Author Topic: Damned Header Bolts !!  (Read 193 times)

Offline Speedy1959

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Damned Header Bolts !!
« on: Wednesday, 14 September 2022, 06:51 pm »
I had noticed a slight blowing from the Number 2 downpipe (centre left exhaust as you sit on the bike), especially when cold. It’s much less noticeable once the engine is hot.

As you may know, although my bike is a late K7 model it has had the earlier 4 into 2 system retro fitted (which I like).

The logic in my head said the stainless hex head bolts shouldn’t be too hard to remove as they won’t have been in that long! (Bike has done just 7,000 miles in total from new).
So I thought I would remove them all and treat them to a generous coating of aluminium Anti Seize Paste. (Higher heat rating then copper slip).
I started to remove the bolts 1 by 1.
The outer 2 cylinders came out with some difficulty but eventually after much turning the bolts backwards and forwards and adding generous amounts of “Kroil” I managed to remove and replace with the addition of plenty of the anti seize.. I even used a small brush to paint the insides of the threads in the holes.

With the 2 outer bolts removed and now replaced with the addition of anti seize I thought I would do an experiment..
I re removed a bolt and obviously it came out very easily..
After a ride out (engine very hot) I tried removing the same bolt again..
Noticeably MORE difficult!
Yes it was harder to remove with the engine hot!
That got me thinking…

Next day: (Cold engine).
Oil cooler radiator released and dropped forwards…
The inside 2 cylinders were FAR more difficult..
I Can’t understand why someone would go to the trouble of changing the exhaust and NOT treating the bolts to anti seize!
I managed to get a single crack from 3 of the remaining 4 bolts, moving back and forwards, with more force than I was comfortable with.
I stuck to using a 3/8” drive stubby ratchet driver so I was less likely to snap a bolt.
I decided to leave over night and leave the Kroil to hopefully do its work..
In the morning 1 of the remaining 4 was removed (eventually).

Next day and after some research:

 I bought a can of “Arctic Freeze Crack It” spray ( )

This stuff freezes down to -50C
I sprayed the head and the exposed threads liberally..
I did 1 bolt at a time..
2 of the remaining 3 bolts came out !!

The last one refused to come out!
It turned back and forwards maybe 3/4 of a turn but refused to go any more.
The stuck one is 4th from the left as sat on the bike..
This is the cylinder that was blowing in the 1st place.

I did notice that when I removed the stubborn bolts neighbour that the collar was loose!
In other words this would account for the blowing exhaust.
I moved up to a full size ratchet and spent around 40 minutes moving this bolt back and forwards as far as I dare..
The long Hex bit I was using was actually flexing.
Its so frustrating that I have removed 7 of the 8 bolts and treated them all to anti seize.
My big fear was snapping the head off.

I decided to cut my losses and leave well alone, BUT I didn’t want the blowing exhaust sound..
I had a bit of a brain storm overnight..
I got an M8 washer and cut a slot into it making it into a “C” washer..
I went back to the stubborn bolt and undid it as much as I dare (3/4 turn)..
Then with the collar loose and with some difficulty I managed to “wodge” the “C” washer into place behind the stuck bolt head and stainless washer that was already there.
I fitted the other neighbouring bolt and tightened them both evenly..
I only managed just less than half a turn on the stubborn bolt, so this says to me that its connected and seated properly with my home made “shim” fitted.

I started the engine and absolutely no blowing from any of the exhaust head bolt areas..

A bit peed off that I didn’t manage to remove the bolt in the end..
But bloody relieved that I cured the leak and didn’t snap a bolt!

Power is how hard you hit the wall....
Torque is how far you take the wall with you !

Offline Hooli

Re: Damned Header Bolts !!
« Reply #1 on: Wednesday, 14 September 2022, 07:14 pm »
Nice bodge, I'd probably do the same rather than snap bolts.

Offline froudy

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Re: Damned Header Bolts !!
« Reply #2 on: Saturday, 17 September 2022, 05:04 pm »
Interesting to know for reference that with a hot engine the bolts are harder to remove. I've always understood that the alu expands quicker than the steel bolt when heating up making them easier to get out. Having re thought that, I'm pretty sure that the alu does expand quicker, but once it gets to a certain temp, the steel bolt also starts to expand thus making it tight again. I imagine that there is a short time frame to get the bolt out before it too expands and tightens up again..I could be wrong.

If the bolt heads are really rusty, I've always smacked a 1/4 drive 12mm multi point socket over the bolt head. The impact caused by hitting it on "Breaks" the rust seal where the bolt passes through the collet. If you notice, when the bolts shear off it's usually in the collet rather than flush with the head itself.

PlusGas is your best friend here along with NickelSlip grease when refitting the new bolts.
Assumption is the mother of all fuck ups!

Offline Speedy1959

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Re: Damned Header Bolts !!
« Reply #3 on: Sunday, 18 September 2022, 12:05 pm »
Hi Froudy..
I agree about the ally expanding..
BUT.. To think a bit outside of the box, does this mean it expands into the hole thats drilled and tapped that the bolts go into, thus gripping the bolt tighter?
My bolts are stainless Hex headed bolts that someone in the past went to great trouble to replace when they converted my 2008 bike into the earlier 4 into 2 system..
I am totally amazed they didnt use any anti seize..
My default anti seize of choice in the Auminium based version.. As you say it can stand a much higher temp than copperslip.

Lastly none of the bolts (in my case) were seized into the collets / flange.. They were actually seized into the ally head as the collets were loose in some cases when I slackened the bolts I could actually loosen. (Hope that makes sense)...
For now I will live with the one seized bolt as its now not causing a blow by leak...
The other 7 I well and truly treated with Aluminium anti seize very generously !!
Power is how hard you hit the wall....
Torque is how far you take the wall with you !


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