Sheared restraining bolt for exhaust pipe joint

[rocker]

Can't possibly imagine I am the first to experience this much feared faux pas, but have managed to shear one of the bolts restaining the exhaust pipe joint. Gave up after that, but still need to remove others and now have this sorted! Anyone else been fated with this, and how did you overcome? Have previously posted concerning exhausts and have gone for OS Pipes who will do me a pair of downpipes for £180. It is their stipulation that I remove the old pipes myself that has led to this latest setback.

[Steve Lake]

what bike?
was this the header pipes?
exhaust studs in the head?

[KirriePete]

As Steve (one of the many) says - is it the studs holding the headers in the head or another connection further downstream?

If it's the head studs then you could try copious quantities of Plusgas (other penetrant fluids are available, but nowhere need as effective) and heat, you may be lucky and get the remaining studs undone.  If not then it's time to drill:

1.  Get the remaining top of the stud as smooth & flat as possible (Dremels are good at this)
2.  Centre punch the stud as near to the actual centre as possible
3.  Start with a 3mm drill and go slowly, lots of lubricant, keep the drill straight down the middle
4.  Expand the pilot hole with a 4mm, then 5mm, then 6mm - hopefully the remnants of the stud will peel out of the head like an orange peel, if not:
5.  Use a 6.8mm drill and VERY CAREFULLY open up the hole once more - this will expose the thread tops in the head if you've drilled straight down the middle.  If you're off-centre you will be drilling out the thread, not a great heartache as the next step is to tap a new one, it'll just be a bit off-centre.
6.  Using an M8 x 1.25 tap, slowly recut the thread, maximum 1/4 turn at a time and back off.  Lots of lube, lots of patience.  If you have trouble getting started try a quick zip with an 8mm drill just to get a lip of a couple of mm, no more.
7.  Get some new studs from Honda (expensive) or a length of M8 x 1.25 threaded bar (stainless steel is good) and cut studs to suit (not as expensive).  Remember to use some form of barrier when putting the new studs in - copaslip or the like.

Slightly skewed studs aren't a huge issue as the 'zorst clamps have a fair amount of leeway, as long as we're not in the 'Marty Feldman' league it should be OK.

Go on, ask me how I know this, I dare you!

Oh alright - edited to add some piccies:

Before:



During:
Phase 1 - smooth the stud (notice the cross on top - Dremel for centring - it worked OK)



Phase 2 - drill out



Phase 3 - tap



After - shiny new studs:



Oh yeah - make sure you get rid of all the swarf or your engine will have a very short lifespan with it's new zorst!

You're welcome

[crackedhead]

Nice job that you've done there Pete. Out of interest, who is doing the work on the Camshaft for you?

[KirriePete]

I thank you kind sir - all done by hand - no drill stands or nuffink here!

As for the cam - dropped in to Agra Engineering in Dundee, they don't do it in-house but he uses some firm in Kent, didn't give me a name.  Looking at the standard of the work they do, I figured they would know where was best.  Chatting to the guy(s) only reinforced that attitude - proper old skool engineer types, not quite half a Woodbine behind the ear but you get the drift.

[themoudie]

I'll trailer the F650 across Pete! Water jacket 2mm off the back of the studs and the whole cast from soft drink cans!

I'm going to have to get the digit out!

Regards, Bill.

[Steve Lake]

As for the cam - dropped in to Agra Engineering in Dundee, they don't do it in-house but he uses some firm in Kent, didn't give me a name. 

Are 'Kent Cams' still in business?

looks like it  http://www.kentcams.com/

[KirriePete]

As for the cam - dropped in to Agra Engineering in Dundee, they don't do it in-house but he uses some firm in Kent, didn't give me a name. 

Are 'Kent Cams' still in business?

looks like it  http://www.kentcams.com/

Looks like they're the chappies.

Oooh, just seen they do a race profile cam for Arfur ..... credit card already melted ..... must resist...

[guest18]

hmmmmm wonder how much......

[guest564]

I have a Kent cam for an XBR, its a very poor grind, quite different timing from one side to the other. They also ground the lobes very small so the rocker angles are all wrong and the tappets don't hit square. I wouldn't buy another one, I think that its best to get one welded up and reground.

[KungFooBob]

My HRC spec cam from Joy turned up last Friday, I need to slot the cam sprocket and work out how to 'dial' it in, looks like a very professional job.

[guest564]

The sprocket is very hard, I had mine spark eroded. Timings is pretty straightforward to set up. I usually set it up as I build up the engine.

You must check valve to piston clearances before you turn the engine over with the valve clearances set.


Set up the degree disc on the alternator side of the crank with a strip of metal bolted to the crankcase as a marker. Set up the dial gauge on the piston crown and rotate the crank to measure 1mm piston travel either way, then split the difference. Its a lot more accurate than trying to determine the exact point of TDC with the dial gauge.
Assemble the top end and set the valve clearances, then set up the dial gauge on one tappet. You will have to make/find some sort of cap to go over the end of the tappet or the gauge will slip off/fall down the slot.
Check where the valve is at 1mm lift and write this down, repeat for all 4 valves. The HRC cam was spot on but you will probably find that your timing varies a bit so you will need to judge the best timing. Move the sprocket so it times up right and you're good to go.

Inlet Opens 45 BTDC
Inlet closes 50 ABDC
Exhaust Opens 60 BBDC
Exhaust closes 35 ATDC

First time with a new cam I usually set the valve timing with the piston removed and then reassemble and check the valve/piston clearance.