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Hey,

I have a '81 CM400T I picked up dirt cheap late last year. I threw a couple hundreds bucks of fluids, tires, couple of minor aftermarket parts. Mostly maintenance-y kind of things.
Long story short, I put about 1,100 miles on her so far and the past little bit it seems to be slipping out of gear as I shift into second. At first I thought I wasn't fully engaging second gear, but it seems to happen most often when I'm in fairly high revs and really giving it gas. Typically happens when getting on the freeway. Any ideas whats going on with it?

I haven't had to crack open the engine casing or anything. It runs like it was brand new off the show room floor.
I've done an oil change, front brake pads and caliper rebuild, threw a replacement battery at it, and did an aftermarket headlamp assembly.
Hoping to not have to open the case, but if it doesn't straighten out, looks like I may have a winter project to play with. Any insight into this problem would be greatly appreciated.
 

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slipping out of gear is a problem dude, how was the oil that came out of the engine , bits of metal?? and how was the oil filter cover floor, bits of metal flakes??

if not selecting prop[erly and gear not fully home, it can jump out of gear, but most likely gear "dogs" ( dovetail type drive, just like dovetail joint in woodwork but only a degree or so ) ) chipped/worn, so engine strip down.
 

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Before assuming the worst.
Adjust the clutch properly. Back the lever end adjuster all the way in, now adjust the case lever cable end so you have @1mm of free play, less is better than more. You just need enough for clearance of the release bearing. Now adjust the hand lever end to suit you.
When you changed oil you did use JASO MA rated oil, correct? Automotive oil will cause clutch slippage and other problems.
 

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Second gear gets shifted into and out of the most of all the gears and takes the brunt of abuse of sloppy shifting.
If the bikes slips out of second into neutral under hard acceleration that very often is the smoking gun that there is transmission wear there.

Does it happen in any other gear at all? Try getting on the gas and shifting into 3rd and 4th. If it slips in any other gear, then yes, likely you are simply have your clutch slip.
Could be due to 'regular' motor oil with friction modifiers, but is more likely due to an improperly adjusted clutch cable or a very worn clutch.
I've had mine slip due to being out of adjustment, and fwiw, I adjust that cable all the way until my clutch friction pads were too worn and my clutch release lever popped out the bottom of the clutch on my Kawasaki. Even with the clutch being that worn out, the clutch still did not slip if the cable was adjusted correctly.
 

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sp1.jpg sp2.jpg
cam1.jpg cam2.jpg

I found some pictures I've done for gear slipping problem. Gear slips and gets into
another position means shift-drum is turning. I tried to stop it.
2 pictures of roller spring before and after and 2 of cam-plate?(i don't know what to call this)
before and after. Apparently 2nd gear position looks unsteady at first.
I re-shaped all the positions to fit the roller dia and to settle deeper.
I did one more on shift drum(to reduce the thrust clearance, no picture).
Maybe some of them was(were) wrong thing to do but worked.
 

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If the clutch cable adjustment doesn't correct it, I would suspect the shift detent at the end of the shift shaft as dawnrider proposed. Some times the little wheel gets out of line with the lobes as well and doesn't hold the shift shaft in position. I had to 'bend' the arm to meet properly. This will require removal of the right engine cover. An excellent time to check your balancer adjustment as well.
 

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What you're describing is really common on higher-performance sport bikes that get abused (i.e. banging it into second in stoplight drag racing). As GreenMM stated, second gear takes the brunt of sloppy shifting. The "dogs" (protrusions on the sides of the gears that are used to engage/disengage them from the adjacent gear) get rounded off and keep the gears from completely engaging or locking up, causing the transmission to slip out of gear. Couple of photos that may help this make more sense:

qpjbj4.jpg
Good gear on the right, buggered gear on the left.


Gear Dogs Rounded.JPG
Can you see how these would tend to pop out of engagement? Unfortunately, the fix is to replace the damaged gear(s) in question. Seems like the previous owner might have been a bit harsh/sloppy with his shifting...
 

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There you have it ... in its progression of investigating ... delving deeper and deeper to discover the cause.
 
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