Re Threading - Helicoil - stripped threads etc.

MarJay · But it's British! Joined: 15 Sep 2003 Karma :

Hi people,

I have a bit of an *ahem* issue with my TT600. I believe that I *may* have stripped the thread out of the cylinder head when fitting my crash mushrooms...

I know it is easy to do, and I saw some bits of swarf come out of the hole when I removed the bolt again. The bolt still screws in correctly, and I didn't put a lot of pressure on it in the first place. Admittedly I didn't use a torque wrench, but I was just doing it up carefully with an ordinary ratchet. I can't see how I sripped the thread, and in the workshop manual it says to use threadlock on the bolt. I am hoping that the bits on my garage floor I took to be swarf were in fact old threadlock...

My questions are thus:

How can I be sure I stripped the thread?

How difficult is putting in a thread repair such as a Helicoil?

I take it I will have to remove the engine from the frame?

How do I find out what pitch the thread needs to be on the Helicoil?

Please Help!
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British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F; Cheap project: CBR900RR FireBlade
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

cagiva gezzer · World Chat Champion Joined: 17 Mar 2003 Karma :

When i manage to strip threads there are always bits of curly maetal pubes that come out if you stick a thin screwdriver in the hole.

I get the mechanics from my dad's engineering firm to recoil my bits, but they do it in a few minutes.

To select the correct insert you just try threading the inserts onto the old bolt.
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"because one stroke isnt enough and four strokes waste two"

kasandrich · Trackday Trickster Joined: 20 Oct 2004 Karma :

The question is, does your mushroom do up tight OK now, or does it just keep turning?

If it does up OK now, you are probably OK
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Richard

CBR1000FM

Robby · Dirty Old Man Joined: 16 May 2002 Karma :

I'd just screw the mushroom back in, gently, and see how it feels on the way in. If its a bit rough, try the stinkwheel technique of turning half a turn, backing off a quarter, turning another half turn and so on.

If you have buggered the thread you need to drill out the old thread and a bit more to fit a helicoil anyway, so be utterly sure its knackered.

MarJay · But it's British! Joined: 15 Sep 2003 Karma :

cagiva gezzer · World Chat Champion Joined: 17 Mar 2003 Karma :

Just a thought. Are these mushrooms 100% nylon? If so, they will compress as you tighten them and you'll have to compress them a lot until you reach the same torque as stated in the manual.

Do the mushrooms come with instructions?
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"because one stroke isnt enough and four strokes waste two"

MarJay · But it's British! Joined: 15 Sep 2003 Karma :

loply · World Chat Champion Joined: 24 Mar 2004 Karma :

40nm is not a lot. The nut on the rear axle will probably be 100nm or so.

But its imposibble to describe how much 40nm is, you need a torque wrench
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Yamaha SZR660 Caution to the wind, the throttle pinned!

cagiva gezzer · World Chat Champion Joined: 17 Mar 2003 Karma :

40nm is very tight. The highest settings on mine are ~50Nm for the front wheel, ~70Nm for the rear wheel and ~75Nm for the rotor/magneto and that takes a good shove with a large wrench.
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"because one stroke isnt enough and four strokes waste two"

MarJay · But it's British! Joined: 15 Sep 2003 Karma :

Well the R and G instructions say tighten it until you feel some resistance then tighten another quarter turn - which is exactly what I have done.

The mushroom is solid and I can't remove the bolt without a socket.

I might bung some liquid threadlock on there to be on the safe side.
____________________
British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F; Cheap project: CBR900RR FireBlade
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

G · The Voice of Reason Joined: 02 Feb 2002 Karma :

Is this just the 'bolt' that goes in, or the nut on top?

The ones I've have had have had a threaded rod at both ends. You screw the rod into the mount, then slip the bung on and do up a bolt on the second thread.

It's this second bolt that has to be tensioned I suspect.

MarJay · But it's British! Joined: 15 Sep 2003 Karma :

Its a one piece bolt that goes through the nylon part (which has a steel sleeve) and then it has an alloy spacer. This assembly all hangs off the bolt which screws into the cylinder head through the frame.
____________________
British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F; Cheap project: CBR900RR FireBlade
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.