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Discussion Starter · #1 ·
Good evening gentlemen,
I have a question on changing shins,
My mechanic, an old time Ducati and Guzzi guy, showed me last time how to measure and change shims in my bike.
The way he does it, without messing with the half rings, is to pull the cams out and release the pressure on the rockers, so it seems quite easy.
What is your opinion on that?

Thanks for reading
Stelos.
 

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Not sure if I completely understand where you're coming from with the not messing with half rings bit, but on the 4V bikes, pulling the cams is pretty much required. Even if everything measures good and you don't need to change shims (unlikely), you should still pull the cams to inspect the rocker surfaces for flaking chrome. You cannot see the area of the rocker that flakes with the cam in place.

I hardly ever pull the left side cam bearings or rocker pin covers. This only reason you'd need to is if you find a bad rocker on that side, or maybe there is evidence of oil leaking in that area and you want to replace the seal. Otherwise, no need to mess with the left side stuff IMHO.
 
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Discussion Starter · #4 ·
Good day and thank you for your comments.
Apologies for the confusion my post brought, it probably reflects the confusion in my mind.
The question should be, do I need to check-replace the half rings and how often?

Thanks again
 

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You don't need to pull the closer shim to specifically check the half rings. If the shim doesn't need to be changed, leave it. Pulling the cams will not disturb the closer shim or half rings. The spring will keep everything in place. You only need to pull the right side opening rocker pin and rocker to remove the cam.

I've never replaced a half ring. I don't believe there is a requirement to do so at a specific periodicity. If there is, I'm well beyond it! I've heard of people finding them broken, but that seems to happen more in bikes that see frequent high RPMs. I do have a couple in my shim kit just in case.
 

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The question should be, do I need to check-replace the half rings and how often?
If the clearances are OK and no shims need changing then leave it - if you change the half-rings it will likely change the clearance meaning you'll need to re-shim, otherwise when replacing a closer shim you'll need to remove the rings anyway - so check them then.

Half-rings can break (my Monster had a couple of broken rings when I got it) but they will still work if broken. The best thing is to replace the rings with MBP collets - then you'll rarely need to change the shims again as they don't (noticeably) wear.
 
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