New springs and valves??

I had sent my commando Mk3 head for decarbonizing and valve laping.

It's all right now it works well although I have not pushed the bike up to the revs as the rest of the engine is all new, my question is ...

Should I have fitted new valves and springs instead of reusing the originals ?

YES!!!!

Depends on how much is any wear in guides and valve stems.

Thanks for your answers !

It does not show oil consumption

NorCat said:

I had sent my commando Mk3 head for decarbonizing and valve laping.

It's all right now it works well although I have not pushed the bike up to the revs as the rest of the engine is all new, my question is ...

Should I have fitted new valves and springs instead of reusing the originals ?

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To be honest you pays your money and takes your Choice, I run a fairly std engine in my MK3, I am not one for change for the sake of change, my valve stems and guides were in good condition, I refaced the valves 45 degree seats in the lathe. I was quoted £98 +VAT to re-cut the seats in the head, as most places seem to think it's OK to just cut the 46 degree seat to the width of a street and pass the head back I decided to start looking out for a set of valve seat cutters, I found a new boxed set of Neway OEM Kit for Briggs and Stratton dealers for £73 on ebay That gave me a selection of pilots T-bar cutter drive wrench, hex keys to adjust the cutter blades and a single dual ended cutter that would cut 46 and 31 degree angles. I decided to purchase an additional 60 degree cutter from the US, this is used to reduce the width of the of the 46 degree seat from the throat side. The extra 60 degree cutter took me past my original budget of £98 +VAT, but I recon they will soon be offering a return on investment . As part of the rebuild I replaced the cam and had the followers re-faced, I opted to replace the 43 year old Valve springs with a set of Andover's finest .

If it's not using oil then your bore/pistons valve guides /valve seals etc are all ok
If your springs are badly worn it could lead to premature camshaft/follower wear
Personally I'd leave it well alone and just ride the bike
Cheers

Esme, I wish you were my neighbor i'd be dragging all kind of heads over to touch up instead of lapping till the pits are gone.

NorCat, if you have your old valves and guides and really want to know go on ebay and get a micrometer and small hole gages. Its all about measuring valve stem and guide hole. Is it straight or worn barrel shaped? And how much clearance between the two.

Thanks for your info!

The bike is an Mk3 and had a Combat cam with lobes in bad condition, one lifter was broken and the other 3 no perfectly straight so it was all replaced with AN Mk3 standard pieces, the springs ... Where not!!

Edgefinder, I have no idea, I took it to the rectifier to do the job, I have not the ability to dismantle the top end to pieces for verification, I would probably shoot my ages in the process, I relayed on their experience.

Ayes..

Valve springs are not expensive and do wear out. You can reliably measure compression distance and attendant spring force at the specified distance. Jim Comstock and Dave Comeau can tell you a lot more about the metallurgy and useful life of valve springs (many posts on this forum to this point). For me it's a no-brainer, the more judgement you remove from a rebuild the better and longer lasting the results will be. If a valve spring breaks it can cause some serious damage.

I replace valves, guides, springs, keepers, insulating washers, retaining washers and seals on any head that has no history or wasn't rebuilt by someone that I know and trust. Anyone that tells me that they, simply, drive the guides out never hears from me again. A lot of services plane the gasket surface as a matter of course, they never hear from me again either.

Penny wise and Pound foolish, think about it. Replace the springs!! "Pay me now, or pay me, a lot, later. Or, better, "why didn't we have a enough time to do it right initially, but we have time to do it over"?

I wish Jim could clone himself, he is one of very few I trust to do it right the first time.

A parting thought: I think of my Nortons as poor mans Vincents; keep them maintained, in good condition and they can part of your retirement or your legacy. Keep cheaping out and your Norton begins to look a lot like a yacht (a hole in the water where you throw money).

Stock springs on a Combat cam will be pretty well sacked out in 7 or 8000 miles.

The only way to know for sure is with a spring pressure gauge.

My set of Neway cutters spends more time loaned out than at home. Could retire a wealthy man if I charged rental.

RoadScholar said:

A parting thought: I think of my Nortons as poor mans Vincents; keep them maintained, in good condition and they can part of your retirement or your legacy. Keep cheaping out and your Norton begins to look a lot like a yacht (a hole in the water where you throw money).

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Having owned both, I would say that owning a yacht and owning a Norton is pretty much the same thing; It's just the size of the hole that is different. Admittedly, a lot of the expense is choosing to buy something - like my just-purchased set of Premiers and the CNW rearset - as opposed to a parts needed to keep the bike running!

In reality, I totally agree that a Commando is a poor man's Vincent and one of the few (only?) classic brittbikes that, IMO, is suitable for daily riding in modern traffic conditions from piddling around town to twisty back roads to 80+MPH interstate riding. Once properly restored or rebuilt and maintained, it is reliable and pretty much trouble free. BUT it does require considerably more inspection/maintenance than a 750 Honda of the same year!