Exhaust to head question.

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Has anyone else had this happen on just one?

20150430_191344.jpg

20150430_192045.jpg


I got it back in place, but still have a slight exhaust leak. I have ordered all 4 new gaskets for them. Any thoughts??

Gary.
 

ST1100Y

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LOL! :lol:

Yes, the famous M7 nuts... never leave da house without a spare in your pocket... (don't ask, in '99 I chugged across half of Europe with one missing... ;-) )
They can come off if frequent checking their seating is neglected and/or they haven't been properly torqued to begin with...

The issue is, that it now would be wise to check all, gaining access however means removal of the heat shields and by the looks those bolts will snap off...
And since one downpipe already came loose, replacing all exhaust manifold gaskets (at least the two at the shown LHS head) seems recommendable as well...

Anyway, the M7 manifold flange nuts are used on 1100 and 1300 (possible other models as well), likely that a lister can offer to drop a spare one into a bubble-mailer and send it to you...
(I lurked on eBay till a full set from a wrecked 1300 came on for peanuts... but the postage for one sent from Europe to your place would cost more then I'd paid for the 8 pcs set...)

What would you need if going for the full job (item numbers for doing both sides):
- 8x 90304-MM5-000, nut, flange, 7mm (that's the one you're missing)
- 4x 18291-MN4-920, gasket ex pipe (copper gaskets manifold to head)
- 8x 95701-0601000, bolt, flange, 6x10 (bolts fixing the heat-shields on the manifolds)
- 2x 94103-06400, washer, plain, 6mm (washers for forward bottom fixing heat-shields)
- 8x 18292-415-000, packing protector (secret tip/improvement from pre '94 models! Place them between the heat-shields and the exhaust bracket to eliminate rattle/ping...)

The bolts fixing the heat shields will likely shear off... don't bother, you drill out the stub: a) punch a centre dent, b) place a big flat screwdriver between pipe and bracket (avoids puncturing the downpipe!), then pre-drill with a 3 or 3.5mm bit, c) carefully widen with a 4.8mm bit but keep centred (possible the remaining metal of the stub will already fall out), d) re-cut the threads with an M6 bit for blind-holes (their shorter)

Once the heat-shields are off, you can deal with the manifold gaskets, remove the nuts holding the flanges, gently pulling the downpipes down, small screwdriver to pry out the old gaskets, then place in the new copper rings (I always "glue" them in place with some copper slip or thick marine grease so they won't fall out the exhaust ports while working), seat the downpipes into the ports again, apply a slight smear of copper slip on the M7 studs, place the chromed nuts back on, set the flange plates evenly!, torque nuts with not more then 12Nm/8.85ft lb...

Now the heat-shields with the "new" packing washers:
Insert the new M6 bolt from outside and slip a packing over the threaded part from the inside, they'll grip there.
Apply some copper slip onto every bracket we just re-cut the threads, we want to avoid them rusting shut again...
Gentle place the heat shield towards the downpipes and "feel" the M6 bolts into the brackets and set them 1~2 turns by hand, then the next bolt, etc...
Don't forget to put the large washer on the low forward facing bolt...
Once all are have found their threads, tighten them evenly (don't overdo it though, re-cut threads and that...)

Button her back up and go ride silently again ;-)
 

SupraSabre

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They only time I have had any come off, was when I took them off. Probably a Friday afternoon bike at the factory. When they got to those nuts, they were getting ready to leave and forgot to tighten them up. Since you are replacing all of the gaskets (I would replace the nuts too), you'll be fine!
 

ST1100Y

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They only time I have had any come off, was when I took them off.
The one I lost was rattled off my prev '92 ST on the very bumpy roads in the Spanish Pyrenees (comming from a Pan-Gathering in Evora, Portugal) while on the way to Paris, France for the '99 Pan-Rally (Island Tour + the introduction of the ST1300...), 4 days on a noisy, farm-tractor ST were quite annoying ;-)
The Honda factory support at the Rally had no M7 exhaust flange nut avail, neither the local French crew, nor the escort/convoy from Honda AuSTria... tires, headlights, wheel bearings, brake pads, drive splines, whole crash-kits... but not a single nut for the exhaust manifold... :D
While kneeling half way below my '92 ST on the parking lot even a Japanese Honda representative appeared, asking what I actually needed to wrench on my bike there... so I pointed: M7, specials size, not avail... and the Japanese gentleman responded with their unique, throaty "ooohhhh..."... :lol:

During dinner a German rider approached me, handing me self made long-nut (prev M6, widened to M7), telling me he had the same issue once, since then he always carries some along...
I thanked, armed myself with a flash-light, rushed out onto the parking lot, pulled the access-cover and got that flange fixed :cool: (thankfully it was an accessible one, not covered by the heat-shields)

So the tour back to the south of France, Corse, Sardena, back to Italy, Swiss, and back home across Austria continued with a "silenced" ST...

Back home I took all off, rebuild as described above... never an issue since...
 
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GreenZR
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Thanks guy's!
I do have spare parts from my 91 parts bike. I have already replaced the missing nuts with the spares. Still have a bit of leaking going on. That's why I'm going to replace the gaskets. Could it be something other than the gaskets?

Gary.
 

ST1100Y

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Could it be something other than the gaskets?
Don't think so... once the flange came off the manifold moved out the gasket, which are soft, not reusable, stuffed copper rings, the pipe "imprints" into during first attachment; once the pipe moved, it'll never hit the same spot on the (now flattened) gasket...
Once you've new gaskets all will be fine again, but it'll require the procedures I wrote above...
 
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GreenZR
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Don't think so... once the flange came off the manifold moved out the gasket, which are soft, not reusable, stuffed copper rings, the pipe "imprints" into during first attachment; once the pipe moved, it'll never hit the same spot on the (now flattened) gasket...
Once you've new gaskets all will be fine again, but it'll require the procedures I wrote above...
Since it still leaks a little, I thought the old gasket might have gotten out of line just a little. I didn't have time to drop both sides & was pretty sure I would need new gaskets. That is what I'll do when they come in. I did break the front lower bolt on the heat shield and will probably break at least one on the other side. I have a metric tap & die set. So no problem with that repair. Parts are ordered, but we are camping and I won't be able to start on it for another 10 days.
 
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Just went through this process on my 91. I removed the entire exhaust to remove the oil pan. Broke 2 heat shield bolts on one side but no broken m7 studs. I was able to heat the broken shield bolts and get a pair of vice grips on them and they came right out.

Found some pipe to head gaskets real cheap on ebay, they were coiled which to me looked different than oe.

Got it all back together with no leaks but the m7 nuts seemd to tighten forever before the torque wrench clicked, and I could not get a torque wrench on the inner nuts of both front cyl's.

Sent from my SCH-I605 using Tapatalk
 
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GreenZR
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All is quiet now! I was able to replace the gaskets in about 2 hrs work so far.

20150515_194520.jpg

This was the leaking one.

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No wonder it was leaking.

20150515_202703.jpg

I still have to put all the plastic back on. I'll finish it tomorrow.
 

ST1100Y

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I was able to replace the gaskets in about 2 hrs work so far.
Brilliant! :yes:
Seems you also got the heat-shield bolts out nicely; remember copper-slip or at least anti-seize there.
And while engine and frame are already exposed, a layer of ACF-50 for conservation/corrosion inhibition (it'll gonna have that "new car stench" for a while though ;-) )
 
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