1972 cb450 meltdown

Disassemble top end. Inspect valves and pistons. If a valve is very bent, you will probably have to replace the guide on it just from the act of removing the bent valve.

Check valve stem for bends by rolling on a piece of glass.

Get new parts as needed. FOLLOW INSTRUCTIONS FOR RE ASSEMBLY.

Have fun :/
 
Dudes thx for the replies i truly appreciate it. even though it sucks having to rebuild the top end, at least i no whats wrong with it and am on the path to recovery. thx again for your time, help,and support. ill post what i find tonight.
 
The clutch on a lot of the old honda twins have a ballbearing at one end of the clutch pushrod. The 450's have it in the left engine cover inside the clutch actuator. Make sure that is there. That can cause weird issues and have you frustrated for a long time. Once you drop it it can be near impossible to find also as it rolls anywhere... I'm on my phone and away from home but you can find the part number and order one. They are still a production item used on several Honda items, even pressure washers and mowers for that part.
 
frogman said:
Mark if you would have read the first post he said he still had that ball...
Click to expand...

My apologies. I did read it but got slightly distracted in the 3rd large paragraph and started to skim over it and missed that portion... Disregard my previous post and like the other guys said. Make sure the other things are dead on and double check in the Honda repair manual.... You may well just be missing something simple and kick yourself once you find it. ;D
 
mark13018 said:
My apologies. I did read it but got slightly distracted in the 3rd large paragraph and started to skim over it and missed that portion... Disregard my previous post and like the other guys said. Make sure the other things are dead on and double check in the Honda repair manual.... You may well just be missing something simple and kick yourself once you find it. ;D
Click to expand...

Yeah, he missed timing the cams correctly... or at all.
 
so i checked everything...and it WAS hitting a valve. so i took the covers off, broke the chain and aligned the cams (properly this time lol). adjusted the clearance and now all i have to do is put the chain back on along with everything else. Ill do that tomorrow. thx again for the guidance.
 
Once you touch a valve with a piston it is done. Like like I said before, they are pretty soft and stems will bend. Which means you will have a leak in the cylinder and you will be losing compression if you leave it in place. You can also damage more stuff just by running it so main suggestion now is to stop, pull the engine, take the head off, and pull that valve.

If it is even remotely bent you should have that valve guide examined by a professional for cracks. You don't want to put a newer valve in a cracked guide, nasty things can happen. Replace it if needed, hell replace them all had have a nice valve grind done as well. These engines can benefit from some breathing modifications since they can REV quite high if tuned correctly.

Its fixable and lucky for you, the bike wasn't RUNNING when it dropped a valve. That tends to ruin a lot more than just a valve.
 
Please listen to frog man about the valves! It hurts me to imagine you kicking it over with a bent valve. 99.9 percent chance it's bent. You WILL be tearing it apart again in the near future. An engine repair shop turned mine around in 2 days for $75. Another bike of mine had a bent valve and I sent it to Schumann motor works in Portland to redo the guides and recut seats. He's good and had everything needed in his shop. Do it once and do it right! Or do it over and over again and never have a good running bike.

-boulevard
 
Even if it doesn't look bent..... It is bent and you wouldn't know unless you removed it which is hard without the right tools and then rolled it on glass. Even if by an act of God it wasn't bent chances are your valves could stand to be re seated

-boulevard
 
Just want to pile on this one. Tear it down and rebuild. It's not going to get any cheaper.
 
Why would you "slap it together"? Follow your manual-- hell, buy another different manual and reference that as well. Engine assembly should be done with patience and great attention to detail.

And just because I feel like it needs to be said... If you don't have a torque wrench, buy one.
 
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