Broken Cam Roller Tip

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Joe Joseph

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Sep 3, 2024, 3:22:57 PMSep 3
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I rode my Super Alice for about an hour when, as you would expect, about half a mile from home, it stopped. A teardown showed that the exhaust cam follower tip broke off at the point where the pushrod sits in the pressed in cup. 

Has anyone had a similar problem? Was it bad exhaust clearances in my part or just metal fatigue. I had checked clearances before the ride but maybe they tightened up with heat? 

Joe

IMG_8759.jpg

Jerome Kimberlin

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Sep 3, 2024, 3:34:26 PMSep 3
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Hi Joe,

I haven't seen that before.  You probably should just make a new one from 4140 or ground flat stock.  If you don't want to program it on your CNC, it will weld but these things are forged steel so might not be as strong as a new one.  Wonder why it broke but I guess the appearance of the break shows it.

Cheers,

JerryK

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RICHARD YAMANE

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Sep 3, 2024, 4:07:33 PMSep 3
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Just an amateur's educated guess but I'd say it was probably a stress riser coming from some rough machining combined with metal fatigue. Before any mechanical stress from a tight valve would happen, the engine will lose compression and run badly, backfiring through whichever valve is tight. It may also become hard or impossible to hot start.
If running a hot cam the increased lift angles will add stress to the part.

Rick Yamane
Importer of Vape/Powerdynamo ignition systems and Polisher of bikes at Motion Pro

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Joe Joseph

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Sep 3, 2024, 4:08:25 PMSep 3
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Jerry

Far be it from me to dare to question Carlo Guzzi’s design skills but it does look like a rather sharp corner where the loaded tip meets the down flank of the follower. The tip overhangs the sides that flank the roller quite a bit. 

I have an IMOC this Saturday and I might just weld it up  while I wait to order a new one, assuming that is, I can find one. Rather than weld just the tip I might cut it back at the dotted line and machine a new part with a greater cross section for welding. 

Joe




Joe Joseph

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Sep 3, 2024, 4:15:00 PMSep 3
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Rick

Good point! I didn’t notice any backfiring or loss of power. In fact, I was twisting around on the bike to pat myself on the back as the thing was running really strongly. I noticed a shiny section on the bottom of the tip which looked like something had impacted the tip at some point. Since there’s nothing inside the timing chest that could have hit it this must have happened outside the engine. That must have caused some internal stress leading to the break. 

Do you know if these parts are available? While I can make this, I have a long list of other projects that are not available off-the-shelf that I have to complete. 

Joe

RICHARD YAMANE

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Sep 3, 2024, 5:38:29 PMSep 3
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I don't know if these are available or not but as was recommended to me, I would check with Guzzi Retro. I think they'll have the parts books online so you can look it up yourself and order by part number.

Rick Yamane
Importer of Vape/Powerdynamo ignition systems and Polisher of bikes at Motion Pro

Joe Joseph

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Sep 4, 2024, 10:45:43 AMSep 4
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I’ve got Patrick’s manual and the parts catalog. I’ve emailed them - fingers crossed. It’s been a while but I’m assuming Stucchi has closed shop?

Joe

Gordon de la Mare

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Sep 4, 2024, 12:21:20 PMSep 4
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my personal advice based on experience is thaf Stucchi moved from Mandello and they say accept an order but nothing ever shows up.
I will not deal with them again.


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