A tow bar on a V7Sport? – 27 Nov 2017.

All year I have been threatening to fit a tow bar to the V7Sport which generally has caused some amusement whenever it’s been mentioned. Nevertheless I did make a start on fabricating a hitch at the beginning of July. The plan had been to have it fitted and useable by the MGCGB Guzzi Festival in August but, what with one thing and another, I was nowhere near being ready and I went on The Fire Bike instead. I had been reluctant to post my progress as I went in case it all turned out wrong. However, today I’ve revisited the project and have decided to file a report as I can’t see why it shouldn’t work.

Firstly, why would I want to do such a thing? I enjoy attending camps and rallies and, having towed my trailer behind The Fire Bike, have found this to suit me. I can carry whatever I want for a comfortable weekend (without being too silly) and don’t have to crush everything to fit into panniers. My stuff stays dry and I can carry bulky but light items which I would usually have to leave at home. Now I will have a choice of bike to take on these jaunts.

Next I had to come up with a design. I don’t mind the Fire Bike being permanently fitted with a hitch but I wanted something for Rhino that could easily be removed. I’ve looked at tow hitches fitted to other Tonti framed Guzzis and found that there seem to be two main types. The first sort is bolted to the same bolts on each side that fasten the lower frame rails to the main bike frame. Tubes/bars then run back to the tow ball. This lot is then held up by stays to the rearmost part of the seat tubes where the seat pivots on a V7Sport. The second type of bracket is fastened to the upper part of the frame and then curves down in an S shape to the tow ball behind the wheel. This is then stabilised by bars running forward to the footpegs. I decided to base my design on the first style.

The first difficulty was that, on the V7Sport, things are very busy in this area on the left side due to the rear brake arrangements. The brackets can’t be fitted on the outside of the frame joint because the brake pedal is there. On the inside there’s not much clearance between frame and swing arm.

What I decided to do was to make a heavy metal bracket to connect to the two bolts and to the bolt on the footrest bracket that mounts the silencers. I could use this to then provide mounting points behind the pillion footrests and build the tow bar proper back from there. The flat brackets would be able to remain in place when the rest of the tow bar is removed.

To this end I removed the footrest brackets and used them to mark out hardboard templates before cutting out the final version. It turned out that, due to the restricted space on the left side of the frame, I couldn’t quite do things as I had wanted. I found that I could mount the plate to the forward bolt in the pair but not the rearward one. The nut on that bolt is already chamfered to gain clearance and the thickness of the plate would make it hit the swing arm. I did think about using a half thickness nut but realise this would have to be chamfered and I wouldn’t be able to get a spanner on it. I did make a smaller nut (17mm instead of 19mm) but it still didn’t really work. In the end I drilled a clearance hole and left that bolt alone. On that side the plate will be held by the one bolt here and the other where the exhaust mounts. The modified pattern is a slightly different shape to maintain strength. It was offered up before both metal plates were cut and fitted. I had to replace three of the frame bolts with slightly longer ones.

I had to cut some packing pieces to fit between each footrest bracket at the silencer bolt and my new plate.

The two unpainted plates have been left on the bike since then and you’d only notice them if you went looking for them.

I bought some solid steel bar from Eifion who made the tow bracket/pannier frame for my V7 loop. I got the same stuff as he had used. A lot of time was then spent measuring and working out how these bars should be bent. I made a template board up and then took it with the bars back to Eifion who bent them to fit. It would have taken me ages. He did it in 10 minutes.

I did weld flat plates to the forward ends of the bars after cutting them to length but that’s as far as it went. I’ve not had time to do any more since the beginning of August.

I’ve now got the bike up on the bench and the bars bolted to their brackets at the front end. The rear section is positioned on my old home-made lift. I constructed this about ten years ago to hold my old 750S3 when I put it together for the first time. It clamps to the edges of the bench and has a thread to raise the cross piece on each side. I had intended to cut it down as its height gets in the way sometimes. I’m glad I didn’t!


Experimental valve clearances – 7 May 2017.

Well, I’ve finally sorted out all my old posts following the Photobucket debacle. I’ve done what I always should have and hosted my blog photos here in WordPress.

As I indicated in my last post, I have got a bit behind with things which is why this is the first of a couple or so posts with a date well in the past!

Anyway, down to business.

The valve gear on The Racing Rhino, my V7Sport, is really noisy. I know that Guzzi engines are always bad in this respect but I can’t see why there still needs to be so much noisy clearance even when the engine is really hot. However, it is important that there is always some clearance as there will be damage caused if a valve is held open due to a lack of clearance. I have friends who have run very small clearances but I am loath to do this and am naturally cautious.

The first thing to do was to see what clearances I actually have. According to the book they should be 0.25mm both for inlet and exhaust. I removed the alternator cover so I could turn the engine using the rotor bolt.

I started with the right hand cylinder so, having removed the spark plugs I turned the engine over until the D mark was in the window of the clutch housing.

and removbed the rocker cover letting it hang on the breather hose.

I measured the valve clearances using a “go/no go” method with my feeler gauges. Clearances were close to 0.25mm as they should be.

After some research I decided to use “Roper spec” – clearances recommended by Pete Roper as safe. These are 5thou inlet and 7thou exhaust or 0.13 and 0.18mm.

Right hand side adjusted, I did the same on the left ( with the S mark in the window).

I went for a ride and the valve gear was marginally quieter. There was still a clatter with the engine really hot so I feel reassured that I won’t be burning any valves with these settings. I don’t think I’ll risk going any further though.

Rhino gets a new battery – 31 Mar 2017

The other week I finally got around to taking Rhino for his MOT (annual road worthiness test). Before I could go I had to charge the battery despite having charged it only a couple of weeks before. There are no parasitic drains on the battery of old bikes like these so I knew that the time had come for replacement. It is worth noting that the old battery was bought in March 2003. I’ve still got the receipt. 14 years ain’t bad. It was a Hawker Odyssey and was much smaller than recommended for an old Guzzi.

The new battery is a Motobatt MBTX30UHD the same as I have fitted to The Fire Bike. This is the correct size at 32Ah but is physically shorter than the original “wet” battery the bike came with.

I had soon extracted the tired old battery and the cage I made to hold it. Next I added two rubber buffers – one each side – to support the new battery. I had bought these during the rebuild but left them off to fit my home made battery cage instead.


I also bought the original style battery straps.



The hook on the longer strap appeared to have been fitted the wrong way up so I changed it. Now it won’t try and “dig in” to the battery.


Having never had these fitted before, I established from a photo in a manual that the longer strap with the hook goes to the back.

the straps locate behind and are then held down by tags. At the rear there is a tag on the frame and the strap is easily snapped in place because it can be pushed past the plastic lower mudguard section.


The front one is more difficult because the plate below the battery, joining the frame to gearbox has to be loosened to get the strap in place. It goes here.


I put a luggage strap around my new battery to make it easier to get in and out.


Then put the battery in place. It is a snug fit between the rubber buffers. Joining the two heavy rubber straps was tough going. I also added a zip tie to the long strap to stop me pulling it apart with my cack-handedness.


According to the parts book there should be a rubber bung in the middle of the long strap but it doesn’t seem necessary.

I ended up using diagonally opposite cable terminals as these just seemed easiest. I like the way these batteries have these connection options. My lifting strap was tightened so that it can’t move about but can be slackened to give me a hand hold if I need to lift the (heavy) battery out.



Wheel balancing, take 2 – 30 Jul 2016.

Having successfully balanced the wheels on The Fire Bike, I decided to go ahead and do the same for The Racing Rhino, my V7Sport. These weren’t balanced when the new tyres were fitted. A lot of what follows repeats stuff I’ve done before but I’ve got the time to set it out again!

I started with the front wheel which is the important one to balance. To get it off:

  • Put the bike on the centre stand.
  • Disconnect the front brake cables from the hubs by first loosening them at the brake lever end. This is to maintain the relative adjustment of each brake shoe.



  • Slacken the wheel spindle nut and loosen the clamp bolts in the fork lowers.


  • Jack up the bike under the sump so the front wheel is clear of the ground. I use the trolley jack I still have from my days of working on old cars.


  • Remove the spindle nut and withdraw the spindle.
  • Lower the wheel to the ground complete with the brake hubs.
  • Make a note of which way round the wheel goes to maintain the direction of tyre rotation and to match the brake drums with their shoes.

The wheel and its spindle can now go in my home-made balancing stand.



It was clear that the wheel did need some weights added so I gave the rim a clean then put it back in the stand. I marked the highest point of the rim and started to add weights with masking tape until the wheel was balanced. The wheel now stopped in a different place each time it was spun and would stay wherever it was put. It needed just 15g.


The area the weights would be stuck to was cleaned with cellulose thinners and the weights fixed permanently. The rims on the V7Sport are Borrani Record “Cross”. This means they are more deeply valanced than those fitted to my V7 700 and means that there is room to stick the weights to the inside of the valanced part.


The front wheel was refitted to the bike and the jack removed from under the engine.

Getting the back wheel out of the V7Sport is so much easier than doing the job on my loopframe V7. There are no panniers in the way and the rear mudguard hinges up so the wheel can be got out without the need to raise the bike or lean it on its side:

  • With the bike still on the centre stand.
  • Slacken and disconnect the brake cable from the brake hub.
  • Remove the brake torque arm.
  • Remove the wheel spindle nut.
  • Slacken the clamp bolt in the swing arm.
  • Undo the “thumb bolts” and raise the mudguard.


  • Remove the wheel spindle while holding the wheel and brake plate in place against the drive box. Note that there is a thick spacer washer on the spindle  between the swing arm and brake hub.


  • The wheel, together with the brake hub, can then be pulled off the drive splines on the bevel box, lowered to the ground and removed backward under the raised mudguard. Why aren’t more bikes fitted with hinged mudguards like this?


The wheel was then cleaned and balanced in the same way as before. It took a lot of weights (as did the rear wheel on the V7 700).

I must have over-greased the drive splines on the wheel before. The grease had been flung around inside the hub on the drive side and some had found its way out between the wheel and the bevel box. I had begun to think that the big seal in the bevel box was failing again but, no it’s grease. It’s sticky and doesn’t smell like gear oil at all.


I think the drive splines on the hub are showing some wear but are OK for now. I checked the spokes in this wheel, having had some loose ones in the past due to broken spoke nipples and couldn’t find any.

When it came to refitting the wheel, I cleaned the grease from the splines on the wheel and drive box then re-applied it but, more sparingly this time.

I haven’t added Oko sealant to the tyres on this bike yet ( as I did to The Fire Bike) but probably will do so soon.

5 Aug 2016 update: I have added the measured amount of Oko Puncture Safe to the tyres now.

  • Front 90/90-18 has 200ml.
  • Rear 100/90-18 has 225ml.

I went for a 10 mile test ride and got home after covering 80 miles.

Gearbox clutch-shaft oil seal replacement – 13 Jul 2016.

Having got access to the gearbox, it was now time to tackle the leak from its front end. Just to backtrack a little, before removing the gearbox I like to tie the clutch arm on the ‘box so it can’t swing about and get damaged. It also means the return spring can’t get lost either.


Once the nuts have been removed the gearbox can be pulled back off the engine. It needs to be pulled back squarely.


I transferred the gearbox to the workbench to take a look at what I’d got. It was clear where the leak was coming from. As I’d expected, the oil seal around the input (or clutch) shaft had failed. You can see where the oil has run down the front of the ‘box.


Luckily there is no sign of any oil getting to the clutch. If this seal fails or the rear crank seal fails on the engine you are usually (but not always) OK as the clutch itself is housed inside the flywheel away from the oil.

To reach the oil seal I had to remove the clutch hub which is held in place by a peg nut and a star lock washer. These can be problematic. The first thing to do is to find which slot in the nut has got a tag from the washer folded into it.


I abused a small screwdriver to start levering the tag clear. Then used a punch with a flat end to knock it back out of the way.

To undo the peg nut holding the splined hub you ideally need three Guzzi special tools. The first is a bracket you bolt the gearbox to so that it can’t move about. The second is a tool to fit the splines of the hub and hold it still (I keep meaning to pick up a worn out clutch plate to make one from). Finally you need a four-pronged socket to fit the hub nut.

Years ago I made a special socket by grinding a 30mm socket. It’s ugly but it works. To hold the hub nut still I used some rubber on the splines and a set of stilsons which are equally nasty.



The hub then just slides off the splined shaft. The back of the peg nut which goes against the hub is curved as is the lock washer. This is so you can reach a tag to bend it forward. Both nut and lock washer were in good condition so I could reuse them.


It seems that when I fitted the gearbox I broke one of my own rules. I would say that it’s worth replacing this seal whenever you have the box off because it takes so much work to reach it. However, I can see that this is still an old seal and, what is worse, I replaced the clutch hub and still left the old seal in place. This was just asking for trouble!

I also recognised some old damage I’d forgotten about. It’s very old (1970s), from before I owned the bike and is to the part of the gearbox where the seal fits. I don’t know what could have caused the wear but something appears to have let go in the clutch housing at some time. The oil seal itself has been rubbed as well.


I tried to get the old oil seal out by putting a self-tapping screw in it and levering on it but the screw just pulled out.


However it weakened the seal enough to be able to put a small screwdriver in the hole and lever it out that way. I noticed there is some damage to the face where the seal sits. It looks like a little triangle. I think it should be fine and won’t cause any problems. In the photo it looks neat enough to be supposed to be there.


That wear to the “boss” on the front of the gearbox caused me a bit of a problem. Normally you would knock the new oil seal in until it is level with the surface. However the surface is now crooked. I measured the depth of the housing to the outer race of the bearing with my calipers.

9.87mm at 12 o’clock.
9.74mm at 3 o’clock.
10.17mm at 6 o’clock.
9.64mm at 9 o’clock.

I made a mistake with my first attempt. I set the seal in square but too deep so that it was partially recessed. Of course it was ruined taking it back out again. I had bought two seals which was lucky. The second time I carefully tapped the seal in until it was flush at the 6 o’clock position. This meant the seal was standing a little proud elsewhere but it was secure. To check that it was actually in square, I held a small steel rule across its face and slid the clutch hub onto the splined shaft to check the back of that was also flat on the rule. I tested it at different angles and I had got it right.


When I oiled and slid the clutch hub partially into the seal I could see that the witness mark from the old seal also lined up well. The hub was pushed on properly and the locking washer inserted. It locates in a slot in the shaft.


That peg nut was tightened by hand then some means was needed to lock the hub again. I didn’t resort to the stilsons this time. Instead I used a piece of wood and a small scrap of metal to jam the splines.


I can’t find any torque figure for this nut so just did it up as tight as I could manage and then bent a tab of the lock washer forward.


I had intended to change the oil seal at the output end of the gearbox as well while I had it on the bench. They are both the same and is why I had bought two seals but, now I haven’t got one spare. There was no sign of any leak from the back of the ‘box so I decided to refit it as it was. At least if this seal fails it can be reached just by taking the wheel and swing arm off rather than having to dismantle the whole bike or crab the frame.

Before refitting the gearbox I remove the rubber blanking plug that you use when timing the engine, from the side of the gearbox. You also need to have a long-handled screwdriver handy. I get the ‘box on the mounting studs and, if the clutch hub doesn’t slide into the driven plates I can turn the hub a touch with the screwdriver through the hole until it goes together. I find that easier than having the ‘box in gear and turning the output shaft.

Un-crabbing the frame!

This is basically the reverse of the dismantling process (but you might swear in different places). There are a few things to remember;

  • Leave the final tightening of the frame/footrest bracket bolts, front and rear engine bolts, the lower crashbar mountings, and the screws holding the plate under the battery to the gearbox until they are all in place and screwed home.
  • Adjust the swing arm bearings so there is no slack but they do not bind. The pins should project from the frame by the same amount on each side (7.1mm both sides in my case) before fitting the lock nuts.
  • Take the opportunity to grease the splines on the back of the gearbox, the driveshaft, its sleeve and the bevel box as you refit them.
  • Leave the final tightening of the four nuts holding the bevel box to the swing arm until after you’ve got the rear wheel in and the axle tightened. this is to make sure the axle is properly aligned and can be removed and inserted easily.
  • Grease the splines between the rear wheel and drive box.
  • Also grease the bushes that hold the gearchange crossover shaft in the lower frame rails.
  • Adjust the rear brake cable.
  • Adjust the front brake cables at the lever to keep the two front brake drums synchronised.

The reassembly took a little longer than the dismantling because I spent some time cleaning the exhaust system and putting it together with silicone sealant. My experiment with this was a success so I’ve done it again. The only problem is that you have to leave the exhaust and sealant for 24 hours before running the engine.


As it happened it was two days before I could get back to working on the bike. Today I removed it from the bench and re-did the carb synchronising just in case! There was no gear oil leak and this afternoon I went for a quick 50 mile ride. All seems fine.

Before going out I had removed some of the blueing from the exhaust header. I don’t use commercial chrome cleaners usually as they can damage/remove the chrome surface. However I tried a little this time. I didn’t try to get rid of all the discolouration but just reduced it. The blueing didn’t reappear during the ride but I’ll just have to see how it goes.


“Crabbing the frame” – 7 Jul 2016.

A couple of days ago I said how, while synchronising the carbs on my V7Sport, I noticed what appeared to be gearbox oil dripping from the bikes’ clutch housing. I had considered using an oil additive that claims to soften and swell oil seals to stop leaks but decided the gearbox would have to come off for the job to be done properly.

The engines and gearboxes of Tonti-framed Guzzis cannot be removed from a rolling bike. Instead the frame has removable lower rails so the main part of the frame can come off the power unit. Moto Guzzi tell you to do this by removing the frame and everything else from the engine/gearbox unit and then wheeling it away on the front wheel. Then the gearbox is then separated from the engine. I’m not sure who came up with the idea (possibly Pete Roper) but there is another way to access the clutch and gearbox without as much dismantling and with fewer bits ending up littered around the workshop. This has been termed “crabbing the frame” (although I always thought crabs moved sideways). It involves hinging the main frame upwards around the front engine bolt. I’ve used both methods in the past and find the “crabbing” method easiest when it comes to putting things back together and working alone. There’s still a lot of dismantling to do though.

I got the bike up on my lifting bench. The wooden platform is for me to stand on when putting the bike on the centre stand. Today I couldn’t do it! The bike kept sliding back instead of coming up on the stand. The wooden platform also allows me to put the bike on the side stand while I think about what to do next. I held the front wheel in the clamp, tied the front of the bike down then jacked under the sump until I could deploy the centre stand by hand. Then I let it down onto the stand and slackened off the wheel clamp. I need the bike on the main stand so I can get the rear wheel off later.


I drained the gearbox oil and left it for ages as it was cold. I measured how much came out. 670cc of the original 750cc. That’s over 10% lost in a very short period of time. I’ve still only done 540-odd miles and it hasn’t been leaking all the time!

To crab the frame;

    • Remove the fuel tank.
    • Battery out.
    • Remove the four front screws from the plate under the battery to the top of the gearbox.


    • Disconnect the front brakes. I slacken the cables at the lever and disconnect them from the dual pull adapter. This gives enough slack to remove them from the brake hub plates without altering the adjustment of the cables relative to each other.


    • Remove the front wheel. This needs to be done so the forks can move down when the rear of the frame is raised. I have to remove part of the bench wheel clamp (only two bolts) and jack the bike up a little higher to get the wheel out. I count how many turns of the jack screw it takes so I can lower it by the same amount after.
    • Remove the silencers.
    • Remove the exhaust crossover. I’m pleased to say that the silicone sealant I put on the joints worked and allowed them to come apart OK.
    • Remove the nuts, bolts and spacers from the exhaust header to frame P-clamps.


    • Remove the starter motor.
    • Remove the starter motor relay with its bracket.
    • Disconnect the rear brake cable from the brake back plate.
    • Disconnect the brake light switch wiring.
    • Remove the brake torque arm.
    • Remove the rear wheel.
    • Remove the right hand suspension unit. I remove it completely although this isn’t strictly necessary.
    • Remove the rear drive box from the swing arm – four nuts. I leave the driveshaft and connecting sleeve inside the swing arm if possible. If you don’t want to change the bevel box oil store it so the pinion is at the top so the oil won’t leak out. I also use some large nuts as spacers to secure the pinion when the box is off the bike.


    • Remove the brake and gearchange pedals.
    • Disconnect the gear linkage from the spline on the back of the gearbox and remove the gearchange cross shaft. I’m talking about the one that had the pedals at either end.
    • Support the wing arm and remove the left hand suspension unit. Again it could just be disconnected at the swing arm end.


At this point I like to reassure myself that what is left of the bike is good and stable on the bench. There’s not much weight on the centre stand and this will be folded up soon. I tie my bike down with ratchet straps on each side. They are made to sit down between the fins of the cylinder barrels so they can’t move. At the same time I make sure that they aren’t squashing any cables etc.


Back to the dismantling;

    • The swing arm has to come off now. I undo the clip holding the rubber gaiter to the gearbox and try to pull it off the ‘box as much as I can. Then remove the lock-nuts from the pivot pins. Before taking the pins out I like to measure how far out they are (left – 7.12mm and right – 7.16mm). I also remove the rearmost nuts and bolts from the footrest bracket/frame joints. With the pivot pins out the swing arm should come off with the universal joint held by the support bearing inside.
    • I had to remove my K&N air filters.
    • Crashbar lower mounting where the frame joint is.


    • Now it’s time to disconnect all the cables , wires etc that might be pulled when the rear of the frame is lifted. The ones I found were;
        • Speedo cable at gearbox end.
        • Tacho cable at timing chest end.
        • Clutch cable at lever on gear box.
        • Engine and gearbox breather hoses.
        • Throttle cables at carbs. Don’t touch the adjusters!
        • Wire to oil pressure sender.
        • Disconnect both plug leads and push them back through the brackets holding them under the manifolds.


    • Loosen but do not remove the front engine mounting bolt.This is the one that holds the side stand bracket and will act as a hinge when the frame is lifted from the engine.


    • Remove the remaining bolts holding the footrest brackets on and joining the lower frame rails to the main frame.


You should now be able to pivot the frame around the front engine bolt. Have a piece of wood handy to put across the rocker boxes to keep it in position. I also put some wood under the back of the gearbox just in case although everything would have been fine without.


I found the frame wouldn’t move because the lower crashbar mountings were still blocking the holes. I had to remove the crashbars completely. I had hoped I wouldn’t have to do this as the nuts and bolts at the top are fiddly to get out and even harder to refit later. It all moved after the second attempt. I was still watching carefully to make sure nothing got snagged or pulled.



Once the frame was up I secured the front forks to the bench as a belt and braces measure.


More dismantling;

    • Now the rear engine/gearbox mounting bolt can come out.It’s the front one here.


    • Then pop in a couple of bolts, one each side to keep the centre stand mountings together.


    • Carefully fold the centre stand up by hand.
    • The lower frame rails complete with main stand can then be lowered out of the way.


I now had the necessary access to remove the gearbox and everything was steady on the bench.


With all the removed parts stored safely.


It took me about 4 hours to get to this stage including stopping to write notes and take photos. It could be quicker if you’re less worried about chipping the odd bit of paint!

Carburettor synchronising – 5 Jul 2016.

Having got the ignition timing right it was now time to balance The Racing Rhino’s carburettors.

I took the bike for a short run to get the engine properly warm so it would run properly without choke. On my return I parked the bike with the back end poking out of the garage door. It looked like it would rain but it never came.


Before getting started, I checked there was some free play in the throttle cables and slackened off the throttle damper so the twist grip would snap shut. I use the damper so I can make hand signals as the Rhino has no indicators fitted. I find it also eases the load on my damaged wrist.

The adapters for the gauges were fitted in place of the blanking plugs.


The gauges were placed on a stool beside the bike. The bike shakes too much to read them when they are balanced on the bike seat and they would probably fall off anyway.


My garage heater was set to blow cold air and aimed at the engine block.


I have a pair of Davida vacuum gauges given to me by a friend. I’ve been told many times that dial type gauges are impossible to use as the needles swing backward and forward. Not so with these. They give steady readings. I think they have some sort of damping built in.

Idle speed.

I started up the bike and let it idle. What I am aiming for is for the same reading on each gauge but I’m not interested in what the reading actually is. At the same time I’m looking for the idle speed to settle at something sensible. To begin with the left hand gauge was showing a higher vacuum which means it’s not working as hard as the right side. This is adjusted by turning the idle speed screw which is the big one with the spring behind it.


This screw must not be turned without opening the throttle a little to raise the slide off the screw. It is pointed and acts as the throttle stop. You risk damaging the slide, screw or both. Blip the throttle after each adjustment then let it settle back to idle. What you are doing with this adjustment is setting the two throttle slides to the same effective opening. Here my two gauges give the same reading.


To ensure my gauges are working properly I stopped the engine and swapped them over and checked to see if I still got the same readings. I did. Engine stopped again, I swapped the gauges back so I didn’t confuse my self with which was which.

Mixture setting.

The mixture for each carb is adjusted using the lower partly recessed screws. Working on one carburettor at a time, I screw in the mixture screw until the engine begins to falter then back out to where smooth running begins again. Then I back the screw out a further ¼ turn to make sure the mixture is slightly rich. If the mixture is too lean the engine will run hot and damage can occur.

Once both mixture screws have been set, again with much blipping of the throttle, The idle speed needs to be checked and adjusted again. In my case this was because the idle speed had increased.

I let the engine rest for a bit while I made a cuppa. It had been running for a while on the centre stand by now and I thought it should be allowed to cool a little.

Throttle balance.

Now both carburettors are supplying fuel/air to the engine in the same amounts. They will also allow each cylinder to idle at the same rate. The third stage is to ensure that when the twist grip is turned both throttle slides begin to lift at exactly the same time.

Move the rubber covers from the throttle cable adjustment screws on the tops of the carbs ready. Now with the engine idling open the throttle a little bit. Not a great handful! both gauges should show a decrease in vacuum at the exact same time. If one gauge drops first it means that throttle slide is lifting first. This is adjusted by either loosening that carbs’ cable or tightening the one on the other side. The adjusters have lock-nuts so, using a pair of 8mm spanners release the lock-nut and wind the adjuster in or out.

In my case the right hand carb started to work first but I couldn’t slacken off its cable as there was no more adjustment available. I had to tighten the left one. Remember that it’s important that there is some slack in the throttle cables.

I took my time to get the adjustment right and was rewarded with the needles on the gauges moving together and by the same amount.

Possible reasons for the blue chrome.

One reason for all this tuning was to look at why just the right hand exhaust header has turned blue. In the past both headers have discoloured on my Guzzis by a similar amount. Chrome discolours because of heat. In my case I think this is due to a combination of factors.

  • The ignition was a little advanced on the right. This can make an engine run hot. The left may have been advanced as well but I couldn’t tell once I had adjusted the right hand contact breaker points timing.
  • At idle the right hand cylinder was set to run faster than the left.
  • The right hand side was working harder than the left as its carburettor  throttle slide was lifting first.

Just standing in the garage the bike does seem to sound crisper and appears to be running even better than before.

Something I didn’t want to find.

Unfortunately I can’t take it out for a test run. While tuning the carbs I noticed oil dripping from the slot beneath the flywheel where the engine casing and gearbox join.


I put a pan underneath to catch it as it was dripping quite heavily. I sniffed the oil. It’s from the gearbox. It’s Tuesday and I wanted to take the bike to the Llandovery Motorcycle Weekend on Saturday. It looks like I have my work cut out to get it fixed in time. I might end up going on The Fire Bike instead.