Just got back an hour ago from John O'groats. Over 1200 miles with only one issue: water in the mag pickup after a night of rain. Otherwise I am as chuffed as a shed-load of locos.

One thing I'd appreciate your views onis that during the 1200 miles she consumed about 2.5 litres of oil (straight 50). Is this excessive?

You need to fit one of the rubber covers over the mag pick up/lead. Smother the HT lead where it exits the pick up and the top of the pick up with Vaseline before sliding the cover into place...

I would say your oil consumption is excessive...Ian

email (option): ian@wright52.plus.com

Congratulations on completing the 'end to end' by the way...It is a gratifying exercise for sure and still a challenge on an old bike...Ian

email (option): ian@wright52.plus.com

Just put the oil and petrol in and have fun, after all its your experience so enjoy it. Fuel and oil consumption are relative to which ever marker you chose
Well done and someday I hope to wear out the same roads as you.
Regards
Richard

Ian and Richard, thanks for your encouraging replies. I will look out a rubber boot for the mag,

Whenever I parked up the bike it would leave a small pool of oil under the engine breather, I am wonderinmg if the ring gaps are excesive leading to higher crankcase pressure which in turn is forcing oil out. My fellow rider did not see blue smoke except occasionnally when pulling away.

You are getting excessive blow by.
Mine would do the same thing when being over reved.
Oil poured out of the breather tube.
A new valve and longer hose on the end of the breather went a long way to slowing it down.
The previous bore had a big gouge where the gudgeon pin had come loose and it was chronic oil tosser at anything over 1/2 throttle.
In a couple of months time when the weather is not as much fun pull the head off and check the bore.

From my very unreliable memory usual oil consumption is 50ml /100 miles of steady cruising.
Lots of the period magazines would print oil consumption figures but makers never did.

I fit a very tight o ring to the HT lead before the cap, fitted with some rubber grease .
Fit the boot then push the O ring down tight onto the end of the boot.
O rings got changed every couple of years when they got loose.

email (option): bsansw1@tpg.com.au

Thanks Trevor. The bore should be OK as the barrel was relined and bored 3000 miles ago. I might have been overgenerous with the piston ring gaps when rebuilding the engine though. I'll check it out over the winter, In fairness to the engine I have spent a high proportion of the last few days riding with the twist grip against the stop!

I have ordered a rubber boot for the ht pick-up and had planned to use a bit of silicon sealer with it but the o-ring might be a better idea as the silicon might stick the hyt lead to the cap making removal harder.

If you had the throttle to the stop I'm not surprised at the oil consumption

email (option): jeremy@clogmaker.co.uk

Right on WFO pumps crankcase fume out the breather like there is no tomorrow.
Add to that the amount of splashing creating tiny oil droplets that blow out with the crank case fume.
This is why the breather got moved to the timing cover and then they had to add a splash shield on it.
Side valves are not supposed to be ridden like that .
They are supposed to plod along at peak torque which from memory is around 3700 to 4000 rpm.
If you find you are regularly running WFO then you might want to consider taller gearing.
When I was running the really high gearing it did not toss anywhere near as much oil as latter on when I decided to forget riding with the speed merchants and only go riding with people who understand the meaning of "at a gentleman's pace"

email (option): bsansw1@tpg.com.au

I should point out that full throttle was used to maintain forward momentum, not high speed! There's some steep hills in the highlands (and some strong headwinds!):grimacing:

Does it matter? You have achieved your goal and enjoyed yourself, it's just a minor cost of fullfilment! None of us are getting younger nor our machines so have fun while you can, I just wish I could take my own advice!
Richard

Dean,
I don't think a bigger piston ring gap can lead to high oil consumption.
Certainly not if the rest is OK, like piston, bore etc.

Richard; very true and encouraging words. To be honest, when I set off I never really believed that either I or the bike could complete the journey. Its not that I don't believe a well sorted M20 could do it, but I knew mine was assembled by an idiot!

Michel: I was thinking that large piston ring gaps could increase crankcase pressure and thus a leakier engine and a bit of oil burning.
But I am not going to sweat it for now, especially as today I discovede that the small oil pool on the floor is commng from the chaincase.

The good news is that my earlier attempts to address the gearbix leak seem to have been successful with no need for top ups during the trip.

Some bad news is that a wayward speedo was not due to water ingtress as I suspected but to to the drive coming loose and the effective change in cable length damaging the drive shaft in the speedo.

And blimey, who knew that field stands were so complicated (well not me for sure). Mine had worked loose at the frame clamps, and remebering I was not convinced I'd got the clamping mechanism sorted originally, I took it off and examined it a bit more closely. Some heat and wire brushing and a sleeve and spring appeared! All cleaned and assembled properly now and another lesson learned. Satisfying but given how I overlooked this and other issues makes me womnder if I should be allowed nice things:grinning:

Because there is no seal between the crank case & the primary chaincase oily fume from the engine will blow in there.
The "seal" was originally a close fit with a slinger behind it.
That close fit is by now 10 times bigger ( or more ) than it was when the engine left the factory so the engine leaks like a seive into the primary.
The story is the same for the gear box.
On the original set of cases for my M20 that gap was enormous so after 20 miles oil would be pouring out of the sliding plate.
The fix was to make the primary drive hole in the crankcase concentric with the drive shaft ( oval to the tune of 0.015" ) then make a new spacer that was a close fit to the enlarged but now true hole
I was always going to get it machined to take an oil seal but never got around to it.

email (option): bsansw1@tpg.com.au

As far as the primary goes, I butchered an old, knackered, sliding plate and with a bit of scrap ally and a 2 quid seal made this.



seems to work OK but doesn't stop all the other oil leaks :sob:

Pearson used to offer something similar to these, dunno if he still does but they were expensive - add the word Goldstar and treble the price :stuck_out_tongue_closed_eyes:

If you are taking the engine apart at any time then fit a sealed ball bearing on the drive side and this will stop pretty much all leaks from engine to primary.