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Discussion Starter · #1 ·
I am having some problems determining if my cams are properly set up and could use some help from those who have done this before. I have gotten zero info back from the cam manufacturer.

I just rebuilt the motor on my 1976 T140V and put in a new set of Megacycle 51005 cams that call for degreeing-in. Specs as follows:
Intake to open at 41 BTC and close at 61 ABC and lobe center at 100 degrees.
Exhaust between 63 BBC and 39 ATC and center at 102 degrees. Both have 282 degrees duration and call for .010 valve lash.

Both cams were set to the factory timing marks and were not degreed-in. However several people said that I should degree-in so as to gain full benefit of these cams which offer more oomph at lower revs than the standard cams. They also commented about possible damage etc. I did run the bike and it seemed to run fine. Because I am babying it to break it in, I am unable to comment whether or not I have made any real performance gains.

Anyway I tore things apart again and used a timing wheel and a dial indicator on the rockers. I know, I should set the dial indicator on the cams themselves but I am getting a bit tired of all the on and off again and figured that while accuracy may suffer, the results should be the same. According to my setup, I am dead on in the valve timing using the the opening and closing specs. However the lobe centers which I understand should be the maximum point of lift are both out. The intake maximum lift is about 10 degrees too late at about 90 BTDC and the exhaust is about 10 degrees too early at about 90 ATDC.

I should mention that I also installed a set of mushroom tappet adjusters but I don't believe should affect timing wise. I am retaining the standard radius cam followers.

I am not sure how to proceed at this point
 

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Third bike

You have to take the measurements off the lobes or the lifters/followers. The .10 is not valve lash. It is the amount of lift where you start and end the measure. The lobe center or centerline is not necessarily the point of max lift. It is the "halfway" between the opening and closing points of the lobes. So if you advance or retard the cams it also changers the "centerline".

The degree wheel goes on the crankshaft. You then need to find absolute top dead center. I like to set the dial indicator on the lifter. Rotate until you find the lowest point of the lobe and set the dial to Zero. Now turn the crank foward until you have .10 lift. This is where you take the measurement. Should be 41 degrees btc. Continue to rotate crank until the indicator rises and falls back to .10. Now you should be at 61 abc. The lobes should be clean and dry. Any oil or lube could effect the readings.

Hope this helps
 

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Discussion Starter · #4 ·
They indicate that both the standard and the "R" type followers were acceptable although the R were were specified.

The problem I am facing I am beginning to think is terminology. Different manufacturers, different countries all use closely related terms. "Lobe center," I take it, is not the same as "lobe-center angle." The lobe-center angle is the mid point of maximum lift while I am beginning to believe that "lobe center" is a somewhat meaningless term that simply is referring to the midpoint between VO and VC. If that is the case, trying to measure lift with a dial indicator will never point to lobe center.

Am I right
 

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Terminology can be confusing. Lobe center and Lobe seperation angle are two completly different things. Lobe center or centerline is what we are concerned with. I would be difficult to find correct lobe center buy simply trying to measure maximun lift. Most "performance" cams will dwell at max lift. Most builders (engines in general) prefer the centerline method because its the most accurate. Here is an article I found. Its for a small engine. The set up will be different , but the actual measuring is the same for all motors and cams. http://www.compgoparts.com/TechnicalResources/Tutorials/CamshaftDegreeing.asp

( Lobe seperation angle is the number of degrees between the intake and exhaust centerlines)
 
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