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VFR750 VFR750 is offline
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Join Date: Mar 2004
Location: Windsor, CT
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How to Avoid Common Cam Timing Problem

I suspect we have all done this: Timed the cams "properly" and then found the right hand side WAY out of adjustment. And hopefully you found it before you ran it, or otherwise avoided bending the exhaust valves.

The problem is caused by letting the idler arm drop when you remove the clamp or mechanical tensioner for the hydraulic tensioner.

I PROVED that just be letting the idler arm drop, the chain WILL drop off the lower edge of the intermediate shaft sprocket, and you will UNWITTINGLY rotate the crankshaft a "small" amount to get the tensioner on. This is the dreaded cam timing jump happening. BTDT.

You pulled the tensioner and let this happen:


You are now officially screwed.

Because you see the idler can't quite move up enough to get the tensioner in:


So then you rotate the crankshaft to "free the chain"



The cam did not move, but now the crankshaft is off exactly one chain pitch. Or about 20 degrees (!) retarded. Which means your exhaust valves are REALLY open as the piston is coming up. Carnage is likely, unless like me, you had deep pockets in the pistons. "Deep Pocket$" can only help so much.

Use Tie Wraps after you have set the timing correctly:


Now you can safely remove the mechanical adjuster and install the pinned hydraulic tensioner:


Pull the pin


Now you can cut the tie wrap


Left hand side is not as critical because the loose chain lays over the top of the intermediate shaft sprocket. The tie wrap just makes sure the chain always stays in place between the cam sprocket and intermediate shaft sprocket.
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Mike

'82 911SC, SSI, 22/29 tbars, 22F/22R Adj swaybars, Bilstein Sport, Elephant polybronze & monoballs, Cambermeister bar, turbo tierods, Carrera oil cooler, front brake cooling ducts, Sparco Sprint 5 & Recaro SRD PAX seat, Teamtech harness, DAS Sport rollbar.
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