Valve Noises - Cover Clearance

There's been a couple of questions and videos on here with posters querying engine noises. Strangely I had a very 'tappetty' top end after a ring and barrel paint job over winter. I'd also remade my rod end head steady in aluminum and found a nut hitting the head mounted bracket. That was fixed but I still had a really bad tappet noise at 2100-3000 rpm. Running under load I noticed when I touched the LH valve cover with a gloved finger it diminished. Pulled the cover off and found the adjuster top had been touching inside the cover. These covers (repros) have been on the bike for 6-7 years. Seems I must have reversed the position when last removed as the casting is different top to bottom. See pics... may be of some use to someone

Delete Post Valve Noises

Scrub that post of mine, complete b*****ks on my part, adjuster cannot possibly touch inside cover, just plasticined the clearance.

Keith,
That valve stem looks a little battered??

Cash

That valve stem looks a little battered??

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It is but I turned it 180 deg and hoped it would be OK. Has run 400 miles and valve has not rotated so it's still on the good side. Just pulled the adjuster and it's knackered. My exhaust rockers have always had poor geometry and this one is the worst. Ordered a couple from RGM today.

Keith, a couple of RGM exhaust rockers won't do you no good (their geometry are all equal). It's probably the geometry of your valve guide and valve seat.

Looks like the valve is too deep in the head, badly worn valve seats are generaly the cause. Replace with hard seats. The standard valve seats needed alittle lead to survive. I've done the conversion on old 4 cyl Porshces, old British cars and bikes and BMW twins. There was lead in the gas when all these relics were made. Hard seats, and good exhaust valves cures the probblem.

Ken G.

My valves looked the same Keith,also recessed seats,when the head was off I shortened the valve stem back ,which removed the hardend end and put lash caps on them,they sell them for triumphs,it's only a stop gap measure as really it needs new seats,but you can also improve your geometry abit. I figured the lash cap on the end of the valve stem would be a hell of alot better than the tappet adjuster.

Looks like the valve is too deep in the head, badly worn valve seats are generaly the cause. Replace with hard seats.

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That is entirely possible but they are not as bad as they were before the head job in Jan 06. Previously the valves were so pocketted they were flush with the seat edge. It was a 'Cyl Head Shop' job (well known over here with both good and bad rep. and uses non Norton valves so it is also possible the lengths are different). They use Serdi floating cutter machines to cut the seat and strictly 'no grinding' afterwards. It seems to work as the seats are in good condition after 10k miles. Hot compression test this winter after turning the bad exh valve 180deg was 180/185lbs (with new unbedded rings).

My valves looked the same Keith,also recessed seats,when the head was off I shortened the valve stem back ,which removed the hardend end and put lash caps on them,they sell them for triumphs

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I thought about these but I need to remove the head again. Just adding a cap would make it worse. I only do about 3500 a year so it will have to last till next winter.

Check the valve length, I buy after market valves and they are alittle too long, I cut them to the proper length and cut the collet grooves in the stem. Valves too deep in the head not only mess up rocker geometery but also increse installed spring height, whitch can lead to valve float and bent valves and push rods. You can keep resurfaceing the seats, but with unleaded gas recession will continue. If it is a show bike and not run much is one thing, If you want to ride it hard seats are a must.

Ken G.

Check the valve length, I buy after market valves and they are alittle too long, I cut them to the proper length and cut the collet grooves in the stem. Valves too deep in the head not only mess up rocker geometery but also increse installed spring height, whitch can lead to valve float and bent valves and push rods. You can keep resurfaceing the seats, but with unleaded gas recession will continue. If it is a show bike and not run much is one thing, If you want to ride it hard seats are a must.

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Seats are definitely for lead free fuel (new in Jan 06). It was a big selling point for the head specialists over here when leaded finally got phased out a few years ago (long after you guys). In an annual 3500 miles the clearances don't close up and the other valves are fine even though the RH exhaust has the same poor geometry as this LH. This has no significant wear nor do the inlets. I'd agree on the valve length possibility though contact point was as bad with the previous specialists work from '97 and that used genuine Norton valves. I've concluded I have an aftermarket adjuster that has worn badly and consequently damaged the valve.

motoracer8 said:

You can keep resurfaceing the seats, but with unleaded gas recession will continue. If it is a show bike and not run much is one thing, If you want to ride it hard seats are a must.

Ken G.

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I am going to call BS on having to do a valve seat change to harder seats for unleaded fuel. I have 21.000 miles on mine from rebuild and have NO valve recession. on two others I help with maintenance it is the same way, NO trouble with valve recession and and all of these bikes are run pretty hard. sounds like a machinist wanting to empty your pocket's.

Gotta side with Bill, If you have ever touched a cutter to the valve seats on a Commando you would find them really hard. They will laugh at high speed cutting tools so bring on the carbide or a grinding attachment. Been into a number of these heads and sometimes we have to use a slightly over size valve to get the pocketing aspect dealt with, never a wear related, just duff work from the factory or someone claiming to know how to work on heads. Because they are so hard you will be using slow RPM's and high feed pressures to make a chip, if your not ready for this you can get chatter that can only be removed by more cutting. If the the machinist makes this mistake are you sure that they will admit it? Or just blame bad gas.... witch is easier? As in all things finding someone with the attitude that the object (head) is good and workable and not in need of major redesign is the hard part. A lot of horse power can be left on a table of your "head specialist" in the form of tiny meal chips, be very careful who you chose.

Commandos left the factory with hard valve seats and no change is required for unleaded fuel, Many heads had their seats replaced (with those of the same material!) unnecessarily due to the panic over the phasing out of leaded fuel a few years back.

I agree with Dave M and if you use Black Diamond valves (definitely best valve available) you are trouble-free. After 40.000km on original (recut) valveseats, resleeved (K-line)guides and new Black Diamond valves it still looks fine to me.

I am going from my own experence with a MKIII I bought new in 77, at around 40,000 miles, middle 80's lead was long gone by then, exhaust clearence would disapear in 2/3000 miles, I knew what was happening, I had been working on Porsche's for 25 years, almost all of the 4 cyl. air cooled cars needed exaust seats. I had put valve seats and guides in several motorcycle heads as we had the equipment to do it, BMW motorcycle heads from about 78 through 82 or83 were the worst, better seats cured that probblem. Valve seat recession was happening on my own machine, I replaced the seats and used standard Norton valves the machine now has 72,000 miles on it and holds it's clearence well.
I also have a 75 BMW R75/6 with 168,000 miles on it, it has its origonal valve seats, valves and guides have been replaced, the seats remain.
I worked on the head from a 76 Trident not long ago, the seats were worn some but I belive most of the wear came from worn out valve guides, the seats were saved. Many of the automotive machine shops would rather not to work on old motorcycle heads because they are bodged beyond resonable repair, or are afraid of damaging a erreplaceable part. I'm not saying all valve seats need to be replaced because you are right many do not, but I have replaced alot of valve seats over the years mostly from valve recession.
I am retired now and do not need the money, I have no axe to grind. I would rather ride than fix cylinder heads. Every now and then someone from one of the British bike clubs I belong to will bring me a head to fix, most of them have seat recession, most certinly worn valve guides. Ampco 45 guides, and good quality valves and seats generaly cures valve probblems.

Ken G.

I'd also remade my rod end head steady in aluminum and found a nut hitting the head mounted bracket. That was fixed but I still had a really bad tappet noise at 2100-3000 rpm.

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FWIW even after replacing the exh adjusters and reducing that damn tapping noise it was still there at 2000-3000 rpm. I cleared out the rocker shafts in case there was a blockage since I didn't feel there was much oil in the head and it seemed to get better. But it was still tapping away so I pulled the tank again and took a closer look at the head steady base where I'd previously clearanced it for one of the rod end nuts. Yep it was hitting here even with 3/16" clearance. Shows how much the whole engine & cradle assy can move and that's with 'good' 9000 mile old ISO's. I read Ludwig saying recently there is only 1mm of movement, well obviously not on mine!

If the photo was taken with the bike on its main stand the clearance will be taken up as soon as it's off.

Cash

Thanks Cash. Yes, that pic is on the stand but have other pics on wheels. Engine moves up about 1/4" and back 1/16". Revving at idle in the problem speed range there is a big gap......it's under load (slight or heavy) that the prob occurs. Have ground more off but not ridden yet. Just an annoying issue I had to resolve and tell the world about, bit sad I suppose!!