Exhaust, carbs ‘n’ other stuff – 4 Jul 2014.

I didn’t realise how long it’s been since I posted something. It doesn’t feel like I’ve mad much progress but visits to the fettling shed have been frequent and it turns out I’ve done more than I thought.

I’ve sent off the bits for chroming and am told it should take about four weeks for them to come back. Hopefully this means they’ll arrive before I go on my hols. I’m glad I’ve not got much to do as the cost is… significant.

A new exhaust system

My replacement exhaust system has arrived. Rhino has never had a complete exhaust system approaching the correct type in all the time I’ve owned him. There’s been a two-into-one, a full 850T3 system with the big silencers with outside seams that just rotted away. Then I modified the T3 crossover so I could fit reproduction V7Sport “shark gill” silencers but I haven’t looked after these very well and they’ve rusted. These will be salvaged as my powder coater says he can re coat them black and they can go on my other bike, the S3. I just had to trial fit the new system and thankfully all went well but I’ve taken it all off again and stashed it for now.

The new silencers are slightly longer than the previous ones and I’ve no idea if either of them is right. The new repro silencers have a less bulbous flare at the end. The original type would have been straight with a sharp cut off. Also the “shark gills” don’t seem so open but I’m not going to fiddle with these as I’ll only have the chrome off. Internally they are different. I can see right through these unlike the previous (and the original?) type. A common criticism of the original silencers was that they were too quiet and restrictive and owners fitted Lafranconi silencers instead. Perhaps these, marked as Silentium but possibly made by Busso, will be more free flowing. The Busso silencers on the S3 sound beautiful but are showing their age. I’m tempted to try and pull the baffles out of the new silencers just to see what they are like. With the screws removed they do move a couple of millimetres but I’ve left it as some force will be needed to get them out. Then putting them back will require lining up the screw holes as well. Some scope for trouble I think.

Anyway here is a new repro silencer with an old one. The quality of the welding and chrome is a whole lot better.

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Proper cross-over pipe

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You can see that the header pipes have got the correct curve.

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I fitted them using some special header screw-in clamps I bought many years ago. I can’t remember where I got them. There was a problem with the original Guzzi design. They would work loose allowing the pipe to vibrate in the port, wearing the threads. This was almost impossible to repair. To minimise the problem there were extra clamps to secure the pipes to the lower part of the frame (I still have to get/make these) and the header nuts were often lock-wired to a hole in an engine fin (hole fifth fin down in photo). These special clamps are deeper than the originals and have a lock ring that you tighten up against the cylinder head to prevent vibration undoing the nuts.

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Carburettors.

The original V7Sport’s VHB30 carbs have not been used since around 1980. I set to and rebuilt them using kits bought from Dell’Orto containing gaskets, O-rings and sealing washers. There were a number of parts that were clearly for other model carbs and were redundant. Referring to the diagram in my manual I took the left carb completely to bits being careful to note where each jet came from. There didn’t seem to be much muck but I cleaned everything with carb cleaner and compressed air and examined all the parts. This is the first time I’ve had one of these apart and I assume all the jets are to original spec but, what do I know? The jets aren’t marked with anything that corresponds with sizes I’ve seen listed apart from the cold start jet which is correct. Getting the O-ring off that starter jet wasn’t difficult as it fell apart but putting the replacement on gave me sore fingers! The throttle slides show only the slightest surface marks and the plastic sleeve in the carb outlet was fine. It seems that replacements for these two parts are no longer available.

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In that photo the accelerator pump parts are back together as I was worried about losing tiny parts. Reassembly was easy and I checked that float height was correct before I put the bowl back on. I had it together then saw there was something wrong with the throttle cable adjuster. I realised it was missing a lock-nut and when I got one from a spare carb found it was the wrong size. Someone, along time ago, has fitted what looks like a bike brake cable adjuster.

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It should be the smaller one so I carefully removed the new gasket from the old carb top and fitted it to the one from the spares carb and fitted that. I refitted the carb to the inlet stub and then to the cylinder head using two new 3mmm thick gaskets. My gasket set had included gaskets for here but they were much too thin. You need these to be the proper thickness and also to have the thick fibre washers under the fixing screws as they are designed to reduce heat soak from the engine to the carb bodies.

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So one down, one to go. Second time around was much quicker. All the internal parts of the right hand carb were good although all the jets were loose. I also noted that the throttle stop screw and idle adjustment screws were a long way out – 4 1/2 turns as opposed to 2 1/4 turns for the left carb. Perhaps this was because of those loose jets. Sadly the original metal cold start lever (flip choke) was broken and I had to fit a later replacement. Functionally they are the same but the new one has a plastic leaver and a different fitting plate. Never mind, this one is on the inside of the carb when it’s fitted.

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T’other stuff.

You might remember that when I rebuilt the forks I was short of the special screws which fix the internal dampers to the fork top nuts and then take the instrument mounts. I searched all my usual sources but couldn’t find any replacements for the bent ones I’ve got. Both my bikes use these and three out of the four are really bent. I gave the one good one and some 13mm stainless steel hex bar to my mate, Bunny, who produced four accurate stainless copies – enough for both bikes.

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I’ve also been painting odd bits and pieces. Some bracketry should really be zinc plated but it’s all paint for now. When at a loose end I got the Solvol out and and had a go at the brake and gear levers. They’re both pretty scarred, the brake lever clearly having hit the ground at some point. I would have to remove a lot of material to polish out the damage so they’ll stay pretty much as they are. I did see that TLM had a new brake lever in stock but it was over €150.

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