Author Topic: Cams without backlash  (Read 187 times)

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Guaire

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on: April 07, 2021, 12:38:23 am
I'm putting cams in my Bullet B5. I can't get them loose enough all the way around the cycle. At TDC there is some slack, some play in the cams. Then there are tight spots. The exhaust cam has no play at about 90 degrees from TDC. I have tried to loosen them up with the spindle while at TDC, but the cams go back to no play. Any thoughts how I can get the crank around without the cams going tight?
  The crank can be turned, it isn't so tight that the crank can't be turned over.
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AzCal Retred

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Reply #1 on: April 07, 2021, 01:13:33 am
Unless something bad happened to the cam spindles or drive gear in the crank or the drive shaft protruding from the flywheel, the new cam gears aren't true and round. Try a different set if you don't have a way to check them with dial gauges. Do you still have the old cams?

You could also remove the intake cam to see if that isolates the problem. If it still binds with only the exhaust cam, maybe that's the culprit. If it's a problem with the actual crankshaft or primary gear, it should get tight twice per revolution of the crank.

In the picture it looks like the exhaust cam teeth are barely engaging the primary, maybe this just the angle the picture was taken from? Some Prussian Blue is useful to check tooth engagement.
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Guaire

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Reply #2 on: April 07, 2021, 01:57:39 am
Hi AZ - These are modified RE cams. I’ll try the exhaust by itself and see if there’s a difference.
BG
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gizzo

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Reply #3 on: April 07, 2021, 06:20:19 am
It looks like the lifters are still in there. You're sure it's not the valve springs pushing on the cam lobes causing the tight spots? Yeah I know that sounds too obvious. I didn't know you could get the cams out with the rockers still in but triangle Pete says it's doable?
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ace.cafe

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Reply #4 on: April 07, 2021, 12:52:46 pm
It looks like the lifters are still in there. You're sure it's not the valve springs pushing on the cam lobes causing the tight spots? Yeah I know that sounds too obvious. I didn't know you could get the cams out with the rockers still in but triangle Pete says it's doable?

Right.
First order of business to to get the load off the cams before setting lash.

And it is possible that the cam gears are not concentric with the center. I have seen that quite a lot on iron barrel cams.
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TrianglePete

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Reply #5 on: April 07, 2021, 01:27:38 pm
It looks like the lifters are still in there. You're sure it's not the valve springs pushing on the cam lobes causing the tight spots? Yeah I know that sounds too obvious. I didn't know you could get the cams out with the rockers still in but triangle Pete says it's doable?

Two things I have learned about the RE cams    They are not all the same    they vary in all dimensions.
The good thing is they are very hard ( as hard as American lifters )  that is why I don't like to leave the
de-comp trench open.

I can change the cams without changing the oil  or taking off the valve cover or tank.   Thats  R&D

Plan on making video this summer when a young friend visits with a smart phone.  Also intake change


Guaire

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Reply #6 on: April 07, 2021, 01:59:57 pm
Right.
First order of business to to get the load off the cams before setting lash.

And it is possible that the cam gears are not concentric with the center. I have seen that quite a lot on iron barrel cams.

I'll do that today.
   Thanks, ACE!
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