Topic: 72 cb750 pops out of 1st (now fixed )

[a4x4spit]

hey Im new here had my cb since 1976 and kept it I had a problem with the trans poping out of second  gear ,so I got a suposidly good lower end & trans so I swapeed upper end & electrics from my bike to the new motor put it all back together & the new motor/tranny pops out of 1st gear now.( just Ideling on center stand it pops out & wont stay in under load either  ) my question is is there a common cause for this (and/or the 2nd gear) issue  problem Im hoping between the 2 transmissions I have I can get one that works I guess tomorrow Ill split some cases to see whats there any advice will be apriceated

[HondaMan]

Popping out of 2nd is often a worn set of dogs on the C5 gear, while popping out of 1st is often either a bent shift fork or damaged shift drum (look closely in the fork groove on the drum).

[a4x4spit]

I spent all day putting the bike together & getting it running  then finding out it pops out of 1st and tearing it apart again ready to lift out again tomorrow. I read a 11 page post about spliting cases & trans problems  I have a set of shift forks & drum I bought on ebay before I stumbled on the "GOOD"lower end thanks for the response

[a4x4spit]

got the cases split & the only thing that stands out is a slot on the shift drum looks warn its not the same as the new one I have thats for sure and it seems to make sense when I see how the drum moves shift forks does this look like it could be the cause of poping out of 1st

[greasy j]

popping out of 1st is easy to fix. leave your foot on the shifter.

[a4x4spit]

thought of that &it didnt work

[HondaMan]

Check the fingertips on the shift fork, too. They might be scarped up and burned. Or bent a bit. If you have another newer one, now's the time to change it!

[a4x4spit]

I do have a shaft with shift forks that came with the new(er )drum that Ill put in tomorrow it really helps to know where to look

[a4x4spit]

I got the bike all back together and it seems to work fine on the centerstand(which it did not before )....MAN that is a long days work . I replaced the shifter drum & shift forks & shaft I also put all the gears that attached to the shift fork toward the middle of the engine the dogs looked a little rounded off  which  ment taking apart my other  engine 's lower end and swapping some gears    .. Ill take it for a ride tomorrow .. thanks for the info  HondaMan  Ive had this bike since I was 17 and am going to keep it going

[HondaMan]

I got the bike all back together and it seems to work fine on the centerstand(which it did not before )....MAN that is a long days work . I replaced the shifter drum & shift forks & shaft I also put all the gears that attached to the shift fork toward the middle of the engine the dogs looked a little rounded off  which  ment taking apart my other  engine 's lower end and swapping some gears    .. Ill take it for a ride tomorrow .. thanks for the info  HondaMan  Ive had this bike since I was 17 and am going to keep it going

Cool, 4x4!
Ride on!
I've had mine since I was 20.