Jump to content

Repairing thread on the clutch slave cylinder


Recommended Posts

After changing out my front sprocket, without much force I managed to break one of the threads of the clutch slave cylinder/ front sprocket cover. Now I can't get the cover on and I essentially have no clutch.

I bought a Helicoil kit to repair the thread but the tap is not long enough to fit all the way down the hole. The shank is also too big and gets stuck when trying to drill further than the thread length.

I tried looking online for longer taps but I found nothing helpful. The hole is about 2.25in deep.

The bolt is M6x1.0

 

 

image.thumb.png.8d2a682e222213456f28bfd061c82b80.png

 

image.thumb.png.b2ee01915dfb453280f4c3a4c494e356.png

 

image.thumb.png.f77fe6f6711c90a7e2115fdf300d4a0b.png

^^^ the shank is too wide and it won't go in further than the thread length without destroying the hole

 

 

Thanks

Link to post
Share on other sites
  • Member Contributer

I've often wondered about this. 

 

Is there any particular reason that bolt has to be so long with threads so deep in that hole?

 

What if we tap hole close to surface of hole and use shorter bolt?

 

I've seen tonnes of helicoil repairs come apart. Might be OK for permanent repair that's never disassembled, but upon removal several times, lots of them come apart. I prefer more durable solid inserts. Such as EZ-lok or Time-serts.

 

https://www.belmetric.com/m6x10-c-217_218_228/ts1610-m6x10-timesert-kit-p-1499.html

  • Like 1
Link to post
Share on other sites
2 hours ago, DannoXYZ said:

I've often wondered about this. 

 

Is there any particular reason that bolt has to be so long with threads so deep in that hole?

 

What if we tap hole close to surface of hole and use shorter bolt?

 

I've seen tonnes of helicoil repairs come apart. Might be OK for permanent repair that's never disassembled, but upon removal several times, lots of them come apart. I prefer more durable solid inserts. Such as EZ-lok or Time-serts.

 

https://www.belmetric.com/m6x10-c-217_218_228/ts1610-m6x10-timesert-kit-p-1499.html

image.thumb.png.40d88635b266e9898aec51a4b2a22b5a.png

image.thumb.png.6dce2139340203a3ddf68ac4b82ec5e5.png

 

if you look at the first image you can barely see a gasket poking out. The threading is past that gasket so the bolt is holding the slave cylinder in place and another cover in between the transmission and drive sprocket.

So, I don't think threading just the surface would be a good idea.

  • Like 2
Link to post
Share on other sites
  • Member Contributer
3 hours ago, styran said:

After changing out my front sprocket, without much force I managed to break one of the threads of the clutch slave cylinder/ front sprocket cover. Now I can't get the cover on and I essentially have no clutch.

I bought a Helicoil kit to repair the thread but the tap is not long enough to fit all the way down the hole. The shank is also too big and gets stuck when trying to drill further than the thread length.

I tried looking online for longer taps but I found nothing helpful. The hole is about 2.25in deep.

The bolt is M6x1.0

 

 

image.thumb.png.8d2a682e222213456f28bfd061c82b80.png

 

image.thumb.png.b2ee01915dfb453280f4c3a4c494e356.png

 

image.thumb.png.f77fe6f6711c90a7e2115fdf300d4a0b.png

^^^ the shank is too wide and it won't go in further than the thread length without destroying the hole

 

 

Thanks

 

Can you use a grinder to slim down the shaft to fit the opening?  You'd be tapping aluminum,  so it seems unlikely the tap would break. 

 

When I remove that cover I make a cardboard template to ensure each bolt goes on the correct place and always use an inch-pound torque wrench to tighten the bolts.

 

Link to post
Share on other sites
6 minutes ago, Cogswell said:

 

Can you use a grinder to slim down the shaft to fit the opening?  You'd be tapping aluminum,  so it seems unlikely the tap would break. 

 

When I remove that cover I make a cardboard template to ensure each bolt goes on the correct place and always use an inch-pound torque wrench to tighten the bolts.

 

Is there a specific torque spec for these bolts? I broke the thread by applying barely any torque at all.

Link to post
Share on other sites
  • Member Contributer

Yes - IIRC 9 ft-lbs, 108 in-lbs on a small TQ wrench.   Same for the clutch cover.  All the steel bolts that thread in to the engine case deserve special attention due the consequence of stripping them out.

 

  • Thanks 1
Link to post
Share on other sites
  • Member Contributer
10 minutes ago, Magneto said:

 

Kind of expensive, but considering the situation worth it.

Link to post
Share on other sites
  • Member Contributer
10 hours ago, DannoXYZ said:

I've often wondered about this. 

 

Is there any particular reason that bolt has to be so long with threads so deep in that hole?

 

What if we tap hole close to surface of hole and use shorter bolt?

 

I've seen tonnes of helicoil repairs come apart. Might be OK for permanent repair that's never disassembled, but upon removal several times, lots of them come apart. I prefer more durable solid inserts. Such as EZ-lok or Time-serts.

 

https://www.belmetric.com/m6x10-c-217_218_228/ts1610-m6x10-timesert-kit-p-1499.html

 

Yes, it's just a cover, essentially, and there are other fasteners holding it in place (there are even dowels).  The only problem I can see is that there isn't much meat at that point in which to tap a larger diameter thread.  But the long tap option is probably what I'd try first.

 

Ciao,

 

JZH

Link to post
Share on other sites
  • Member Contributer
1 hour ago, JZH said:

 

Yes, it's just a cover, essentially, and there are other fasteners holding it in place (there are even dowels).  The only problem I can see is that there isn't much meat at that point in which to tap a larger diameter thread.  But the long tap option is probably what I'd try first.

 

Ciao,

 

JZH

 

 

 

I'd see how things function without that one bolt, prior to throwing $$$ at it.

 

image.png.b6b3248dbd949825c9e51f274e2544a7.png

https://www.bike-parts-honda.com/honda-motorcycle/800-MOTO/VFR/2007/VFR800A6/Engine/WATER-PUMP/13MCW601/E__0900/1/38097

Link to post
Share on other sites
  • Member Contributer

Why not epoxy the hole with the bolt in? The bolt should be lubed first and the epoxy won’t stick. 
 

When epoxy cures then bolt gets backed out and voila - new threads. Lots of YouTube tutorials. 
 

If it was mine I’d build the hole up with alumiweld rods and drill/tap. You can also do this with the bolt in place as above (alumiwekd won’t stick to steel so the threads will be perfect). These are low temp solder-like rods that can be melted with a torch. Repaired a few things with them in the past. 
 

Best, 

 

Stray

  • Like 2
Link to post
Share on other sites
  • Member Contributer

I think he needs a tap specific to Heli-coils, which may be a different pitch than a normal tap. The hole might be too deep for a time-sert which I do agree are by far the best.

 

You can do what I did on my kid's Honda 80 dirt bike, considering the depth of the threads - Take the fairings off, and lay the bike on it's side. Mix up some titanium epoxy, or JB Weld, and put it in an infant medicine syringe with a small tube on the end. Fill the hole with the epoxy - ONLY PART WAY. When it sets up, drill and tap it.  You will actually need a RELEIVED tap as some aer just long, but may not fit in the hole. Also when you drill it, make sure you put tape on your drill bit so you don't go too deep. I would not go more than 4mm past the lenth of the screw FROM THE OUTSIDE OF THE CLUTCH COVER - otherwise you might get into an oil galley or water jacket. You can also test the depth of the hole without the clutch cover if you use a pointed pick that is thin and long enough to measure the depth.

 

 

tap.jpg

  • Like 1
Link to post
Share on other sites
  • Member Contributer

Great ideas.  Having that bolt doing its job is important - the clutch puts a lot of pressure on that cover.  Leaving one bolt out will work for a time - over time the a-symmetric force on the cover will result in it flexing ever so slightly each time the clutch is cycled.  Long term the cover can fatigue and possibly crack or break.  If it fails sufficiently, the clutch will be in-op.   If it were mine, that would happen when I'm some multiple day's ride from home . . . my $.02.  YMMV. 

  • Like 1
Link to post
Share on other sites
  • Member Contributer

Good point.  But how much is a spare clutch cover?  ⁉️

 

Ciao,

 

JZH

Link to post
Share on other sites
  • Member Contributer

The clutch cover is extremely brittle - super thin aluminum "pot metal" casting. When I cut mine for the Budget Streetfighter, I was gripping it with vise grips, and it broke. I ended up just chunking pieces of with said vise grips, then ground it to the final shape. Any off-axis flexing and it snaps!

  • Like 2
Link to post
Share on other sites
  • Member Contributer

Helicoil taps are the same pitch as the thread being repaired BUT are bigger in diameter.

You first drill the failed thread out and then cut a new thread with the special tap.

To Helicoil that thread you need to remove the selector assembly cover, the one behind the sprocket, so as you are down to the base crankcase where the actual thread is.

Then you repair it and reassemble it all.

No use at all trying to repair it further up the hole and using a nut tap is only the same thread diameter as the standard M6x1 thread.

 

Do it once and do it right.

  • Like 2
Link to post
Share on other sites
  • Member Contributer
13 hours ago, HighSideNZ said:

Helicoil taps are the same pitch as the thread being repaired BUT are bigger in diameter.

You first drill the failed thread out and then cut a new thread with the special tap.

To Helicoil that thread you need to remove the selector assembly cover, the one behind the sprocket, so as you are down to the base crankcase where the actual thread is.

Then you repair it and reassemble it all.

No use at all trying to repair it further up the hole and using a nut tap is only the same thread diameter as the standard M6x1 thread.

 

Do it once and do it right.

I think the issue he is having is that the "special tap" will not fit down in the hole being repaired. Additionally, I'm not sure the "special tap" is a standard pitch, as it might be proprietary to Helicoil, and therefore he may not be able to get a longer relived version of the "special tap".

  • Like 1
Link to post
Share on other sites
  • Member Contributer

The pitch has to be the same pitch as the damaged threads, but the diameter is different.  According to Helicoil, the taps are called "STI" (Screw Thread Insert) taps and they are not just larger standard taps.  That makes sense, as larger standard threads usually have different (larger) pitches, so the new tap would have to be a "fine" thread version with exactly the right diameter to accommodate the Helicoil wire.  There could be a coincidental match, though...

 

Ciao,

 

JZH

  • Like 1
Link to post
Share on other sites
  • Member Contributer
On 4/3/2021 at 2:22 AM, RC1237V said:

I think the issue he is having is that the "special tap" will not fit down in the hole being repaired. Additionally, I'm not sure the "special tap" is a standard pitch, as it might be proprietary to Helicoil, and therefore he may not be able to get a longer relived version of the "special tap".

Hence why I said the shifter case should be removed so as you can get to the base thread and repair it correctly.

If you could get a longer version of the Helicoil tape you would end up threating the outer shifter case as well as the damaged thread in the crank case.

Not ideal or wanted as you could end up with the helicoil partially in both parts.

Phil

  • Like 2
Link to post
Share on other sites

Well about three weeks ago I took an angle grinder like what @Cogswell said and I managed to thread the whole hole. Once I got three helicoils in I put in the bolt and tightened and the bolt got stuck. What ended up happening is the bolt split in two with the thread portion of it stuck one inch down the hole. It is lodged in between the crankcase and the gearshift linkage cover. I definitely should have taken the cover off before sticking helicoils down that deep hole. So now I'm really in trouble and I can't even get the cover off cause the bolt is keeping it in place. I had to remove the water pump so I can access the hole easier but I'm unsure of how I should proceed. I might get a nail the size of the hole and hammer it a couple times to make a center indentation and drill the remains of the bolt down to the top of the crank case so I can get the cover off at least. It is so deep & small and it is impossible to see if you are drilling on center. 

 

I'll post pictures tomorrow.

  

On 4/1/2021 at 4:32 PM, HighSideNZ said:

Helicoil taps are the same pitch as the thread being repaired BUT are bigger in diameter.

You first drill the failed thread out and then cut a new thread with the special tap.

To Helicoil that thread you need to remove the selector assembly cover, the one behind the sprocket, so as you are down to the base crankcase where the actual thread is.

Then you repair it and reassemble it all.

No use at all trying to repair it further up the hole and using a nut tap is only the same thread diameter as the standard M6x1 thread.

 

Do it once and do it right.

I really wish I saw your reply before doing what I did cause now I'm really fucked & I don't know how to get this thing out

Link to post
Share on other sites
  • Member Contributer

You cannot "stack" helicoils as they will never line up perfectly. You will need to drill the bolt out with a cobalt left hand drill bit, and remember to run your drill in reverse. Yes, some sort of center punch will help, and if it is too skinny, then wrap it with masking tape tightly and evenly around it so it fits snug in the bore. 

 

https://www.ebay.com/itm/283884915096?chn=ps&norover=1&mkevt=1&mkrid=711-117182-37290-0&mkcid=2&itemid=283884915096&targetid=1068323850910&device=c&mktype=pla&googleloc=9032190&poi=&campaignid=11614425263&mkgroupid=114834261282&rlsatarget=pla-1068323850910&abcId=9300456&merchantid=8047204&gclid=EAIaIQobChMIpeOVkIj_7wIVwRt9Ch2mJA5tEAQYHCABEgKp5PD_BwE

  • Like 2
Link to post
Share on other sites
  • Member Contributer

I might be able to help you get that out and get it fixed. Where are you in the Bay Area? I sent you a PM....

  • Like 2
Link to post
Share on other sites
  • Member Contributer

RC1237V, your generosity is only exceeded by..........the magnificent bike you ride!:fing02:

Link to post
Share on other sites
  • Member Contributer

I have reverse drill bits, as well as a special 6mm broken bolt drill that can thread on a stud, in a tapped hole, or the correct sized bore....

 

 

20210415_184046.jpg

20210415_184112.jpg

  • Like 1
Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...

Important Information

By using this site, you agree to our Privacy Policy.