Question on ST1100 cams and the dual gear setup

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I've never seen cams in any other bike that used this spring mechanism, the drive sprocket was always bolted directly to the cam. Never paid close enough attention when R&Ring the ST cams to even give this a thought. I know Honda engineers are considered god-like on this forum, but this seems like over-complication for very little benefit. <Stepping into flame-retardant suit>
It's what separates the engineers at Honda from those at say . . . . ummm . . . . Harley Davidson? :)
 

ST1100Y

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The pins in the spring mechanism broke, both of them. Catastrophic failure.
Ouch! Debris flying around in the valve train could have indeed been lethal...

It's what separates the engineers at Honda from those at say . . . . ummm . . . . Harley Davidson? :)
:crackup...almost blew the morning coffee through my nose onto the keyboard on this one... :clap2:
 

wjbertrand

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I've never seen cams in any other bike that used this spring mechanism, the drive sprocket was always bolted directly to the cam. Never paid close enough attention when R&Ring the ST cams to even give this a thought. I know Honda engineers are considered god-like on this forum, but this seems like over-complication for very little benefit. <Stepping into flame-retardant suit>
The term "sprocket" implies a chain driven vs. gear driven cam. Chains are inherently quieter so no such noise abatement technology is needed. Note that the ST1300 uses a timing chain and has simple bolted-on sprockets as you describe. The way that the heads protrude on both sides, would probably have made the gear noise quite apparent without the split gear. No doubt Honda found this unacceptable toward their design objectives of refinement and quiet running. Honda employs the same technology for the alternator drive with the twin split, spring loaded driven gear. Even with all of that, the ST1100 motor is still somewhat infamous for its Jetson's mobile whine.

I think what must have happened is when the cam was reinstalled the spit gears were incorrectly meshed with the drive gear forcing them in the wrong direction breaking the spring load mechanism. In millions of miles of ST1100 experience has there ever been another instance of this failure? If so I would bet it was due to improper assembly and not a random failure.
 
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yeah, agree with you on this being a rare event. That brings up the question, is there anything special you have to watch out for while re-installing the cams to make sure you don't break it? I guess I'll mark the teeth next time and look out for any movement between the two gears.

The OP wasn't doing the job for the first time, so he knew what he was doing. And he noticed that the two gears had moved by a tooth when he dropped the cam back in, so I assume that happened when the cam was out of the engine, but can't say for sure.
 
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Slydynbye

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yeah, agree with you on this being a rare event. That brings up the question, is there anything special you have to watch out for while re-installing the cams to make sure you don't break it? I guess I'll mark the teeth next time and look out for any movement between the two gears.

The OP wasn't doing the job for the first time, so he knew what he was doing. And he noticed that the two gears had moved by a tooth when he dropped the cam back in, so I assume that happened when the cam was out of the engine, but can't say for sure.
Ditto, I for one have been wondering what I did wrong when I dropped my Cams back in wrong causing DAMAGE when started.
My guess was that I had misaligned the 2 Cam gears out of phase as described. Just a different point of failure.

So, what is the proper technique for alignment when re-installing Cams after a Valve adjustment or when installing a Cam with one that hasn't been marked?
 

ST1100Y

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Methinks loss of tension/wear down over mileage/years makes it possible at some point to mesh them wrongly...
 
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So I guess what Jeff is saying is if you don't have both of the driven gears teeth aligned, then when you tighten the cam down one of the teeth from the driven gear may force the two driven gears in opposite directions, and the rotation breaks the little pins in the spring mechanism. I guess the lesson learned is to make sure both sets of driven teeth are perfectly aligned before putting the cam back in.

I'm curious to hear back from the OP on the tooth alignment before and after tightening the cam down. If I understood his comment, the driven gears teeth had already moved by a full tooth relative to one another before anything was tightened. If that's the case then it seems possible that the spring mechanism was already broken prior to any tightening forces being applied.

Or, there's sufficient force involved just by seating the cam back in place by hand to force the two driven gears in opposite directions if things aren't aligned properly, which seems a little hard to believe given the small forces. Those little pins have to be tougher than that.
 
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wjbertrand

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Since the ST1100 has an external belt to drive the cam drive gear, I don't think the condition of the belt would have anything to do with the mesh of the gears. I don't recall having to do anything special when installing the cams. The split gear's teeth are not splayed far enough that they would drop into separate “valleys†in the drive gear. I never had to force them into alignment first, they would/should align naturally as the holders are seated. I suppose if the spilt gear was already a full tooth off when removed, it'd be possible for corresponding teeth on each gear to drop into separate valleys of the drive gear. Maybe these springs and stops are easily damaged if accidentally turned the wrong direction?


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Sorry for the delay in responding but I was away on business travel and also wanted to wait to respond until I had the new/used cam in my hands and had some quality time in the garage to install it, that was this past weekend.

Summary: I can find no causation for the failure of this cam.

Details: It is true that I have had ST1100 cams out and in many times before, but still I looked and tried to see if it was possible to incorrectly mesh the gears so as to split the tooth gears forcing the spring action in the wrong direction, I could not. To mesh the gears incorrectly (not out of time, but splitting the teeth) seems impossible, it would take a considerable force to push the cam down into its fully seated position that I'm betting you would first strip a bolt or crack a cam cap/holder.

I believe the cam failed and the teeth moved sometime after removal (or as it was removed). I should have noticed how upon re-installation of the cam (before noticing my marks were off) that the cam dropped right into place because the two cam gears were in alignment, it took no pressure to seat the cam.

I have seen brand new parts fail, I have also seen parts with 100k miles on them fail. It happens, QC check fails, improper heat-treating, parts built on Friday afternoon, etc.

Mom always said I was one in a million. Thanks for all who chimed in. Bike is up and purring again, new timing belt - check, clutch pack and springs measured - check, rebuilt clutch slave cylinder - check.

-mtnpat
 
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I believe the cam failed and the teeth moved sometime after removal (or as it was removed). I should have noticed how upon re-installation of the cam (before noticing my marks were off) that the cam dropped right into place because the two cam gears were in alignment, it took no pressure to seat the cam.
I'm guessing its possible that the small pins failed a long time ago and you couldn't tell until you removed the cam and the spring loaded mechanism moved. Since the gears are meshed while the cam is installed, the two gears aren't going to move relative to each other with everything bolted down. Then when you removed the cam the spring pressure caused the two gears to shift by a tooth, which your markings confirmed.
 
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Just another thought... not all of the 12 camshaft holder bolts are 45mm, 4 of them are 40mm.

FWIW, whenever I've had my cams out for shim adjustment I've marked the gears so they went back on exactly as they were when pulled.
The 4 x 40mm ones fit the camshaft holder inner holes and the 45mm for the gear end cap and 45mm for camshaft holder outer boltholes
 
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