Topic: Helicoil in stripped caliper/fender bolt holes on Left fork lower

[evanphi]

Turns out my PO was trying to kill me!

Got my new fork tubes from CycleX all nice and installed


Then I am installing the left side fender/caliper bolts (6mm), and they just keep turning and tuuuuurning... FACK.


Them's some nice stripped out holes. Might even have been some remains of blue loctite... BAH. The 8mm on bottom is fine, thankfully. That is what kept me alive these past three years of ownership!

Has anyone successfully Helicoiled these holes before? This is really my only option at this point... other than a plug weld and re-tap, but I don't want to alter the structural integrity of the fork lower by adding so much heat.

[PeWe]

I do not see the photos.
I also have bad thread in one of the holes in the fork keeping the caliper bracket. I used a longer bolt + blue loctite if I remember correctly. I'll repair it better before sping. Either helicoil type or Time-sert. I think I'll do the time-sert.

[evanphi]

I do not see the photos.
I also have bad thread in one of the holes in the fork keeping the caliper bracket. I used a longer bolt + blue loctite if I remember correctly. I'll repair it better before sping. Either helicoil type or Time-sert. I think I'll do the time-sert.

I tried a longer bolt, but only got 3mm worth of good thread. Not enough.

[calj737]

If you feel confident, drill the hole for a larger bolt (8mm) then tap with a standard pitch. There's ample meat on the boss for a larger hole. You'd be drilling for a helical anyway, and there's little harm in upsizing your bolt.

[evanphi]

If you feel confident, drill the hole for a larger bolt (8mm) then tap with a standard pitch. There's ample meat on the boss for a larger hole. You'd be drilling for a helical anyway, and there's little harm in upsizing your bolt.

I thought about that... what say you about these though? Seems like there isn't much on the inside of the bosses for some reason.

[70CB750]

Evan:

Yes, I did helicoiled all 4 M6 on Dorothy's lowers.  I got tired of loosing those M6s too , every so often there would be one missing.  I bought metric helicoil kit on ebay, since it was cheaper than couple of singles.

Anyway, helicoiled, put some serious miles on it and when I took her apart everything was still holding well.  I did not feel like going one size bigger because of the brake arm holes.

[calj737]

I thought about that... what say you about these though? Seems like there isn't much on the inside of the bosses for some reason.

.236 for a 6mm, .315 for an 8mm. Split that, 0.039 either side of the hole. I think if you measure it, you would find it safe. Or heli-coil it. Neither approach is deep enough into the boss to penetrate by my math. I'm be curious to the OD of the heli-coil?

[evanphi]

I did not feel like going one size bigger because of the brake arm holes.

This is the other thing, I don't want to get into drilling EVERYTHING. I can get a M6 Helicoil kit for 30$ locally. Drill out the holes with 1/4" bit, tap, and insert. Whew.

[madmtnmotors]

I did not feel like going one size bigger because of the brake arm holes.

This is the other thing, I don't want to get into drilling EVERYTHING. I can get a M6 Helicoil kit for 30$ locally. Drill out the holes with 1/4" bit, tap, and insert. Whew.

+1

Helicoils are easy, especially since you are only drilling and tapping aluminum. The Helicoil threads are much stronger than the original aluminum. I usually give the new thread coil a drop of red locktite prior to insertion and then will use antisieze on the bolt just to keep the red locktite from grabbing the bolt. You might be able to use the bracket as a drill guide, but make sure the hole in the bracket will accommodate the drill bit. I do not recommend enlarging the hole in the bracket.

[RRRToolSolutions]

Guys, I would fix those with Time-Serts. I've used these for years to repair threads like these.

Gordon

http://www.timesert.com/html/install.html#

http://www.timesert.com/index.html

[Flyin900]

+1 on the Time Sert.

Best repair you will ever do and you will only ever do it once. Not as cheap as a coil... But you get what you pay for IMO.

Will have to drill a larger hole though for the Sert, so that seems to be an issue for the poster.

[mystic_1]

Will have to drill a larger hole though for the Sert, so that seems to be an issue for the poster.

No bigger than the one you'd be drilling in order to install a helicoil.

I like timeserts because they seem stronger to me, but that's just a feeling.  The also look nicer when installed, which appeals to my OCD side 

Either way you go, be aware that you should drill out the old threads completely, to the bottom of the hole, so they don't interfere with your new bolt when you go to install it.

Also make sure there's enough depth to the holes for the insert your are using, both helicoils and timeserts are available in different lengths.

mystic_1

[PeWe]

Time-Sert is not cheap but needed. Big-Sert cost some more but will help when welding is another alternative.
I have ordered from here: http://www.ebay.com/usr/threaddoctor

Time-Sert when the thread goes bad, Big-Sert when the helicoil has gone taking the alu on the way up.
I fixed 2 cam tower studs threads in the head where the helicoil went up. Big-Sert + loctite 272 solved it.

[Kenzo]

If just a single disc system...couldn't he switch the forks, move the caliper to the rear location and leave the stripped slider threads unused?


Cheers,
Kenzo

[madmtnmotors]

I just made this repair two weeks ago. Took longer to remove the front wheel and fender than it did for the ten minutes it took to install the Helicoil. 

[jonda500]

I like helicoils, I have a 500 with many helicoils fitted and so far none of them have failed, John

[evanphi]

Did the helicoils today!

[madmtnmotors]

Did the helicoils today!

Looking good! Makes you wonder what you were worried about before?

Even has the first coil turned in past the first thread as it should be.