The right fork drain plug hole is stripped so the 6mm M6 screw keeps rotating when I try to tight it. However, if I put in an 8mm screw, then I can apply the recommended 5 ft-lb fine (it locks). Could the 8mm screw affect the internal functionality of the fork?

Why those screws are only 6mm is beyond me-they’re too easy to over-tighten and strip. I had the same issue as you. So that I didn’t have 2 drain screws of different thread diameters, I drilled and tapped them both to 8mm. I can’t remember what their length was but they were just ever so slightly longer than the 6mm ones. I used 2 washers and then torqued them to 7nm (I think). They don’t leak at all.

Even if the 8mm screws protruded into the fork tube a bit you’d have to hit one nasty-ass pothole to bottom-out the stanchions in my opinion.

RS Rider wrote:Why those screws are only 6mm is beyond me-they’re too easy to over-tighten and strip. I had the same issue as you. So that I didn’t have 2 drain screws of different thread diameters, I drilled and tapped them both to 8mm. I can’t remember what their length was but they were just ever so slightly longer than the 6mm ones. I used 2 washers and then torqued them to 7nm (I think). They don’t leak at all.

Even if the 8mm screws protruded into the fork tube a bit you’d have to hit one nasty-ass pothole to bottom-out the stanchions in my opinion.

That depends on where you live. . . . . .

The last time that I changed my fork oil I had one one of the bolts start to twist the threads out.  I took the bolt out, cleaned everything really well and put it back in with a bit of RTV gasket.  It has held out quite well since and I will drill it out and tap it for an 8mm bolt the next time I change the fork oil.  That was about 20k kms ago so I will likely be doing this at the end of the riding season.

They can be helicoiled. A member of our group of K Kronies SSD suffered a stripped drain plug on one of our workshop days. He suffered a terrifying ride as Micks pillion up to Repco for a Helicoil kit. Once his shaking stopped he fitted the Helicoil and all was right in his world. When fitting Helicoils it is extremely important to get the drilling and tapping square, a spotter is definitely required.
Regards Martin.

Done both - helicoiled and oversized to 8mm. I have no preference as each is equally as good and it depended on what I had to hand (or didn't have to hand!) at the time. In both cases you need to strip the forks right down and degrease the sliders to ensure no swarf gets inside. Alternatively, if you've some experience with drilling and tapping, a smear of grease on the drill and tap will capture just about all of the swarf if you do it slowly. Just remember, when tappping, 'in one-quarter, out one-half' to lift the swarf and reduce the strain on the material that you are tappping. Back out and clean the tap every full turn.

You can also flush out the swarf with fork oil or ATM fluid. Alternatively you can vacuum or suck it out with a suction gun or wet dry vacuum cleaner. We used the grease method.
Regards Martin.

Seems a common problem.  I was able to get away with not tapping it out but just using an alternate bolt just a few threads longer, and a sealing washer.  I'm sure that will fail at some point and I'll still have to tap it out at that point.

A common problem alright, across all makes and manufacturers. Ham-fisted owners not reading torque settings. My (so far working) rule of thumb is 'finger-tight, plus one-eight of a turn'.

Dai wrote:A common problem alright, across all makes and manufacturers. Ham-fisted owners not reading torque settings. My (so far working) rule of thumb is 'finger-tight, plus one-eight of a turn'.

Yes, one of the marks of an experienced mechanic is that ability to "feel" the proper torque for a given fastener. 

Knock on wood, but in nearly 60 years of wrenching I have only stripped out a couple of holes, usually in places where the alloy was corroded and the threads were damaged taking the screw out.  In spots like that, even using a torque wrench can strip out the threads.

For years we would give out the proper torque specs for a particular job to workshop customers who requested them. One day a gent asked for a spec and we supplied it to him. A week later he was back with a broken aluminium flange and accused us of providing him with an improper number. When asked what he was given he stated a number three times higher than what the manual states. He threatened legal action. We stopped giving out specs with the ongoing suggestion that the Google Gods will tell you what you (think) you need to know.

It's a seesaw, and one not always with a happy ending for one rider at the end of the teetering board: giving out the factory specs helps a customer to potentially 'get it right', on the other hand, giving out the factory specs also helps a customer to do his own damage.

A coupla weeks back an 'I do it myself' customer had his bike towed in with a leaking and damaged rear brake caliper snuggled into the middle of his R1200GS rear wheel spokes. He suggested he'd torqued the caliper mount screws correctly after replacing the brake pads and rear disc. In fact, the forward screw had sheared off the flange on the final drive. However, the rear screw's threads were intact and the screw itself captured by the metal shim that holds the ABS sensor cable in place. The hole of the rear flange mount was as new, unmarked, suggesting no stress was applied there. The caliper simply pivoted forward into the rear wheel when the rear screw unscrewed enough to allow the caliper to flip forward and shear off its mount. It was a near US$8,000 repair bill with labour, tax, a new wheel, final drive, caliper, brake pads, disc, rear brake hose and associated hardware. 

Always dab a touch of bright paint on a screw or bolt that has been verified as torqued correctly.