Honda CB250: Reader resto

Date 14.11.2013

Presented by
  • Motorcycle Trader

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Honda CB250

SALVAGING THE SAD AND SORRY

It won’t impress the judges, but Nick Clarke’s Honda CB250 proves any shed-built bike can be more than the sum of its parts. His motto: “Discard nothing”.

Don’t look too hard. It’s neither correct nor original. This was an exercise in preventative salvage rather than restoration to prevent history frittering away into oblivion.

I acquired a ‘retired’ pair of early 1970s Honda CB250s for a modest sum, closer to beer and gaskets than legal tender. Unfortunately, there are no ‘before’ photos, but you know what a basket case looks like – spiders, oil and dirt linked to the dread of not knowing what’s missing.

The first had already served well beyond its design brief as a learner for several generations. Despite refurbishment along the way, it was weary, considerably less than pristine, carrying the scars of novice experiences, but was essentially complete. With serious oily incontinence it would never rust.

The second was simply a victim of stupidity, only 17,000 miles young but devoid of some pilfered parts and suffering the excoriation of time. It had a sparkplug 10 ranges too hot and ate a piston, whence upon it was parked.

Between the two and some random-but-available parts, I have what you see here. It is a true bastard being of unknown parentage.

The Honda CB was more popular in 350 form but in South Australia 250 class registration is much cheaper so more were sold here than other states, making it a rather uncommon toy now. They were exactly the same bike except for pistons, slightly lighter rods, carby jetting and badges.

They are the essence of mass production and well-concealed engineering minimalism, with as many parts as possible being made from metal pressings or castings that required the least finishing from raw as practical. Over time they have proven to be as tough as nails.

The 10,500rpm redline – intimidating to the Poms in 1971 but passé to the Japs – is easily exceeded, to no real purpose, but without angst. Racing versions run to 13,000rpm.

The Type 1 cam, the warmest of standard profiles, accentuates the top end, heralded by the changing note at about 7000rpm, the arrival point of enthusiasm. Now being a 250, below this level it makes noise and uses fuel but doesn’t do much else. It needs to sing to go and 7000 to 10,000rpm is the honey spot, with that rich and evocative Honda howl.

Mechanically, it is Japanese conventional: roller bottom end, standard-style gearbox and clutch, single OHC and eccentric rocker adjusters. Machining economy gave this motor an appetite for high revs via light valve train components, which is part of why they are so successful in historic racing, particularly in the US and the UK.

Machining economy can also be a weakness. The cam and some lesser components run directly in the aluminium castings and need clean oil for longevity. There is no paper oil filter, only a centrifugal sludge trap, meaning oil changes have to be frequent. To this day, parts are readily available and not particularly expensive, especially for the 350 version.

So, out of the two arose a parts bin special, not all Honda, but faithful to the period. It was never going to be an expensive all-out restoration, so chrome is minimal, limited to redoing the exhaust headers.

The paint colours are the black and silver of earlier models because it looks good and was easy to do. The die-cast wing badges on the tank always go ‘ping’ on removal, being replaced by decals out of England.

The front brake is ex-racing Suzuki T500 with standard linings, the rear is Yamaha R5 having a nice cush drive (the original Honda system is appalling), and Suzuki donated a halogen headlight.

Since the speedo drive is inactive now, a $25 electronic bicycle unit does the job and can be accurately calibrated. The alloy rims are spares from the shelf.

Discard nothing. Even the leftovers have gone to a similar project by another chap, who is building a café racer with a serious motor. I await.

 

*****

More reviews:

> Reader resto: 1977 Honda CT125 review here

> Reader resto: Honda CBX1000 review here

> Reader resto: Honda CB750F review here

 

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