0.125" valve clearance!!

500 miles on PW3 cam and new tappets when clatter, clatter, clatter...... stopped to check clearances and found 1/8" on LH exhaust. Closed up and tentatively fired her up again and limped home. Have drained the oil and other than a little fur on the magnetic plug there is no sign of metal in the oil. I''m guessing a stellite pad has come off a tappet so will have to pull the whole lot down. The alternative is that I've worn out a lobe in 10 hours, now I know the PW3's are supposed to be a little soft but that's a record. Since it went from OK to noisy in just a few seconds the tappet seems the culprit. Not happy :x

Unlikely to be the cam as its unlikely to wear on the base circle which is where it would have to for increased valve clearance. I wore a lobe out on a PW3 in 70 miles but thats another story.
Best

Keith1069 said:

500 miles on PW3 cam and new tappets when clatter, clatter, clatter...... stopped to check clearances and found 1/8" on LH exhaust. Closed up and tentatively fired her up again and limped home. Have drained the oil and other than a little fur on the magnetic plug there is no sign of metal in the oil. I''m guessing a stellite pad has come off a tappet so will have to pull the whole lot down. The alternative is that I've worn out a lobe in 10 hours, now I know the PW3's are supposed to be a little soft but that's a record. Since it went from OK to noisy in just a few seconds the tappet seems the culprit. Not happy :x

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Keith maybe it's not the stellite pad but one of the pushrod ends which wasn't completely seated over the pushrod.
Best of luck

For what it is worth, keeping the tip of the digital vernier out of the recessed nipple in the bottom of the upper pushrod tip measure approx. .120 to .130. That being said, I suppose the head will have to come off the varify.

How do your tappet adjusters compare to one another? As in, does the left and right equal in exposed thread etc?
Or are they really out of wack?

I can't tell you how many times I was sure they were all set after torquing only to undue it.

Head removed and no signs of damage to pushrods or valves. Barrels removed and no sign of cam or tappet wear, mercifully. So back to the head looking for a fractured rocker (they were lightened in the past), nothing, then another look at the adjuster and this is what I found, never heard of this and they were new Andover parts.........just pleased that's all it was though not so happy I had to disturb the barrels, should have looked more closely and the head could have stayed on!!

Hi Keith, lucky escape really. I always use old tappet adjusters anyway, so as they've been around a while they are proven parts!

I did have a stellite pad come off a follower once....ran for about 100 miles (race miles!) . the motor was a bit rattly, but there was no wear on the PW3 cam...I'm still using it. I think they work harden pretty quickly. Mine has done 15 seasons racing, and is still perfect. The follower did wear away once the stellite was gone, but the cam lobe was fine.

It was fortunate but a bit pi**ed I didn't look more closely. When I reset it in a layby I did it by feel. Oh well. I did notice I kept having to adjust the exhausts more than normal after new cam and tappets etc (3 x in 500m). The inlets didn't need touching but took a look at the other 'New' AN part on the RH and there is significant wear so I'm not risking that and ordered AK versions from RGM since other than the usual wear they have been OK and are still on the inlets after 28k. The only other good news is that in anticipation she would need more fuel with the PW3 I raised the needles to the top.....the chambers, pistons and valves are all very sooty with no sign of usual tan coloured exhausts. Looks safe to lower the needle a notch again.

Unlikely to be the cam as its unlikely to wear on the base circle which is where it would have to for increased valve clearance. I wore a lobe out on a PW3 in 70 miles but thats another story.

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Yep I wasn't thinking straight, obvious really and the sump plug would have looked like a 100 yr old oak if the whole lobe had worn away.
How did you 'do' the cam in 70 miles??

Keith1069 said:

The only other good news is that in anticipation she would need more fuel with the PW3 I raised the needles to the top.....the chambers, pistons and valves are all very sooty with no sign of usual tan coloured exhausts. Looks safe to lower the needle a notch again.

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Oddly enough, cams don't always need more fuel, a good one just uses it more efficiently! On my "standard bore/stroke" 750, 11:1 comp,big valve, PW3, race exhaust etc, I'm only using a 240 main, needle in middle, 105 needle jets and No4 slides (Mk2 34mm Smoothbores)

Yes it could be more efficient with the cam and I really should try and get it on a rolling road. I was playing safe but it's quite amazing how tolerant these engines are to widely varying needle range mixtures. For years it was on the lowest setting (top groove) and ran fine though I felt it was maybe a little lean and always idled better with the needle higher even though it should not have any effect there.

Keith1069 said:

How did you 'do' the cam in 70 miles??

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Well I didn't it was a me that was "done" with a dud cam. It was at the time when there was a PW3 famine and all the suppliers that sold them where waiting for a new batch. One supplier that had one wouldn't sell it to me as it was his race bike spare but when the new batch was iminent he "kindly" sold it to me so he would have one of the new improved ones as a spare when they came along. When I got it it was obvious it had been fitted to an engine and there was slight scuffing and discolouration to the black finish on one lobe. I was a bit concerned about it but convinced myself a well known dealer wouldn't have sold it to me if it hadn't been right so fitted it anyway (lesson, always trust your insticts and not anyone else). I took great care checking for coil bind etc when fitting the cam and timed it spot on and all was good with brand new lifters. Fired her up never let it run below 2000 revs to make sure it was well lubed and she ran great. About 70 miles later I was coming back from a bike meet and the bike was feeling rough and vibrating, when I was home I took the tank off and started checking bits but could not see anything obvious so thought I would check the valve clearances while I was about it. Rocker covers off kicking it over to get the valves in the right place the problem was obvious 3 valves loads of lift timing side inlet about a 1/4 of the lift. Thats when that sick feeling came over me, engine out again and full rebuild. The supplier replaced the cam but insinuated it was something I had done which was bollox as when I put the new replacement cam in everythin was thorougly checked again and nothing else was changed and I never had a problem with that one. The refacing of my new followers new gaskets etc and my time rebuilding it again and all that cast iron going round my engine was all down to me no offers of compensation there. With hindsight it was obvious that cam was either dud on one lobe (unlikely) or had been fitted and and turned over in a coil bound engine and had damaged the surface, I just wish I had refused it and insisted on another one rather than fitting it without question.
We live and learn.

Yep, trust no-one, even those experts with rave reviews in the press and elsewhere. Don't they always blame the customer, not that there aren't incompos out there but there's been 2 or 3 cases I know of in recent years where Norton specialists have done a poor job on engine builds and machining. In none of them did the customer get an apology, just a 'don't bother me' it's your fault. Not been caught like that but like you say you learn from the experience.

The only other good news is that in anticipation she would need more fuel with the PW3 I raised the needles to the top.....the chambers, pistons and valves are all very sooty with no sign of usual tan coloured exhausts. Looks safe to lower the needle a notch again.[/quote]
hi keith,every thing else being the same ie carbs,air filters,exhausts,the one thing that determines needle position or jet sizes is your comp ratio,for example 2 identical bikes other than 1 has 7to1 comp ratio the other has 11 to 1 comp ratio the higher comp motor will need smaller mains,leaner needle position