Oil pressure relief

Dmftoy1 · Jan 3, 2015

68 Norton Commando

Bottom end together, valve timing set properly, etc.

Should I be disassembling the pressure relief assembly that screws into back side of timing cover and replacing the spring or checking anything? Factory service manual is moot on the topic. Mick Hemmings video doesn't say anything either. I've spent a lot of time/money on the rebuild and would hate to be screwed by a $5 40 year old spring.

Any advice great fully accepted.

Hobot · Jan 3, 2015

The only oil pressure gauge kit offered *long term* by factory was non bar mounted shop use only, for initial start up testing of oil pressure to guide relief valve diddling for *low-safe* enough cold condition starts - then remove for real life use when oil PSI can drop to zero w/o any worry of oil starvation from blown out oil nipple to TS cover sealing. Counter intuitive as this is to ordinary concepts Commando PRV function is to prevent too hi PSI not raise it so guage even registers, though nothing wrong to set so some oil pressure shows on heated freeway cruise. The people who wrote Norton Service Notes have special notice against oil gauge fitting, I'd go against too.

Dmftoy1 · Jan 3, 2015

Would you disassemble and clean? Replace internal spring? Just wondering if I need to do anything before re-installing

Northton · Jan 3, 2015

Take it apart. Make sure the piston moves freely. Mine was seized. Did not even have a spring. I believe the Hemmings dvd mentions this in the timing cover replacement section.

toppy · Jan 3, 2015

I fitted a new one from RGM which is in fact made by SRM. It is made of stainless steel and comes pre set and tested to a releave pressure of 60psi.

Fast Eddie · Jan 3, 2015

toppy said:
I fitted a new one from RGM which is in fact made by SRM. It is made of stainless steel and comes pre set and tested to a releave pressure of 60psi.

Me too!

Some say it is expensive. For me it was a bargain, for the peace of mind!

ashman · Jan 3, 2015

Just pull it aprt and give it a good clean as it does get a bit of gunge in there, if the spring look suss then replace it.

Ashley

Matchless · Jan 3, 2015

I also have the SRM valves on both Commandos & also on the TR7. Well worth the money. Failing that, strip & check the original & fit a temporary pressure gauge into the rocker line. When it's apart you may find just a spring & piston or sometimes a shim or two. These were fitted by the factory to get the correct figure. You should get around 50 to 60psi @ 3000+ rpm, & about 20 to 30 psi at idle with hot oil (20/50). Don't get too hung up about pressure though. It's the volume of oil that's just as important.

Towner · Jan 4, 2015

Normally the spring did not wear out. The best you can do is to clean it and checked it with a gauge as already mentioned. With a new spring you have to check it anyway.

Ralf

Dmftoy1 · Jan 4, 2015

Thanks guys!

Dmftoy1 · Jan 17, 2015

Just thought I'd report back. Piston was stuck and even once freed it would not come out through the rear of the housing. Decided to replace the body, piston, and both washer/gaskets. I put it back shimmed as it was from the factory and will test it to see if it needs addl shims.

Wonder if anyone has experience with the old Brits pressure gauge setups? I know there's some controversy but seems to me if I have to measure pressure anyway now might be good time to also install a gauge I could monitor all the time?

Bernhard · Jan 19, 2015

ashman said:
Just pull it aprt and give it a good clean as it does get a bit of gunge in there, if the spring look suss then replace it.

Ashley

If you had some gunge in there then I would seriously suggest that the crank wants splitting and cleaning especially if the engine has done an high mileage.

Oil pressure relief

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