Pitting on Cam
08-21-2004, 03:01 AM
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Pitting on Cam
Been the proud owner of nine YS engines in my six years in RC. Overall, been very pleased with the engines. I have a question about cam wear, what is normal, what is not, etc.
I seem to experience what I would consider abnormal cam wear my 140's. The wear is localized on the cam lobes and looks like pitting or a grinding of sorts. The metal looks like it was gouged out. The area of damage is typically only 3mm long and maybe 2mm wide on average, centered on the width of the lobes, right where the tappets would ride. As for timing, the damage is typically on the sides of the lobes right where they start to lift/decend, but recently I found damage to the highest lift portion of one lobe. The rest of the cam lobe will look fine with little wear; example, the DZ I took apart tonight for cleaning had damage on the top of the exhaust lobe and a side of the intake lobe. The metal was dug out thru the coating on the cam in these two locations. The lifters/tappets often have no significant wear. I don't experience a noticable power drop with a cam in this condition and it generally takes 20+ gallons before I notice a problem. I've seen this occur in two 140Ls and a 140DZ.
Lubrication seems fine and everything is very wet with oil when I dissemble. I'm running Wildcat 30% heli mixed with an extra 8oz of Klotz HeliGlow lube. The only user induced damage I can think of is an occasional backfire when running up the engine shortly after starting when the engine is cold. This is rare, but it has happened twice in the last 20+ gallons.
Q: Would a back fire cause the damage I describe? Suggestions on how to avoid? Is this type of cam wear normal or expected after 20+ gallons? Etc. Thanks.
I seem to experience what I would consider abnormal cam wear my 140's. The wear is localized on the cam lobes and looks like pitting or a grinding of sorts. The metal looks like it was gouged out. The area of damage is typically only 3mm long and maybe 2mm wide on average, centered on the width of the lobes, right where the tappets would ride. As for timing, the damage is typically on the sides of the lobes right where they start to lift/decend, but recently I found damage to the highest lift portion of one lobe. The rest of the cam lobe will look fine with little wear; example, the DZ I took apart tonight for cleaning had damage on the top of the exhaust lobe and a side of the intake lobe. The metal was dug out thru the coating on the cam in these two locations. The lifters/tappets often have no significant wear. I don't experience a noticable power drop with a cam in this condition and it generally takes 20+ gallons before I notice a problem. I've seen this occur in two 140Ls and a 140DZ.
Lubrication seems fine and everything is very wet with oil when I dissemble. I'm running Wildcat 30% heli mixed with an extra 8oz of Klotz HeliGlow lube. The only user induced damage I can think of is an occasional backfire when running up the engine shortly after starting when the engine is cold. This is rare, but it has happened twice in the last 20+ gallons.
Q: Would a back fire cause the damage I describe? Suggestions on how to avoid? Is this type of cam wear normal or expected after 20+ gallons? Etc. Thanks.
08-24-2004, 12:56 PM
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RE: Pitting on Cam
The case hardening on the cam gear had worn through. I'd suggest getting it in to service as soon as possible as it will only become worse. It's nothing you did which caused this problem.
08-27-2004, 02:46 PM
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RE: Pitting on Cam
Dave, thanks for the response. I believe I bought the engine the last week of July last year so it is one month out of warranty. I really need the engine for the rest of this season as it is the only one I have that will pull my primary 2M ship, so I'll just order a new cam from Central Hobbies and replace it myself ASAP. Thanks again for the help.
