Tow hitch for The Fire Bike, part 3 โ€“ 29 Jun 2016.

Here is the final part of my story about fitting a tow hitch to The Fire Bike. While the paint was drying/hardening on the pannier/towing bracket I turned my attention to the towing electrics.

I wasn’t sure if I was going to use the standard 7-pin UK towing socket and looked for more compact alternatives. However, I couldn’t find anything I liked better. I decided the best place to mount it was beside the number plate to a bracket sandwiched behind the plate. I drew a card template then cut the bracket out using my old “Monodex” cutters which I’ve kept from my car restoring days.



It will screw behind the number plate using the lower mounting bolts.


I trial fitted this to the bike but found it rattled and needed 2 additional small screws to reduce this. Here you can also see that the bracket has been bent forward so the socket will clear the left hand pannier when fitted.


It was clear to me that, If I wasn’t careful there would be a “rats nest” of wires below the tail lamp and behind the number plate. This was because I still wanted to keep the connections for the lights I’ve fitted to my top box. Piggy-backing connectors together wasn’t going to be the answer. I decided to use a connector block which would allow four way connections. Only ones with screw down terminals were compact enough. The top connections would be for the wires from the bikes’ main loom and to its original lights. The lower connections would be for the top box and trailer wiring.

I cut the terminals from my top box wiring and replaced them with ring terminals and made a short ground connection.


Then I added ring terminals to the end of a length of 7-core trailer cable. Only 6 of the wires are used. The blue one is for a fog light and is held out of the way with heat shrink.


Rather than remove the terminals from the bikes’ wiring I made a pile of adapters and fitted them to the connector block. There is also a link joining terminals 2 and 3 together. This is because trailer wiring usually has left and right side tail lamps on separate circuits but, of course unlike a car, a bike only has one to feed them.


The connector block was fitted with a bracket so it could be mounted to the lower tail lamp bracket bolt and the bike wiring connected up and tested.


It’s still a bit “busy” back there and I might end up changing the bike wiring to ring terminals and junking my adapters after all.

I fitted the top box and trailer connections to the lower part of the connector block and then checked the number plate hardware would go back without trapping the wiring.


The towing socket was wired up and fitted to the plate I made using its rubber seal. These sockets are easy to connect up and wiring diagrams are easily found on the net.


Next the trailer wiring and top box connections were tested. Everything worked as it should.

The paint on the tow bracket was still not hard enough to handle so instead I gave the bike a wash to get rid off all the sand/dust that came down in the rain the other day.

This afternoon I remounted the chrome top rack and fitted the new pannier/towing bracket. I had to go and borrow a 1 1/8 in spanner to fit the tow ball to the bracket. It had to be held with a Stillson pipe wrench but I managed not to scar it. The panniers finally went back on and the job was pretty much done. I just added a rubber buffer to the back of one of the towing socket screws so it can’t dig into the pannier when I plug the trailer in.

I think it all looks OK.



I need to hitch it up and go for some test rides now.

Oh, just one more thing. I made up a kerb weight plate for the bike and an unladen weight plate for the trailer. They’ve been stuck on with some double sided tape designed for fixing badges to car bodywork.


Update 30 Jun 2016.

I have made a little change. Looking at the photos last night I was concerned that the socket for the trailer electrics obscured the “6” of the number plate too much (also see the comments below). I’m not concerned about the plug obscuring the number plate when the trailer’s plugged in as there’s a number plate on the back of that. It’s actually legal to remove the plate from the tow vehicle and fix it to the trailer. The UK regulations state;

“A registration plate must be fixed on the rear ofโ€”
(a) the vehicle, or
(b) where the vehicle is towing a trailer, the trailer, or
(c) where the vehicle is towing more than one trailer, the rearmost trailer.”

So there you go!

There isn’t clearance to fit the socket below the registration plate so the best I could do was to raise the socket in line with the top line so it will only cover the blank space next to the “E”. The regulations that apply to the old-style plates say there must be a 10mm margin beside the letters/numerals and there is 40mm here. I could have a plate made with the top row aligned to the right giving even more space but that, though legal, would look a bit odd.

Here are photos of the revised set-up with the bike solo and with the trailer plugged in. I should have done this in the first place.




Tow hitch for The Fire Bike, part 2 โ€“ 26 Jun 2016.

Well, late the other evening, I had a phone call from Eifion at Tobruk Engineering to say that my new pannier frame/towing bracket was ready. I set off the next day on The Fire Bike to fit it at his works. It’s only 20 minutes each way but, before I got very far, the heavens opened and we had a welly-filler of a shower so I had to don all my waterproof gear.

I was impressed with the workmanship. Eifion has produced a copy of the original pannier bracket but in steel bar instead of tubing. He has added the lower strengthening points as we agreed but not the upper diagonal braces as he felt it was strong enough already. Having seen the finished article I am inclined to agree. At the back, of course is the 6mm thick plate to take the tow ball.

We offered the bracket up to the bike and it bolted straight on. Quite a bit of time had been spent getting it right. It’s not just the welding. All the bends, brackets and mounting points had to be accurate. Eifion built a jig first using the original rack and got everything spot on.

It wasn’t so wet on the way home but somehow the bike and I ended up filthy. It looks like we were covered in wet sand. Within half an hour of getting the bike in the garage, the new frame had begun to rust – Welsh rain and sea air!

Of course I had to offer the trailer up to the bike to see how everything would sit. By now the sun was shining in through the windows.



Once again I got my wife to measure the height of the tow hitch while I balanced on the bike. After adding on the height of the tow ball, I calculated that the distance from ground to the mid point of the ball was 388mm. This is 23mm higher than I had worked out originally (365mm). This actually makes things better as we get closer to the 35mm difference I had been aiming for. Trailer coupling height of 420mm less bike tow ball height is 32mm. That’s good enough for me.

I fitted the panniers to the new rack after making rubber pads to go between the pannier boxes and brackets as all but one was missing. The panniers fitted straight on.


Now everything had to come apart again so that I could paint the new bracket. Being made of steel bar it’s heavier than the original rack but, surprisingly, not that much.


The following day I had to drive past the works to do the supermarket shopping and called in to pick up my original rack. Here are the two together for comparison. You can see the extra bracing between the lower loops of the framework.


Since then I have spent an hour rubbing the metalwork down with emery cloth before giving my new bracket two coats of red Hammerite Smooth paint.

Painting that thing wasn’t very easy. I put a threaded rod through the two front mountings to give me something to hold on to and then clamped it in the vice by the tow ball plate. That meant I could paint everything apart from the plate and turn it round to get to the other side.


While the paint was still new and a bit soft I scraped off the paint that had got onto the tow ball mounting plate. This was so I wouldn’t get a line when I painted that part. That last bit then got its two coats of paint as well.



I’ll need to leave the paint to harden before trying to fit the rack to the bike and even longer before I try and rub the runs down – oops. In the meantime I’ll have to make the electrical connections and will be back with part 3 soon. The colour of the Hammerite isn’t far off the bikes original but it’s a bit too orange.


Adding vacuum take off points to the V7Sport – 22 Jun 2016.

Since putting The Racing Rhino back on the road it has performed beautifully. It’s strong, pulling right through the rev range, ticking over properly and is just a joy to ride. However, almost immediately the right hand exhaust pipe turned yellow then blue. I’m not sure, but I think it’s continuing to slowly get worse.

Chrome turning blue is caused by it getting hot and there are various reasons why this might be. A weak fuel mixture is a common cause but, in this case, if anything the bike might be running slightly rich as it now has air filters where originally there were none. Carburettor jetting is still standard. Both spark plugs are the in same condition – a sort of brick red with the odd sooty spec on them. Ignition timing has been checked twice and the valves readjusted after re-torquing the cylinder head nuts. I have also successfully removed all the leaks from the exhaust system using silicone sealant.

Interestingly, my previous experience has been that both exhaust headers will go blue pretty quickly on these bikes. So the problem side could be the left, possibly colder one. Another suggestion has been that the quality of the chrome is different on each pipe and that is why they behave differently. The cylinders of the Guzzi engine are offset with the right hand one further forward. This means there is a shorter distance for the very hot exhaust gasses to travel to the bend in the exhaust header on that side, and so more blueness.

Just before writing this post I saw that Hans, another Guzzi WordPress blogger, is having the same issue with his newly restored 850GT here – I paste the link into Google translate to see what’s going on.

Anyway I decided that one last thing I could investigate further was the carburettor balance. Perhaps there is more load on one side than the other. I wanted to use my vacuum gauges but there were no vacuum take off points. I’ve done this on The Fire Bike which has had them added at some point by a previous owner. Later Guzzis have a drilled “boss” on the intakes for the purpose.

Here is the drilling added to the left hand intake manifold of The Fire Bike


and this is the same point sans drilling on The Racing Rhino.


I had considered making this modification when the bike was being rebuilt but “chickened out”. This time I plucked up the courage and reasoned that, if I made a total mess of it, I would buy a set of later inlets with the fittings already in place.

I disconnected the battery and removed the fuel tank so that I couldn’t damage it with my ham-fistedness. I took off the air filters and then set about removing the left-hand carburettor.

I undid the clamp that holds it on the manifold and managed to wiggle it free without removing the throttle cable or fuel line. The three allen bolts holding the inlet manifold to the cylinder head were undone and the manifold taken to the bench.

These are my vacuum take off adapters which have an M6x1.0 thread


I spent a lot of time measuring where the hole was drilled in the V7 loopframe manifold and copied that carefully although I’m not sure how critical this actually is. I was finally happy(ish) and marked the spot with a marker pen. You might be able to see in the photos that I had made several attempts at this!

I don’t have any expensive tooling but managed to get the manifold clamped in a machine vice, supported at what looked like the correct angle and positioned in my hand-cranked pillar drill. It’s old (90 years old?) but can be relied upon to drill a hole accurately. I drilled a small pilot hole first.


Cutting the M6 thread requires a 5mm hole so, after checking that the pilot hole was at the correct angle, the larger diameter was drilled.


The thread was then cut.


I carefully removed any swarf from the manifold as well as any sharp edges. I measured the thickness of the manifold casting through the hole as 5.7mm. The blanking screws fitted to the V7 loopframe manifolds are 10mm long. Fitted to my newly tapped hole it’s too long but, again, I’m not sure how much this matters.


I made a shorter blanking plug (about 7mm), added a fibre sealing washer then refitted the manifold and carburetor.


I repeated the job on the other manifold. Here the carb is off and hanging by the throttle cable.


Once this manifold had also been drilled, tapped and plugged everything was reassembled – air filters, fuel tank and battery ground cable.

I checked that the bike started and ran properly. I don’t think the plugs in the take off points leak at all. With the engine running, I sprayed them with “easy start” to see if the engine “picked up” and it didn’t.

I think the modification has been a success and hope to soon have a go at balancing the carburettors using my vacuum gauges. I did this on The Fire Bike a while ago with good results.