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”
Published - Nov 20, 2017
So things are getting weird. For clarity, other than popping out of gear which is the reason for the tear down, my it250 runs super crisp. Gobs of power. Compression is spot on. After taking the cylinder off, the piston looks perfect. Zero scoring on piston or cylinder. Rings also look perfect. So I didn’t […]