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#279442 10/17/09 10:24 am
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Hi All,
Got my new you-beaut Megacycle cam. Instructions say to degree it in. That's OK, can check it. BUT, how do I alter the cam timing if I need to? I tooth at a time? That's approx. 16 crank degrees per tooth by my calculations. Is the only other option an offset key?

Question asked in advance of checking. I just hope its close enough that I dont need to do anything.

Once again, thanks for any help or comments.

Ray


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What the Triumph people use is 50T camwheel with 3 equi-spaced keyways.By using a different keyway,this gives 1/3 tooth increments.7 keyways would give 1/7 tooth increments.11 equi-spaced keyways also works for a 50T gear.
As long as the number of keyways does not divide evenly into the number of teeth on the gear,and the number of keyways is a prime number,you can get fine increments by using different keyways.

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Which cam did you get? Be aware that the high-lift cams need the case clearanced for the lobes. I wouldn't worry about how to change the timing until you've checked it. Mine was right on.


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Offset key?

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A similar device to a bent drill used for drilling curved holes ;-)


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Thanks All,

Pete, unfortunately BSA dont use gears with multiple keyways. Guess it's always possible to get some new keyways machined.


Alex, thanks. Got the 542x2 - slightly longer duration, same (?) lift (.356" at valve) as standard. Clears cases fine. I was hoping as it was a Megacycle it would be spot on.

Thanks
Brizzo


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Quote

As long as the number of keyways does not divide evenly into the number of teeth on the gear,and the number of keyways is a prime number,you can get fine increments by using different keyways.


I don't see why you couldn't have 40 teeth with 4 keyways with each keyway 1/4 tooth off from the next for example.


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hh #279579 10/18/09 10:31 am
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Offset keys are used to adjust the cam timing on cars all the time. It doesn't take much offset to move it a few degrees either way.

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Hi Brizzo,
I'm a little late to the party, but how do you like the X2 cam?

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Hi sd,

Now that was a while ago. I wore out a couple of cams pretty quick when I first built this bike which was around then. First problem was cheap ebay valve springs that were coil binding. Took me a while and advice from this forum to sort that out. Ultimately I now use SRM valve springs set for their spec on seat pressure. They are good. I did switch to synthetic oil some time back and that made things a lot better for engine wear. (flame suit on).

I did look in dm's thread that ran for a bit asking about the X2, but told myself I really couldn't help much as I didnt have anything intelligent to say. When I fitted the X2 I was replacing a cam that had about 3/16" worn off the lobes so no real comparison. I was still getting the bike sorted so didnt really have a good understanding of it to make comparisons. But I dont really recall a big difference. The X2 was one of the cams that got worn out. I've had it built up and reground. I asked for the same profile and cam grinder said he found it to be the same as a profile he had on file. Motor has been on that format since 2017 I'd take on board Allan G's comments in your thread about the X2 and standard 68-473 profile. The bike has good mid-range and pulls really nicely in top gear (21/47 gearing) at around 60mph for passing But, head has been Mark Parker-ised by myself and that made the most (and best) difference of all.

Sorry, I dont really have a strong impression.

Ray

Last edited by BrizzoBrit; 01/18/22 11:58 am. Reason: correct cam #

BSA 1969 A65F
BSA 1966 A65H
Triumph 1968 T120
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& too many projects!
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No need to apologize. I appreciate the feedback anyway. Cheers!


Moderated by  Allan G, Jon W. Whitley 

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