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Discussion Starter · #1 ·
i put the bike (CB450 1973 K5) into first and it jumps in and out of gear. every other gear seems to work fine so far
i have pulled the shift drum stop assembly apart and it has noticeable wear. i am going to fix this issue then move onto the inner gearbox but hopefully i wont have to.
my questions are
what is the original size for the gear stopper roller?
what is the original size for the neutral stopper roller?

I am also pulling apart my parts motor and am having trouble due to rust. the shift forks retaining pins are stuck. one of the clips came out the other two broke off flush with the fork housing. anyone got any good ideas on how to remove these pins? i tried drilling but they are hardened. or can you remove the shaft another way?
what are the fork ID specs maximum wear size for left/right and center?

i know this issue has been covered but was having trouble finding the info i needed

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this bike has been an absolute nightmare so any help would be much appreciated
cheers
matt
 

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Re-assemble the gear shafts and the shift drum back into the crankcase upper half. Turn the shift drum into the first gear position and see if the shift dogs on the 1st-2nd gear slider are properly engaged. Try to pull them apart with your fingers and see how deep the dogs stay engaged. Examine the gear dogs for wear and rounded-off corners that may be pushing things apart under load. Wear on the id of the fork is not as important as as wear on the tip or if the fork is bent.
 

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^^^as above, and as far as the detent rollers are concerned - the outer diameter isn't as much of an issue as the slop on the shaft of the arm. the rollers rarely wear down in size, but they get loose on their shafts and cause inaccurate shift drum positioning in each gear stop, and the star-shaped end that mounts on the shift drum gets worn on the tips of the "star" which can also affect correct shifting. Sometimes the pins get wear areas on them as well
 

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The part you show in photo 1 is trashed, no fixing it. New ones come with new pins already.
The smaller (neutral) roller is never an issue, it has a very strong spring assembly, as you'll discover when you reassemble it.........
The larger roller gets loose and wobbly - if it is, it needs to be fixed or replaced.
Neither part is that easy to find.
This done, your shifting problems will probably be solved without pulling the engine and cracking the cases open.
 

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Discussion Starter · #5 ·
thanks everyone especially bill lane
the bike is an on going project that i brought as an impulse buy on ebay always liked the look of the old honda CB's and have done a fair bit of mechanical work to honda XR/XL throughout my childhood which i quickly discovered are a completely different breed. i picked the bike up found out it was seized and down the rabbit hole i fell or into the money pit however you see it. now 6 months later i have finally got it up and running with what feels like everything going wrong or screwing me around and now i have gearbox problems, the fun never ends.
the motor is still in the bike and i'm hoping with repairing this shift Assembly i wont have to remove the motor from the bike and split the crank case
bill where do you recommend trying to get a new gearshift drum center star part? I'm in Australia and Honda Aus don't won't to know anything about it. There's a site called cms honda that might have a part? otherwise im stumped?

Cheers
Matt
 

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thanks everyone especially bill lane
the bike is an on going project that i brought as an impulse buy on ebay always liked the look of the old honda CB's and have done a fair bit of mechanical work to honda XR/XL throughout my childhood which i quickly discovered are a completely different breed. i picked the bike up found out it was seized and down the rabbit hole i fell or into the money pit however you see it. now 6 months later i have finally got it up and running with what feels like everything going wrong or screwing me around and now i have gearbox problems, the fun never ends.
the motor is still in the bike and i'm hoping with repairing this shift Assembly i wont have to remove the motor from the bike and split the crank case
bill where do you recommend trying to get a new gearshift drum center star part? I'm in Australia and Honda Aus don't won't to know anything about it. There's a site called cms honda that might have a part? otherwise im stumped?

Cheers
Matt

That part (and the large roller) are pretty hard to find - took me quite a while (years) to find my spares.
If CMSNL has one, better jump on it, though shipping is a killer from those guys.
Most used parts of this type are a coin toss, especially if you can't examine them in-hand.
 

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Discussion Starter · #9 ·
i have now replaced all the parts of the detent shift assembly and it fixed the jumping in and out of gear problems mostly. it has developed a slip almost like a worn clutch but it is more sudden and abrupt than any worn clutch that i have ever come across you are going along and suddenly you don't have any drive and a second later it lurches back into drive? no horrible grinding noises or anything like before so has to be clutch i suppose? i disconnected the cable to eliminate that as the issue what else should i try before buying a set of clutch plates? i measured the plates when i had it apart and they were within specs?

it also doesn't run as well as could be desired i had the carbs apart and cleaned them checked the jets did the usual type things. i have synchronized the carbs set the idle and cables ect. i currently running without air filters while i figure out the issues just wondering if that is the main issue? its also bored out to 71mm (0.040' oversize) wondering if i will need bigger main jets or if it still should run alright STD ?
 

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Running without air filters will definitely decrease performance. Boring the cylinders does not require carb changes as the volume increase is negligible.

When you feel it slipping do the rpms/tach increase? I would not expect worn clutch plates to produce the symptoms you describe.
 

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Discussion Starter · #12 ·
there isn't a noticeable increase in revs during slippage it feels like someone is pulling the clutch on and quickly releasing it causing it to lurch into drive not like a surge in power? ive had worn clutches that run on or do the opposite and slip under power and is not like those symptoms will do it at 3-4000rpm in first gear for example?

i am running oil i got from my local mechanic for motorcycle clutches i will go and find the container for specs if that is thought to cause these symptoms?
 

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I suspect the damage from jumping in and out of first gear for a while is already done to the shift fork involved, and potentially damage to the engagement dogs on those gears as well. Sounds to me like you'll need to tear down the bottom end for a proper transmission repair as the detent repairs did not fix the problem
 

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Could also be that the clutch plates are sticking then freeing themselves, after leaving the bike standing for a couple of days select 2nd gear while it's on the main stand then pull the clutch lever in and try to spin the rear wheel by hand. If you can't then they are sticking, for the reasonable price of a new set I'd replace them.
 
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