Hi , I ‘m after tips on tightening down the old dome type water jacket head. Should there be an internal nut on the outside of the spark plug sleeve for the water jacket to press against ? I don’t want to overtighten the two castellated nuts and damage the aluminium jacket head. Also there’s a fair amount of corrosion of the aluminium around this area, I was wondering if any one has tried a sacrificial zinc washer to negate this.
No nuts below water dome, the insert should have shoulders on it for the seal to sit on. I fit the seal then drop on the dome without the outer cork gaskets and very lightly tighten the securing nuts, then measure the gap between the dome and barrel, this will give you the thickness of the required cork gasket. I smear a small amount of silicon to both sides of all the gaskets, then just tighten the securing nuts gently and evenly, I use an old angle grinder peg type tool which is only four inches long without too much effort. I have seen the shoulders missing due to corrosion and they have been replaced with string wrapped around the insert, not by me I’ll add. If the water dome is badly corroded around the nut securing area Alan Noakes will repair this with inserts. Kev
I made this little tool for the water dome nuts. I was lucky to find a suitable socket made of tube but you might as well use a round tube and weld a big nut on top of if. The purpose of the drawbar that’s screwed into the spark plug hole is to hold down the tool in firm contact with the water dome nut. I also included a spring washer in the setup. Otherwise you can obviously not unscrew a tight dome nut with the tool in place. The spring washer allows you to turn the tool a fraction of a turn without having any actual slack. Maybe overengineering but a rusted and damaged dome nut takes some effort to free!
Regarding corrosion, it’s most often caused by using water only. A 50/50 mix of ethylene glycol (ordinary glycol) and water should keep corrosion away. Be sure that you get a glycol that’s stated safe for aluminium. Don’t use modern propylene glycol or long life type glycol as they are not supposed to be used in old engines.
Always change the glycol mix after two years, as the rust preventing properties does get lost with time, even if you don’t use the bike.
By the way, I was told by an old radiator repairer: Never leave an old radiator stand dry. The hard deposits that always present in old radiator, could crack and later start floating around.
Thanks for the replies, I’ve made a tool to tighten down the dome nuts out of a grinder spanner. I’ve brought 2 mm cork gaskets for the outer seal , my current problem is that the old dome has corroded so I’ve used another one , but this one gives a gap of approx. 3mm because of the shoulder / dome contact. Is it possible to use two gaskets ? or can I reduce the height of the shoulder ?
Why not, yes use 2 gaskets if that’s what you need.
You can see the problem in the photo.the replacement dome has been repaired at some time but unfortunately it increases the outside gasket gap to 3mm meaning that I need to fit a thicker dome gasket or double up a standard one, has anyone else had this problem? the original as you can see on the left has a recess to take the inner seal , also note the corrosion.
You could just cut your losses and get a new item from Scottparts.
A new casting would get rid of a lot of problems, and I think the cost is not too great
Are you sure the dome at the front does not have an old seal still in it ? if not they both need work, the rear dome right hand side in your pic is what they should all be like. Lower pic is a very corroded and damaged dome which is really fit for the bin but I did a cheap repair with Balzona just so the engine can sit with water in it as previously the crankcase was found to be filling up with water and after testing Im pleased to say the water system is now tight, (barrel to crankcase seal had gone and the water leaking from the dome seeped between the barrel and crankcase). The top pic shows the seats which the seal will sit into. Not the best but it works.
If the seats have been repaired on the front dome in your pic, you could use a Dremel or similar to grind down the repair or get it milled as if its thick I doubt you would get the nut on.
➡ I’ve ordered some 105 mm x 5 mm O-rings so I’ll give that a go first, keep you posted.
Why all this talk of doubling up gaskets. In my gasket box, I have cork and composite gaskets in a range of thicknesses from 0.035, 0.040, 0.090 and 0.100″. Also I have copper /asbestos central gaskets in thicknesses ranging from 0.115, 0.125 and 0.135″ plus additional thin washers at 0.035″
Have you checked with the spares scheme on available sizes?
When I was faced with this problem, I finished up making custom ferrules to give the correct clearance with just one gasket. Two or more gaskets never worked for me.
Oh , thought 2mm gasket were the thickest available
In the past I have made the outer water dome sealing rings/gaskets out of various thicknesses of canvas-reinforced rubber sheeting. Dead easy, using a sharp scalpel or craft knife to cut the ID. The OD can be cut the same way or even with a big pair of scissors. The ‘granulated cork’ ones are best avoided because antifreeze tends to leach through it, leaving deposits of glycol on the outside, which damage the lacquer finish on the barrel. Owners see that happening and think that the dome needs more tightening down, but that won’t stop glycol coming through the cork.
I was thinking about trying 2 or 3 5mm. Concentric o-rings, what do you think? I’m not sure how they would stand up to the temperature. Also I don’t want to use any seals containing metal on the inner seals what would you recommend?