So I got pissed off at my bike today, and as I was putting the seat back on (which is secured with a metal bracket which screws into place with a 10mm hex-headed nut), I wasn't really paying attention. I believe I have cross threaded it, or worse, stripped the threads completly..

It's as far down as it will go, by that I mean there's no gap between the flange thing of the nut and the bracket, however I cannot undo it, nor can I tighten it further. It'll spin, going from tight to loose in 360 degrees. It gets tight at roughly the same point and becomes loser at pretty much the same point. (by tight and loose, I mean the resistance to being turned, from being able to be turned by hand to requiring a socket)

My seat is on securely enough, however I now can't get it out because it just spins. I've tried using a pair of random pliers I found in a dusty tool-chest to twist and pull but to no avail (maybe some decent pliers may help). This is somewhat worrying because, firstly, I plan to remove the crappy power restriction which was fitted today, and secondly, access to the battery is under the seat, along with access to the engine and basically every other part you'd need to service.

I've attached an image to help clarify. Any help would be appreciated.

As you claim to be or want to be some sort of mechanic or engineer with some form of experience, I shouldn't need to point out that the 10mm A/F bolt head isn't a 10mm bolt. It is, most likely, a 6mm (x 1mm pitch) bolt, which usually has a 10mm A/F head.

Anyway, it sounds like a cross thread to me. The thing to do is remove it. Then buy a rethreading kit (unithread do them, commonly called a Helicoil kit) for an M6x1.0 thread.

You then use the supplied drill and tap to, err, drill and tap the hole to the correct size. You must ensure that you drill and tap squarely to the original thread and not to the new direction it goes in since you messed up.

One it's drilled and tapped you wind in a coil of stainless steel that is roughly diamond in cross section - the Helicoil itself - using a special tool. Break the tang off after it's in. Then, using a fresh, undamaged M6 bolt of the right length, fit your seat carefully this time.

Lengths of Helicoils are usually quoted in Diameters (hence an M6x1.0 1.5 Helicoil is 1.5 times 6mm long WHEN INSTALLED, which is 9mm. You'll have to choose a length that suits the application, but it's rare to use 1.0. 1.5s and 2.0s are much more common.

Your local fastener supplier will probably carry them. The whole kit is a few quid, but you need the specific tap (and drill, but you can get away with using a standard drill of the quoted size.

Good luck.

i would suggest that drilling it out would be the only way to be able to get the seat off again. 10mm head will be 6mm thread, but to save damaging the hole that the bolt is in, i would use a 5.5mm drill bit and drill slowly and very carefully directly down the centre of the bolt head. Once you get far enough, a push with a flat blade screwdriver will be enough to pop the head of the bolt off.

Once that is done and the seat is out of the way so you can get better access to the remaining part of the bolt, i would select something smaller, maybe a 4mm drill bit, and then, again, slowly and carefully, drill down the middle of whats left of the the bolt, making sure to keep the drill as straight as possible so you don't damage the threads of the part of the bike any more.

Eventually, you'll be all the way through the bolt and all the bits of metal left around the outside should be able to be pushed out with something like a small philips screwdriver, although they may fall out as you are drilling.

Quote from tristancliffe :

As you claim to be or want to be some sort of mechanic or engineer with some form of experience, I shouldn't need to point out that the 10mm A/F bolt head isn't a 10mm bolt. It is, most likely, a 6mm (x 1mm pitch) bolt, which usually has a 10mm A/F head.

Anyway, it sounds like a cross thread to me. The thing to do is remove it. Then buy a rethreading kit (unithread do them, commonly called a Helicoil kit) for an M6x1.0 thread.

You then use the supplied drill and tap to, err, drill and tap the hole to the correct size. You must ensure that you drill and tap squarely to the original thread and not to the new direction it goes in since you messed up.

One it's drilled and tapped you wind in a coil of stainless steel that is roughly diamond in cross section - the Helicoil itself - using a special tool. Break the tang off after it's in. Then, using a fresh, undamaged M6 bolt of the right length, fit your seat carefully this time.

Lengths of Helicoils are usually quoted in Diameters (hence an M6x1.0 1.5 Helicoil is 1.5 times 6mm long WHEN INSTALLED, which is 9mm. You'll have to choose a length that suits the application, but it's rare to use 1.0. 1.5s and 2.0s are much more common.

Your local fastener supplier will probably carry them. The whole kit is a few quid, but you need the specific tap (and drill, but you can get away with using a standard drill of the quoted size.

Good luck.

Alternatively.......use Napalm :hbomb:

Quote from tristancliffe :

As you claim to be or want to be some sort of mechanic or engineer with some form of experience, I shouldn't need to point out that the 10mm A/F bolt head isn't a 10mm bolt. It is, most likely, a 6mm (x 1mm pitch) bolt, which usually has a 10mm A/F head.

Anyway, it sounds like a cross thread to me. The thing to do is remove it. Then buy a rethreading kit (unithread do them, commonly called a Helicoil kit) for an M6x1.0 thread.

You then use the supplied drill and tap to, err, drill and tap the hole to the correct size. You must ensure that you drill and tap squarely to the original thread and not to the new direction it goes in since you messed up.

One it's drilled and tapped you wind in a coil of stainless steel that is roughly diamond in cross section - the Helicoil itself - using a special tool. Break the tang off after it's in. Then, using a fresh, undamaged M6 bolt of the right length, fit your seat carefully this time.

Lengths of Helicoils are usually quoted in Diameters (hence an M6x1.0 1.5 Helicoil is 1.5 times 6mm long WHEN INSTALLED, which is 9mm. You'll have to choose a length that suits the application, but it's rare to use 1.0. 1.5s and 2.0s are much more common.

Your local fastener supplier will probably carry them. The whole kit is a few quid, but you need the specific tap (and drill, but you can get away with using a standard drill of the quoted size.

Good luck.

Very good advice, that bit was gonna be my next post!


I think he needs to get the bolt out first though, so between our 2 posts he should be sorted.

S14, If you have totally killed the threads in your bike than it may be possible to tap a new, bigger thread, depending on how big the piece of metal is. The next sensible size would be M8, which is an 8mm thread, and has a 13mm head.

The first thing I'd do to get the bolt out would be to use a longer lever. Force it out. If it shears off then you're no worse off. You then drill it out (as Dan suggested), collapse it in on itself, and Robert's you mother's brother.

Tristan, Agreed!

If doing banger racing has taught me anything, it is how to remove broken and damaged parts under pressure and with time limits, nobody wants to miss the next race!

I considered myself pretty good at getting stuck things like bolts free with the minimal damage and time wasted. But having wandered the odd Banger paddock I can see I'm terrible at it in comparison!!!!!

i usually end up in a right flap and shouting at nobody in partcular, it is through pure miracilous luck that it all happens in time, usually.

Do you have room to drill it out, then use a nut and bolt to secure the seat. This would get around the helicoil solution. Though, the helicoil is more elegant.

Might be good for you to get a set of left hand drill bits, or a set of easy-outs.

Quote from S14 DRIFT :

So I got pissed off at my bike today, and as I was putting the seat back on (which is secured with a metal bracket which screws into place with a 10mm hex-headed nut), I wasn't really paying attention. I believe I have cross threaded it, or worse, stripped the threads completly..

It's as far down as it will go, by that I mean there's no gap between the flange thing of the nut and the bracket, however I cannot undo it, nor can I tighten it further. It'll spin, going from tight to loose in 360 degrees. It gets tight at roughly the same point and becomes loser at pretty much the same point. (by tight and loose, I mean the resistance to being turned, from being able to be turned by hand to requiring a socket)

My seat is on securely enough, however I now can't get it out because it just spins. I've tried using a pair of random pliers I found in a dusty tool-chest to twist and pull but to no avail (maybe some decent pliers may help). This is somewhat worrying because, firstly, I plan to remove the crappy power restriction which was fitted today, and secondly, access to the battery is under the seat, along with access to the engine and basically every other part you'd need to service.

I've attached an image to help clarify. Any help would be appreciated.

mmmhmm. sounds like you did strip it. Let me ask my dad. He is so filled with mechanic wisdom, that if he gave some away, it wouldn't matter to him. BTW, if your bike is your avatar, sweet bike man! Is it a Honda? Or Kawasaki? How about Suzuki?

Quote: Did you know that Bill Gates is so rich, that if he saw a $500 dollar bill on the sidewalk, he would waste so much time and money just by picking it up?

Levering it out is the better option IMO. The threads are already gone and you won't do any more damage to the hole, although you can damage other parts of the bike if you have to lever hard, but if the bolt is crossthreaded there shouldn't be too much resistance, just make sure you pull directly up and not any other direction.

Problem with drilling, at least for me, is getting the drill lined up exactly square to the hole. Bolts also tend to be a bit stronger than your normal piece of sheet stock and it can take a bit to work through the bolt, especially if you do not have very good bits that are maintained properly.

Helicoil is your better option for replacing the threads. Alternatively you can oversize the hole and go with the next size bolt. Drill and tap accordingly, make sure you stay on the same thread scale between the thread and the bolt. But I would only do this if there is plenty of material around the hole.

Quote from PAracer :

Do you have room to drill it out, then use a nut and bolt to secure the seat. This would get around the helicoil solution. Though, the helicoil is more elegant.

Jamie - do not do this. Replacing a bolt with a nut and bolt is the absolute last resort. It's a horrid solution, and such bodges should be banned under international law.

Quote from PAracer :

Might be good for you to get a set of left hand drill bits, or a set of easy-outs.

It's not a sheared off stud at the moment, so they won't help. If a socket and lever can't get it out then a drill or easy-out won't. I've yet to see an easy out work in anything other than a demonstration (which was artificial).

Quote from Christopher Raemisch :

Levering it out is the better option IMO. The threads are already gone and you won't do any more damage to the hole, although you can damage other parts of the bike if you have to lever hard, but if the bolt is crossthreaded there shouldn't be too much resistance, just make sure you pull directly up and not any other direction.

An M6 bolt will take a LOT of force. I'd have to look up the values (or work them out), but I'd be surprised if an M6 8.8 bolt will hold much less than a tonne in tension!

Quote from Christopher Raemisch :

Problem with drilling, at least for me, is getting the drill lined up exactly square to the hole.

Take your time. File the end flat and centre pop it. Then get a friend to help watch the drilling angle and keep you square.

Quote from Christopher Raemisch :

Bolts also tend to be a bit stronger than your normal piece of sheet stock and it can take a bit to work through the bolt, especially if you do not have very good bits that are maintained properly.

I doubt it'll be a hard bolt like a 10.9 or 12.9. Assuming it is an 8.8 or lower grade of bolt then you won't have any problem drilling it with a sharp drill (and sharpening a drill isn't that difficult).

Quote from Christopher Raemisch :

Helicoil is your better option for replacing the threads. Alternatively you can oversize the hole and go with the next size bolt. Drill and tap accordingly, make sure you stay on the same thread scale between the thread and the bolt. But I would only do this if there is plenty of material around the hole.

You could do this, but it's inelegant. Depends how good you are at mechanics. I wouldn't accept it personally. But S14 is his own person and can decide if he wants to do a proper job or not. For starters it'll be good practice.

Hmm, ok guys. Well, I've read all of your suggestions and I appreciate the help that you've all put forward.

As some of you may know I'm not exactly the richest kid on the block, if I **** it up I'm screwed. My bike is my world, sounds cheesy I know. The seat is on in a way in which I'm safe, and it's not like I'm competent enough to strip my bike down to the throttle bodies to remove the shitty 1/8" travel throttle restriction. I'll just leave it for now, my bike's used daily and has no alarm so there's not an overly large drain on the battery.

I'll most likely take it to the local dealer and get them to have a look at it. The next time my Dad comes over, I'll probably get him to have a quick glance over it. He's pretty handy when it comes to removing things like that. Failing that, when I get it taken it somewhere to remove the restriction, then I'll likely just not mention it, pretend they did it and just get them to fix it.

(Grip driver, the bike in question in a Z750. That's a Kawasaki, the bike in my avatar is my old RS, which is an Aprilia )

Quote from S14 DRIFT :

to remove the shitty 1/8" travel throttle restriction

Lol, that's how it is restricted? That's a bloody stupid way to restrict a bike. What exactly are the restriction rules? I'm guessing you're allowed a certain amount of horsepower, right?

It's 33bhp limit for 2 years. It's restricted on the throttle nowadays on the FI bikes because it's better for the engine than the air intake one which causes rough running.

I've done nearly 1000miles on a bike with 100bhp at the back wheel as a direct step up from a 125 and I've never nearly once put it into a hedge. Besides, I didn't even speed, most of the power was used when overtaking, which I now can't do...

However there have been situations where if I didn't have the power, I could have been in some serious doo-doo.

I ride more aggressively with the restriction than I do without, probably because it's pissing me the **** off.



It'll be coming out ASAP.

If you can get a spanner on the other side of the bracket why dont you drill out the old thread, put a longer 6mm cap head bolt in with a lock nut on the other end

Or

http://cgi.ebay.co.uk/ws/eBayI ... 311c0a0aad463d6a3ffeabbc2

Ahh, my Bad. It's not actually a bolt. It's a screw with a hex-head thing.

It just pops into the hole in the bracket and then screws in to the (presumably) frame of the bike which I'm guessing is threaded, although I can't remember.

As I said, I can't be bothered to risk screwing it up, so I'll just leave it and let someone else deal with it.

Quote from S14 DRIFT :

It just pops into the hole in the bracket and then screws in to the (presumably) frame of the bike which I'm guessing is threaded, although I can't remember.

Highly unlikely it will go directly in to the (sub)frame even on that bike (btw is it a new Z750? or old?), far more likely to be screwing in to a lug welded on to the frame.

It's a 2004 Z750. There's not much need to panic, though. Went to my local dealer and they'll sort it when they take the restrictor off (estimated time = 1 hour = £50+vat)

have you tryed heating the top of the nut then smacking her with a flat head to make the screw driver fitment...


works wonders.

I'd try but I don't want to **** it up any more, I'll just leave it till it goes in for the restrictor kit removal.

Quote from S14 DRIFT :

As some of you may know I'm not exactly the richest kid on the block, if I **** it up I'm screwed. My bike is my world, sounds cheesy I know. The seat is on in a way in which I'm safe, and it's not like I'm competent enough to strip my bike down to the throttle bodies to remove the shitty 1/8" travel throttle restriction. I'll just leave it for now, my bike's used daily and has no alarm so there's not an overly large drain on the battery.

If you don't want to get a proper repair kit then you have a couple of options. Firstly check the bolt isn't damaged, this is very unlikely if you have used a bolt that is either the same age or newer than the rest of the bracket. If you're using badly stored very old stock, which is never a good idea and only really likely to be an issue with unusual hard to find sizes with classics, it is possible that the bolt thread has crumbled away without damaging the internal thread on the bracket (very unlikely but always worth checking first).

The next very gash solution is to simply run the correct tap down the thread and see if it can cut through the cross threaded bit, your only likely to get away with this if you stopped quickly and didn't force the bolt right down to the bottom of the thread, if the bolt head can touch where it needs to when tight then forget about this (also note you will probably have stripped it by overtightening if this is the case).

If all of this fails and for whatever reason you don't want a repair kit then drilling the internal thread out and putting a nut on the end of the bolt is possible, but is a horrible solution and should never be done. The mechanically better way of doing this would be to tack the nut on so that it is captive on the bracket, but if you're going to spend a few minutes welding it then it would be a lot easier to use a proper thread repair kit.

Quote from andybarsblade :

http://cgi.ebay.co.uk/ws/eBayI ... 311c0a0aad463d6a3ffeabbc2

Rivnuts are the most horrible gash solution. If they're used to replace a hole like this then they will be a lot weaker and a lot less elegant a solution than repairing it properly. When they're used to try and prevent the need for fitting a captive nut to bolt something through thin metal they rip up what they are being put through and are liable to pull through when you don't want them to because of their inability to spread pressure and when you take them off they are guaranteed to turn, not too bad unless the muppet in question has decided to use a rivnut into a double skinned component :doh:

Quote from ajp71 :

Rivnuts are the most horrible gash solution. If they're used to replace a hole like this then they will be a lot weaker and a lot less elegant a solution than repairing it properly. When they're used to try and prevent the need for fitting a captive nut to bolt something through thin metal they rip up what they are being put through and are liable to pull through when you don't want them to because of their inability to spread pressure and when you take them off they are guaranteed to turn, not too bad unless the muppet in question has decided to use a rivnut into a double skinned component :doh:

I would agree with this however its only a screw to hold the seat down as as such a riv nut should do the job fine (aslong as the seat is not over torqued to 50nm)