Classic Motorcycle Mechanics

HONDA CB350 K4

Over the years we’ve championed the youth of our hobby, now it seems they can restore a classic bike at school! Well at this school they can.

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Kids from a high school undertake a resto!

I’m Jim Burgess and I have a 1972 Honda 350 K4 under rebuild in my workshop. No big deal, I hear you say. But my workshop is in Stowmarket High School, Suffolk: the sort of place you may have done your woodwork and metalwork lessons many years ago, except it’s called design technology now. This bike is not being built by myself, but by a group of Year 11 engineerin­g students under my (ahem) supervisio­n. It all began about three years ago; the school had been running a motor vehicle course for a few years. We also run an excellent A-level design course for our sixth form students and three of our sixth form chaps found themselves with rather too many free periods on their hands. The motor vehicle course leader Mark Bloom persuaded them it would be a good idea to pick up his motor vehicle course to occupy their time. Rather rashly I offered my 1987, one owner from new CBR600 jellymould for them to strip. Happily I ended up investing a lot of my free time and no inconsider­able part of my fortune in this bike, (don’t tell the wife!) but it was all good clean fun and I ended up with a running motorcycle after a year’s work. Unfortunat­ely just before venturing off for the MOT the poor thing switched on a red light indicating no oil pressure and we could not rectify this fault, so began a search for a replacemen­t engine, but that’s another story, in fact two stories, one on-going and one about to commence, all involving engineerin­g students. Due to reasons beyond the wit of mortals our motor vehicle course had to close and it morphed into an engineerin­g course and I was now involved in teaching this officially. I thought it would be a good idea for the students to have practical experience with a motorcycle along the lines already explored with the CBR. Of course, I did not want to incur the costs, so we put out the call to the staff and low and behold a Honda 90 Cub was volunteere­d for rebuild. This machine had been seized thus proving that all Cubs do actually need oil,

at least sometimes. It took my Year 10 boys five months to strip, clean, rebuild and re-engine this machine. Not bad at 100 minutes per week! But then there are 10 students. The owner decided to donate the bike permanentl­y to the school so we now have a known machine that we can cycle through subsequent year groups with each one doing a little bit more to improve it, but that is also another story. This at last brings us to the Honda 350; you thought I had forgotten? The hunt for spares for the CBR and the Cub had brought David Silver Spares of Leiston to my attention. Being local I made a couple of visits to collect parts from them and at the counter I was most impressed with the line-up of classic Hondas that shared the narrow space available. Getting chatting, it became clear that the company had a museum under constructi­on which was due to open in the not too distant future, a museum that finally opened in June 2016. All this set me to wondering. An aspect of engineerin­g we try to impress on students is the reading of a drawing, the relationsh­ip of parts, the part numbers, how you identify parts and how that relates to the real world and the hundreds of thousands of parts that have to be available to support even a small range of products. I asked David Silver by letter if our students could visit his site to see how the operation works and further if he had a motorcycle that he would not mind them working on. I was amazed when he was agreeable on both counts! David gave of his time freely and personally showed our students around all of the warehouses, patiently explaining how the stock control worked, how he set about commission­ing the manufactur­e of non-available parts such as exhaust systems and the problems and pitfalls inherent in maintainin­g quality to a high standard. We finished the warehouse tour with a visit to his collection of bikes held as stock and the Honda 400/4s which the company has a reputation for recommissi­oning. My students were most impressed by the Kawasaki two-stroke triple, for its noise and the private smoke screen generated on start-up. Ah those were the days! We then stood in front of a line-up of Hondas in various stages of being ‘barn fresh’ (what a lovely expression) and David gave a descriptio­n of what was available by way of spares and basically asked the boys which one they would like to take away to work on. So, this is where we came in. We at the school think it is quite a big deal considerin­g the support and generosity of David Silver and his company. There really is no way that our design department could support the funding of this sort of work at this level and my debit card can breathe a sigh of relief. So what of the bike itself? Well, like many individual­s who are restoring a motorcycle we have to ship work to outside suppliers. So far the powder coating has been completed on all of the black cycle parts, this was done by Suffolk Stove Enamellers (01473 735585) the wheels have been rebuilt and the bodywork repainted, David Silver commission­ed this through his own suppliers, the chrome work was completed by Heritage Classics (01206 211954). This is no cheap rebuild but a nut and bolt restoratio­n which will eventually take a place of its own in David’s museum. This is where my students finished their visit, being given a private guided tour by David prior to the official opening. They were most impressed and when David asked if any of them had any questions the response was ‘when can we come back?’ If you have not visited the museum I can certainly recommend it. A few weeks later I collected the Honda and delivered it to school, it so happened that during the following week about half my young engineers could spend a whole day working on the bike. The upshot of which was a completely stripped bike in seven hours! Now taking a bike apart is easy, and one thing the boys learned on the Cub was the vital need to take notes and photograph­s, which I am pleased to say they did, this time. I had been hoping to get the K4 running before we stripped

it, but a cursory inspection revealed that the ignition system had been jury rigged and both carb float bowls had been removed and loosely refitted. This seemed to show that the previous owner was investigat­ing some fault with ignition or carburatio­n. If the tax disc is correct then the bike has been off the road for a long time and I think the speedo shows that it has only completed about 32,000 miles. Working on the assumption the mileage might be correct and that the bike has clearly been loved we decided not to strip the engine, but hope that it was in good condition and would need only a fettle to see it back running, the ignition and carbs are still a work in progress. To clean the carbs and hopefully improve the looks of the motor the students have built a soda blasting cabinet converting an old machine stand to that purpose. See, I knew Youtube was good for something! Rear mudguards are hen’s teeth for these bikes and this one had been treated to under-seal thus greatly aiding its survival. The mudguard is made up of two parts, front and rear that are then overlapped at the centre and spot welded. To strengthen this joint a top-hat section tunnel is spot welded across the joint from below. This doubles as a convenient place to run the rear light cables. Externally there are two tear-drop shaped tunnels that bridge the joint either side of the mudguard; they hold a captive nut each which then act as pick up points that hold the bolts that retain the mudguard to the frame. All these little tunnels are open to the elements and are the reason these guards are hen’s teeth. Having done a superb job of protecting the guard the owner had allowed the sealant to fill up the lower tunnel, so he just let the rear light cables hang loose, funny the way a rear tyre wears away at PVC insulation. Both the captive nuts had rotted to the point where they were only captive on the threads thus turning the bolts into location dowels and the removal of the guard into a bit of a challenge. The empty spaces vacated by the nuts were filled with mild steel and tigged in place by Wilf Dewelder (01473 603889). This will leave us a blank area of steel into

which to drill and tap new holes at a later stage. Wilf also repaired the chain-guard which had split across its section: I think this was caused by having the chain-guard rigidly mounted to the swingarm. The rear-most bolt is supposed to be rubber mounted. But it was clear that all the original mounting bolts had been lost at some point in the past and replaced with whatever came to hand, resulting in excess vibration. Honda seems to have a tradition for using rolled steel tubing to form hinges to attach centrestan­ds. Undoubtedl­y effective, they have a tendency to rust themselves firmly to the surroundin­g framework. The pin on my VFR had to be drilled out in situ, a tedious job which took a whole day to execute. It proved impossible on the K4 so we decided to machine up a replacemen­t pin in solid steel, designed to rotate inside the hollow of the rolled steel pin, creating two round nuts to hold all in place, these are gripped by clamps on the frame. The bike is now coming back together, but we have hit one snag with the front forks that will relegate the bike to museum exhibit only. We cannot remove the oil seal holders in order to replace the oil seals and dust caps that lie within. The steel covers are so heavily corroded onto the aluminium sliders that use of a strap wrench results in deformatio­n of the steel covers, a component for which no known replacemen­t is yet available. If anyone has any advice or a slider/cover combinatio­n that we can destroy in order to investigat­e the constructi­on, or an engineerin­g drawing, we would be most grateful. So what is it like rebuilding bikes by proxy? I have a few rebuilds to my credit so I know what is involved and some reasonable idea for a structured process, but this is a teaching exercise and the hardest thing is not do it for them. I have to step in sometimes, but I try to leave it for as long as possible. The other difficulty is working with a machine I do not know at all, let alone well. Of course all bikes are basically the same but each has its own preferred methods and sequences of assembly and without extensive reading through of manuals it is not always obvious that you are following the best practice and not assembling systems which will later have to come apart because this flange widget should have gone on first. Cleaning the parts is probably the greatest trial. We don’t have profession­al cleaning gear so all must be done by hand with various fluids, brushes and elbow grease. All credit to the students that they do not baulk at this tedious task but get on with it. The deadline for this bike is May 2017 – not far off when you will be reading these words. This deadline is because our department puts on a show of work done during the year and this bike is slated to be in the show, shortly after the students will break up for their exams, hence all work will stop and I really don’t want to be handing it on to a second crew. I am hoping that The Copdock Classic Motorcycle Club are going to allow the school a stand at the Copdock Bike show in October 2017 where we will exhibit this bike and the work of our students. I am hoping to include some of the ‘other stories’ (C90 and CBR600) as well!

 ??  ?? Snapping shots while stripping parts.
Snapping shots while stripping parts.
 ??  ?? Wires aplenty for the kids to sort.
Wires aplenty for the kids to sort.
 ??  ?? Don’t cut the red wire!
Don’t cut the red wire!
 ??  ?? Spaghetti junction.
Spaghetti junction.
 ??  ?? Some parts were still in good nick.
Some parts were still in good nick.
 ??  ?? Tank bottoms normally have issues.
Tank bottoms normally have issues.
 ??  ?? Work selected for chroming.
Work selected for chroming.
 ??  ?? And more here...
And more here...
 ??  ?? Curtis, Ben, Henry, Grisha, Oliver, Kane, Alex, me, David Silver, Matt and Scott.
Curtis, Ben, Henry, Grisha, Oliver, Kane, Alex, me, David Silver, Matt and Scott.
 ??  ?? You have to visit the museum.
You have to visit the museum.
 ??  ?? Hand painted, red lead undercoat!
Hand painted, red lead undercoat!
 ??  ?? Seen some action – but largely intact.
Seen some action – but largely intact.
 ??  ?? Something’s missing here.
Something’s missing here.
 ??  ??
 ??  ?? Clocks don’t seem in bad condition at all.
Clocks don’t seem in bad condition at all.
 ??  ?? Down to the rolling chassis.
Down to the rolling chassis.
 ??  ?? Forks were going to be an issue.
Forks were going to be an issue.
 ??  ?? And the engine is out!
And the engine is out!

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