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Discussion Starter · #1 ·
Hey guys, im a newbie here, and have a 73 Cb450 K5. the 2nd gear in the transmission is worn and needs to be replaced. I have a replacement gear and am ready to start the tear down.
1. Is there any words of caution i should know?
2. Any tools and/or procedures?
any help is greatly appreciated. Thanks -Dan
 

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Welcome aboard Dan! We're glad to have another 450 owner anytime.. ;)

More knowledgable folks will check in here soon..


GB :mrgreen:
 

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I would suggest doing a compression test before you rip into your motor. Anything lower than 150 psi indicates some top end work will be required. You'd hate to tear down, rebuild and then discover yer burning oil or lacking power.

As noted others' (more knowledgeable than myself) are sure to help out along the way! Welcome.
 

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Get the "opposing" gear (the gear next to it that engages that one) too.
If you're doing it because it jumps out of 2'nd, there were two gears and a shift fork involved with that fix.

You'll need an oil filter bolt tool, available at MotionPro for less than $10.
Might as well get the alternator puller too, same place, also less than $10.
You'll find links here to both those tools, just do a Search.

Get a seal kit too, and the advice to check your compression first is sound - do it all at once.
 

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Discussion Starter · #5 ·
I appreciate the welcomes guys. Yeah the bike jumps out of 2nd gear. It can be kinda challenging to go from 1st to 3rd while pulling onto the highway - gotta have quick feet hahah. The bike has around 8k on the odometer. so the top end should be rebuilt. unfortunately i cant afford it at the moment, (going back to school in a week)
But the top end will be rebuilt probably next summer. Thanks for the info guys.
Cheers -Dan
 

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Wanna sell her? What's your location if so? Your profile only had a 4 digit zip code so I couldn't tell..

GB :mrgreen:
 

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My 450 is getting worse and worse about popping outta 2nd, as well. Geez, it needs a camchain and top end reseal, too.
Anyway, what is it specifically that goes bad? Does the shift fork[#3] get worn to thin, the slot in the gear[#12] to wide, the shift drum pin[#4] out of round, all the above?



NE
 

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Usually, it's wear/heat fatigue/bend on the fork, or the engagement "dogs" on the slider gear and the holes in the gear it engages.... I have seen the fork guide pins and the labyrinth in the shift drum wear as well, but this is usually from "powershifting" without using the clutch.... Check the roller detents as well, they are a point of contention on the 450's....

As long as you have it apart, check everything, replace ANY "iffy" or not-to-spec parts......Complete trannys are on eBay a lot...generally under $30....
 

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CurbTiger said:
My 450 is getting worse and worse about popping outta 2nd, as well. Geez, it needs a camchain and top end reseal, too.
Anyway, what is it specifically that goes bad? Does the shift fork[#3] get worn to thin, the slot in the gear[#12] to wide, the shift drum pin[#4] out of round, all the above?
NE
It would be the counter second (#5, rotates freely, turned by the mainshaft 2'nd gear, #10), counter 5'th (#6, which engages with it and turns the countershaft) and the fork on the rider's left.

 

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Discussion Starter · #10 ·
Well, i took the head and jugs off. This was a first for me, im used to rebuilding 2 stroke engines (slightly easier). this was also a the first time i used a cam chain breaker. Here is the condition of everything:
Head - could use a bead blasting and hot tank, but otherwise good for having 8k miles
Jug - great, no ring ridge at all, no scratches either
Pistons - look good, usual wear for 8k miles

Tomorrow is the day i tackle the bottom end (oh ****) ill let you know how it all goes fellas
 

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NOS351WCM said:
Well, i took the head and jugs off. This was a first for me, im used to rebuilding 2 stroke engines (slightly easier). this was also a the first time i used a cam chain breaker. Here is the condition of everything:
Head - could use a bead blasting and hot tank, but otherwise good for having 8k miles
Jug - great, no ring ridge at all, no scratches either
Pistons - look good, usual wear for 8k miles

Tomorrow is the day i tackle the bottom end (oh ****) ill let you know how it all goes fellas
Can't tell anything about your valves from the way they look.
You need to fill the ports with acetone and watch for leakage.
You should have checked your compression before tearing it down, like someone previously said.
Now you're just assuming everything is ok......it will suck big-time if you put it all back together and discover your compression is sub-par.
 
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