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Old 04-19-2015, 11:07 PM   #1
dalla OP
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Rocker end play issues

Hi all

I have a big problem with my R90/6. My left side cylinder had quite a lot of valve pinging noise. I found excessive endplay on both inlet and exhaust rockers.
The bike has been standing for 1 year so i don't remember how it used to be. But i adjusted the endplay according to guides here one the ADVrider, and started it up. Now the noise was gone, but after 10-20 miles i developed again. Took it appart again, and found that the bolts holding the rocker shaft supports were sligthly touching the rocker arms. Can this cause the endplay to become loose? It is also fitted with 2x14mm bolts, which i belive is of the old type? The other 2 is 15mm. The 14mm looks like this:



Can this cause the endplay to develop again after a short ride?

As mentioned both the 15mm and the 14 mm bolts were sligthly touching the rocker arms, i have machined these a little down so it is no longer touching. Then i took the bike for a ride again, and the problem came right back.

Any ideas would be appreciated. Thanking in advance.

Dennis
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Old 04-19-2015, 11:17 PM   #2
ME 109
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There should be no need to machine anything. Something is very wrong if that's the case.
More pics of the rocker ends etc?
I'm not sure what you're holding, but it's ugly.
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Old 04-19-2015, 11:31 PM   #3
disston
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Are you saying the nuts on top of the rockers are loose? So you tighten them but they become loose again?

Sounds like the cylinder stud threads are pulling out in the engine block.

There were a number of changes in parts used during the /6 years. Check this page on Anton's site;
http://largiader.com/tech/rockers/
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Old 04-20-2015, 12:33 AM   #4
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No the nuts are not loose. But somehow the rocker posts are shifting/moving. It is a night mare tighting them too, as if not very careful, the rocker arm will start binding. I am sure that it isn't pulling out the cylinder studs. I think it is a combination of old worn nuts and posts that might not be square. Just wondering if anyone else have experienced this?

I have just ordered new one piece posts from motoren israel, with new shafts, bearings and nuts. Hopefully that will do the trick.

I am wondering though if it is using the wrong type rocker arms. As the round edge protudes over the top of the post, and therefor it can touch the nut very sligthly.
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Old 04-20-2015, 12:55 AM   #5
disston
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The early rocker shafts used a 14mm nut. I think this was one year or even just a part year thing. Then they all got 15mm nts. The 14mm nuts fit a smaller end shaft. The 14mm nuts are NLA. So when you try to use the 15mm nuts they hit the rocker and restrict the rotation. You can grind a bevel on the end of the rocker where it hits the 15mm nuts or you can switch to a later set up that has thicker end blocks.
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Old 04-20-2015, 01:12 AM   #6
Bill Harris
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That is what I would say the problem is, too-- 15mm nuts used on older rockers/rocker blocks. Grind a bevel on either the rocker arm or the face of the nut that so the nut does not contact the rocker arm.

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Old 04-20-2015, 01:36 AM   #7
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Thanks guys. I am pretty sure that this is the problem too. We machined the nuts sligthly yesterday, but i don't think that we got enough. So that is probably the problem. But now i bit the bullet and bought the Motoren Israel posts, and this should be a thing of the past.
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Old 04-20-2015, 01:42 AM   #8
disston
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What year is this bike? There were a lot of changes all years of the /6.
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Old 04-20-2015, 01:54 AM   #9
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Quote:
Originally Posted by disston View Post
What year is this bike? There were a lot of changes all years of the /6.
I should learn to stay out of the old bike questions seeing I have a '81
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Old 04-20-2015, 02:12 AM   #10
dalla OP
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It is a pre 9.1975 engine. But it is really a bitsa bike. The frame is a /5.
However it uses the old design rockers, with square posts but still with needle bearings.
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