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Post by jerseyboy on Jan 2, 2015 23:38:26 GMT -5
What is this for,,I don't see it on all rocker assemblies,,is it for some sort of pollution control or what?  |
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Post by JerryScript on Jan 3, 2015 0:06:08 GMT -5
I believe it's a kickback arrestor, though I'm not sure that's the exact name. It prevents the engine from turning over in reverse in case of an improper firing of the plug (can happen during low voltages at startup). I've also read about, but haven't seen, a decompressor. It releases one of the valves to prevent kickback, or to help during starting. I'm pretty sure alleyoop knows more about them. |
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Post by JoeyBee on Jan 3, 2015 1:06:34 GMT -5
I believe that is called the camshaft stopper plate.
If you have one of these you can not rotate the engine counter-clockwise when adjusting valves. If you do, even the slightest, the clearances will be off.
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Post by jerseyboy on Jan 3, 2015 11:37:24 GMT -5
It has a small tit that rides on the camshaft and is designed to go in one direction only,,man Im surprised the little tit hasn't busted off the way this thing has kicked back..when I take mine apart next week I will take a closer look..the motor still kicks back once in a while..was just curious,,thought it was some sort of EGR related part.I dont think its a great design to have something drop into the cam and try and stop kickback.
Guess if my new A10 cam doesn't have a little hole or channel for this device to lock into I will just grind the tit off and use this rocker assembly..no worries
Thanks guys!!
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Post by dyoung1167 on Jan 3, 2015 13:39:58 GMT -5
i've heard different things about these such as keeping it from running backwards, which makes zero sense, but maybe for kickback, though not to stop it, just to keep from slamming the carb and with high pressure air when it happens. heard horror stories about turning the engine back even a little (for maintenance purposes such getting TDC) as mentioned above and it is very hard to disengage bla-bla but never once has it given me a single problem when adjusting my valves and i have to turn it back some almost every time. whatever it does i think it needs high speed and turning the engine by hand doesn't count. i have looked right at it while doing this and it has never moved or affected my rocker arms.
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Post by jerseyboy on Jan 3, 2015 14:19:01 GMT -5
It depends on how many channels there are in the cam for how often it will catch when spinning backwards,,if there is only one spot for it to catch then you can spin the motor backwards some depending on where the channel is according to the tit.But if there are many channels then it will sort of act like a ratchet and you wont be able to turn the motor as much before it catches...hmmm..well anyways thanks for the replies,,now I know what the heck its there for,,IMO another poor design of wasted engineering.
As for ACR or automatic compression release on these small motors,,Ive seen where they have a slight high spot on cam that hits the tappet where the exhaust valve will be held open a crack just at low RPM to help start the engine,,once the motor gets over 300 or so RPM's the valve will not even notice the high spot and run normal,,not sure exactly how it works (centrifugal force maybe cancels it out my guess) but the high spot must be in a different spot from the exhaust lobe..and if the valves are too loose the ACR wont even work..I have this on my 14hp Kawasaki FC-420V mower motor.The GY6 has so much compression that an ACR might not be practical.
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Post by alleyoop on Jan 3, 2015 15:00:40 GMT -5
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Post by JerryScript on Jan 3, 2015 15:04:49 GMT -5
Thanks alleyoop, camstopper, couldn't remember the name! |
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Post by jerseyboy on Jan 3, 2015 15:13:40 GMT -5
Ohh..thanks Alley!,,there is only one spot that it hits,,that's why you can move the motor backwards some once in a while..I still don't like the idea behind it...I think the motor would be better off just spinning back wards than the valvetran getting slam hammered..I don't think its actually possible for a 4 stroke to run backwards..I've seen small 2 strokes run backwards,,they don't run as good as they do forwards but I've seen it on my model airplane.
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Post by alleyoop on Jan 3, 2015 15:30:59 GMT -5
4 strokes will run backwards but no power happens on some of the old hotrods.
Alleyoop
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Post by dyoung1167 on Jan 3, 2015 15:40:09 GMT -5
i hadn't noticed that before but then it wasn't in my thoughts when in there. that said i just went played with an old one of mine. trying to say this right so bare with me
the piece on the rockers he pointed to is what the piece you pointed out sits against during normal rotation and otherwise doesn't move (it's stationary and the cam turns freely in it). it (your part on the cam) IS one way like a good open face reel, meaning when i turn the cam backwards it goes with it and doesn't slip BUT, as it comes around full circle the stopper on the rocker assembly is spring loaded (in the reverse direction) and allows it to go right on by, so in essence, there still seems to be nothing it's actually doing. Again, maybe it's a high speed thing that i can't duplicate with just my hands turning it, but as it sits it in no way affects anything.
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Post by jerseyboy on Jan 3, 2015 17:14:12 GMT -5
Well the tit is rounded off on the forward spinning side,,its squared off/FLAT on the back side,,so when the motor is running forward the rounded side of the tit slips past/OVER the square extruding piece on cam,,when going backwards it will lock right into place,,just like a ratchet...or fishing reel like mentioned...Im seeing it now,,thanks guys!!
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Post by dyoung1167 on Jan 3, 2015 17:27:37 GMT -5
Well the tit is rounded off on the forward spinning side,,its squared off/FLAT on the back side,,so when the motor is running forward the rounded side of the tit slips past/OVER the square extruding piece on cam,,when going backwards it will lock right into place,,just like a ratchet...or fishing reel like mentioned...Im seeing it now,,thanks guys!! the opposite. in forward the part on the cam stands still due to the part on the rocker assembly and the cam spins freely. in reverse it spins WITH the cam but the part on the rockers is springloaded in the same direction and just lets it go right on around, nothing stops the cam from going in either direction. going to video it. |
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Post by jerseyboy on Jan 3, 2015 18:54:54 GMT -5
Perfect,,thanks!
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..BAD TO THE BONE..