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Too much oil in sump


Can anyone help me with this please:

My 57 Dominator 99 seems to have too much oil in the sump.

The return to the tank is a constant heavy flow and the force is enough to blow oil out of the filler if the cap is removed and even though a new cork seal has been fitted to the cap it leaks badly.

The cylinder bores are good and have been lightly honed and new rings fitted.

i seem to lose a fair amount of oil out if the crankcase breather.

all this seems to indicate that there is too much oil getting to the sump

Any ideas 



Is it a new event on a bike that used to be OK, or a new bike? Or has some major work just been completed? It sounds (to me) on first reading like an assembly issue.

Hi David

I bought the bike a year ago and understand that it had been stood for a very long time. I did a fair amount of work to re-commission it such as draining the oil, removing and cleaning the oil tank, replaced oil pipe hoses, plugs leads etc etc. It wet sumped after just a few hours of standing and so I fitted a manual valve to the oil feed line.

When I got the bike there was a long piece of plastic tube fitted to the breather tube which almost touched the ground I'm guessing that the previous owner had problems. I covered about 500 miles last year and the bike ran reasonably well but did blow out a fair amount of oil from the breather. On a fairly fast run on a warm day it began to nip up and I had to pull over and let it cool.

it got me home and a few days later I removed the head and barrels.      The LH piston was scuffed and the rings were stuck in the grooves.

I also found that one of the valve guides was very loose in the head. The head has now had new valves & guides fitted.

the cylinder bores were in reasonably good condition and have been lightly honed to glaze bust them. I managed through the forum to find a NOS set of rings to fit the Hepolite pistons.

On dismantling I've found that this engine has been breathed on it has Atlas inlet valves fitted, polished rockers, gas flowed ports, hi-comp pistons and looking at the cam I think that is a bit special.

I also took the opportunity to remove the timing cover and overhaul the oil pump. When I removed the pump there wasn't a gasket fitted between the pump and the crankcase. (There is now). I also replaced the pump to outer case seal. I also removed the oil over pressure valveand cleaned/inspected it.

Does that throw any more light on the issue?

Many Thanks

Terry Guy









What you are describing is an over-abundance of oil.  Yet the partial seizure, scuffed bore and seized rings point to a lack of oil.  I'm wondering if the crank is full of sludge, and the oil is having to go everywhere else. 

Your motor seems to have been modified a lot.  What oil pump and drive gears does it have?  If it has the later 6-start pump gear, has the rest of the system been modified along with that?  The feed holes in the cases need to be larger, plain rocker spindles, etc etc



The oiling system on these motors is a bit of a fine balance. The head and drive side piston often run a bit short of oil.If the rebore was less than 4 thou clearance  they can nip up ,although in theory they should be fine. The oiling system is sometimes modified to "solve" things and can make it worse in other ways. The oil return to the tank should become intermittent after a mile or two when the crankcase is cleared. If this is not so then something is wrong ,Could be large gear pump with high speed drive fitted but original (or restricted) return piping, Too much oil diverted to head with a Jubilee tank fitting,(oil going in circles). Oil tank needs a clear breather and not to be filled too much as it can get pressurised by the return. In normal classic use my motor barely warms the tank, not  enough to stop condensation so I run with a low tank.A motor can take a couple of thousand miles to bed in and stop over blowing thro the breather(some never run in!). Weak mixture or poor timing can overheat a piston. High comp pistons,need backed off ignition  and harder plugs, A bit of good detective work needed by someone who knows all the wrinkles!!.

Hi Paul,

Thanks for your reply. The blocked crank could be a possibility. I was hoping to avoid a total strip but it may be necessary .

I'm new to Nortons and didn't pay attention to the pump drive I also didn't replace the crank/timing cover seal ( it looked OK and I hadn't purchased a replacement ). I'll have the cover off again check the pump gear and replace the seal. Your analogy does make sense it could well be a blocked crank.

regards Terry


If too much is being pumped back then too much must be being delivered. If the crank were blocked there would be less oil flowing in. I think you are correct and the timing case lip seal is not working. The other possibility is the pressure relief valve is stuck open or has the wrong spring. That happened to me once and there was oil and smoke all over the place! 

Hi Robert,

Thanks for you response. I am convinced that there is too much oil getting in the sump and possibly not going where it should. I'm thinking that it might be a good idea to test the oil pressure. a low reading may indicate that it's taking an easy route which would probably necessitate a full strip down anyway. I don't know where the best place to a reading from is though?

I did weaken off the fuel mix by dropping the needle a notch. There wasn't a choke fitted to the bike but it would start and run in cold weather easily which didn't seem right. I put the seizure down to the very loose valve guide allowing air to be drawn in and weakening the mixture, a hot day and me giving it too much welly.

You might be right about the timing, I haven't touched this but the bike does have the propensity to kick back if I don't swing the pedal with conviction. It also runs a bit "heavy" at low revs but certainly flys when opened up.

I'm sure that the oil tank is not pressurising it's all been off and thoroughly cleaned and the breather hose renewed. However the oil does return with some force.

best regards

Terry Guy


Hi David

Thanks for your reply.

yes I agree that it's being delivered but it may be escaping via a route of less resistance in which case a greater volume may be pulled through. The pressure relief valve is also another possibility. I have removed this and cleaned it thoroughly. Initially I thought there may be   Spacers missing from it because there was no resistance when the domed nut was fitted but on reading the forums I understand that this is correct i.e: "the assembly can be heard to rattle when shaken".

please note that despite my issues the bike does not smoke unless of course I don't turn off the manual anti drain valve and start the bike after it's stood for a few days.

many thanks 

terry guy



Oil is not compressable so  whatever the pump  flows will be delivered ,no more, no less.a faulty seal will not allow more oil to flow,it will just go to the wrong place. As the scavenge side of the pump has greater capacity than the delivery side ,the return should contain air eventually. Norton cranks don't block easily . And they usually manage to suck oil through with the centrifugal action even if the pumped supply is not good.They have been known to survive high revs with no pressure at all.


Robert... of course.. you are correct that the path it takes is ultimately irrelevant!  Return must exceed delivery after the wet sump has cleared.  Is it just wet sumping and will sort itself out after 5 minutes or so?

Surely it's not possible to fit the pipes so the return ends up delivering, and vice versa? Ending up with more delivery than return? 


Yes, do an oil pressure test with the engine and oil properly warm.  Bear in mind that pressure can be lost if the timing cover lip seal is faulty, the rubber button between pump and timing cover is split or has insufficient compression, or the pressure relief valve is malfunctioning.  It could be stuck open or closed....

Do not be concerned if the oil pressure is low at idle, it may be around 5lb on a good engine, rising to 40ish at a fast idle.  The first Model 7s had a tank-top oil pressure gauge, but owners got upset about low idle pressures while hot, so the factory solved the problem by deleting the gauge.

Does anyone have a spare Dominator oil tank return union?    My bike had insufficient oil up stairs, and the previous owner did several bodges.  I fitted a blanking plate to give more rocker oil feed.  I want to experiment with the oil feed rate



The return side of the pump is normally double the size of the feedside, this is achieved by the gears being wider. So as already mentioned the return side should be a mixture of air and oil once the drain back to the sump is cleared. There are 4 potential reasons for the return flow to be constant, there could be more.

1. The return side is also being used to feed the rockers and if too much oil is going to the rockers it drains to the sump to be returned again removing the effective over capacity.

2. The oil is being aerated inside the engine from possibly blowby so effectively increasing the oil volume and again removing the over capacity. The return oil flow will be constant but have micro bubbles in it and look milky, sometimes the oil level in the tank seems to increase.

3. There is a short circuit in the feed side eg a seal is missing and the feed oil is going direct to sump with no restriction to reduce the flow which you would get if the oil went to the proper place ie the big ends which create a restriction. With this the oil pressure will be low on the feedside.

4. The sludge trap is blocked, the pressure increases and the pressure release valve is fully open and you get a short circuit to the sump. Less flow than with 3 but the oil pressure will be high.

Hi John,

Thanks for your reply, I've now got lots of things to look at.

pressure testing is the No1 and so I've ordered a pressure testing kit from RGM along with a timing cover/crankshaft oil seal and a timing disc.

I'll report back my findings.

Thanks everyone 

Terry Guy


Not sure if this will help but i have just rebuilt a Commando engine which had stood idle for 40 odd years. It had covered 16k miles. i decided to do a full strip down. The results were piston rings jammed in the slots, sorted by a rebore and new pistons.  I took the crank to pieces to sort out the sludge trap and found barely any sludge at all.

You haven't over filled the tank by any chance?


Hi John,

Thanks for your reply. I'll check that but from memory the level is about 75mm down from the top.

Oil pressure gauge test kit, timing cover seal various gaskets etc all arrived yesterday from RGM after being ordered on the net Sunday evening. Over the past year I've purchased a lot of parts from this company and am extremely impressed with the general quality and the quick turn-around. Hopefully I'll get a chance this W/E to carry out further investigations.

Best Regards


Terry Guy

Hi Again Robert,

I understand that the standard ignition timing for a 99 is 32 degrees BTDC.

as mentioned earlier my machine is fitted with Hi-comp pistons, however I don't know what compression ratio they give. Would you have an idea of how far I should retard the ignition?

Are we looking at around 30 degrees BTDC.


Thanks again

Terry Guy




Yes ,possibly.  You can judge the timing by looking closely at the spark plugs earth strap once you have it running cleanly, Normally you will see a faint band of colour across the strap  where the heat has burned off deposits ,should be somewhere close to the bend on the long part. But this only works if you have the correct plug .


Hi again Guys & Gals,

Just had another thought:- As I mentioned earlier the top end on this bike has been rebuilt and new valves, guides etc fitted. The gasket face of the head was also ground on a sheet of plate glass and carborundum paste

On its first run I covered about 25 miles only to get home and find that it was making an unusual cracking noise. On closer inspection I could see that I had a lot of oil leaking from the rear of the RH head gasket (oil drain hole area) and it was blowing at each combustion. On checking the head bolts they were all extremely loose.

I'm an Engineer by trade and I know they were fully tightened when I put it together, I'd even purchased the special slim sockets to fit down in recesses.

 I went around the head fastenings several times again until all were tight and on starting up the blowing and the oil leak had ceased. In the back of my mind I'm now wondering if I should have removed the head and replaced the gasket? I also remember that this gasket wasn't a very good fit and had to be eased over barrel spigots.

Could my oil problem be a blowing head gasket? 


Terry Guy




You could do a compression check. Steel head bolts need re=doing a couple of times. Stainless ones can be weak and stretch ,I don't like them.


Unlikely that the loose bolts explain oiling problems. But the bolts going loose does sound like bad news - the only time that happened to me was when the central rear underside nut would not tighten up because its thread was stripped.  A helicoil fixed it.

Going back to the oil pumping.  If it pumps continuously into the tank from the large gear wheel side of the pump, it must empty the sump eventually because the delivery side is smaller.  It makes no difference which way the oil travels inside the engine.  If oil is coming out twice as quickly as it is going in, it must empty itself in a few minutes even if the sump is completely full of oil.  Some Commandos apparently wet sump when running at high revs because the scavenge side of the pump is not collecting the oil.  But in that case the symptom is too little being returned to the oil tank, not too much.

Are you certain this goes on all the time, and is not just for a few minutes until the wet sump is clear?

The only other option I can think is that the outlet nozzle into the tank is too small or partly blocked, so the oil backs up and the air inside it gets compressed and it squirts out in a much thinner stream then usual.  The usual jet is perhaps about 4 or 5 mm across and continuous if the bike has wet sumped, and then after a few minutes it becomes a bit more sporadic as air bubbles come through with the oil.  But maybe if the exit nozzle right inside the tank is too small, it might come out in a much narrower continuous stream and, although it still carries air, the air would be much less noticeable because it would be compressed by the geared pump?

If your main issue is oil coming out of the tank and all over your trousers - they all do that if over filled.  Remember not to fill it up before starting up, because it will end up grossly over-filled if it has wet sumped.  It cannot come out of the tank filler unless it is well over filled (unless it has frothed up grossly).

I apologise if all this wet sumping business is well known to you!  But all comments seem to be clutching at straws!  My bet is that it is simply over-filled (although that does not explain a continuous returning oil stream after a few minutes to clear the sump).


Hi David,

Yes of course you are correct its not possible to constantly pump more out than is going in.

The problem is that it seems be doing this whenever I stop and take a look. It may be that when I ride the bike the return is working correctly or maybe not returning enough. 

I'll carry out a pressure test over the weekend and maybe ride out to the country where I can race the engine and not upset neighbours and observe the flow back at higher revs.

Can anyone advise where the oil level should be, I've got it about 3" below the filler neck?

With regard to the tank outlet nozzle:- It certainly doesn't appear small, I'd say the jet of oil which comes out is at least 3mm dia.


All the Best

Terry Guy


Hi Robert,

The bolts are steel. What really surprised me was just how loose they had become after 20 miles or so.

Reading back through the forum I've now found a number of articles regarding poor quality composite gaskets. I have to say I wasn't impressed with the quality of the one I fitted and may go to a solid copper item.

I'll re check the fixings over this W/E.

Thanks again Robert


Hi Guys,

The best laid plans of mice & men etc.

I didn't get as far as hoped investigating my oiling issue this weekend. However I did manage to hook up an oil pressure gauge to the tapping just beneath the Pressure relief valve.

I half expected a low pressure reading but was surprised to see 70PSI at tickover. As I increased the engine speed it rose to 80 PSI and from then on stayed at that reading.

I've temporarily secured the gauge with cable ties just below the Fuel tank so that I can look down in see the readings whilst I'm riding. Unfortunately the weather conspired against my plans and it threw it down with rain so no road test.

Now I've already stripped and cleaned the pressure relief valve and found nothing untoward. When you put the cap on it does not compress the spring (If you shake it when assembled it rattles) hence why I thought I might see a low pressure reading.

Note: that the pressure readings are with cool oil as I couldn't give it a run..

Also during this brief "on the centre stand" run I could see the engine was breathing quite heavily out of the crankcase breather pipe and there was some oil loss from here.

Could high oil pressure throw the oil around inside the crankcase more than normal and allow it an easier passage out of the breather?

Any more thoughts?











The spring rattling is correct, normal routine is to remove shims until it just starts to rattle, however with cold oil the pressure is also set by the size of the oil hole the excess oil uses when its being dumped to the sump. Hence why you get a higher oil pressure on cold oil than on hot as the cold oil cannot get away fast enough through the small hole. The oil pressure figures you are seeing are good but a hot test will be needed to confirm, you are looking for a minimum of 10 psi per 1k revs with a max of 50 to 60 psi but would not complain at 70 psi on a hot engine.

If the high pressure inverts the seal in the timing cover then the oil gets dumped into the sump instead of feeding the crank and will give excess oil in the cases, but then the pressure also drops as the oil has an unrestricted route to sump giving no back pressure so this seems doubtful based on your pressures.


Seems on the high side. The INOA tech digest says that cold oil about 60 idle, .45 approx. warm. Did you measure the length of the relief valve spring? I found a too long spring recently. Just to get better understanding. What grade oil and what temperature do you have? Do you have head oil from the return side and scrolled rocker spindles? Have you checked amount of oil in the sump after a run? And a a day later to check how much it wet sumps?

Hi Michael,

I need to take the bike out on a run to get the oil hot unfortunately work and weather has prevented since I fitted the pressure gauge over the last W/E.

Oil is Castrol classic 20/50 and yes I have scrolled rocker spindles with the oil feed taken from the return line of the pump.

I have a manual valve fitted in the tank to pump line which I close after each run but I will look at removing the sump plug after a run just to see how much is sitting in the sump during normal running.

Does anyone know how much I should expect to get out straight after a run?   

I haven't measured the relief valve spring length and will do but I suppose it might pay me to replace the whole assembly just to be sure. Who knows maybe in the past someone lost the original spring and found one which fitted but has heavier gauge wire etc. I keep discovering a lot of performance upgrades to this machine so who knows what else has been done to it.

It originally belonged to the 3 times IOM TT winner Harold Daniell for the first year of its life and then most of the rest of its life (55 years) it belonged to a Mr Bevan who came from the London/Dartford area. Unfortunately the dealer I purchased this bike from had obtained it from the deceased Mr Bevans estate and its mechanical history has been lost so I have a non-standard machine which I'm attempting to get to grips with .

Many Thanks





It was common for the dealer to put his name in the book , so I would not read anything into that. My 99 has Harold as the First name in the book too. 

Hi Robert,


What year/month is your 99?. Mines early January '57. The second owners entry isn't until February '58 so it sat in the shop for a long time.

When is the second owner registered in your machine?



Hi Terry, My 99 was built just after 3/9/59 and registered  as a 60 model. First by Daniel on 15th feb 1960 and then by the first owner /Rider on 11th March 60. .He kept and used the bike up to around 1970 when it was written off . It was fitted with Avon handlebar fairing,combined fiberglasslegshield/engine enclosure and alloy paniers and suitcase top box. Machines built after August were usually coded for the following year. Mine was the 86th made of this model (a 99 DL) out of about 1250 in total. My bike was used by a photographer to travel Europe  following the  GP races. I have met the first owner and received photos from that period. I would be interested in any history of my first DL an 88 reg VAP807. was in full touring trim Avonaire fairing ,Craven panniers etc. I think its now described as an 88SS in black and chrome!.


Hi Terry 

How are you getting on?

If you decide to strip the engine I think there is a club CD that you can buy for yours. I used the Commando one and it was invaluable giving full details on stripping and reassembly with some clever savings.


I got a bit fed up with the mess under the bike and on the back tyre so I fitted a 3/8th rubber pipe to the breather and hard soldered a pipe into the oil tank  ,I also increased the tank breather to 3/8ths and ran it onto the rear chain guard. I don't loose any oil now and the rear chain looks ok. The only downside is under cool running there is a bit of condensation emulsion in the tank neck.I may have to fine tune the pipe layout to get the moist fumes out.If I were you I would look in the Ex valve chambers with the motor running , should be a minimal amount of oil being delivered. 

Finally got the chance for a run out this afternoon.

The bike started easily and ran well initially. Oil pressure from the start was 70psi at idle only going up as far as 80 with any throttle opening. about 2 miles up the road out of the town I pulled over and checked the pressure again. It was now 30 at idle and about 60 at high revs. I did note that there is some blue smoke when the engine is raced but not loads.

I continued on and covered about 30 miles on country lanes and dual carriage ways finishing off on a A road run of about 5 miles at 70mph. At the end of the run the oil pressure was down to 5psi at idle and 20 psi at high revs. I can feel a complete stripdown coming on now. 

unfortunately I didn't get the chance to drain the sump as unexpected visitors curtailed my spannering, however although oil is still coming from the breather it is definitely less than my last run so maybe those rings will need a fair bit of bedding in.

Need to find time to do a bit more investigation but I fear the worst.






I'd remove the pressure gauge. That's what Norton did.  Do the big ends rattle? Mains are balls and rollers and don't develop pressure. If the big ends are OK, what will a strip down achieve?


Could be that going thro the timing cover checking pump/valve and seals is all it needs .Be a shame to strip it all down for nothing. 

Hi David

its certainly not the smoothest engine at low revs but there again it's had a number of tuning upgrades done to it which I was unaware when I bought it. It does seem to have a bit of knock if laboured at low revs. When I had the barrels off I couldn't feel any vertical movement in the conrods. I still need to check the ignition timing and the auto advance unit action so that may help but that drop in the oil pressure has concerned me.

I will do a few more checks before I pull it apart





It is incorrect for the pressure relief spring to rattle. If you have any doubts about the valve, obtain a new spring so that you know the length is correct and adjust it such that it is just held. On no account should any preload be applied, but the spring should definitely not rattle

If anyone tells you this is incorrect then they shouldn't be dealing with engines.

Regards, Ian. TVNOC


I ran in my rebored 99 the old fashioned way and it blew oil out for years. Then I took it round Brands fast enough to shake the carb off and the rings bedded in.  I run it slowly for a mile or two in order to clear the sump. As an experiment I am now running 10/40 fully synthetic. Seems ok.Time will tell.


If the motor is a bit knocky  at low revs and kicks back  I would retard the ignition a couple of degrees ,try 28 .  You could also try a fill up of top grade fuel. If you have ignition points ,opening or closing up the gap a couple of thou is an easy way to tweek the timing (can't remember which way!!).


Hi Ian,

I've not had the chance to get back to my 99 to progress the further investigation of my issue.

There are quite a number of threads on the forum which relate to this valve and the fact that when shaken it is normal, and in fact, should rattle.

However as an Engineer myself this doesn't ring true and I am sceptical. When I get the chance to get back to the machine I'll spend more time trying to understand this valves operation and may even replace it with one of SRM's units.

I'm wondering if the fact that the piston in this valve is not held home with some spring pressure may be a reason for low oil pressure at low revs when hot? 

Thanks for your input




Hi Robert,

I'm in the throws of having my workshop replaced with another garage size building and consequently at present my Classic bikes and cars and equipment are all shoe horned into my double garage to a point where I can barely get in. Hence no work on the Norton and no drives/rides out on these nice Spring days because I can't get anything out.

It wont be long before I can move into the new building with plenty of room and easy access (note to self: Don't by any more toys). At the end of May I retire from full time (all time in fact) and then battle can re-commence in earnest. 

All the Best





Yes its taken all this time for me to road test my 99 since carrying out work on it last year. 

After my last post back in April 2019 I took it on another run and about 15 miles from home it started running erratically and stalled when I pulled up in a villiage. I removed the plugs which were quite black and put in a spare set but couldn't get it to start. Plugs out again and kicking it over I couldn't see a spark (Although if was a very bright day). Eventually it did start and I rode steadily home. The plugs were very black and sooty which I thought must be burnt oil but the electrode was very white. Looking at a spark plug condition comparison chart it showed a possible cause as being a weak spark. This prompted me to also rebuild the mag alongside replacing the timing case oil pressure seals and anything else which I found needed doing. When I stripped the mag I found it to be full of oil. I cleaned and rebuilt it fitting an easy cap condenser new seal and bearing insulators spending a lot of time shimming the cam housing to get the opening point of the contact breaker as close to 180 degrees as I could.

in the timing case I replaced both chains & tensioner and oil seals. Whilst setting up the ignition timing using degree disc I also checked the cam timing and it appears to be fitted with a Dunstall road cam. The clutch centre also had to be replaced (centre spline had worn through). Oil was changed to a straight 50 and I've routed the crancase breather pipe up and over the rear mudguard to exit at the bottom of the rear number plate because of the mess it leaves on the underside.

When fired up for the first time in the garage it ran very well although still spitting oil from the breather pipe. This was towards the end of November 2019. Alas weather and the pandemic put paid to road testing until now.

First run out last week was just for half an our or so and it seemed much improved with idling oil pressure at 20psi when hot and 50psi at 70mph in top gear. A few days later I went out for an hour or so and initially all was good, however after about 20 miles (A roads and country lanes) it started to run erratically again, I returned home on dual carriageways at 50/60 mph and it ran reasonably well but stalled as I pulled up at home. I put it away in the garage somewhat pee'd off.

Next day I took the plugs out and they were very black and sooty. It was at that point that I realised that it wasn't oil but carbon was running too rich. Now this is where it gets interesting:-

I knew that it had a bigger than standard main jet fitted (280 instead of a 250) but assumed this had been correctly done by the previous owner because of the engine upgrades as mentioned in earlier posts. The needle was set in its lowest position so no scope there.

With this in mind I ordered  250, 260, & 270 main jets. Yesterday I started with a 260 main fitted and the needle set in No3 slot with clean plugs. I covered some 40 miles and the bike ran well but towards the end I could feel at low speed riding it was going off a little.

I stopped and removed both plugs and they were sooting up and so I cleaned them and refitted them and replaced the main jet with the 250. Once again I could feel an improvement with smoother acceleration and better low speed running after another 40 miles all was well and I returned home and removed the plugs. These had a much closer to normal appearance but still slightly sooty. Now, I still have the option of lowering the needle to weaken the mixture more or even go down another size on the main jet but this seems a bit odd considering the mods done on the engine. On reading up a bit more regarding Monoblocs it advised that needle jets are prone to wear so I've ordered a replacement along with a new needle. However it was whilst looking at the parts list for my carb that I suddenly realised that it's been fitted with a 389 rather than a 376 although the jetting etc is the same.

Sorry for my ramblings but I'm now wondering where I go from here?Can the 389 be successfully set up to run on my engine bearing in mind that it's fitted with high compression pistons, Dunstall road cam, gas flowed head and manifold, Atlas inlet valves and goodness knows what else.

Does it make sense that with these mods and a carb with a bigger bore that I'm running on a main jet which is standard for an unmodded   machine?

What do you think guys?

Terry Guy










I have had similar issues over the years. Firstly when I fitted 6 start gear set to the pump. Too much oil gets blown around and can flood the mag/dissy. Back to the 3 start set. Rings not run in,Compression blow by oil gets dumped out of breather, Breather routed to tank .Breathers to and from tank increased to 3/8" . Carb needle jet worn, replace.Idle jet loose. Tighten before fitting cap.Float hanging up, back to brass float. Plugs too hard, Plugs now in production don't seem to be able to self clean once oily,switched to fine wire electrode expensive ones. Fuel can vary Runs Rich on Esso synergy ,weak on std EO5. Head oiling very poor,Jubilee type restrictor fitted,too much oil  to inlets ,and too much oil going in circles not going back to tank, restrictor size adjusted till oil to head just enough , Rings run in after mad session  at Brands Hatch .New needle jet not made properly (no air bleeds) drilled them myself. Small adjustments to pilot settings cleans up plugs. Starts well,now,no misfires no smoke ,a bit weak though. Tried different fuel levels,now std.. Honda sits sulking gets no attention,does not need any,Boring thing.


This is frightening me, engines that need so much tinkering with, it would make a narcissistic Trophy Wife look neglected, what chance has my 99 engine, that has been stood for a rumoured 45 years got of running without hiccups, after a strip-down and clean up and hopefully not too many replacement parts?

I do not mind some fine-tuning and experimental R & D, but surely there has to be a strategy for getting things right, like a check list of initials things to do to prepare the way for Norton Nirvana.

Even, Hercule Poirot, would be "pulling his hair out", with this one, perhaps because the engine been altered from spec' things are worse than normal.

Best, I sacrifice a few Lambs, to the God of Motorbike for assistance with mechanical peculiarities of the Norton kind.




Hi Robert,

I believe that the fitting of a new timing cover/crankshaft seal has returned my oil pressure to an acceptable level and it's going where it should and not mainly emptying itself into the timing case.

on the last run and a number of stops to check it seems as though any oil from my extended breather is greatly reduced maybe the bores and rings are bedding in, certainly if I've been running with a rich mixture it wouldn't have helped the situation.

engine is still a bit knocky when laboured but so far I've resisted tearing the bottom end apart. Timing is set at 32 degrees before tdc or thereabouts (a bit of a compromise to get left and rh cylinders the same) and so I may try knocking it back to say 28.

at last I feel I'm making some progress and if I can get the mixture/plug fouling issue corrected l'll be on a winner but my real question is :- will I ever be able to get it to run properly on a 389 Monobloc?


This is just normal running issues,wait till you get to use the clutch and expect to be able to sit in traffic with the lever pulled in (if you are strong enough), put in gear without a crunch, find neutral at traffic lights, ride without slip. Mine now does all these normal things. Not  many do.  Once you have a bike that goes well you can worry how you are going to stop!!.Why the TLS brake lets you roll backwards on hills, and the SLS did not. Why does it mark its spot like a pi----ing dog.


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