Acceptable / normal oil consumption

[Oddjob]

Surprised Julie didn't say yes or no for Graham or maybe that would be a bit cheeky, I hate it when my missus volunteers me for jobs.

[350Simon]

Surprised Julie didn't say yes or no for Graham or maybe that would be a bit cheeky, I hate it when my missus volunteers me for jobs.

Yep I know that feeling!




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[Cappodimonte]

What would be considered normal for a 350/400 sohc?

I've done 500 miles of running in new pistons and rings, the bores were properly machined and honed and I know that my valve guides are on the upper end of the serviceable limit.

Oil level is just above the min mark on dipstick after 500 miles. Is this acceptable or should I really get the head reconditioned?

I'll be honest I can't detect any smoke from the exhausts in my mirrors while riding or at idle but my friend said the other day there's a faint haze when I'm giving it the beans.

Having seen your missives and having worked on Hondas whilst in the trade I never came across any Honda car or bike that had a 500 mile per pint consumption. There is something seriously wrong and with the data you provided I’d have walked away from that one as it appears to have been done on the cheap.
No way would I have taken it down to piston rings and honing without doing work on the whole head with complete strip down, that’s a recipe for problems that you seem to have incurred. If one valve stem has loosened then the whole shebang needs doing. Another fault could be the piston rings being put in the wrong piston step or even upside down in the right one and yes I came across that but not on a Honda.
500 mile run in and giving it ‘The Beans ‘ is not conducive to running an engine in even a Honda. I wish you all the best with it but I suspect you have inherited a moving money pit.

Cheers
Simon

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[Cappodimonte]

As a thought, what oil have you used?
If you use modern 0-30 oils then that will go up past th e pistons and down the valve stems.
You should use  a 10-40 mineral oil or equivalent, Hondas clearances we’re close but not to todays micron standards.

[350Simon]

As a thought, what oil have you used?
If you use modern 0-30 oils then that will go up past th e pistons and down the valve stems.
You should use  a 10-40 mineral oil or equivalent, Hondas clearances we’re close but not to todays micron standards.

No idea what oil was in it but it came out very very black and thin so I suspect it was breaking down which wouldn't help.

I've filled her up with 10W40 mineral oil and done another 100 miles so far, I'm now not getting any smoke that I can see while riding, a small amount if I blip throttle hard on the drive.

Just going to put some more miles on it this week and if it uses a load then I'll replace the guides.

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[Cappodimonte]

Motorcycle engines which are unit construction and use the same oil for moving engine parts AND the gearbox have a really tough life with the result they will get broken down quickly hence Hondas short service intervals of the 70/80s
Hope that changing to a thicker oil viscosity helps you out, bear in mind your bike is an old lady and should be treated like a lady.
I’ve seen and heard so called modern bikers scream the engine till it hits the Rev limiter, a sure fire way of drastically reducing engine life.
The oil being very black and thin to me points to it being modern synthetic 0-30 oil which is unsuitable for classic bike engines.
Good luck with your ongoing biking.

[K2-K6]

"No idea what oil was in it but it came out very very black and thin so I suspect it was breaking down which wouldn't help."

Usually associated with running too rich, either from carbs being altered to excess or more normally far too much running with engine cold/choked to allow excess fuelling past the piston rings into the oil. The giveaway is oil smell (compare old to new) as it will generally stink of unburnt fuel.

The gearbox doesn't colour or dilute the oil in use but often it's pointed to as culprit in these scenario. Honda service interval is an acknowledgement of overall fuelling strategy which ultimately comes from the necessity to run slide carbs too rich ideally for a decent longer oil term, essentially it will dilute the oil and reduce viscosity.

Sensible to start with new oil and monitor condition, see what it looks like at 500 and 1000 miles etc.

With short runs and often on choke though you'd expect the oil to be knackered by about 500 and well short of Honda service specification.

[350Simon]

"No idea what oil was in it but it came out very very black and thin so I suspect it was breaking down which wouldn't help."

Usually associated with running too rich, either from carbs being altered to excess or more normally far too much running with engine cold/choked to allow excess fuelling past the piston rings into the oil. The giveaway is oil smell (compare old to new) as it will generally stink of unburnt fuel.

The gearbox doesn't colour or dilute the oil in use but often it's pointed to as culprit in these scenario. Honda service interval is an acknowledgement of overall fuelling strategy which ultimately comes from the necessity to run slide carbs too rich ideally for a decent longer oil term, essentially it will dilute the oil and reduce viscosity.

Sensible to start with new oil and monitor condition, see what it looks like at 500 and 1000 miles etc.

With short runs and often on choke though you'd expect the oil to be knackered by about 500 and well short of Honda service specification.

Thanks for this really useful information K2-K6.

I couldn't believe how black the oil was considering its only done 500 miles. I'm used to only seeing that on diesel engines.

Have been starting the bike with a small amount of choke and running for 2 to 3 mins on the drive at a high idle of about 2-2.5k rpm.

After this I can knock the choke off and the bike will idle perfectly at 1200 rpm. Then I set off.

Is this excessive? I'm not one for constantly adjusting the idle speed screw, I like to set it when the bike is hot and leave it alone.

I'm pretty sure mixture when on throttle is spot on but I might whip the plugs out in a layby after a full throttle run to check.



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[Nurse Julie]

Not sure what work your engine had done prior to you getting the bike but if Graphogen had been used during the build, the oil will come out black at the 1st oil change.

[350Simon]

Not sure what work your engine had done prior to you getting the bike but if Graphogen had been used during the build, the oil will come out black at the 1st oil change.

Hmmmm indeed a possibility.

I hate the stuff but that's another topic entirely.

I had strip and clean a freshly rebuilt engine with no oil pressure once because the oilways in the crank were blocked with graphogen.

Ever since at work we only use the oil the engine will be run on as assembly lube. Then build up oil pressure before cranking.



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[Nurse Julie]

Not sure what work your engine had done prior to you getting the bike but if Graphogen had been used during the build, the oil will come out black at the 1st oil change.

Hmmmm indeed a possibility.

I hate the stuff but that's another topic entirely.

I had strip and clean a freshly rebuilt engine with no oil pressure once because the oilways in the crank were blocked with graphogen.

Ever since at work we only use the oil the engine will be run on as assembly lube. Then build up oil pressure before cranking.



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Yes, some people slather the Graphogen on like buttering bread 😂😂😂. Graham (Trigger) has always used Graphogen on new mating parts fitted in the engines but he's never had restrictor jets blocked due to excessive use.

[Cappodimonte]

When rebuilding any engine gearbox or axle I only ever used the oil that was going to be used in the workpiece, as I stated earlier with motorcycle engines that are untitary construction with oil being used for gearbox and engine the oil has a much harder time in that it goes through compression forces in the cam,crank pistons  rockers etc but very high shearing forces in the gearbox as gears mesh together under load..
The oil used has therefore a rough life with the result oil changes were a lot more frequent than they are now. This is due in no small measure by synthetic oils being far more resistant to breakdown and shearing forces but the clearances now are in microns, thousands of a millimetre not thousands of an inch which allow modern machines to use 0-30 oils whereas our classics need 10-40 oil which is thicker due to larger ( in comparison) clearances.
In days of old where cars had engine, gearbox and back axle the oils used were 20/50 for engine, 75/80 for gearbox and 90/110 for back axle due to the different forces exerted on the oils, in a motorcycle like Honda the oil is expected to combat all the forces in one.

[taysidedragon]

Cappo, I don't disagree with what you posted, but a major reason for thinner oils now is the push to get better and better fuel consumption.  Thinner the oil, less drag and resistance.

Also, nearly all vehicles now are watercooled, which allows for better temperature control and therefore closer tolerances.

My Triumph Tiger 500cc is unit construction but still has separate engine and gearbox oils. All the unit Triumphs before the reborn Hinckleys are like that. I believe the other old Brit bikes were built the same way, but I'm not familiar with them.

[Cappodimonte]

You are correct in that modern oils are thinner along with a host of other engine management systems aiding fuel consumption to increase mileage per gallon. The major difference is that modern engines are using clearances in microns (thousands of a millimetre ) not thousands of an inch as per 70/80s Hondas and especially Triumphs/BSAs etc. use modern oils in a classic bike engine and it will go straight past pistons and down valve stems which will cause you problems with burning oil
Classic bikes use classic thicker oils, simple as.

[McCabe-Thiele (Ted)]

On the subject of modern fully synthetic oils most owners of modern cars rarely need to top up the oil between services - they falsely think that they are not burning any oil at all.

To combat the sulphur impurities in petrol that would combine with moisture to form corrosive acids they add special ingredients to synthetic oils (micronised chalk is one) to neutralise the acids - over time these neutralised products build up in the oil replacing what oil has been used /burnt off making the oil level appear stable.

If you happen to be close to a scheduled oil service then make a long Motorway trip you can suddenly find your oil level drop dramatically (up to a litre in a couple of hundred miles) as these products are burnt off. This can help explain sudden unusual amounts of oil being used on a motorway journey. It also emphasises the need to change oil regularly especially on short journey work.

This is based mainly on my own anecdotal experience with oil consumption in cars.