Thumper Diaries

The sun came out today and the temperature went up to 4° Centigrade. I decided to take the chance and road test Thumper now that I’ve done all my winter modifications.

The saddle definitely lifts me up by a few inches. I realised this when I looked into my mirrors. They were way off. The single saddle being higher means that my hips aren’t as cramped as they were with the old flat seat which actually means I’m more comfortable on the bike. The ride was better too, those extra springs under my arse make a big difference.
I have to admit, I get more pull out of Thumper with the new air filter and new carburettor jetting. He gets away like a scalded cat and the top end is more open. I didn’t press it because it’s still very cold here and the roads may be a bit icy in places but I was up to the 100 km mark in a couple of places and didn’t realise I was going so fast.

I took one of my usual routes round the western side of the island of Amager. This is flat land and the wind gets across it unhindered so one has to bear that in mind, so, easy did it. Heading first south and then west I reached the coast in about a half hour. I stopped virtually at the waters edge and decided to take a break, stretch my legs and smoke a cigarette.
A stunning view, clear air and skies and glorious early year sunshine. The quiet was broken only by the sound of geese flying overhead and the wind in the grasses that line the shore. This, I thought, is what it’s all about. Getting away for a while and living life. Next time, I’ll take the camera. In the meantime, there’s a picture below of the local power station taken from the shore where I stood.

Eager to try the bike in a more urban environment, I rode back towards home through the suburbs of Kastrup, carefully dodging the 4 wheeled motorists and the cyclists, the latter of which have no respect for the rules of the road. No problems with the bike, Thumper does as is expected and no uneasy moments.

So I’m pleased with the results. Even if I did get cold fingers..!

What is a PAV? It’s a Pulse Air Valve that takes some unburned fuel and air mixture from the intake manifold and redirects it to the exhaust pipe just after the outlet port.
It is a device that supposedly will cause any unburnt particles in the exhaust to be burned and thereby reduce emissions. Nice, if it works. Which I don’t entirely believe.
If your national rules don’t require it, then neither do you. I don’t. So off it comes as it restricts the exhaust.

Removal is a piece of cake. No electrics involved, it merely unscrews from the exhaust pipe and the valve in the tool box. Unscrewing the armoured pipe will allow you to remove the valve from inside the box. The whole removal takes seconds rather than minutes. There are some resulting holes to be filled though.
One in the toolbox, one on the exhaust and one on the inlet manifold.

The inlet manifold is a bit of a quandry. I don’t trust the EU with their regulations and such so I decided to keep the little brass tube that works as the outlet from the intake manifold, intact. So I cut off a half inch of the neoprene tube that connected it to the PAV and screwed a slightly oversized screw into it. This becomes, effectively, a cap for the outlet which, by its removal, will allow me to reverse engineer the job if time and conditions dictate.

The toolbox was blanked by two oversized steel washers and a rubber washer, all held in place by a through bolt creating a sandwich of washer, toolbox, rubber washer and steel washer. The rubber washer is mainly for waterproofing. A dab of black gloss and the job is a good ‘un.

The exhaust pipe hole is blanked by a purpose made cap purchased from Hitchcocks.

For now, at least, my winter modifications are complete. I want to ride Thumper now I’ve done with the tinkering. A wash and a good polish is all he needs but that will have to wait until the sun is shining again.

I couldn’t wait any longer. The cold weather has loosened its grip on us for a day or two so it’s off to the shed and get the saddle exchange done.

Getting the indigenous double seat off is easy. Four nuts and a quick pull on the sissy bar and it came away with no problems. The problems came later.
While I had the seat off, I fitted the electrics cover which obviously protects the wiring loom sitting directly beneath the saddle. It also helps to keep the bike looking tidy, so if you’re considering a seat change yourself, go the extra couple of quid and get one. It is well worth the investment.

Now, on to the refit. The saddle comes with a fixing set. Two plates, oblong, rounded corners, four bolts complete with washers and nuts and no instructions. The springs which hold the saddle up and cushion your ass are polished externally only and, again, no fixing instructions. So you’re on your own Jack. Deal with it.
The nose end of the saddle has a mounting on the underside comprising of a metal tube on a fixed axle and a bolt welded centrally. The nut which holds this in the fixing bracket will fit into the bracket but one cannot get a spanner to it to tighten it. The bracket works like a housing which absolutely encloses the nut and when fitted, there is no access to the nut, so I tightened as much as I could with my finger tip and that will have to do.

The springs mount on the saddle retaining studs which are too short to go through the electrics cover, the spring and the fixing washers. Next job then, is to loosen the studs and screw them as far out as one dares and then mount the spring. The spring is cunningly designed so as to not allow a grown mans finger to get in between the coils and maneouvre said washers and nuts. Frustratingly so. This is valid for both ends of the springs, which leads to some fairly colourful language when you get to fit the fixing plates underneath the saddle. Gravity is always against you in these situations.

I finally got it all in place but not without tea, cigarettes and a good deal of cursing. I’m pleased with the result but I believe there must be an easier way to fit these things. Maybe I should get my inventor hat out and see what I can do.

Anyway, here’s the result:

After I’d posted this, one of my online friends pointed out that I may just have gotten things a little wrong. As my father would have said in his day, it’s all ass over tit.
The fixing plates should mount on the seat studs, the springs should be mounted directly under the saddle and the fixing plates adjusted radially to accommodate a more upright stance for the springs under the saddle.
I did as Pete suggested and it all makes much more sense now! So he gets a mention in dispatches here and if ever I run into him, he’s good for a pint or two. Here’s what it should look like:

The madness continues after the air filter rebuild. Having removed the old air filter box the resulting void left my electrics rather exposed and left the bike looking untidy. I’d had a bit of a winge about this on the Hitchcock forum and some bright spark told me that there was a cowling that could be fitted to cover the coil and exposed leads and tidy up the appearance of the area behind the carburettor and air filter.

I thought, ‘Gotta have it.’, so the hunt was on again for parts for Thumper.

I soon found it and, while I was at it, I ordered a single saddle and a top cover for the electrics which will, eventually, sit under the saddle when I re-fit. At the moment, the weather is so cold and that includes the inside of the shed where Thumper lives, that I may not get around to changing the saddle just yet.

But I digress. Having received all the bits in the post, I decided that this simple little job of attaching the cowling would be easy. It was, but one has to remove the toolbox to get at the fixtures, so the job took a bit longer than I thought it would. That is not difficult, but with freezing fingers, it took its time. It isn’t the removal that’s tricky, it’s putting it back where it came from that gets you!

The cowling sits on the old filter box mountings and one of the toolbox supports doubles up as the top fastener. Fitting was relatively simple and the whole job was done in well under one hour. The end result is impressive and elegant. Gone is the gaping hole where the old filter was and the coil and leads are neatly tucked away from the vulgar gaze. Aesthetically pleasing.

Had I known about this cowling before I changed the air filter, I would have ordered the whole kit at a single stroke and saved a bit on postage costs. Chalk one up to experience.

I hope you’re all taking notes…

Or something very close.

I’d been toying with the idea of actually using the right hand tool box as a tool box instead of an air fiter housing. Two options are available. One is to rebuild the tea caddy-like filter box and the other is to fit a conical air filter directly to the carburettor. I opted for the latter.

I found an S&B conical filter that comes with an optional shroud which offers some protection from the rain and other evils. Having checked that it will fit the carb, I ordered the two parts and set about rebuilding the machine.

Actually, it wasn’t that simple.

If one changes the air intake from the restrictive system it was to the open free draw that it now is, one also has to re-jet the carburettor. If it draws more air, then it needs more fuel, otherwise it will run lean and destroy the piston.

So I had to re-jet. I rang my suppliers of all things good and we agreed on a jetting that would solve this issue and parts were duly dispatched.
This meant I had to pore over technical notes as I’ve never stripped a carburettor before but after reading it all through a couple of times, I felt reasonably confident about tackling the job.
In fact, that bit of it all was easy. I removed the carburettor from the bike, re-jetted the carburettor, found and fixed a fault with the choke locking mechanism and fitted the filter and shroud, all in about thirty minutes. Not bad for a newbie, I thought. Proud of my achievements, I refitted the carburettor and attempted to start Thumper.

So, fuel on, ignition on, engine set to run, choke and kick. Three kicks and he was running. Yay! Success.
The subsequent road test went well too.

Only one problem niggled at me now. The carburettor is only supported by the rubber connector between it and the cylinder. It sort of dangles in the air and bobs about a bit. Actually, I could hear the carb knocking against something under the tank as it moved about. I decided I needed to support the filter side of the carb.

There is no part to be found that will do this. So I had to fabricate a bracket and figure out how to mount it. The tank retaining bolt is slightly behind the carb and the filter shroud is mounted to the filter by the large jubilee clip which holds it in place. This fortunate coincidence provided my two points of contact.

I bought some aluminium strip and set to work with a bench vice and a pillar drill and finally made the resulting bracket. Here’s a picture of it, in situ.

The whole thing sits very solidly in place now and the carb no longer jumps about. Cost? Pennies.

The right hand tool box is now fulfilling the purpose I wanted it to. The holes that fed the air ducting have been blanked off and I can fill the box up with tools, cables and other spares that may be needed on longer trips.

Sometimes, I even amaze myself!

Here’s a handy little add-on to your Bullet.

I got it from Hitchcocks and it didn’t cost me a fortune. You know how hard it can be to see your watch when you’re wearing gloves and tearing down the road at 50mph, so here’s the answer.

The clock sits over the fork nut on the headlight nacelle and screws fast with a tiny allen screw.

The one pictured above is black-faced, but mine’s white so I can see the time easier. I’m getting old.
Needless to say, I nicked the picture from H’s catalogue. Hope they’ll forgive me..!!

This could be very helpful on long haul trips. I tend to pace myself, riding for an hour, or whatever suits me and then take a break, light my pipe, pee, eat, drink my tea or anything else I need to do and then continue on again.

It’s not that I’m obsessed with time, in fact I have all the time in the world now, so I don’t have to care how long it takes to get from A to B but I do like to know how long my ass has been in the saddle at any given time.

In November 2013 I reached 60 years of age and officially retired. Early. Leading up to retirement I had built up a few hobbies to enjoy in my otium but decided I would be lacking something if they didn’t get me out of the house. The idea suddenly occurred to me, that I could recapture some of the joy of my youth, motorcycling, which I gave up as marriage, kids and responsibility put too many demands on my time. Now free of the kids and the dreaded work, I thought, “Why not?” and told the missus I was getting a bike.
Surprisingly, she said ‘OK, but get something nice, not one of those Japanese things.’
The hunt, then, was on for a piece of ‘British Iron’.

I spotted Thumper on a website. A dealer some miles away had him up for sale on commission and I rang him up. Thumper, he told me, was as new. He’d only covered 1756 kilometers and the previous owner had bought him as a last fling at life. The man was dying of cancer and had always wanted to own such a bike. He bought Thumper in 2005 but soon became too ill to ride the bike further and it was placed in a garage.
There it stayed for 8 long years gathering dust. And so it was, I bought Thumper.

Getting him road-ready was relatively easy. A wash, a go round with the grease gun and the oil can, check the tyres and battery and some fuel.

Getting him registered was a bit of a trial but after the roadworthiness test and a word with a local workshop, Thumper was finally mine, street legal, registered and ready to go.

I put 1000 kilometers on the odometer before winter drove us into the shed.

I can’t wait for the Spring…