Rocker Adjuster - what is correct length ?

Previously Tony Ripley wrote:

Previously mike_haworth wrote:

Bike is 1959 Dominator '99' - history largely a mystery ! I found it impossible to set valve clearances directly due to poor condition of adjusters and lock nuts. The replacements at 13/16" in length, supplied by RGM, are too short. The ones currently on the bike are 1 & 1/16" long - 1/4" longer.

Does this mean RGM have supplied the wrong ones or does it mean I have shorter valves or a non standard head fitted ? Are there any other Norton twins that have the longer adjusters fitted ? Would they fit mine ?

Mike

Hi Mike,

According to my information, the part numer T2074 is 1.031 inches long. (total length)

This is used on 88 and 99 at least.

Tony

Hi Tony,

The ones sold to me by RGM are 7/8" long, but they are the Allen Key type so can fit flush with rocker arm. Even if I put the lock nut on the underside they are still too short !

Mike

Previously philip_hannam wrote:

Please post some photos of the bits and pieces. Cylinder head. rocker arms and adjusters. Plus.....if possible measure the length of each pushrod and checkout the camshaft lobes. problems with either of these will affect valve clearances.

Have you got an extra thick cylinder head gasket or compression lowing packer between the barrel and crankcase?

Attachment may help with checking the pushrod sizes.

Philip, It may come to a full strip down but, as of now, it's still fully assembled, so I am unable to photograph or measure the various components. As I purchased this bike for a lot of money as a fully sorted riders bike I will be extremely upset if this problem is due to excessive wear on critical parts. It certainly went well prior to my tappet investigation. I am also surprised that it has fitted none standard tappet adjusters. I wonder where these came from ? Many thanks for the attachment. I guess it's going to prove to be very useful !

Mike

Previously robert_tuck wrote:

Seems most likely that the wrong pushrods are fitted.I have the same problem with a Rudge. Could also be earlier cam followers?.Whatever is the cause its also very likely to ruin the valve guides if not sorted. In the past I have paid good money for pretty restorations that have been total mechanical cock ups.If you want to get into old bikes buy a cheap complete tatty runner and do it yourself. Earn the right.

Robert, I do also have a tatty one (1959 Model 50) which I am gradually restoring. I bought the Dommi ( a bike highly recommended by Paul Miles of Classic Rider notoriety) to have something to ride in the meantime. It was put together by someone he knew well and whose engineering prowess he respected. I am not saying this means everything is perfect and I have no records of how much use, and what kind of use, this bike has had since the rebuild. Thanks for your comments. I take it all on board.

Mike

Previously ian_cordes wrote:

There are 3 different rocker adjusters. i think you will find the standards ones are longer than the ones you have, which are meant to be lightweight; check out RGM website. There are also the mushroom-headed ones, but I believe the standard adjusters are the ones you need. In addition, you can add lash caps to the top of the valve stems, which in effect increases their length by 0.040", or 1 mm. These can be added without any stripdown.

As for whether RGM sent you the wrong ones, it depends what you ordered.

Ian

Ian, thanks for responding. I have been corresponding with RGM and I always stress the year and model of the bike when ordering parts, in the hope that they know which parts are correct for the machine in question. This said, a 60 year old bike may have been through all sorts of repairs and rebuilds and of course things may have been changed. As things stand I have fitted the new allen key style adjusters with the locknut on the underside of the rocker arm. Each of the four new adjusters protudes a different amount above the rocker arm. Is this OK ? Is it OK to fit adjusters in this way or does it herald problems down the road ? Compression is good and the bike starts and runs well, and a lot more quietly.

What are lash caps and what is the benefit to be had from fitting them ?

Mike

Previously ian_cordes wrote:

Mike. I think you need as a starting point to use the correct length adjusters; the standard ones. It sounds as though you 'phoned your order through to RGM. It may be best if you go on their website in order to see exactly what is available, and order accordingly. The lightweight ones you have are shorter than standard. What is wrong with the adjusters that were fitted when you bought the bike? You mentioned poor condition of the nuts, but you now have new ones, which could perhaps be used on the old adjusters? If not, buy a new set, 067546 is the RGM part number.

You appear to have been able to obtain correct adjustment, by fitting the locknuts underneath?

Two things about the adjusters protruding at different lengths above the rockers arms. I would say this is not uncommon, given that valves have been lapped in over the years, maybe some receding more into the head than others. As an aside, this, from a rocker clearance point of view, would work in your favour in this situation, allowing more of the valve stem to protrude above the guide. Also, having measured various pushrods, I have found quite a variance in length of those supposedly the same part number. This does not help!

Robert is right; with the correct adjusters fitted and clearances set, you need to check the sweep of the adjuster tip over the valve stem as it opens, in order to check the geometry. The sweep of the adjuster tip should start and finish at equal distance from the centre line of the valve stem. If it does not, then the length of the pushrods is incorrect for the valve/cam/follower set-up which you have. The lash caps may well solve the issue, without resorting to an engine strip. They are hardened steel inverted buckets which simply drop over the top of the valve stem, in effect adding 0.040" to the length of the valve. This can make a big difference, whilst also preventing wear of the top of the valve stems. As Robert said, without the correct geometry, rapid valve guide wear can result.

Ian

Ian, thank you for this most comprehensive reply. It gives me plenty to think about. I will take the head off and check everything in the way you've suggested.

Mike