Author Topic: Tech Tip: An Approach to Header Bolt Removal  (Read 3797 times)

Offline gsxbarmy

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An Approach to Header Bolt Removal
« on: Wednesday, 08 February 2017, 08:56 am »
NOTE: This thread is also available to download as a PDF file from the Downloads (General) Section

These notes document how one owner managed to remove broken header bolts from his machine, as such they document the approach he took. As such they should be considered as an outline for consideration should you find yourself in the same situation.

WARNING:    Whilst if you are mechanically knowledgeable this is possible to do yourselves with the help of a couple of mates, patience and a little confidence, if you are at all unsure, you are strongly recommended to consult a specialist engineering firm to undertake the work for you, as the last thing you want to do is ruin your cylinder head.

NOTE (1):    Prevention is better than cure! When assembling header bolts (or studs) it is recommended to use Nickleslip on the bolts (or studs) in preference to Copaslip as Nickleslip will work at much higher temperatures than Copaslip (which possibly could dry out, although if you don’t have Nickleslip is better to use than nothing!)

NOTE (2):   if you believe your header bolts are going to be difficult to undo – or may potentially snap when you try to undo them – it is worthwhile soaking them in Plus Gas (preferably) or WD40 for the week or so preceding you undertaking the job. Apply Plus Gas or WD40 every night right up until you start to pull down your exhaust system

NOTE (3):   As mentioned above, if you do need to drill out the studs, it takes time and patience and a couple of mates on hand with the same temperament to assist.


The procedure below only applies for exhaust header bolts which may have snapped upon removal, leaving a broken off part of the bolt in the header and is only a guide, there is no guarantee that this will work for you if your stud has broken.

First off – prepare. To drill studs out you will need good access so as a minimum you will need to undo the oil cooler (it’s worth considering removing the oil cooler, also possibly dropping the front wheel and mudguard if you need to drill). Be careful if you just leave the cooler hanging on its hoses as, as we all know, OEM oil coolers are quite fragile, especially around the pipe mounts. Also make sure you have all the necessary tools to do the job to hand or know where to get them locally (so don’t do this job on a Sunday perhaps – DIY places don’t hold sets of taps typically and that the sort of tool you may need if you have to drill out studs).

We found that removing the oil cooler, front wheel, mudguard and forks worked well for us and made it easier to work on the bike overall, given we knew we had to drill some studs out.

In terms of tools consider you’ll need long enough 6mm hex bits to get into the head of those M8x25mm cap head bolts that are the header bolts. For shifting tight bolts my recommendation is stacking a 3/8” ratchet to a ¼” drive socket with a 6mm hex bit, as there is very limited clearance between the frame and you will need to go “straight” onto a header bolt. For removing “stiff” bolts you will need a firm construction using quality tools (i.e. Halfords Pro) to stand the best chance of getting any real grip. Cheaper tools may not fit as well or could break.

Two things to be aware of here:
•   Don’t use hex bits with ball ends. Whilst these are useful for getting to bolts at obtuse angles, they are a looser fit than going straight on with a hex bit and the last thing you want to do is round the inside of a head by using one of these when taking the tension off a header bolt (once the bolt is loose, by all means use them then for unscrewing the bolt)
•   Why not use sockets with long hex bits to undo the bolts? Truth is the sockets with long hex bits don’t work very well on seized or hard to move header bolts and can (potentially) round the inside of the bolt. However they are very handy to have for putting the bolts back in on re-assembly as they can sneak in between the confines of the small space between the frame and headers


So – you come to a bolt which won’t move and is potentially solid, what can you do. We mentioned about prepping the bolts using Plus Gas or WD40, but if on the day they are still solid – what are your options?

Essentially the bolts are 25mm long of which 17mm sits within the head. Plus Gas / WD40 will only penetrate the first couple of mm’s whatever you try. At the factory Suzuki dry installed these studs (no stud lock at least, something to be thankful for I suppose), why they didn’t use copaslip or nickleslip is anyone’s guess, but they didn’t thus the bolts over time cold weld and corrode themselves into the head.
 
Best options here if you come across a jammed bolt is either to pressure (whack) the bolts or heat them using a blowtorch to break the friction (some start the engine to warm the head up and then whack the nuts, if you do that do wear a pair of heatproof gloves as it gets damn hot for obvious reasons!

Our approach was to put a socket and the bolts and whack them, we also used a blowtorch around the bolts to heat them and used plenty of Plus Gas on them as we wound them out (including winding some back in and then out again 2 or 3 times). This worked for 5 of the bolts but 3 still snapped. This is where you start to need the patience as this process just takes time, you can’t rush it. Our belief of the bolts that snapped was that the corrosion was deeper into the head – where we couldn’t get at it.


The bolts that snapped left 5-10 mm stud sticking out. It was at this point that we discovered after going to the tool shop that these (expensive) stud extractors are totally useless for this situation (they are all designed for cars with nice long head studs) as they all need, by design about 20mm of stud to grip on.

Be prepared at this stage to saw the end of the bolt off close to the head (with a Dremmel). On the flat surface this leaves, centre punch then pilot drill a hole, followed by using a larger drill to remove the old stud. You need cobalt drills to suit tapping the resultant hole out to 8mm (so you need the first, second and plug taps for 8mm x 1.25mm pitch).

WARNING (1): Don’t wiggle around with cobalt drills, they are very sharp and will drill through a stud, but they are very brittle, if one snaps off in the stud it will be a nightmare! You need them because they are sharp, as ordinary drills will just “bounce” off or skid around on the surface you are attempting to drill.

WARNING (2): Don’t use Eziouts. They are super hard and if they break on the stud below the head surface it’s an engine out and spark erode job to repair. For that reason alone we didn’t even think of using them to remove these studs.

When drilling you might just get lucky and be able to pick out the old thread, just like they show in a book, in real life, you won’t! Just plan to tap.

Murphy’s Law states that you’ll need a Plan B “just in case”. Let’s call it “The 8mm re-thread plan” Why? Just in case your drilling goes a tad large. It would be useful if you have access to an 8mm helicoil set, which takes larger drills and taps to install, so if the 8mm plan (Plan A) goes wrong you have still have a plan B.

One question you might have is “do I need an expensive jig to go in straight”. In a perfect world this is correct, you do. But in real life with a good mate and a good Vernier gauge, you can drill straight (this proved vital through the day, don’t do this job without one).

The next step really depends on what headers you are fitting (or re-fitting). If you are fitting SBS (or Black Widow as they now call themselves) headers, they have a thicker header retention plate and sit off the head like the originals do. So depending on what headers you are fitting, measure this up and also the depth (using your vernier) of a good hole. Subtract the plate and clearance thickness from the bolt length (incl for the cylinder head considering the original thread depth that way you’ll know how far to drill and tap. In most cases, including for refitting standard headers, it’s about 17mm).

We found there is lots of clearance between the 8mm bolt and the Internal Diameter (ID) of the clearance holes on SBS headers, this means if your stud isn’t 100% straight it won’t matter, you have a bit of wiggle room (in fact you have lots).

One person drills (note: pilot then tap drill) whilst a mate sits alongside and watches / guides re the up and down angle (the driller can sort out the side to side angle) to keep the drill nice and straight when drilling the hole (so this is where the mates come in again, as this is a 2 person job. If you have a good eye, it can be done by yourself and is not as big an issue as you may believe). If you are not 100% confident, you could purchase an exhaust stud drill plate to help keep the drill bit aligned; one tip I did see from a friend was to bolt one (possibly two) of the OEM exhaust clamps on (assuming the stud on the other side didn’t snap!) using a slightly longer bolt so that it is aligned over the stud you are drilling out. If you do do this, remember to take the depth of the tool or clamps into account when measuring the depth to drill - Use the vernier regularly to check depth. Alternate between pilot and tap drill to make the holes. Let the drill cool regularly and dip it in oil to lubricate.


Once the remains of the studs were out we tapped the holes. You can’t use one of those straight bar woodworker type tradition tap bars, you need one of the T shaped ones or you won’t get in - you can’t turn a straight bar as the frame is in the way.

So once all the stud remains were out, and all the holes tapped, we put it all back together again. A few notes:

•   During re-assembly, we used stainless M8x25 1.25 pitch long header bolts – same size as OEM. The Suzuki input torque is 23Nm (16.5ft/lb) using no grease or stud lock. Given we were using Nickleslip (see Note (1) at the top of this write-up) we ignored all that (as when you use a grease, you need a slightly lower torque to compensate - Using copaslip the recommended torque is 70% of a dry assembly, so we assumed the same for Nickleslip). We decided to torque the headers to only 10Nm and used lots of Nickleslip and new copper gaskets. Once fitted we ran the engine and checked for leaks. All was good.

•   In my opinion there is no way you need 23Nm to hold the headers on, 10Nm gives a gas tight seal using new copper header gaskets and there is no way that assembly will fall off your bike. However, once you have covered 500 miles following re-assembly, do just check for loose bolts and re-torque as necessary.

•   As we suspected, if any of our bolts were slightly out of true re angle it really didn’t affect the re-assembly as there was a little leeway overall, sufficient to accommodate slight differences of our drilling. Liberal amounts of Nickleslip helped as well.

•   When re-fitting your exhaust system, you need to make sure that it all aligns, and this can be a bit tricky. The best place to start is with the bolt at the back of the collector box, inserted loosely and then mount up the headers, link pipes and exhausts all loosley – so in effect the whole system is just hanging on the bike. One tip here is some copaslip on the gaskets where the headers fit into the collector box, as it enables you to make slight adjustments without skinning your knuckles! First step is to make sure that all the headers are fully engaged in the collector box across all four pipes. Once in nip up (but don’t yet tighten. You now can nip up the headers at the cylinder head (but again not tighten (there should still be some, nut not much movement in the system). Lastly, jiggle the exhausts and link pipes to align the whole exhaust system and torque it all up. If at any time you can’t get enough movement for alignment, just back the nuts and bolts off a couple of flats to give the movement you need. Check once complete that all headers are firmly pushed into the head and collector. Sorted!

One last point. If you are buying replacement M8x25 aftermarket header bolts make sure you buy the 1.25 pitch type (they are also available aftermarket in 1.00 pitch). Suzuki definitely use the 1.25 pitch as standard! Likewise make sure you have the right “pitch” tap!

And that’s it. With a bit of confidence and assistance from some good mates it is a job you can do yourself. If not, then the alternate is to locate a local engineering company who can do the job for you and either transport the bike – or the engine – to them for them to undertake the job.

Nothing to do.............all day to do it....I love retirement :lol:

Offline V_i_c_i

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Re: An Approach to Header Bolt Removal
« Reply #1 on: Friday, 07 April 2017, 05:59 pm »
For removing steel bolt from aluminium works great HNO3  :onya:







But it is healt dangerous without experiences!!! You will do it on your onw risk!!!

 

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