Skip to main content
000000 000003 000006 000009 000012 000015 000018 000021 000024 000027 000030 000033 000036 000039 000042 000045 000048 000051 000054 000057 000060 000063 000066 000069 000072 000075 000078 000081 000084 000087 000090 000093 000096 000099 000102 000105 000108 000111 000114 000117 000120 000123 000126 000129 000132 000135 000138 000141 000144 000147 000150 000153 000156 000159 000162 000165 000168 000171 000174 000177 000180 000183 000186 000189 000192 000195 000198 000201 000204 000207 000210 000213 000216 000219 000222 000225 000228 000231 000234 000237 000240 000243 000246 000249 000252 000255 000258 000261 000264 000267 000270 000273 000276 000279 000282 000285 000288 000291 000294 000297 000300 000303 000306 000309 000312 000318 000321 000324 000327 000330 000333 000336 000339 000342 000345 000348 000351 000354 000357 000360 000363 000366 000369 000372 000375 000378 000381 000384 000387 000390 000393 000396 000399 000402 000405 000408 000411 000414 000417 000420 000423 000426 000429 000432 000435 000438 000441 000444 000447 000450 000453 000456 000459 000462 000465 000468 000471 000474 000477 000480 000483 000486 000489 000492 000495 000498 000501 000504 000507 000510 000513 000516 000519 000522 000525 000528 000531 000534 000537 000540 000543 000546 000549 000552 000555 000558 000561 000564 000567 000570 000573 000576 000579 000582 000585 000588 000591 000594 000597 000600 000603 000606 000609 000612 000615 000618 000621 000624 000627 000630 000633 000636 000639 000642 000645 000648 000651 000654 000657 000660 000663 000666 000669 000672 000675 000678 000681 000684 000687 000690 000693 000696 000699 000702 000705 000708 000711 000714 000717 000720 000723 000726 000729 000732 000735 000738 000741 000744 000747 000750 000753 000756 000759 000762 000765 000768 000771 000774 000777 000780 000783 000786 000789 000792 000795 000798 000801 000804 000807 000810 000813 000816 000819 000822 000825 000828 000831 000834 000837 000840 000843 000846 000849 000852 000855 000858 000861 000864 000867 000870 000873 000876 000879 000882 000883
English French German Italian Spanish

Valve caps

Forums

My Inter's exhaust valve head is bruised by the tappet. It has no chamfer (oddly?) and I'm going to grind one using a Dremmel before I extract it.

Do others use valve caps? Or are they too likely to escape? The top of the exhaust valve is one of the places on my Inter that has least oil, so I need to remember to grease it regularly (moly grease probably). Also...make certain the tappet tip is dead square to the rocker...

Permalink

Spreads the load, protects the stem and machinable to adjust the rock angle.  Why wouldn’t you....

 

cheers Jon

Permalink

The top does not look very pretty. I'm certainly going to replace the tappet, and assumed I should replace the valve. But if I do add caps, it will need to be a bit shorter anyway.

Attachments
Permalink

To wear that profile into the stem suggests a lack of rotation of the valve, probably due to lack of lube at the guide, a partial seizure and then a reluctance to turn.  I guess the guide is fairly worn also.  The cap solution is the way to go, there were a set of 4 on EB up to today with little interest at £12.  PS; the adjuster is not the tappet, that’s the bit that contacts the cam.... they are also replaceable should you have a wear issue there.

good luck Jon

Permalink

Thanks Jonathan.  The guide is fine - relatively new bronze.  I'd be surprised if the valves turn in service - with hairpins etc.  (after writing this I see from elsewhere that they are supposed to rotate..don't understand how - unless it's later engines?)  But I think I'll go for shortening it and adding caps.  I might even make my own - they'd better be hard (or hardened) but off the shelf sounds good.  I've just looked at the spares list - part 3046 'rocker adjusting screw' needs to be changed.  Now to work out how to cut 80 thou off the valve stem and keep it square.  I think they had caps post war - but that's a bit of hear say.

Franks lists 20thou clearance for exhaust valves.  I wonder why so much?  The impact must be huge.  There's very little to expand differently in the cam box, so the hot clearances must be similar.

Now it's worn, the rocker surface in the adjuster slides nicely in the worn surface of the stem - could have been designed that way!  I bet that's how a lot of them work - these engines are well known for flogging on well after they should be described as worn out (allegedly).  Perhaps because of the amount of oil that surrounds everything apart from the tops of the exhaust valves!

 

Permalink

Hi David,

   The reason the valve clearance is so much on the exhaust valve is because the valve material is austenitic steel which has a very high expansion rate and was originally KE965 grade. Another factor is an OHC engine is a fixed measurement as opposed to a push-rod engine where cylinder expansion affects the valve clearance. This alloy of steel valve is non-magnetic and has a high temperature stability. These were machined to give a 4 thou clearance in a 3/8th inch guide and appear loose when new. A bronze guide in a cast iron head in not the best fitment as the bronze expands quicker than the iron and distorts, this may be why the valve has not been rotating. A cast iron guide is much better as this material requires very little lubricant to work satisfactory. As a rule of thumb, cast iron head/cast iron guide, aluminium head/bronze guide. Do not use an austenitic valve on the inlet as this valve is constantly cooled by the incoming fuel. If you want to get a working clearance run the engine until spitting hot, have a set of feeler gauges ready and measure as soon as you stop the engine, minimum at this temperature should be at least 2 thou. The valves are relatively soft and can be filed by hand. Beware of modern valve material as this may have been intended for a water cooled fitment, so do some checks.

Permalink

Thanks Richard. To be honest I don't know  the guide material...I thought I could see some yellow on the inlet but exhaust is black. I'll scratch it off and check. It was built by a well known Inter expert so I hope and expect it was correct. On Doddington web site are some assembly notes, where they say valves begin to rotate at maximum revs. I doubt if this engine has been over 4500rpm. I don't know if that's relevant! Now it's apart I want it to be as good as possible, but there's no point in buying a new valve if I shall shorten it and fit a cap anyway. They don't seem to be much marketed in the UK.

I'll start a new post shortly about meshing the top bevel...

Permalink

What a wealth of knowledge we have access to. I always found the 12 /20 thou settings a bit  extreme and tend to reduce them to a noise level that sounds right after a piping hot run. But I've  not ventured down to 2 thou yet...

 They can take a lot of hammer if they are set up right, Any motor that can take the punishment of a TT will be fine on the road, we rarely if ever get to those extremes nowadays. As you believe the guide is a recent replacement is it so for the valve?  Is it a soft material replacement as Richard suggests.  Magnet test would give some indication, and get a magnifier on the   removed valve to check there is no stelite cap friction welded to the stem. 

Take off the burr with a file first.  I would say a grind would be the best way to resurface.   As its such a light touch I would use the side wall of a wheel mounted in the lathe chuck and the valve stem located in a fixture (fit sized hole in a block) mounted to your tool post would work.  Don't let the heat build up and cool quickly after dressing.  How  much to  take off  depends  on thickness of  cap and  your  Half  lift  measurement (at half lift your adjuster should be square and central to the valve stem/cap)

How many of the valve grinding machines from the repair shops have gone in the bin...  

 The caps are termed by our american cousins as "Lash Caps" should you be searching the  internet for some.

 

Go steady

 

Cheers

Jon

Permalink

While I was repairing the head on my 31 model 20 I asked Mike Pemberton if I should use iron guides again , his replay was to use colisbro guides..Reading up on these guides I see they can be used in iron or alloy head.

I used Chevy big block valves cut to size and like my Ariels I used  valve caps only because they do make sense.

 

 

Permalink

Interesting, Ian. I can't find any 3/8" ones in UK. I'm not buying from Aus...£57 postage for a start! I have read on the ever unreliable web that stainless valves must be used with bronze and not chrome stems. I don't know what kind is the one I ordered. I'm going to reassemble with the old one becauseI know it works. I'd rather go back to it later if it wears annoyingly quickly, than have a bike resting in the shed! It's a single..much easier to remove and replace the head than it is for a Norton Twin!

Permalink

Thank, Michael. USA and out of stock! The last item I bought from US had a price of $16, but cost with postage about $40, and took four months to arrive! International trade is somewhat vague it seems to me. I think it was lost for weeks in a post office in Michegan.

I've just been told a friend of a friend has one. I hope it will arrive in the post. 

I've also been told by a long time owner and racer...they all do it, so put up with it for as long as possible! I'm going to use moly grease on it from now on.

 

Permalink

Thanks Michael - no joy.  A friend tell me his friend has some...I'm hoping one will turn up in the post. Otherwise I'll just keep the tip greased with moly grease and keep on adjusting when I need to.

Permalink

Hi David / all,

   The NOC shop has a couple but they are not cheap at £35 each plus post and VAT. Paul Norman at racingnorton has a large selection of new valves at around the same price

 

Norton Owners Club Website by White-Hot Design

Privacy Policy