Reliable camshafts

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No change in lifter clearance is not a good indicator of no cam wear. Clearance is checked on the base circle which doesn't get much stress.
Jaydee
 
maylar said:
So, on the subject of "reliable" cams, what can I expect for life & wear from a stock 850 cam that I bought from Norvil back in 2009? Bought followers too, which had to be lapped before they'd fit the cylinder bores. This is what came out of the motor after about 35,000 miles:

Reliable camshafts
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As the cams need oil to lubricate their hardened lobes, have you ever checked the oil pressure in the timing case? And if the 850 still has the oil to the top end lubricating the cams, from the oil return feed, opening or checking the oil feeds here might not go amiss.
 
jaydee75 said:
No change in lifter clearance is not a good indicator of no cam wear. Clearance is checked on the base circle which doesn't get much stress.
Jaydee
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That's true although it does indicate no undue follower wear.
As I mentioned, ignorance is bliss.
I do think there would be some grindings showing up on the magnetic drain plug if the cam is wearing like those in the photo.

Glen
 
Nortoniggy said:
This is the 2nd cam I removed. Worn quite a bit.

Reliable camshafts
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Thats one of the worst 750 cams I've ever seen.

Not every 850 has bad cams. Notice that its usually just one lobe that goes bad on the 850s. But I don't think the 750 cams had as high a failure rate as the 850s.

You can get slow gradual of cam wear without too much metal showing up in the oil, or it can be so fine that it won't stand out. It can take a long time and be spread out over several oil changes. But if something wears out in a hurry or if the hard surface of the cam comes off in one oil change then you're going to see it if you look for it.
 
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jseng1 said:
Thats one of the worst 750 cams I've ever seen.

Not every 850 has bad cams. Notice that its usually just one lobe that goes bad on the 850s. But I don't think the 750 cams had as high a failure rate as the 850s.

You can get slow gradual of cam wear without too much metal showing up in the oil, or it can be so fine that it won't stand out. It can take a long time and be spread out over several oil changes. But if something wears out in a hurry or if the hard surface of the cam comes off in one oil change then you're going to see it if you look for it.
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There was nothing on the magnetic sump plug to indicate any problems so I think the wear was quite gradual. I do around a thousand miles a year, sometimes less, and change oil annually or sometimes biannually. The performance of the bike seemed OK too.

I only found out that the cam was worn because I bought an Alton electric starter kit and split the cases to correct a problem with the threads of the inner primary chain case joint. Quite depressing when I lifted the barrel and saw the state of the cam.

Ian
 
Nortoniggy said:
There was nothing on the magnetic sump plug to indicate any problems so I think the wear was quite gradual. I do around a thousand miles a year, sometimes less, and change oil annually or sometimes biannually. The performance of the bike seemed OK

Ian
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Your 1K mileage a year could be the cause, as the most wear occurs on start up from cold and lying stationary for a long time. To counteract this, you could remove the exhaust rocker cover and squirt engine oil into the engine before start up, or drill and fit an elbow breather to that cover and squirt oil down the tube before waking your bike from a long lay off.
BTY does your crankcases have the U sides on the camshaft, that help retain oil to the cam?
 
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I doubt the low mileage is the cause. I rarely drain the sump before starting so there would be a lot of oil splashed on to the cam as soon as I turn the engine over. More than you'd get by dropping some down the pushrod tubes. I start the bike and get going, rather than letting it run at low speed while cold.

I have the normal 750 combat type crankcases so, as far as I know, there isn't anywhere for much oil to sit.
 
Currently these are the most reliable cams I know of. The Web cam at top has hard welded lobes (58 HRC hardness) but you have to start with a used cam core. The two lower cams are new EN40B billet steel cams by Newman that have the extra expense of being plasma nitrided. The plasma nitriding comes out harder (60HRC) than the regular nitriding (58 HRC). Plasma nitrided cams have to be special ordered in batches. The bottom cam is for Atlas/Domni.

Reliable camshafts
 
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MexicoMike said:
"Luck of the draw I guess ..."

Or all based on improper cam break-in... ;)
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In regard to proper camshaft breaking procedure I copied these instructions from a camshaft manufacturer's web site (Kelford Cams). All the other cam manufacturers that I checked give similar instructions.

"Start the engine and immediately bring to 2,500 rpm. Timing should be adjusted, as closely as possible, to reduce excessive heat or load during break-in. Get the engine running fairly smoothly and vary the engine speed from 1500-3000 RPM in a slow acceleration/deceleration cycle. During this time, be sure to check for any leaks and check out any unusual noises. If something doesn't sound right, shut the engine off and check out the source of the noise. Upon restart, resume the high idle speed cycling. Continue the varying "break-in" speed for 20 - 30 minutes. This is necessary to provide proper lifter rotation to properly mate each lifter to its lobe. Should the engine need to be shut down for any reason, upon re-start it should be immediately brought back to 3000 rpm and the break-in continued for a total run time of 20 - 30 minutes."

From what I understand the first half an hour or so is critical for a camshaft and if it doesn't get broken in properly it will be subject to early failure. I wonder how many people have carried out this sort of run in on their new Norton cam? I must say I wasn't aware of this requirement until a few years ago. It's certainly part of my routine now.
 
bsaboss said:
From what I understand the first half an hour or so is critical for a camshaft and if it doesn't get broken in properly it will be subject to early failure. I wonder how many people have carried out this sort of run in on their new Norton cam? I must say I wasn't aware of this requirement until a few years ago. It's certainly part of my routine now.
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Do you think Norton did that? Does any OEM?
 
maylar said:
Do you think Norton did that? Does any OEM?
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I've no idea what Norton did. All I'm saying is that cam manufacturers certainly recommend running in as described - check their websites. To me it's a pretty simple thing to do and if it means the cam has the best chance of lasting then it seems like cheap (i.e. free) insurance.
 
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