stripped thread fork drain plug

[RSMike]

Every thing was going well with my fork seal replacement and gator fitting when this happened. I only tightened up to the specified torque with a torque wrench (9nm) but it was too much.

I think it was already a bit dodgy last time I replaced fork oil but I forgot about this.

The only way I can get any purchase on it now and tighten up is without a crush washer, which probably is not going to work.

What are my options?

[Bob_Roller]

Drill the hole over size and use a larger diameter bolt .

Don't know if a 'helicoil' or threaded insert type repair will work in this application, due to not a lot of metal thickness in the area .

[montmil]

May not need to drill but simply use a bottoming tap to go up one size. Use that crush washer.

As you've discovered, the aluminum is easily stripped by steel threads... and the manual torque rate is way too high. Snug is good enough for gubmint work.

Drain the fork oil to wash out aluminum swarf. Pump the front end to get a good squirt. She'll be fine, mate.

[georgesgiralt]

Hello An Heli-Coil (TM) will fit. I have at least one  in place.
In the mean time you can put Drei Bond or Hylomar sealant instead of the crush washer and see where it goes.
Ihad the same issue when last replacing the fork lip seal..... So I had to dismantle again and go to the shop to have the helicoil fitted. If you are gentle the seal won't be hurt.

[RSMike]

May not need to drill but simply use a bottoming tap to go up one size. Use that crush washer.

As you've discovered, the aluminum is easily stripped by steel threads... and the manual torque rate is way too high. Snug is good enough for gubmint work.

Drain the fork oil to wash out aluminum swarf. Pump the front end to get a good squirt. She'll be fine, mate.

I have a tap set that starts at M3, any idea what size this thread is?

I might try the sealant like George suggests as a temp fix in the meantime, see how that goes

[georgesgiralt]

M6 I think if I'm not mistaken. Better check with an M6 nut before making mistakes. ...

[Rob Valdez 79 R65]

suecanada did this AGES ago.  Same thing - using a torque wrench.

A torque wrench is BAD NEWS on this particular fastener.  Not only is the manual's figure too high, but when one only uses technology and "a figure" (especially with steel into aluminum), it is bound to mess up.

This is definitely one fastener that needs only "feel".  And snugged up, as mentioned above.
If it leaks, you can try tightening a little more (NEVER with anything more than the small 10mm box-end spanner).  If it is still leaking, I would try some sealant.

[suecanada]

Rob's right I did this stripped bolt on the front fork ages ago and tried an helicoil that never worked as it came out next time I tried to change the fork oil...came out all broken up. So I used sealant and have never changed the oil since!

So Monte what do you mean when you say "use a bottoming tap" and go up one size. I know about going up one size but what's a bottoming tap??? Derek has taps and dies in the workshop....do you mean I pick one that is slightly bigger whatever that would be and screw it up that wee hole??? :-/

As Rob says Only use the 10mm wrench in the tool kit and just breath on the other end for a just-snug fit. The other 10 mm. bolt I never touch is the final drive oil check bolt at the rear of the final drive. I am convinced I'd wreck it just looking at it! Paranoid...nah...hah!!! I always empty the final drive into a measured beaker and either put it back in the final drive or replace the lube if needed. Good way to keep a check on lube migrating from final drive into driveshaft in any case. I seem to be always short of final drive lube but I think mine is leaking out not migrating I guess.

[marcmax]

Hi Sue. A lot of taps have a taper to aid it getting it started but the downside is it has to go through the material past the taper to cut full threads all the way to the end. The result is the tap would extend all the way into the interior of the fork tube, increasing the amount of aluminum swarf that could inside.

A bottoming tap has straight sides and cutting threads all the way to the end, allowing you to thread a blind hole all the way to the bottom. In this case, with careful use, you could re-thread just to the length of the existing hole without the tap intruding into the fork leg, minimizing the amount of foreign material that you have to get out.

[montmil]

Good on ya, Marc.

I'm up to my ass in landscaping projects and have had little time for the compuKer.

[RSMike]

OK, thanks all for all the info.

I did the temp fix with sealant and no washer. I have refilled the fork and no leaks, though I have not ridden it yet. I did give it a few good compressions though ans so far its holding

If it holds I will leave it until next time. When it needs doing I will take the slider off and tap it. That way I can rinse out any swarf. I forgot to measure the length of the bolt before I closed it. If anyone knows the length, that would be great as I can then source one to be ready to do the job next time.

[Luca]

Is the fork tube just a plain cast aluminium?

If so you could probably take it to (or do it yourself) a welding shop and have them fill in the material a bit.  Then drill and re-tap.  If it is electrically welded (as opposed to gas) your weld should be considerably (at least with steel it is 2 times) stronger than the base metal, which should give you some insurance in the future.

Be careful tapping aluminium.  The tap will turn easily, but aluminium will gall much easier than steel.

Also, if you have impact tools or feel like dropping your extended socket down an open upper fork tube, you can always drain oil out of the piston retaining bolt hole through the bottom of the fork.

[RSMike]

Thanks, mentioning welding, The other solution I saw on another forum was blob of jbweld in the hole, then screw in the bolt. When well set gently back out the bolt and you should have new jbweld threads?

[Rob Valdez 79 R65]

Thanks, mentioning welding, The other solution I saw on another forum was blob of jbweld in the hole, then screw in the bolt. When well set gently back out the bolt and you should have new jbweld threads?

That sounds tacky. (tee hee)

I don't think I would do it to my bike.  JB Weld junk inside of the fork leg?

[georgesgiralt]

Hello !
Left hand fork has an HeliCoil since the early 90's. Right hand fork leg has it for less than a year.
They are still strong...
I think it depend on the quality of the new thread. If you have removed too much metal, then when threading, the tolerances are too wide and the HeliCoil is not held firmly in place..
But i can be mistaken ;-)