HONDA CB350 CAFÉ RIDER
Eddie’s budget-build four-cylinder café racer goes back together with a home-made exhaust system and a collection of carbs. The time comes to fire it up – you might want to wear ear-plugs!
Eddie’s budget-build four-cylinder café racer goes back together with a home-made exhaust system and a collection of carbs. The time comes to fire it up – you might want to wear ear-plugs!
Before fitting the levers and switches I sat on the bike with bricks in various places under my feet to decided where to put the footrests, taking into account that I had to get the exhausts past them. The bike was then wheeled outside to get a better view and to eye up the exhaust. It was at this point I decided that the tank did not cut the mustard. I wondered if it looked wrong because it was still in the original red (it had been too cold to spray it with black cellulose). So I wrapped it in a bin liner to make it appear black and took another look – it was just plain wrong!
Warehouse Motorcycles only had later tanks in stock, none of any use to me. The guv’nor saw the disappointment in my eyes and allowed me to look through his trade book of all Hondas made. I decided the 400/4 tank would be best. Keeping to a Honda made sense as most of the Honda tanks of this period had the same hidden fixings; a rubber ‘cotton reel’ screwed to the frame with a horseshoe shaped receptacle on the inside of the tank.
I found a few tanks for sale online but with prices from £180 to £300, and this exercise was about making a café racer for sensible money. So the tank issue was shelved and I moved onto the exhaust. If you’ve got four cylinders: display them! That means four pipes. I had already brought four megaphone-type silencers at Kempton Park. Out came the plumber’s pipe bender; a fair amount of scrap pipe was left over while I tried to imitate the Honda racers, but I was pleased with the result. Wrapping them in exhaust tape finished the job.
The pipe bender, set to a half-inch this time, went back to work making the exhaust stays out of 15mm stainless plumbing pipe. Cheap and strong, and once polished these made a fine job. Two pieces of quarter-inch
plywood were clamped to the gussets I had brazed in between the swinging arm before powder-coating, and by trial and error I found the best place for the footrests and levers. The wood templates were then marked out on 6mm aluminium plate which was cut drilled and polished: another job done.
Moving onto to the wiring, I was going to fit the number plate light and indicators to the mudguard. But again it didn’t look right and it added to the unsprung weight. A piece of aluminium was folded up, using a vice and my Workmate, to attach to the seat, and this took a bracket for the number plate and lights. It also hid the wires. Fitting indicators distracts somewhat from the looks, but it needed them for the MoT – they’re also a must for me in safety terms.
Back at the Kempton autojumble, a stallholder was clearing his shed. Lo and behold, he was breaking his own 400/4 and was selling the petrol tank. It had a few dents but was solid; he even had the key to the cap lock. Trying to suppress my excitement I managed to acquire it for £45. You never know what you want to bring home! The new tank required some alteration to the seat as it was longer than the original, and this brought a tear to my eyes.
Maybe someone else with more patience might make a better job of it. I pulled the upholstery back from the front of the seat and cut the base, re-made the fixing bracket and glued the upholstery back. The guys at Viking Seats would not be happy…
Time to get on with the engine. Back in the day, if you were a café ‘racer’ then you’d try to make your bike as fast as possible. Bikes were built to take on anyone else on a bike to the next set of lights or roundabout. These days, it seems to me that lights, roundabouts, etc, are now out-breeding the population.
(On the subject of traffic control, whose fiendish mind decided to build out kerbs to make vehicles going in opposite directions occupy the same piece of tarmac? And then to add insult to injury they have the audacity to call it traffic‘calming’! I wonder what a driverless car will make of them?) My view these days is that the engine should be made oil tight, have the ability to give good lights and be a reliable starter. Save the money on engine mods and spend it on the important things like the next project or wine, women and song. The rest of it you can waste if you so wish!
Two pairs of Concentric carbs were purchased and I made stubs for the carbs and engine with flexible mountings. A twin-pull twistgrip was used with two junction boxes to feed the four 26mm carbs. Smaller carbs were strangely more expensive. I didn’t want to fit chokes as there were enough cables running around already, and I’d see how it cold-started later. I ordered the carbs with the smallest main jets, drilled out the pilot bush and screwed in the smallest pilots possible – after all it is only 87cc per cylinder.
My good friend John offered to let me run the bike on his rolling road dyno. When I made the exhaust pipe, I fitted a boss to hold a lambda sensor on one pipe. I figured that if I can get the mixture set on one, it would be OK for the other three. Surprisingly it fired up fairly easily. I had invested in new coils, points and condensers. The original HT leads had newish leads connected by a twisted wire and covered in gaffer tape – I thank my lucky stars the Previous Owner had not got into the engine!
After the usual cable adjustments, the engine was thoroughly warmed up and taken up and down through the five gears. Gear changing was slick. Unfortunately with four separate pipes it was not possible to connect the dyno’s fan-driven exhaust extraction system – we just had to suck up the fumes! Surprisingly, we got a lean reading when flat out in top gear. Not having any other jets, I drilled out the main jet to the next size and ran it again. A perfect reading was achieved, and a note was made to get four jets of that size. Tickover was impossible as I had to guess the air screw settings on the inside of the handed carbs; there was no way of adjusting them on the bike. Balancing the carbs by adjusting the cables was difficult, as without slack they jammed in different places. I had to figure a way of setting the stock slides while running the engine. I couldn’t stay at John’s place for more than a few hours and I knew this might take several days. In fact it took several weeks, a little at a time; being an air/oil cooled engine I only ran it for short periods. I didn’t want to overheat it so had a cooling fan blowing at it, tucked away under the car port. I did all this when it raining which meant the neighbours weren’t in their gardens. The bike was music to my ears, but possibly not to theirs… By now the weather had warmed up, so I could prepare and paint the tank. I like cellulose for small jobs like these as you can get plenty on and then carefully, minding the edges, rub down. Finally I was ready to get the Honda MoT’d and could apply for a registration number. It was of course agerelated and seven digits, and trying to make a plate of these proportions look OK defeated me. So I decided to buy a six digit number plate and found LIL 350. A little 350? Yes please! So the wine, women and song went out the window and I spent it all on the plate. I limit the first ride on any rebuild to three or four miles, as I like to find any loose fixings that I might not have thread-locked. I always use Loctite on nuts and bolts as it also acts as a lubricant. I remember someone suggesting
using oil on stainless steel fixings to stop the galling – this will stop the seizing but will also encourage loosening as well. I use Loctite 243 Blue on bolts and screws and 225 Red on items that are subject to torque, like sprockets, brake drums and discs to hubs, brake plates, footrest mounts, kickstart and gear linkage spline bolts. Use the red one at your peril as it sometimes requires a little heat to undo.
The Honda’s first ride ended after just two miles. My hip joints didn’t like the extreme rearsets. The standard handlebar grips were also painful for my arthritic joints – my other bikes have heated grips which of course are larger. Moving the footrests and gear linkage was a simple operation, but the rod-operated rear brake had to go. I like rod brakes as they don’t seem so spongy to me but the revised cable set-up works well, with the cable being kept as short as possible.
The next ride, with fat grips fitted, proved entertaining due to the exhaust note. Not only is it loud but nothing much happens below 4000 revs. The five gears are necessarily close so you scream up to 70mph like a demented squirrel, and then back down through the box to slow down. Great fun! Similar to the hilarity you can have with an old small sports car like a frog-eyed Sprite – you need a lot of pilot input to get the best from them. The Honda sounded fabulous without going particularly fast. I hear the superbikes on the dual carriageway on their way to Box Hill. They need to do about 120mph to get the same effect. I might make the Honda quieter… maybe.
I chose my tyres mainly for their looks: Metzeler ME22 3.00 x 18 front and 3.50 x 18 rear, but they work very well on dry roads. The engine performance is very good for a 350; maybe the big carbs tuned on the dyno are helping. All the bits I chopped off weighed around 80lb and their replacements (wheel rims, mudguards, seat and such) weigh about 30lb – so saving 50lb mass must also help. The rear shocks bottom out over sleeping policemen; is my 14½ stone too much? I need stiffer springs – or to stop eating!
I have found the Honda to be a little top-heavy. Raising the suspension by threequarters of an inch has moved the centre of gravity up. Looking at it side-on, you can see that most of the weight is above the spindle line, much like a modern superbike. How different from the 1960s when keeping the weight low was all the rage. Of course the race tracks had long, fast corners, unlike nowadays when you need to flick left and right with counter-steering around all the chicanes, as well as hanging off the bike; the rider sitting on rather than in the machine.
The gearbox is a delight, but the clutch is quite heavy for the power it needs to transmit. Viking’s seat is good enough for the short rides this bike was made for. Getting a stable tickover, however, has proved impossible. Concentric carbs have a very basic pilot system and the design is as old as me. Also, I think the large carbs can’t get enough gas velocity to work at low revs. The original inlet ports are surprisingly large for the capacity, 24mm, but the original carbs were only 22mm. Still, don’t all café racers have to blip the throttle at the lights?
The fuel consumption, like the noise level, is an assault on the environment. This bike’s a proper little hooligan and even writing about it makes me smile! Perhaps I’ll loosen the oil filter to spread some of the slippery stuff just to make it authentic…