Cb350 twin Exhaust Valve hitting piston
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Cb350 twin Exhaust Valve hitting piston

This is a discussion on Cb350 twin Exhaust Valve hitting piston within the Technical forums, part of the Caferacer.net Forums category; My 1971K3 motor is being rebuilt and I had it all together and it will not rotate a full 720 crank deg. I can rotate ...

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  1. #1
    Member patritag's Avatar
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    Cb350 twin Exhaust Valve hitting piston

    My 1971K3 motor is being rebuilt and I had it all together and it will not rotate a full 720 crank deg. I can rotate it ccw until the
    right exhaust valve opens an almost R top and I can rotate it cw until the left exhust vavle opens and almost left top.

    The pistons are in correctly the arrow is pointing tward the exhaust valves or what honda call up.

    I did have the head resurfaced and I don't know what they took off.

    I suspect it is the resurfacing.

    The timing looked right, same cam but different stock rockers (1972), the rockers were set at there loosest sertting. HELP

  2. #2
    Senior Member roccitycafe's Avatar
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    the valve clearance on that engine was pretty wide, there's no way skimming the head will cause contact unless they took off an eighth or something. also, it sounds like you're trying to run a stock sprocket on the cam and a skimmed head? I'm assuming you know you'll need to slot it so you can redegree the cam properly to make up for the difference in timing now? also, you need to check the rockers against what came out of the engine, I think the 71 and 72 were exactly the same, but I know the type 1 and others were different, so that's possible, but it's likely you have the cam installed improperly

  3. #3
    Senior Member roccitycafe's Avatar
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    the valve clearance on that engine was pretty wide, there's no way skimming the head will cause contact unless they took off an eighth or something. also, it sounds like you're trying to run a stock sprocket on the cam and a skimmed head? I'm assuming you know you'll need to slot it so you can redegree the cam properly to make up for the difference in timing now? also, you need to check the rockers against what came out of the engine, I think the 71 and 72 were exactly the same, but I know the type 1 and others were different, so that's possible, but it's likely you have the cam installed improperly

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  5. #4
    Member patritag's Avatar
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    THANK YOU FOR THE RESPONCE, I WILL CHECK EVERY THING AGAIN.

    YOU TALK ABOUT SLOTING, WHAT AND HOW AND WHY AGAIN, I AM NEW AT
    THE 350?

  6. #5
    Member patritag's Avatar
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    THANK YOU FOR THE RESPONCE, I WILL CHECK EVERY THING AGAIN.

    YOU TALK ABOUT SLOTING, WHAT AND HOW AND WHY AGAIN, I AM NEW AT
    THE 350?

  7. #6
    Senior Member TheGreg's Avatar
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    its the key right next to 'A'. i believe thats the one that you are looking for.
    ask me about my ADD or pie or my cat. a dog. i have a bike. Do you like TV? i saw a rock. hi.

  8. #7
    Senior Member TheGreg's Avatar
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    its the key right next to 'A'. i believe thats the one that you are looking for.
    ask me about my ADD or pie or my cat. a dog. i have a bike. Do you like TV? i saw a rock. hi.

  9. #8
    Senior Member kerosene's Avatar
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    as the head moves downward (skimmed) it will introduce slack in the cam chain. Tensioner can take this away but it doesn't tighten the chain on both sides thus the cam rotates slightly. Slotting means filing or otherwise modifying the bolt holes wider on the cam sprocket so that it can be slightly adjusted.

    something like that.
    -

  10. #9
    Senior Member kerosene's Avatar
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    as the head moves downward (skimmed) it will introduce slack in the cam chain. Tensioner can take this away but it doesn't tighten the chain on both sides thus the cam rotates slightly. Slotting means filing or otherwise modifying the bolt holes wider on the cam sprocket so that it can be slightly adjusted.

    something like that.
    -

  11. #10
    Member patritag's Avatar
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    Thanks I now understand

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