Rocker arms - sorry guys something to worry about

Clive said:

No Nigel I don't want Thiel's big bore kit upgrade and an SCS ECU replacement to set it up so just stop going on about it ok?

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TonyA said:

Yes , head comes off in frame .

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Clive said:

What you can see on the 'posts is indeed wear. This is what I'm trying to impress on owners - a rocker swap is easy - can be done in an hour or two with no specialised tools. Once something else gets damaged then its a whole new ball of fish. It does look a bit worse because the edge is raised. Tried to mike it up which is tricky but looks like it could be ten to twenty thou and it is not parallel with the post because of the canted rocker so what it really needs is taking out, milling and shimming which I will do.

With valve stem I'm really torn - the surface of the valve stem top almost looks as though some case hardened surface has come off but is it case hardened or could i polish it down a bit? Votes?

Anyone give me an idea of how long they would expect to take the engine out to lift the head?

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Stu Bodycote said:

Sorry, missed my name being mentioned. Shame this forum doesn't hyperlink name mentions, like Facebook. But yeah, they strip really well in frame.....its almost as though they knew they'd be in bits alot, so made it easier for the mechanic

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cliffa said:

@Stu Bodycote & @cliffa If you use the @ symbol before the user id, I think it will alert. So, a test.

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Stu Bodycote said:

New Norton were looking into this, as they approached Theil, wanting to buy a number of his kits....I assume to copy and paste. Eitherway, Theil (Thiel...I can never remember) is certainly the way to go.

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Clive said:

It is known that the rocker arm bearings can fail - bind up on the shaft - so it really is something you need to check otherwise the consequential damage can be a lot more expensive.

My 2017 Euro4 CR at 13500miles is one of the latest and best incarnations of the model and I seem to have been lucky with no major issues so I suppose I assumed that my rocker arms were probably ok. First symptom was a rattly noise which was new. I checked the timing chain tensioner and it was ok so I decided to pop the rocker cover and check the rocker adjustment like we need to do every 2 years.

I used the excellent CNW guide and it is fiddly but not difficult to do. On exposing the rocker arms I discovered that one of the inlet rockers was wobbling on the shaft. for those who have not looked at the setup the push rods come up through the head with an oil feed hole through the middle which feeds up through a hole in the rocker adjuster screw ball end which then feeds through a hole in the rocker into the centre on the bearings. The bearings are 2 plain bearings around 20mm outside 16mm inside and 10mm wide. they are pushed into either end of the rocker. The angle of push is a quite offset so the loading is not direct. The bearings at the one end had drifted into the rocker up against the bearing at the other end. This then blanks off the oil feed. The bearings had not seized onto the shaft my thought is that the irregular pressures and poor bearing fit had caused it to deform.

The canted rocker then started wearing the side of the mounting post, the roller, and damaged the end of the valve stem.

So really this should require new rockers, mounting block, valve. Big job. Expensive job. Hence this thread to recommend that you make sure this doesn't happen to you.

New new Norton don't have any rockers on the shelf and won't tell me if they have been updated. Thanks guys your support of the Norton owning community who helped you get the problems of the 961 sorted is just great. Don't blame Scott he's a great guy but hamstrung by the company's policy and will let me know price as soon as rockers are available. Just remember that when bikers see a 961 on the back of a recovery truck or hear that a friend of a friend's 961 is bust they can't tell if it's a TVS or G*rner....

Thiel motorsport in Germany do a refurb service and have a fantastic reputation for their engineering. I am waiting to see if they have spare rockers and can refurb.

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cliffa said:

Clive, do you think it's purely down to the fact that the bush moved that has caused this, or if not, what is the solution?

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DODGY DEN said:

Last year decided to check tappets on inspection the rockers were stiff on the shafts so stripped the rockers out, a couple of bushes were loose in the rockers and showing signs of blueing and dry.

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Stu Bodycote said:

Nope

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Clive said:

Took the remaining exhaust rockers out and they have the bearings rotating and loose. Nothing seized so not sure about oil pressure suggestion just think that offset pushrod action encourages them to move around plus poor original fit? Of course as soon as the bearing drifts in it blocks the oil feed. Don’t have experience of bike engine design to know if this is a common layout?

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City Garage said:

I've offered my advise based upon our experience with them so use it as you see fit. The oil pressure controls the pushrod engagement. Hydraulic tappets need oil to hold the pushrod correctly. Low or no pressure push rod is loose and with the offset rocker can cause problems. You will see chatter marks on the rollers if you use a high power Loupe. We have had multiple bikes in with similar issues but you will need to deal with the rocker holder damage.

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Clive said:

Thanks for this clear explanation it is always valuable to have the experience of seeing a trend on several bikes. I always work by the adage that if I have the problem there will several others suffering the same issue. I will mill and reshim the holders. At what sort of mileage did you see these problems and what resolution to improve oil pressure? Lash caps for the valve stems are something new to me?

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