Project 1970 Honda CB350

Join us on our newest project as we take stock of a badly neglected, but still salvageable, 1970 Honda CB350.

| September/October 2015

  • Our project 1970 Honda CB350.
    Photo by Richard Backus
  • The engine’s all there and doesn’t look too terrible, although all the wiring to it is shot.
    Photo by Richard Backus
  • The seat’s pretty tired and needs new foam and a new cover. Fortunately, the seat pan is fine.
    Photo by Richard Backus
  • The engine’s all there and doesn’t look too terrible, although all the wiring to it is shot.
    Photo by Richard Backus
  • Our project 1970 Honda CB350.
    Photo by Richard Backus
  • Headlamp shell is broken and forks are tired.
    Photo by Richard Backus
  • The drive chain is shot and we’re guessing the sprockets are, too.
    Photo by Richard Backus
  • The engine compression appears surprisingly strong, with 130psi showing on the left cylinder and 120psi on the right.
    Photo by Richard Backus
  • Project Honda CB350 supplies.
    Photo by Richard Backus

The is the first in a series on our 1970 Honda CB350 build project. Read Part II, Part III, Part IV, Part V, Part VI, Part VII and Part VIII for the later installments. You can also watch video of our Honda running for the first time.

Last issue, we told you about plans for our next build project, a 1970 Honda CB350. But “build” isn’t quite the right word, conjuring up as it does images of a one-off custom café or street scrambler. Instead of going the custom route, this time around we’re going stock, taking a tired and neglected CB350 and returning it to original — well, almost.

Almost, because our goal isn’t a restoration, per se — think sympathetic rehab, like our very first project back in 2007 when we returned a tired 1971 Triumph TR6C Trophy Special back to road-worthiness. With that project, we focused on making our Triumph a solid runner. Originality only mattered to a point: We weren’t hung up on making the bike perfect, because the end goal was showing how you could get an old Triumph back on the road without breaking the bank. That’s basically our approach with this next project, but this time we’re going to work a little harder at maintaining our bike’s original styling cues.

We picked the Honda CB350 twin because we think they’re great little bikes. A hugely successful platform (Honda sold an estimated 626,000 CB/CL350s between 1968-1973), the CB350 was Honda’s bread and butter bike. Affordable, reliable and stylish, its popularity continues today for those same reasons. AHRMA racers love them as the basis for fun and affordable racing, and they’ve been rediscovered by a new generation of riders looking for a cool vintage scoot. That’s good — CB350s deserve the attention — and bad — the renewed attention means prices have been going up and true bargains are getting harder to find.

Our bike

Looking at our starting point, you could be excused for dismissing it as a parts bike — or worse. Majorly disassembled, we’ll admit it’s a pretty sad-looking machine, with more than a few detracting elements: The gas tank sat in the sun so long that one side is orange and the other silver from the sun burning off the top coat; the seat is torn; the headlamp bucket is broken; the handlebar controls are mostly missing their guts; the tires were shot 20 years ago; and the chain is so rusty it could probably stand on end. We paid $200 for this glorious mess. Brilliant, eh?

What’s important, however, is what you don’t see. As bought from its former would-be restorer, our CB350 came with several boxes filled with its original parts. Following an all too familiar scenario, the previous owner had started down the restoration road before running out of momentum. He’d removed almost all of the Honda’s hardware for refurbishing, and had even gotten around to rehabbing a few items, including the airboxes, toolbox and battery box, and the chain guard. Our parts stash includes both fenders, the side covers, two tachometers, a nonstock exhaust, the rear shocks, blinkers, electrical components, headlamp, foot pegs, cables, new tank and side cover emblems, and an organizer containing what appears to be most of the bolts and washers taken off the bike during disassembly. Time will tell, but it looks like we have most of what we need, although we know that sourcing the correct exhaust system will be a challenge. Aftermarket units are readily available, but we’d really like to stick to the stock setup.

Yet as bad as our Honda looks, we think we actually have a pretty good foundation. The engine turns over freely, and a quick compression check shows 130psi in the left cylinder and 120psi in the right. The transmission seems to click through all the gears OK, and with only 8,400 miles showing on the believed original speedometer, there’s a good chance most of the internals are fine. Neglected as it was, this CB350 fortunately spent its years of neglect in a shed, limiting corrosion.

That’s the good news. The bad news is the wiring (it will need to be completely replaced), the carbs (they’re stuck and need a total overhaul), the frame (the paint’s shot), the seat (has to be recovered) and all the tinwork (needs repair and repaint). And that’s before we get to the engine, which, actually, we’ll work on first: There’s not much point restoring the cycle parts if the core of the bike’s no good.

Yet we’re pretty sure the engine’s okay. The first step to getting it running is rebuilding the carburetors. We turned to Sirius Consolidated for master kits that include new floats, jets, needles, gaskets, CV diaphragms and diaphragm caps. Once we have the engine running (hopeful, aren’t we?) we’ll be able to determine if it needs any internal work, such as piston rings or maybe a cylinder head overhaul. If it does, necessary machine work will be shipped off to the pros at Millennium Technologies in Wisconsin. We hope to know more on that score by the next issue.

Once we work through whatever basic issues we find with the engine, we’ll infuse some extra reliability into our CB with help from vintage Honda specialists Charlie’s Place. To ensure steady firing, we’ll install one of Charlie’s electronic ignition kits and a set of Charlie’s high-output coils, complete with custom-machined brackets. Charging reliability will get a boost with one of Charlie’s new voltage regulator/rectifier units.

We’ll rebuild the suspension, of course, including replacing the stock shocks, which were notoriously bad. For replacements, we’re turning to Hagon Shocks USA for a set of Custom Classic I shocks, which look almost identical to the original but are guaranteed to give far superior performance. New tapered steering head bearings will come from Dime City Cycles and we’ll be sourcing numerous other cycle parts from DCC, as well.

That leaves a lot of decisions yet to be made. Paint’s a big one, and frankly, we haven’t yet decided what color we like best. Options for 1970 were Candy Blue Green, Candy Gold and Candy Ruby Red. Red seems to be the choice of the day, which has us leaning toward blue-green.

Unknowns aside, we did decide it was time to make a concession to working comfort, so we picked up a sheet of G-Floor Vinyl Flooring for the shop from Better Life Technology. Great stuff, and manufactured just a few miles down the road from us in Emporia, Kansas.

Moving forward

Beyond our initial assessment and a compression check of the engine, we’ve had precious little time to get much done on our CB. That’ll change once we get past the summer show season, and heading into fall and winter we know things will pick up rapidly. The schedule calls for having our CB done early in 2016, and taking a page from Dime City’s latest build, we’re thinking about auctioning it off for charity. Stay tuned. MC

Project Honda CB350 suppliers

Better Life Technology: G-Floor vinyl shop flooring
Buchanan’s Spoke & Rim: Relaced wheels with Mandap chrome rims and chrome spokes
Charlie’s Place: Electronic ignition, ignition coils and mounts, voltage regulator/rectifier
Dime City Cycles: Tapered steering head bearings, miscellaneous hardware
Hagon Shocks USA: Custom Classic I chrome shocks
Millenium Technologies: Custom machine work
Sirius Consolidated: Master carb rebuild kit, seat foam, seat cover, seat strap and buckles

8/27/2015 6:41:59 PM

I lucked into a '70 ruby red true survivor CB350 (4500 miles and stored well)several years ago. Paint is still very nice except for a bit of fading on the headlight. Aluminum bits have aged with grace. Just got the carbs back on after a soak in the ultrasonic cleaner. Last unpickle showed a high speed miss under throttle, which was likely a secondary main jet(never seen that before) plugged. A 50 mile test ride today reminded me of how much torque that little engine has, compared to my Superhawk. It's off to a VJMC rally in a couple of weeks for a couple of rides and a show. Richard, hope y'all at MC Classics eventually have as much fun with yours, as I've had with mine. Great little bike!

8/27/2015 11:26:13 AM

There is no good reason to replace the jets and needles on a low mileage bike. The quality of aftermarket jets is very suspect. Clean everything well. Use the gaskets from the kits, but install the original jets/needles. You will be better off.
8/23/2015 11:12:06 AM

Hi Guy’s; I’m new to this pub, why would you send cylinder repair on this 350 Honda to Millennium? Millennium is a plating facility; early Honda cylinders are plain old cast iron. There are other places who do quality work on vintage cylinders. John Tice

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