Category Archives: Metalwork

ST1100 Miscellaneous Metalwork

First attempt at welding

My first bit of welding, other than practicing on some scrap, was to add some angle strips to the rear frame to support the battery – I wasn’t confident that a fibreglass tray on its own would be strong enough. The orange bit of fibreglass is where the top of the mudguard had to be cut away so the battery could sit lower down.

ST1100 P4 M02 Metal

The seat catch for the dual seat was originally fitted under the rear cross-member, with a metal loop from the seat going through the slot to engage the catch. Re-using the catch seemed like a good idea, so another bit of steel was welded on in front of the battery tray to attach it to. Luckily these welds will all be hidden from public view. The catch used to be operated by a cable connected to a lock, but as the only thing under the seat now will be the fuel tank, a simple wire pull will do.

ST1100 P4 M04 Metal

Brackets – alloy and steel

The left-hand footrest bracket also supports the starter relay and reg-rec. I would have liked to move these components as they stick out a bit and may spoil the lines of the side panel, but there was no-where obvious to put them that would provide a decent heat-sink for the reg-rec. Pan European reg-recs are generally immune from the failures common to other Hondas of the 1990s, probably because they are bolted to a big chunk of alloy and don’t overheat – that’s the upright bit with the projecting bolts in the pic below. The battery used to sit on the plastic tray to the right of it, which was part of the mudguard moulding.

ST1100 P4 M06 Metal

 Having decided to let the relay and reg-rec remain where they are, I cut off the rear part of the bracket, as part of the plan to visually shorten and lighten the bike. A bit of rounding off might improve the cut edge.

ST1100 P4 M07 Metal

The plastic moulding that the starter relay was attached to was part of the battery tray  moulding, so I had to make up a new bracket that could be fixed to the footrest bracket. A trial-and-error card template formed the design, and a bit of the cut-off fuel tank hump supplied the material.

ST1100 P4 M08 Metal

ST1100 P4 M10 Metal

It was while re-attaching the brackets to the bike that I noticed a little bit of water seeping from a bubble in the swing-arm. Prodding with a screwdriver found some serious rot, necessitating a new swing-arm – very disheartening and the main reason that I didn’t touch this project for another 12 months and got on with the PC800 instead.

ST1100 P4 M12 Metal

With a new-ish and very expensive swing-arm eventually installed I did a bit more cutting down of the footrest bracket on the other side. Still not quite right somehow, but getting the bike on the road is now more important than perfection.

ST1100 P4 H12 Exhaust

ST1100 Lights, Clocks & Fairing

ST1100 P3 X07 ed After

Part of the redesign started in 2012 was to get rid of this modified Triumph Tiger front panel. I thought it looked great when I first finished it, but now it seems to look too much like the old Avon fairings that the police and AA used on their BSAs, available today on eBay for 99p. Replacing it with an off-the-shelf supermoto/streetfighter fairing would look silly – just a cop-out. I tried a traditional round headlight as originally intended, but it looked a bit boring. It would also mean having to make a decent-looking mount for the instruments and fix up a fly screen for a bit of wind protection.

By late 2015, in the interests of getting the bike back on the road as soon as possible, I decided to stick with the Triumph fairing. This would conveniently hide and protect the original instruments which I want to retain – mileage of 71k is to be proud of! Having lopped off the panel’s side bulges to slim it down, the brackets I’d originally made to hold the lights in and mount the fairing were lost. Here it’s just taped in place:

ST1100 P4 J01 Front

New brackets to connect the panel with the Suzuki GSXR lights were made from 3mm aluminium and held in place with filler as before. The brackets had holes drilled for the filler to ooze through and secure them. Tidying and painting yet to be done:

ST1100 P4 J04 Front

The fairing looked better when closer to the forks and lower down than before – this meant the clock housing would have to be cut down to remove the projecting mounting points (and make it look less like a car dashboard).

ST1100 P4 J06 Front

More home-made 3mm aluminium brackets bolted to the fork clamps now hold the fairing on. It needed another pair of brackets at the bottom of the fairing to steady it (not yet fitted in this picture). The untidy sides of the cut-down clock housing can be seen, needing some sort of disguise – yet to be devised.

ST1100 P4 J07 Front

The removal for the clock housing mounting points meant it needed a mounting plate, which could bolt to the existing tapped holes in the top yoke. I cut this from more 3mm aluminium, with holes for the speedo drive and clock lights, then carefully bent it round a curved former – in the wrong direction. Having hammered it flat again, I could not quite replicate the nice curves I’d got the first time, but it does the job, and won’t be visible normally. I just hope the re-bending has not weakened the metal too much.

ST1100 P4 J08 Front

The original warning light unit was too large to fit between the clocks and the modified fairing, so I decided to try LEDs – 10mm diameter 12 volt units that light up in various colours. The panel is made from 2mm polystyrene sheet, glued together with MEK solvent. Two brackets bent up from scrap steel are glued to the sides with Araldite. These locate it on the front of the clock housing using the screws that retain the perspex cover. I found it best to drill the 10mm holes for the LEDs slightly under-size and finish them with a file, to ensure they lined up neatly. Strips of copper-surfaced printed circuit board (PCB) connect up the common leads (3 needed to go to negative, 4 to positive, just to make matters more interesting). The non-common leads are soldered to a strip of PCB with the copper coating cut through to separate them. The wires cut from the from the old warning lights could then be soldered to the appropriate bits of PCB without putting any strain on the LED leads.

ST1100 P4 J10 Front

The LEDs were held in place quite well by their leads, but a few blobs of Araldite added after this picture made them more secure. Once I’m happy with the unit I will probably box it in to give it a bit more protection. They appear very bright in the relative gloom of the garage, and may need some smoked perspex over them.

ST1100 P4 J12 Front

The speedometer is installed to check that the speedo drive cable run is clear. It will have to come out again to finally bolt the housing in place, with M5 bolts through the base of the housing and the bracket. There is a slight crack in the perspex cover at the bottom of the rev counter aperture. There used to be two small lugs on the back of the cover and housing with screws holding them together. I used these to attach the housing to the top yoke in the previous incarnation, causing the crack – a regrettable bodge!

Painting will have to wait for warmer, drier, weather.

ST1100 Exhaust

ST1100 P2 X04 Exhaust

After its first year on the road the downpipes looked rather tatty – the rust was coming through the high-temp silver paint. They are supposed to be stainless steel, but they aren’t original Honda ones. I had a spare set of pipes in similar condition, on which I ground off the lugs that once held heat shields (lost before I got the bike). On a friend’s recommendation I took them to Reddich Shotblasting, who cleaned them up, coated them in aluminium then baked on high-temp paint again. Much cheaper than a custom-made set of pipes!

ST1100 P3 X20 Exhaust

They look neater, and the rust has stayed at bay, but they did discolour near the top after more use, so they may need annual painting (from a spray can) to stay looking good. I might get round to removing the belly-pan brackets too.

For the new cut-down version of the bike I didn’t want the heavy and dull old twin silencers that weigh about 5kg each.

ST1100 P1 C03 After

Having had bought an ex-display Scorpion end can at a show I decided to have a go at making a link pipe to join it to the exhaust collector box. This is where the link pipe would need to go.

ST1100 P4 H04 Exhaust

It would also need a blanking plug for the collector outlet where the original left hand silencer went. The only welding I had done was a bit of practice on scrap and welding some brackets to the bike frame to hold the battery under the tail piece. In other words I was a complete novice,  so I started on the plug before tackling the more complicated link pipe.

I’d acquired some 2 inch (51mm) mild steel tube for this – stainless would have been better but apparently it’s more difficult to weld. I cut a short section of tube, took out a few mm down the length and closed it up to fit inside the 48mm collector outlet, with a round bit of plate to go on the end. The benefits of practising on scrap soon became apparent when I burnt away the edge of the plate trying to weld it to the tube. Much welding and grinding later, I had a functional if rough and ready plug.

ST1100 P4 H06 Exhaust

I’d made a cardboard mockup of the link pipe and end can to get the design right before starting on metal, as shown in the ST1100 Redesign post.

The link pipe needed two bends, one just outside the collector to turn the pipe horizontal to clear the footrest bracket and another bend to turn the pipe backwards. The first looked to be about 30 degrees, so a simple cut and shut would do, but the second was 90 degrees and needed to be quite sharp to get the end can close to where I wanted it. A set of three 30 degree angles close together seemed a reasonable compromise. I recently learned that what I was going to make is called a ‘lobster back’, where a series of triangular slices of tube are welded together to make a bend.

I practiced welding on an offcut of tube, but still burned away some of the first joint when I started on the link pipe, mainly because the cut edges were not straight and didn’t meet cleanly. I was doing reasonably well by the third joint when the electronics in my welding mask packed up. This meant having to flip up the mask to position the torch, then close it and weld with the window on its default, darkest setting, i.e. almost blind, so the fourth join was not very pretty. The final part was to make an insert to fit inside the collector. When I tried it in place, the first join was at the wrong angle, so I had to cut the pipe again and make another join. All this was made more difficult by using flux-cored welding wire in my second-hand MiG welder instead of investing in a bottle of welding gas and using plain wire. A lesson learned.

ST1100 P4 H08 Exhaust

The next step was to test it for gas tightness, by taping up one end and putting it in water – bubbles poured out of all the joins! There were so many holes I couldn’t mark them all, and just had to weld over every seam again. After a few more tests and re-welds, the bubbles finally stopped.

After each session of welding I ground off the excess – it looks better, and makes it easier to see where the pinholes are for re-welding. I was beginning to hate angle grinding, and the garage was covered with specs of burnt steel.

ST1100 P4 H10 Exhaust

This is the the point at which I decided I wasn’t going to improve it much more. Despite the terrible appearance it seems to be quite solid. High temperature paint should hide the worst of the pockmarks. It was a worthwhile exercise, but maybe one day I’ll get a professionally made stainless replacement.

Here’s a short video:


ST1100 Fuel Tank Mods

For the ST1100 redesign, having decided to butcher the fuel tank to make room for the battery, the spare tank I’d bought in a job-lot came into its own.

ST1100 P4 F04 Fuel

As it had been left open for a year or two there was no fuel vapour inside so I took an angle grinder to it.

ST1100 P4 F06 Fuel

What luxury, to be able to get an electric drill with wire brush inside the tank! I also treated it with rust killer to be on the safe side. Rapid Metals of Coventry were very helpful in supplying small quantities of steel – some 1.5mm plate to cover the hole in the top of the tank and some 3” tube for a filler spout. The original filler cap and bayonet fitting would go on top of the tube. I did the cutting out and local bike mechanic Jason of JM Motorcycles (sadly no-longer in business) did the TIG welding.

ST1100 P4 F08 Fuel

The two bolts are for a seat bracket yet to be designed at this stage. The fuel pump goes in the hole at the back – the one from the spare tank didn’t work so I transferred the good one from the original tank, with a new sealing gasket. A couple of coats of black Hammerite finished off the tank. One bonus is that it can now be tilted forward to remove it without taking off the air filter.