Navigator top end

John,

There are some shorter bottom fins on the barrels on one side to clear the timing side. I guess the side facing to the camera on your pic is the right side.

Here you see the fins for the timing side:

I secured my tappets with some oil hose pieces during installing the barrels.

During installation I somehow managed to crumple a composite head gasket which resulted in a blow by on the left cylinder.

I then used an annealed copper gasket which I cut in half to get two individual pieces.

No problems so far.

Hi John and Ulli,

Thanks for all this, I am planning a full engine rebuild next winter for my late Navigator so it is really useful and practical stuff. I haven't stripped the top end down yet but given my engine's usual noisy Lightweight valve gear I am assuming the tappets will have the typical 'barrel' shaped wear that so many reports mention. Have either of you replaced the tappets and tappet guides and if so did it make much difference to engine noise? Were the tappet guides difficult to replace? Are they best removed and replaced using a hydraulic press? Did you find much wear on the cams or the cam bushes? I think I have found a source of replacement cams but not the bushes and removal of the primary side bushes is obviously not straight forward. Any advice would be incredibly helpful!

Cheers Nick

Nick,

my engine was not complete when I got the bike, I had to buy the barrels and cylinder heads. I left the tappet guides in the barrels. So I have no before and after comparison.

I am desperatley in need of some +40" Navigator pistons to help complete my special project. If anyone has some new or good used pistons of that size please contact me asap.

Previously Nick Clarke wrote:

Hi John and Ulli,

Thanks for all this, I am planning a full engine rebuild next winter for my late Navigator so it is really useful and practical stuff. I haven't stripped the top end down yet but given my engine's usual noisy Lightweight valve gear I am assuming the tappets will have the typical 'barrel' shaped wear that so many reports mention. Have either of you replaced the tappets and tappet guides and if so did it make much difference to engine noise? Were the tappet guides difficult to replace? Are they best removed and replaced using a hydraulic press? Did you find much wear on the cams or the cam bushes? I think I have found a source of replacement cams but not the bushes and removal of the primary side bushes is obviously not straight forward. Any advice would be incredibly helpful!

Cheers Nick

Hello Nick,

I replaced my tappet guides but had to heat the cylinders in the oven the knocked out with a drift, they came out easily but were real sods to get back in, heat the block and freeze the guides and be very quick. You do need a drift of the right size and pay attention to the orientation of the drain slots. Re the bushes. I replaced mine, quite right, the hardest thing was getting the old ones out. A number of solutions, you could use a large tap and jack them out, I tried a number of things but the best was as per attached sketch. Note I used epoxy to fix the slotted copper pipe inside the bush. Worked a treat but you will need to clean the bush very well, abraid and give epoxy time to set. Gentle heat once tension is on spring and the bush came free. I made my bushes but I think they are available from Norton spares - may be worth checking dominator stock pages. Please excuse crude sketch...I will photo the jig I made and post copy tomorrow. There must have been some sort of brace against the crankcase.

Andrew

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Andrew, thank you so much for all of that, very useful and ingenious! Are the cam shaft bushes identical to those used on the Dommi? I know a local precision engineering company that can make them but at a serious price! I hope mine aren't noticeably worn - Jubilee's I have rebuilt in the past weren't.

Has all that hard work and new parts resulted in a noticeably quieter engine? I know the Lightweights had a reputation for being mechanically noisy because of the valve gear design but I live in hope!!!

Warm regards

Nick

Previously Nick Clarke wrote:

Andrew, thank you so much for all of that, very useful and ingenious! Are the cam shaft bushes identical to those used on the Dommi? I know a local precision engineering company that can make them but at a serious price! I hope mine aren't noticeably worn - Jubilee's I have rebuilt in the past weren't.

Has all that hard work and new parts resulted in a noticeably quieter engine? I know the Lightweights had a reputation for being mechanically noisy because of the valve gear design but I live in hope!!!

Warm regards

Nick

Hello Nick,

well that remains to be seen, life is in the slow lane and though the engine is done, I am now preping to paint, then rewire then hopefully were off. I have to say I suspect that I would have been better off leaving the bushes in place. They are huge and I doubt if any wear would have much impact on performance or noise. I think the tappet guides and correct adjustment of tappets will help a lot though the design of the guides / block lends itself to premature wear. It is about 60 years old and though I expect it to perform reasonably well, it is a twin with fairly crude balance arrangement. It will be interesting to see where the vibration comes in.. I suggest you trawl through the back issues of Roadholder in the archives. I found an article called "Forums and Leaky Lightweights" by Peter Holland, as well as a number of others by Andy Sochanik - look for "Dismantling a Navigator Engine". There are many others and all have gems.

Regards

Andrew

Hi Andrew,

All very useful and I have found Andy's expert advice invaluable! I have never found noticeable wear in the cam bushes on the Jubilee's I have rebuilt so hopefully my Navi' wont need them replacing. Given all the wisdom on tappet wear it seems sensible to replace tappets and guides when the top end is stripped - along with valves and valve guides. I have written to the previous owner to see if he can give me any history of engine rebuilds - it has obviously had the heads and barrels off in the past. Looking at the MOT history it has averaged only a couple of hundred miles a year. I have given it a thorough servicing, rebuilt the clutch, primary side, carb, electrics, forks, brakes and cured a few oil leaks and covered 1000 miles already this year. Although the engine sounds typical of the breed with a hand over each exhaust there is surprisingly little valve gear 'clatter' and it pulls really well cruising happily between 55 and 65. On a recent test run post oil change the top end matched road reports of the day - although I won't be exploring that further in deference to its age! With that in mind I am postponing the engine rebuild and enjoying using it as a fair weather run around - I have to say it really is a very enjoyable bike for country B road work and I love the Roadholder handling and front brake after growing up on Jubilees!!! Good luck with the re-build!

Nick

Hello John,

I have had seven Jubilees/Navigators over say the last thirty years and i have to say that I have never replaced the tappet guides in any of them. You have more experience than virtually anyone else in using old British motorbikes so I think you would regard the Jubilee/Navigator engine as being fairly typical of it's era and construction. It is an air cooled alloy engine so it does rattle a bit especially if compared to later water cooled Japanese/German models but probably no noisier than say the corresponding Triumph- I think that was the 3TA. It probably leaks less than the one Triumph I know from many years ago. Noise and oil leaks were just an accepted fact about old British bikes- probably the very reason why everyone now has a Japanese/German machine if they actually intend to use it for real.

You mention a chipped push rod. One of the Jubilees tricks is for the push rod to jump out of the 'cup' end and you lose that cylinder. Oddly enough it seems to cause little damage except for some chipping. It has happened once to me and also to Andy S.

Question for you. Where did you get your head gasket? Does it fit well? I have a Jubilee engine apart at the moment and the head gaskets (new) that I have here are a farce as they don't fit properly at all. I need to get something better.

Patrick.

I have made my own bucket cam followers and pushrods of my own design. The picture on the right shows what it looked like when I inspected them after 500 miles use. 1500 miles later and the bike is no noisier than when I first put them in. I have removed the sump filter a few times to look for debris or reassurance. It is only an experiment to see if something can be done , to modify the original design in some way. It may end in tears, so I would not recommend it.

GRAHAM

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Hello Graham

You are very obviously a skilled engineer; your design reminds me of the cam followers in the early G series MGB engine which in turn were superseded by the later 1970 18V version. I am certain that you know vastly more than me about cam design and case hardening etc etc.

Hi john The head gaskets which I have are the spigoted Jubilee type and came from the NOCshop but that was quite a few years ago. I lived in Yorkshire at the time and someone on Club Spares at the time agreed then to replace the gasket with a NOS one which was spot on. They told me to keep their dodgy gasket as they were speaking to 'someone' - the supplier- about the poor quality. I managed to obtain several sets of NOS gaskets (Halls I think was the name) but I have now used all these; hence I hauled out the original Club gasket for inspection but it is definitely so poorly made it is unusable. It simple will not fit over the head studs as the hole spaceings are well out wrong.

Hopefully their current new stock is a major improvement.

Patrick.

Previously patrick_mullen wrote:

Hello Graham

You are very obviously a skilled engineer; your design reminds me of the cam followers in the early G series MGB engine which in turn were superseded by the later 1970 18V version. I am certain that you know vastly more than me about cam design and case hardening etc etc.

Patrick.

Hi Patrick I don`t know about that. It is more like kamakazy engineering borne from desperation, when the only source of lightweight spares was second hand, where cam followers were knackered. Hard chrome etched off faces etc, and worn engines made a dukka, dukka,dukka,dukka noise that did not sound good. How many bikes out there are sitting around for want of some desperately needed part? So what gets done about it ?

GRAHAM

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Previously philip_hannam wrote:

I am desperatley in need of some +40" Navigator pistons to help complete my special project. If anyone has some new or good used pistons of that size please contact me asap.

Philip,

I could not find the right oversize pistons for my Jubilee despite looking for several months. In the end I had my barrels re-lined and bought standard size (+0) pistons. The liners were not too expensive, about £30, and the engineering work to re-line was £200. Pistons were just over £100 the pair. Not cheap but I had no alternative.

Regards,

Dennis

Philip,

The only source of new oversize Navigator pistons that I have found is JP Pistons in Australia, they advertise standard, +10", +20" & +40" thou pistons, rings and pin sets. You can order via Ebay Australia at £214.56 a pair or through Thomas Hamblin Precision Engineering Ltd in Bridgewater Somerset 01278 422452 who put me on to them. I haven't used JP Pistons so can't vouch for them but I have used Hamblins to rebuild a Royal Enfield crankshaft, big end, polish and balance a new conrod and piston to a superb standard. They really understand and enjoy working on classic and vintage motorbikes and cars but with quality and expertise they are not cheap! When I do rebuild my Navigator I am going to get them to do the re-bore, crank grind, balancing and re-bushing work. They can make things like camshaft and gearbox bushes, reface and harden cams etc so worth a look. Good luck - if you do go down the JP piston route I would welcome some feedback!

Regards

Nick