Update on my '73 Hi-Rider acquisition.

Update on further work on my '73 Hi-Rider: Have installed a new fuel line assembly from tank petcocks to carbs, new oil supply line assembly from sump to rocker/tappets in the head, and was able to patch the leak on my fiberglass tank. I know everybody says to replace the tank because of possible interior degradation if ethanol fuel was used, but the tank was dry when I got it and I can't verify if it has or hasn't seen ethanol fuel. Will use non-ethanol fuel and see what happens at least for the short term. Installed two new correct plugs. Used the "ticklers", no choke, and the engine started after several kicks. Started and ran and was able to adjust the idle down to about 1.000 rpm and it sat there and idled at that speed. Let it set there and idle long enough to get it up to temp (guessing) 4-5 minutes while running a fan in front of the bike. Although it doesn't seem to be actually leaking oil, it seems to have a slight seepage somwhere because while running, it seems to be burning off oil and giving a hint of smoke. It's not smoking out of the exhaust, but as I say, more like it's burning off an external seepage of oil. Doesn't look like it's coming out of the tappet covers. Now have to ask, was head gasket failure an issue on these bikes, and by that I mean any more so than any other bikes? I'll have to start it again and investigate further, but it looks like it may be seeping at the head gasket. Hope not. Seems I read a post here on the forum that the composite head gaskets needed to be retorqued several times after being installed. I really have no reason to believe this engine has ever been apart. Doesn't appear to have been, can't say for sure.

Was your bike sitting awhile? Could be burning off grime, old oil, greasy fingerprints. Riding it will tell you more than looking at it. Dont panic.

Retorque the head, the bolts come loose and the head gasket leaks, if you catch it in time then it will seal. Well it did for me last time I got the same.

NPeteN said:

Was your bike sitting awhile? Could be burning off grime, old oil, greasy fingerprints. Riding it will tell you more than looking at it. Dont panic.

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According to the last plate that was still on the bike ('81), yeah, it's been sitting a while...., about 40+ years. That coincides about right with the previous onwer's age and story of when he stopped riding it, after he got married and had kids, it was put away and no longer ridden. As you say, I won't panic, just yet anyway.

quawk said:

According to the last plate that was still on the bike ('81), yeah, it's been sitting a while...., about 40+ years. That coincides about right with the previous onwer's age and story of when he stopped riding it, after he got married and had kids, it was put away and no longer ridden. As you say, I won't panic, just yet anyway.

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She'll come around.

Just take it for a ride and then check everything, retorque the head after it has cooled down, make sure the lower front valve covers aren't leaking as when they do looks like a head gasket is leaking, oil comes up the studs if not sealed, give the bike a good degrease before chasing oil leaks, don't chase old oil leaks, clean and then chase them .

Ashley

Reset the valve clearances after retorque. Any timing check done? Nice job bringing this one to life.

Some common leak points to check:
Exhaust rocker covers, typically at lower stud points. Oil will run down and appear to be from the front head gasket area fins. Confirm if the covers are dead flat, as common to find them distorted where they have been over tightened. Flatting them on a plate of glass with wet/dry paper is good to do.

Either of the two forward cylinder head 5/16" studs. The stud bores into barrel can crack into pushrod tunnels, letting oil seep up the stud threads out from under the washer and nut, to then appear on the front fins, like a head gasket oil leak. I've had limited success removing the nut and washer, degreasing and using some sealant under washer to sort the leak. But best way is to address next time head is off, removing studs and using locktite as a thread sealer on those two studs.

Also good to fit some kind of reed valve on the crankcase breather to help stop the pressure forcing oil out any weak points.

The only thing that scares me is your letting the bike idle for that length of time.Not enough oil getting to the cam,etc. I would definitely re-torque the head after the motor is stone cold and using the proper pattern for tightening the bolts.Glad you got it running.
Mike

Tornado said:

Also good to fit some kind of reed valve on the crankcase breather to help stop the pressure forcing oil out any weak points.

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I'd have to investigate the crankcase breather to even see where and how it's attached, but if it vents,even if indirectly to atmosphere, wouldn't that vent the crankcase pressure without a need for a reed valve? Could you explain why I maybe need a reed valve?

To prevent air from entering the crankcase..
Both pistons rise and fall together, pulling and pushing air.
The reed valve opens one way, only on the downstroke.
It is closed on the up stroke, limiting air and actually creating some negative pressure.
Then on the next downstroke it's not pushing all that air.
Otherwise, it is sucking and blowing air continually through the crankcase.
As the crankcase pressurizes on the downstroke, without the reed valve, it's trying to blow all the joints and seals out.
There are several reed valves and they all work.
You can do a search on this site. Took me a while to fully grasp it.
A stock, well fettled Norton is a very competent motorcycle. And yes, there a lot of modifications one can get all caught up in.
My thought on this is, working with a stock Norton, the reed valve is the First modification, then the clutch rod seal.
Then knock yourself out.

A side note. Where I really learned about this was on my KTM dirt bike.
I installed a flapper type valve, with the single cylinder, the idle was instantly better and smoother.
The engine as a whole was much happier..

quawk said:

I'd have to investigate the crankcase breather to even see where and how it's attached, but if it vents,even if indirectly to atmosphere, wouldn't that vent the crankcase pressure without a need for a reed valve? Could you explain why I maybe need a reed valve?

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On the 73 & 74 bikes, breather should be a hose off the timing case where the mag used to sit. Hose runs rearward and up into the oil tank. Some hoses get modded to just vent to air somewhere under the bike. Problem with stock setup is that the pressure pulses are constantly breathing in/out. With a reed valve on the vent hose, breathing out but not in creates a lower pressure within cases, so helps stops oil getting forced out of places.
An easy low cost option is to fit a reed valve off a Yamaha xs650. Ran me about $35 usd. Another option is a custom made sump reed valve that replaces the big sump drain screen fixture. These run $300-$400 usd I believe.

Yamaha reed valve:

Good discussion here:

Tornado said:

On the 73 & 74 bikes, breather should be a hose off the timing case where the mag used to sit.

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On 850s yes but not 750s which had the same rear case breather.

MichaelB said:

To prevent air from entering the crankcase..
Both pistons rise and fall together, pulling and pushing air.
The reed valve opens one way, only on the downstroke.
It is closed on the up stroke, limiting air and actually creating some negative pressure.
Then on the next downstroke it's not pushing all that air.
Otherwise, it is sucking and blowing air continually through the crankcase.
As the crankcase pressurizes on the downstroke, without the reed valve, it's trying to blow all the joints and seals out.
There are several reed valves and they all work.
You can do a search on this site. Took me a while to fully grasp it.
A stock, well fettled Norton is a very competent motorcycle. And yes, there a lot of modifications one can get all caught up in.
My thought on this is, working with a stock Norton, the reed valve is the First modification, then the clutch rod seal.
Then knock yourself out.

A side note. Where I really learned about this was on my KTM dirt bike.
I installed a flapper type valve, with the single cylinder, the idle was instantly better and smoother.
The engine as a whole was much happier..

Click to expand...

Having spent most of my working days in manufacuring, I realize that any manufacturer has to consider the so called bottom line as far as being competitive in their pricing and would have to decide if adding any feature be justified in its' added cost, even if small. That said, if members here have been modifying the crank vent, I have to wonder if Norton took kind of a shortcut on the crankcase venting, if it could have benifitted from some kind of one-way valve, whether it be a reed valve, a flapper valve, or some other type of one-way valve. I wonder if it was a cost saving decision on their part or just an oversight or deemed unnecessay.

quawk said:

Having spent most of my working days in manufacuring, I realize that any manufacturer has to consider the so called bottom line as far as being competitive in their pricing and would have to decide if adding any feature be justified in its' added cost, even if small. That said, if members here have been modifying the crank vent, I have to wonder if Norton took kind of a shortcut on the crankcase venting, if it could have benifitted from some kind of one-way valve, whether it be a reed valve, a flapper valve, or some other type of one-way valve. I wonder if it was a cost saving decision on their part or just an oversight or deemed unnecessay.

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Earlier Commandos had a "timed" breather arrangement directly off the camshaft..such that a port would open on the down strokes and close on the up strokes. It wasn't kept on later bikes, likely b/c it wasn't effective enough (port was quite small) and added costs. Trying to force close to 800 c.c's of air through a small opening in a few milliseconds is problematic. Back in those days, there weren't many bikes using better breather arrangements as far as I know.

1940's/50's technology. Engine was orignally designed as a 500. Timed breather worked fine.
As noted above, higher volumes caused issuses and so on. Honda solved by having 180 degree crank, one rising, one falling.
Equalizing the pressures. Sound like spit though.
Brit twins and Harley's both rising and falling at the same time, creating pressure issues, but sound GREAT!!
Not sure of the evolution of the reed valve and it's application to crankcases.
I know Yamaha was early on with the intake side on their 2 smokers.

MichaelB said:

1940's/50's technology. Engine was orignally designed as a 500. Timed breather worked fine.
As noted above, higher volumes caused issuses and so on. Honda solved by having 180 degree crank, one rising, one falling.
Equalizing the pressures. Sound like spit though.
Brit twins and Harley's both rising and falling at the same time, creating pressure issues, but sound GREAT!!
Not sure of the evolution of the reed valve and it's application to crankcases.
I know Yamaha was early on with the intake side on their 2 smokers.

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2-stroke outboards had it way before then.

The 1969 XS1 650 four stroke parallel twin Yamaha had the reed petal breather.

A better bolt on breather upgrade. Sure, pricey, but you'll never regret any purchase from CNW.

The 72-73 750's actually have the breather in the most desirable location on the engine.

When you have the valve covers off, check the gasket for fit on the cover and the head. Some can have a lot of overhang. Trimming the over hang at the bottom will allow oil to flow past the joint instead of being trapped at the joint.

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franko said:

When you have the valve covers off, check the gasket for fit on the cover and the head. Some can have a lot of overhang. Trimming the over hang at the bottom will allow oil to flow past the joint instead of being trapped at the joint.

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It only takes a small " V" cut in the gasket overhang to prevent the poolage