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Discussion Starter · #1 ·
Hello all,
I've spent the last 6 months restoring a 71 CB 450.
Been testing it all week on short trips in the hood with good results.
Finally today I opened it up hard on the freeway with horrible results.

After about five minutes I started feeling a loss of power.
It would barely do 65.
It then started smoking like a chimney from the breather.
I stopped at a bike shop to rest and it seemed over heated, occasionally making tapping noises and would not hold an idle.
You would have to hold the throttle to keep it running without stall.
.
At the shop I checked the plugs and they looked okay, maybe slightly rich but no oil.
I then checked the oil level and it was to the top point of the dip stick but not over.

Let it cool down for and hour or more, and rode it home on back streets
It smoked so bad on the way back!
I've never in my life seen a breather smoke and gush oil like this. :shock:

ideas and thoughts appreciated.
 

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I really feel with you man. :(
I had a similar experience some weeks ago with my 450 that I have worked on all winter. I hope it's not too serious. I'm not a pro but maybe a blown head gasket?
I think the experts gurus on this site will soon give you some good hints.

BTW you got a stunnig bike.
 

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Well, the smoke out the breather definately means burning oil, so the flame-front is reaching the oil somehow..... (head gasket tear, improper torque sequence, broken ring, ring gaps aligned, or the dreaded fuel in the oil, or just oil overfill...)
Since you've obviously lost some oil by burning and pumping it out and you are still full to the top, ...I'd check the last two first...then check compression and let us know....
 

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Discussion Starter · #4 ·
66Sprint said:
Well, the smoke out the breather definately means burning oil, so the flame-front is reaching the oil somehow..... (head gasket tear, improper torque sequence, broken ring, ring gaps aligned, or the dreaded fuel in the oil, or just oil overfill...)
Since you've obviously lost some oil by burning and pumping it out and you are still full to the top, ...I'd check the last two first...then check compression and let us know....

It only does it when it get hot, wonder if re-torquing the head could help?
 

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In the time it would take you to retorque the heads you could do a compression check and take a lot of guess work out of diagnosing the problem.
 

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Discussion Starter · #6 ·
I did a compression test few months ago and everything checked out. I'll do another today and report back in. The cylinders looked good during plug check, so it hasn't occurred to me as a issue.

How does oil burn up like that with out getting into the cylinder? I wasn't aware that was possible. :?:

Pulled the oil filter covers and there was some minor dirt. Turned over the engine and the oil seemed to be pumping through the orifices fine.

On another note of observation at the bike shop, I saw a oil had leaked out probably both the cylinder and head gasket.
Breaks your heart... Dang... I do have the gaskets for a top end. might have to use them.
 

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450's have been known to puke out all their oil through the breather tube, under sustained high rpm's (it's happened to me).
Pull the engine and brace yourself........
 

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Discussion Starter · #8 ·
tbpmusic said:
450's have been known to puke out all their oil through the breather tube, under sustained high rpm's (it's happened to me).
Pull the engine and brace yourself........
What was the issue in your case?
 

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Discussion Starter · #9 ·
Compression test...
Left - 120
Right - 25
I see nothing wrong with that, whats the next step... :D


Suppose I should just open another thread in the project area.
ahhhhh crap


Man, I'd love to get my hands on a Honda 450 shop manual now. The Fulmers one I have is not so complete.
 

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Simpson said:
Compression test...
Man, I'd love to get my hands on a Honda 450 shop manual now. The Fulmers one I have is not so complete.
I'm pretty new to this forum but I have been working on my own 1970 CB450 project as well.

I found a reproduction of the Honda Service manual for the 450's on helminc.com. It wasn't cheap but I find it very usefull and it contains a lot more info than my Clymer manual. I usually go back and forth between both manuals just to make sure I have 'all' the info I need.

http://www.helminc.com/helm/search_serv ... ss%5F2=AHC

I do however have yet a third place to check for info and tips....thanks to this forum!!!

Cheers!
 

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Discussion Starter · #11 ·
Woohoo, found a nice copy of the Honda manual. It looks to be on the same level as the Clymers.
The more I think about it, a blown head gasket fits the bill.
Pulling the engine this weekend and taking the head off.

What are people using to split and crimp the cam chain?

Can someone recommend a tool and where to buy it?

Recommendations for lifting the engine from the frame are welcome too!
 

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Simpson said:
Woohoo, found a nice copy of the Honda manual. It looks to be on the same level as the Clymers.
The more I think about it, a blown head gasket fits the bill.
Pulling the engine this weekend and taking the head off.

What are people using to split and crimp the cam chain?

Can someone recommend a tool and where to buy it?

Recommendations for lifting the engine from the frame are welcome too!
I've got a MotionPro chain tool that is good for cam chains as well as drive chains. They've got a couple of different models so you can see them here.

http://www.motionpro.com/motorcycle/too ... nAod6CtCag

A second person is one way to get the motor out or you can lay the bike on it's side, remove the bolts, wiggle the frame to loosen it and pull the frame off the motor. Not pretty but it works.
 

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Discussion Starter · #14 ·
Looks the rings failed on the right cylinder. Little worried about the cylinder wall surface finish.
Hoping I can hone it out smooth.
Appears some alum material has tranfered to cylinder wall but not scoring.
 

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Discussion Starter · #17 ·
Anyone know where to get new Valve guide seals? Figured I'd replace them while its apart.
 

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Simpson said:
Anyone know where to get new Valve guide seals? Figured I'd replace them while its apart.
Your local Honda dealer can still get them.
 

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Discussion Starter · #19 ·
This is driving me crazy. I can't find the valve guide seal in the parts list, or listed on any internet site.

Anyone know the part number for this thing?
 

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Simpson said:
This is driving me crazy. I can't find the valve guide seal in the parts list, or listed on any internet site.

Anyone know the part number for this thing?
14791-292-000
CAP, VALVE GUIDE SEAL (Honda Code 0142737) - $8.10 each from Honda........

Same part for all 5-speed 450's.
 
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