Off with his head, part 3 – 29 Jan 2017.

As I said yesterday, I’ve decided to repeat the work on the left hand cylinder, mainly for the sake of thoroughness. It’s also a chance to examine the condition of the cylinder bore and rocker gear.

Oh what fun I had! This time the exhaust header nut was very tight. Not only that, the notches for the c-spanner were a mess. I had to start by knocking the ring nut back and forward a tiny amount and dosing it with WD40 just to get it started. It was clear it had been hit with a punch or possibly a chisel before. It took me about an hour and a half to get it undone. When it did turn, it would still bind at the same point in every rotation. Once off I could see it was clearly distorted. It wasn’t me, honest! However, it was me who let the c-spanner slip and chip the paint on the fuel tank. It was clear that a “Gun Gum” type sealant had been used and was the main reason the thing had been stuck. Happily the exhaust port threads on this side were undamaged.


The cylinder head nuts were tighter on this time but, when I lifted the rocker bracket, there were no O-rings where they should be. It turned out that they were fitted to the four long studs under the head gasket! Don’t do it like this.


Again the rocker gear is in very good condition. It looks nearly new. It’s strange that this (expensive) work appears to have been undertaken but basic mistakes made.

Once again the cylinder barrel is the chrome plated type and in very good condition. The two bottom O-rings were where I would expect to find them.

Putting everything back together was easy enough but I discovered this chip out of the rocker bracket.


It’s where the shaft-locking screw goes on the exhaust side. When reassembling the gear I was careful not to let the end of the lock-washer catch in the hole. I don’t feel able to weld the chip as the bracket is a casting. I think, at some point, I’ll run the engine with the rocker cover off to see if oil is pumped out of here instead of lubricating the rocker and shaft. Hopefully it will seal. If not, I might look for some sort of “plastic metal” to repair it but an oil-soaked casting might prevent it “taking”.

Again I have put the rocker cover back on without adjusting the valve clearances. This is while I turn my attention to the mullered exhaust head nut.

Replacements are quite pricey and the original type don’t seem to be available any more. Instead the better type with a lock-ring (as I have fitted to the V7Sport) can be had for about £50 a pair. Here’s what I mean on Rhino.


I do have a couple of exhaust nuts which have been sawn lengthwise. I did it over 30 years ago to allow the rings to spread a bit to get around the sharper turns on a 850T3 shaped exhaust header. Once past the obstruction they would go back to their original size and screw down on the exhaust and still compress the gasket. The trouble was they would (unsurprisingly) come loose if not wired to a drilled cylinder head fin. At the time this was OK as they’d always had to be lock-wired anyway.


In an effort to save money I decided to try and braze the gap. It wasn’t entirely successful because I couldn’t get enough heat into the job with my little oxy-propane set-up.


I haven’t fitted it to the bike other than to check that it threads into the head easily. The repair seems robust enough. However, I think I’ll be making another order on the Stein-Dinse website. I’ll be hit with the minimum shipping cost again but, what can you do?


Off with his head, part 2 -28 Jan 2017.

I ordered the necessary parts from Stein-Dinse in Germany on Sunday, arrived here in Wales on Wednesday. Even with the minimum postage cost it was still worth it as no one in the UK had all I needed in stock.

I did include base gaskets in my order so the next job was to lift the cylinder barrel. This gave me a chance to properly examine the bore. Unmarked and in good condition.

The pistons are fitted with four rings. Three above the gudgeon pin and one below. I knew early V7s were fitted with these but wasn’t sure if they kept on with this for all the 700s.


I evened out the ring gaps out around the bore then replaced the base gasket. There is an oil drain hole in the face of the engine block. If the gasket is fitted upside down it will block the hole and the rocker box will fill with oil which can’t drain back to the sump. O-rings go on the two short studs (at 6 and 12 o’clock).


Fitting the cylinder barrel isn’t difficult but can be a little hard on the fingers. First I turn the engine by the front crankshaft bolt until the piston is right at the top of its travel. I like to lightly oil the spigot of the cylinder which fits into the engine block as well as the bore itself. The barrel is dropped over the studs and the top of the piston started into the bore. There is a little chamfer at its lower end. This means that you can squeeze the top piston ring with your fingers until it goes into the chamfer. The cylinder should then slide further onto the piston till it meets the next ring. If it won’t go, don’t force it! Check the ring has gone into the chamfer. Repeat the procedure until all the rings have gone into the bore. The last one is the hardest because there’s not much finger space.

It’s now time for the head gasket. I think the gasket I’ve just removed was meant for a 750 as the bore is about 83mm whereas the new one (specific to the 700) has a bore of 80mm. Here the old is placed on top of the new and you can see the difference.


The gasket was fitted but, before I put the cylinder head on I searched in the exhaust port for the old exhaust gasket. There should be a (squashed) copper ring in there. I scraped and picked at the port but couldn’t find the gasket. Now, I know that sometimes these can appear to be part of the head and hard to find so, I decided to get a second opinion. I measured the depth of the threaded section as 18mm and asked the members of the Yahoo Loopframe Group if anyone had a head they could check. Inside the hour I had a response from Charlie saying he had just measured a head and found the depth to be 17mm. I was right then. Someone had fitted the exhaust header without a gasket.

The design of this exhaust fitting means that, if the header becomes loose, it can vibrate in the port and damage the fine threads. There is some damage on this head but it’s still serviceable. A repair can be very expensive.


Before putting the head on, I double-checked that the gasket was on the right way round. Again there is an oil drain hole which must line up with the hole in the barrel.


The head was fitted on the studs then O-rings fitted to the four remaining (long) studs.


The bracket for the rocker gear goes on next and the six nuts (five plus the sleeve-nut) can be torqued down in a diagonal sequence. I do;
– top right,
– bottom left,
– top left,
– bottom right,
– lower one by spark plug,
– top 10mm hex sleeve-nut.
The torque figure is 27.5 ft.lbs. This figure seemed a bit low to me and conflicted with the figure of 29 to 32 ft.lbs (4 to 4.5 Kg/m) given for later Guzzis. After taking advice fro members of the Loopframe Group, I’ll use 32ft.lbs in future.

Fit a new crush washer and refit the 26mm blanking plug over the sleeve-nut. Then refit the rocker gear. Drop the pushrods back where they came from. I like to turn the engine again to get the pushrods as low in the head as possible. Squeeze the relevant rocker, spring and washer back in place on the bracket and a bit of wiggling will allow you to get the spindle back in (screw hole at the top). Turn the spindle with a screwdriver until the locking screw can be refitted.


Only ever use the original type and length of screw. It locks the shaft in place but mustn’t go too deep. The other side of the hole is an oil supply which then goes down the centre of the shaft and out again halfway along it to lubricate the rocker arm on the spindle. The wrong screw might restrict this oil flow.

At this point I refitted the exhaust header but now it does have an exhaust gasket. The threads of the exhaust nut were given a smear of copper grease.


I didn’t do it up tight until I’d got the frame-to-header clamp in place in an effort to get everything lined up properly. I tighten up header nut, silencer clamp and frame-to-pipe clamp in that order.

The oil feed to the head was reconnected using the banjo bolt and new crush washers. I’m careful how I do this as the bolt is naturally fragile, being hollow with a cross-drilling. I use a short spanner.


The inlet manifold and carburettor were refitted and the spark plug screwed back in. I’ve decided to repeat the job on the left hand cylinder so I’ve left adjusting the valve clearances for now. I put the rocker cover on with a couple of screws to keep the muck out for now.


Off with his head, part 1 – 21 Jan 2017.

I had to move some stuff around in the garage today so started up The Fire Bike to temporarily move it outside. I had the choke on and noticed smoke coming out of the RH cylinder when I revved it. I had to look twice but, yes, It was definitely coming from the cylinder barrel to head joint. Occasionally I had noticed a black drip from the head gasket onto the leg shield but had thought it was just a little “weep” and it didn’t always seem to do it. Today it was chuffing out of there like a steam engine. Something had to be done! This is where the leak was.


I took the rocker cover off and put a spanner on the three head nuts you can reach while the rocker gear is still fitted. They were loose! I had a choice. I could just remove the rocker gear and re-tighten the nuts to the correct torque or pull the cylinder head off to take a look. I decided that, if the head had been so loose that combustion gasses could get past then the gasket should probably be changed. So, off with its head!

My first concern was whether I would be able to get the exhaust header nut undone. My experience with these had been that some will never stay tight while others will become stuck fast. This one had never loosened by itself so I feared the worst. However, it was OK. It took just one tap on the C-spanner with a soft-faced hammer and we were away.


To remove the exhaust header pipe I loosened the clamp to the silencer and the frame-to-exhaust clamp. I could just get to this with the leg shield in place.


I disconnected the carburettor, complete with manifold, from the cylinder head.


The next job is to remove the oil-feed pipe from the head by undoing the banjo bolt. There is a crush washer on each side of the pipe.


I removed the generator belt cover from the front of the engine (3 screws) and turned the engine with a socket on the crankshaft nut to take the pressure off the rockers. I then removed the rocker gear from its bracket (remove locking bolt and push the spindle out) and put the parts to one side so they can’t get interchanged. The pushrods were then removed and joined the rocker components.

The cylinder head (and cylinder barrel) are held down by nuts on four long and two short studs. The four long ones also hold down the bracket for the rocker gear. The short ones are top and bottom. The bottom one is by the spark plug. To get to the top one you remove a blanking plate in the cylinder head. There’s a crush washer under this.


It hides a sleeve-nut which takes a 10mm Allen key.


The six head securing nuts should be slackened in a diagonal sequence to avoid distortion to components although, in my case, they were already pretty loose. There is a heavy washer under each of the five ordinary nuts and a slightly different one under the sleeve nut.

Once the nuts are removed the bracket for the rocker gear can be lifted off. There are O-rings fitted to the four long studs under the rocker bracket. These were age hardened and have to be replaced anyway. I picked the rings out to make it easier to get the cylinder head free. Only one came off in one piece.


Now it’s time to lift the cylinder head. It didn’t want to move at first but, little by little, I managed to get it loose without resorting to hitting anything with a hammer. Hurt my fingers though.

It was easy to see how the gasket had been leaking and there was signs of pitting to the surface of the gasket but, I might have been able to get away with just tightening everything up. It’s difficult to tell.


I’ll put in an order for parts tomorrow but, I’m not sure whether to change the base gasket and two O-rings below the cylinder barrel while I’m in here. It wouldn’t be hard to lift and replace the barrel. I’ll buy parts for both cylinders though. I might have some of this list in the garage already.

  • Head gaskets (2)
  • Base gaskets (2)?
  • Rocker cover gaskets (2). I like thick ones if I can get them.
  • O-rings (12)
  • Exhaust gaskets (2)
  • Crush washers for under blanking plugs (2)
  • Crush washers for oil feed lines (4)

I took a look at the coating on the cylinder bore. It’s still a hard chromed barrel. There are those who say bikes with these should not be run as the chrome will flake off causing all sorts of damage. Instead replacement nikasil coated barrels should be fitted. I do know what happens if it all goes wrong. It happened to the Racing Rhino many years ago. Nikasil cylinder barrels for the old 700s just aren’t made. I could have mine stripped of their chrome and replated but it’s expensive and these seem to still be in very good condition with no thin spots or blisters. I could fit barrels from a 750 but don’t want to do this.


I took a look at the rocker gear on the bench. It’s in very good condition. No wear on the spindles or in the pads that contact the top of the valves. It makes me think that some work has been done here not many miles ago and could be why the head was loose. I didn’t know that it needed to be re-torqued. It could also be that the cylinder barrels aren’t 45-year old originals. Old stock chrome ones still come to light from time to time.

I haven’t examined the valves yet but I’ll have a poke around everything else soon.