (Clymer #M323 250&360 twins 1974-77 on page 25) but I cannot find mention of how this travel is adjusted.

Here is a small video of the shifter detent mechanism in play during shift while the rear wheel (output shaft) is moving. The clicking noise is due to the kickstarter gear not fully retracted.

What are your thoughts about possible causes for the incomplete shifting? I had the bottom end open in 2018 to inspect the transmission gearing, and found no visible wear on the gears, dogs, or shifting arms.

 

[ancientdad]

Moving the rear wheel - which is moving the countershaft - isn't always enough to allow proper dog engagement between gears in the transmission... notice how the mainshaft is also turning, including when you're unsuccessfully attempting to upshift at some point... if the gears are all turning the same speed inside the trans, their positions remain the same relative to each other and the dogs on the gears might not all be lined up to engage each speed. As for why it does it when riding, it's likely there is wear on some of the detent parts causing sloppy and inaccurate movements of the shift drum at times.

In case you're not completely clear on it, this is how a constant-mesh bike transmission works internally during gear changes

 

[Scramblr]

Thank you for the info. I am looking at the engagement parts in the transmission but haven't found any that appear worn. I will need to inspect more closely the shift drum. This video is of the gears inside my transmission.

 

[ancientdad]

Note that in your video you are working the parts while turning the shaft that is opposite in the equation - you're turning the mainshaft, not the rear wheel, and the countershaft seal (behind the front sprocket) is "helping" you accomplish the shifts due to the turning resistance of the seal holding the countershaft still when in the false "neutrals" between gears, which allows the gears in the trans to line up the dogs more easily. When you turn the rear wheel as in the previous view, the mainshaft has no resistance and keeps rotating during attempted shifts which does not help slow one shaft from the other and aid in dog alignment (as the varying speeds of rotation between the engine and the rear wheel do when riding the bike). Also, wear on the dogs and openings in the gears the dogs engage into cannot properly be seen in your latest video above, as they need to be viewed from the side to see any appreciable wear or damage, as do shift forks.