A bit of history:
A million years ago I built an SR500 for a bud that raced it in SOS. Didn't like the automatic cam chain tensioner, as it seemed to me that at full chat, the chain would be pushing back on the tensioner and allowing the chain to flap around. Dismembered the tensioner, and made it manual (bolt and locknut pushing on the chain guide). What I needed was a way to know how tight the chain was getting. I poked a hole in the cylinder on the back side of the cam chain tunnel near the tensioner. Then, we got the bike up to running temp, I removed the cover, and looked through the hole to see how tight the chain was, and adjusted accordingly.
Easy, as the tensioner was out in the breeze.
I'm converting my Savage cam chain tensioner to semi-atomantic. Pulled the pawl, and am inserting a length or round stock inside the spring to limit the amount of travel back (loosening) that the tensioner has.
So, once again, how tight is tight enough?
So, I figured I'd do a similar gag on this bike as I did on the SR. For reasons that escape me, I had made a 22x1.5mm flanged nut on the CNC mill. Chalk it up to boredom. I honestly don't remember what this was supposed to fit, so it made the perfect sacrificial nut.
Checked on Ebay and found an corresponding aluminum drain plug (with magnet) from the Hu Brung Poo machine works in China for only $5, delivered! Didn't really want a magnet catching stray metal bits, so I bored out the backside of the plug, saving myself precious milligrams!
Here is the plug and nut assembled:

Next on the agenda was to make a flat surface. Hindsight being 20-20, I realize I should have started with a much bigger hole saw, cut down to the base of the fins and stopped, then gone back with the smaller hole saw. That would have given me a much neater circle.
Ah well.
So I went at it with a Dremel and cutoff wheel. Actually kept going after this pic, so it was pretty flat.

Armen   , I believe it was Verslagen who determined that when the  bike is at temperature the chain tensioner would have to retract 1.5mm to avoid chain stretch . I went with that figure and set mine to retract at about 2.5 mm,  that was at 19000 miles (extended the tensioner )  at the time I first found and joined SSC.  I've just put my bike up for the season , and now have more miles without the paw and spring,  than with it , 38,800 miles on my original factory chain which seems frozen in time ,I have since 19,000 never made any adjustment in tensioner length. I am at this point more worried about guide wear than chain stretch.

Did Armen really just drill a hole in his engine?!!!!

The only real surprise here is that he wasn't trying to save weight!  

I'm wondering why the front guide is showing all those cracks ,is that normal wear? Do they crack as they wear thin?

Oops! How many miles on the motor/guide?

Armen wrote on 10/30/19 at 06:19:14:


Why do that?
Put another hole in the back for a bolt to push against the back of the guide.

DBM  ,has gone that way but I wonder if that won't create a hard spot and localized wear on the guide(?) I often wondered if it would be possible to insert a small high speed bearing ,so it is just proud of the guide in the same relative location,  with the same type of adjustment,  might work.