1978 CB550 Pieces/Parts Hellride

Jimbonaut

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Here’s another attempt at an engine for this bike. I want a kickstart, so I’m going to see what I can make of this CB500 engine I bought for $50
I can only see three other bikes in that photo so yeah it's about time you started making life difficult for yourself
 

irk miller

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Was never able to get the 650 to run full power. Replaced the clutch, ran several ignitions, never figured it out. I literally hate not having a kickstarter and I would much rather run a smaller battery, so the plan I have come up with is to run a 550 bottom end which has a kick start, 650 pistons, bored 550 cylinders for 650 pistons, and a 650 head and cam with a 550 cam sprocket.
 

Rider52

Over 1,000 Posts
Was never able to get the 650 to run full power. Replaced the clutch, ran several ignitions, never figured it out. I literally hate not having a kickstarter and I would much rather run a smaller battery, so the plan I have come up with is to run a 550 bottom end which has a kick start, 650 pistons, bored 550 cylinders for 650 pistons, and a 650 head and cam with a 550 cam sprocket.
I'm not familiar with the 650 engine. Is the head a bolt on or will it require machine work?
 

Sderbyshire

Into Sailing, classic Triumph cars and motorbikes.
That’s interesting Irk, i’ve taken my 550 out to 61.5mm=600cc

never seen a sohc 650 let alone worked on one !
 

irk miller

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That’s interesting Irk, i’ve taken my 550 out to 61.5mm=600cc

never seen a sohc 650 let alone worked on one !
It's a common swap to machine the crown of CB750 pistons and machine down the skirts to get your size piston on the CB550. Not sure you have to do that anymore, as you have done. I assume you've heard of or read the "Gentleman's Express" article which refers to that process. CrazyPJ has a few posts out there about this, as well. The CB650 piston is 59.8mm.

I'm not familiar with the 650 engine. Is the head a bolt on or will it require machine work?
Honda used the same tooling to build the 650 engines, so everything is pretty much the same as far as castings. The 650 head is the better head, since it has shorter runners and it's ported. Honda put the last of their SOHC tech genius into that head. The rocker covers are different, but they match up to by bolt pattern. People tend to like the look of the 550 engine better, but I like the rubber gasket design of the 650 covers.

The sleeves on the 650 have a larger OD, so I can't run them in the 550 case without boring the case. It's easier to machine the 550 jugs to match the 650 pistons. The 650 pistons have a crown, where the 550 pistons are flat top. The 650 also has better chamber design. Dimensionally, the 650 matches the 550 piston in every other way. The clutch is the same on both the 650 and the 550, so I like the 550 bottom end to get me a kick starter. I may pull the starter from this engine altogether.
 

mothgils

Coast to Coast
Excited to see this come together. That was my last plan I had for my 550 Cafe, to run a hybrid 650/550 motor. I have 3 650 top ends sitting in a tote in my shed and plenty of 550 parts if you need anything.
 

irk miller

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Got my jugs mailed to Ohio to the house of @Hurco550 where he’ll do me a solid and deliver them to Mototech. I started taking the bike apart when a CB360 tank I bought for the Floating Donuts build got delivered. I had to go and test the tank on this build, which unfortunately looks pretty awesome. Now I have a problem.

C4D9B58F-93B4-4B6C-AE26-CE33576B94B4.jpeg
 

ridesolo

“Kto ne riskuet, ne pyot champanskoye.”
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My $0.02 worth??? I like the other one a little better. Part of the really unique look of that one was that tank line.

EDIT: Yup, just looked again. The line created by that long n low tank, the seat, and rear fender is what really makes that bike unique and special. Don't mess w/ success!
 
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irk miller

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Going a little backwards here, but I’ve decided I want a kick start bike and the OG 550 bottom end. So we’re doing a 550 bottom end, 550 cylinders bored for 650 pistons and a 650 head. Should be somewhere around 568cc.

ADA6035A-4E2D-4C1A-9E1B-F1B5AE0FCEF1.jpeg
 

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