28 degrees BTDC

Hi guys,
Does anyone know, what 28 degrees BTDC , translate to in mm BTDC..... if the measurement is made with a dial gauge attached thru the spark plug thread on the head.
Is it this possible to check 28 degrees in this manner?

Brewer.

There is a formula in this thread that you can copy and paste into excel or openoffice

http://www.b50.org/phpBB2/viewtopic.php?f=3&t=3011

But to be honest you will be taking on a few extra variables, not sure you can get the Dial gauge vertical as the plug hole is at 45 degrees plus slippage across the piston crown full of carbon. Better to use the dial guage to accurately find TDC on a crank mounted degreewheel and then use the degreewheel and reference 28 BTDC back to the primarycase indicator and then use this to strobe.

28 deg not sure but 31 is 5/16" vertically measured (just did mine the weekend during cam change). That would put you in the ballpark for strobing. Kommando is right about TDC, it's really the only way to do it properly. Using the depth measurement doesn't allow for perfect TDC with piston 'rock' either side of TDC.

Brewer, why would you not simply line up the timing mark on the alternator rotor with the indicator on the outer primary cover?

grandpaul said:

Brewer, why would you not simply line up the timing mark on the alternator rotor with the indicator on the outer primary cover?

Click to expand...

Maybe he isn't using a stock primary cover. Or maybe it's because those marks are frequently off by a couple of degrees. It's a good practice to find tdc with a timing wheel, and use that to check the factory marks, and correct as necessary.

On the other hand, the factory marks are certainly good enough to get it running reasonably well, if your bike has them.

Ken

Thanks all,
I think a degree wheel shall be the solution, as my bike is "missing" the timing mark plate which is normally rivited to the timing cover.

Brewer