2021 – cb450 rebuild
ok… so I rebuilt this bike again. Hopefully for the last time.
I’m making this post to help anyone in the future.
Back in 2013 I had the idea to build a hotrod / high compression cb450.
I don’t know why I had this idea. I was bored and wanted to play around with stuff I suppose.
I started with a good condition cb500t engine, which is almost identical to a cb450.
Back then, I bought a Todd Henning 74mm (+50cc) 11.5-1 compression race piston kit.
I thought, 550cc in a cb450 sounds really cool. It is / was.
I put the piston kit in. I kept stock OEM camshafts.
Bike ran pretty darn good.
Measured compression per cylinder with a gauge was about 205psi. Whoa that’s high.
Bike was def quicker than before when it was stock. I was happy.
Well… fast forward about 6-7 years.
The piston kit had originally come with a copper head gasket. It always weeped oil a tiny bit out the front near the headers.
I also had read that boring the cylinders to 74mm made the sleeves too thin, so the bike might run hot possibly? I didn’t care and ignored all this and did the build anyway.
Over the 6-7 years the bike started leaking oil really bad.
Ran a bit inconsistent and somewhat hot it seemed.
Started leaking oil so bad it was unrideable.
In 2020 I decided I needed to do an engine rebuild again.
I figured I’d learn from my mistakes and make it more mellow for more overall longevity.
The bike is a cb450. If you want a hotrod bike, pick something else… really.
I just want to ride the bike around and enjoy it and not have it break or leak oil or run hot.
I bought another set of original 70mm cylinders.
Cometic fiber/composite head gasket. I’m never running a copper head gasket again.
I bought lower compression 10.1-1 Weisco cb450 pistons (same as Charlie-Place kit) that are the shorter skirts to clear 450/500t cranks no problem. But pistons are still higher compression than OEM 450/500t.
Sidenote – In 2016 I had bought Megacycle 120-40 cams on ebay, but then sold them a few months later thinking they were too aggressive.
So … I sent my OEM cams / followers to Megacycle to get their mellowest street grind, hoping this matches the piston kit well. They chose grind “120-10” which is street-mellow. .350-lift / 244-duration@40˚. Stock OEM cam specs are: .330-lift / 230-duration@40˚ (according to MegaCycle). They said they’re currently revising their spec sheet for the cb450/500t engine also.
Anyway, the goal is to have a mellow piston kit / mellow cam … and have it all match and just be a nice street rideable mellow engine.
I have Mikuni VM32 carbs which I had before with pod filters.
A new Charlie place electronic ignition / coil kit, which replaces an old Pamco kit I had.
All new wiring.
Stock seat and little upright bars.
Tried totally open free flowing exhaust, but sounded like garbage on deceleration.
Switched to semi free-flowing Cone-Engineering Quiet-Core exhaust.
Disassembled frame and replaced any messed up stuff. Cleaned / painted everything.
Put it all together and the bike seems to run good so far.
Hopefully this engine combo will have more longevity to it.
cb450/cb500t engine differences
I’ve said this before but i’ll say it again.
Yes, the cb500t engine has different stroke / crank so if you put cb450 pistons in a 500t motor, the pistons will sit a hair lower than deck height. Doesn’t seem to matter or make a difference. Just make sure you get pistons like the Weisco kit that has a shorter skirt to clear the crank. The Weisco piston is slightly shorter skirt than the Todd Henning race piston as seen in the one picture with them side by side where the Weisco piston is on my credit cards to make level height.
And yes, the Todd Henning race piston kit def did work in a cb450/500t engine, but at this point, I don’t recommend it unless you’re actually racing.
If you want to go fast, buy a different bike.
If it’s a normal cb450 / 500t street bike, keep the engine stock, or do the mellow 70/71mm Weisco kit, it’ll work great in either cb450 or cb500t… probably keep stock cams or do mellowest option available. if you want a few extra HP, get VM32 carbs / semi free-flowing exhaust, and call it a day. Just ride it and enjoy its a fun little 40hp bike.
5 responses to “2021 – cb450 rebuild”
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Published - Dec 4, 2012
How cb450 torsion bars work
As I said earlier in this post… cb450 and cb500t have no valve springs. They have a torsion bar set up. Let’s take a look at how exactly the torsion bar works. It’s pretty cool. Pic 1 – The engines are double overhead cam which means there is a separate cam lobe for each valve. […]
Excellent! Nice job Ed.
That’s a handsome bike. Nice work and write up
I’m looking to start a similar build on a barn find ’72 cb450 I picked up that has been sitting since ’76. I’m already pick pretty much the same parts you used so jm feeling better about the part selections I’ve made. Just curious why you disliked the previous build so much though. I know the leaking and all is an issue but I was thinking of doing a second clone of the one I have and making it a primarily track bike so some detailed input would be appreciated.
@Corey – My input is to keep the cb450 close to stock or do the mellowest performance upgrades possible as I mentioned above. It’s just not worth it to go nuts with it.
The cb450 is such a pain in the ass to work on. Taking the tank on-off a bunch is super annoying with the cross-over tube, you get gas everywhere. The motor has to come out of the frame to do any real work with the cylinder head. The top-end has heat / oiling issues once you start adding more power, so now you have to figure out an oil cooler setup which is a pain in ass. Cam followers are an issue too. All said and done you put in a bunch of time, effort, money, and it’s still not really that fast.
Just keep the cb450 close to stock and enjoy it for what it is. It’s a great, super fun, around-town, zippy bike. I love mine for that. My buddy and I rode a cb450 and cb500t from Philly to Denver and back, in Sept 2010. Go back through Blog posts on this site and you’ll find it. That type of trip riding is def doable on these bikes, if kept in stock form.
If you want a bike to do real performance racing stuff with, go buy a cb750, kz650, kz900, or kz1000. Honestly, I’d also choose a cb550 four or cb650 to make into a performance bike over a cb450 at this point.
Hope that helps.