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Discussion Starter #1
hello i have an 01 scrambler 500 2x4 that im pretty sure has the worn camshaft. idles great but at about a quarter throttle spits fuel back out through the carb. the question i have is when i pull the plug it looks really light brown like its lean? if the exhaust valve wasn't opening wouldn't the plug be black like it was rich?? im pulling the camshaft today to make sure the cam is the problem. ive tried two carbs. one brand new and the bike has the identacle issue with both. valves are set at .006 on both exhaust and intake and timing is perfect. thanks for any advice.
 

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The spark plug should be a straw color if the engine is running right. With a lean condition the plug will go more toward the white and rich would be a black color on the plug.
 

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Discussion Starter #3
ok the plug is brown. would a worn exhaust lobe on the camshaft cause a lean condition or rich?
 

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Probably not - if the valve does not open fully, it will just limit engine performance as the piston struggles with high pressure trying to push the exhaust gasses out.

A worn lobe can be detected easily - first clue is the valves get loose and have to be adjusted tighter (the valves in overhead cam engines typically get tight with use and need to have the clearance adjusted to ease starting - tight valves drop compression making the engine hard to start) - a worn cam means insufficient lift during the combustion cycle - if you just visually observe the movement of the rocker arm as the valve opens and closes and compare it to the intake rocker arm movement, they should be about the same. If you have had to tighten the valves frequently, then the cam and rocker arm may need replaced. If the valves open and close approximately the same amount, then the problem is probably in the carb or fuel system related in some way.
 

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Discussion Starter #5
well i figured it out. camshaft is toast. exhaust lobe is pretty much completely gone and and the intake lobes are on their way out! crazy how it can run great one day. shut it off and fire it up the next day and its shot. time for cam and rocker arms! Good times lol
 

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Discussion Starter #6
Hey guys is there a better oil I can use to try and avoid the wear on the new camshaft. Do you guys have any tips you have tried that has helped. Thanks guys.
 

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I generally stick with the OEM lubricants for all my machines. Never had an issue.
 

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Discussion Starter #9
Well back to the drawing board. so i put the new cam in today. everything went good until i tried to start it. so much compression it would hardly turn over. i checked to make sure the compression release was set right and it was. so next i checked to make sure the valves were set right and all is good. So i took the rockers out and checked out how the compression release is working i found the problem. the ball on the camshaft for the compression release hardly comes out! I looked at the old camshaft and the ball comes out way farther then the new one when moving the release mechanism by hand. Damb ball on the new one barely clears the surface of the camshaft. anybody else had this problem? Thanks guys.
 

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Well that sucks! Did you get an OEM camshaft or aftermarket?
 

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Discussion Starter #11
it was aftermarket. I knew better too but had great reviews so i went for it. when i look at the hole where the ball sits there's still more room for it to come out. Its almost like the actuator or whatever you want to call it is too small to push the ball out all the way. i even tried the original one and its still not far enough. Sucks! oem it is i guess! should've have followed my gut.
 

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Can you send the bad one back? At least get your money back......
 

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Discussion Starter #13
yeah I'm thinking so. just a hassle. I wish i could get this one to work but im thinking not. Sucks
 
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