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1Back to top Go down   Corroded exhaust header flanges on 16v Empty Corroded exhaust header flanges on 16v on Sun Mar 08, 2020 1:17 pm

stanthomas

stanthomas
Silver member
Silver member
I've pulled the exhaust off my '91 K100RS 16V.
 As you can see in the pic, the flanges are badly corroded. Looks like flanges are permanently attached to the pipes on 16Vs. My plan now is to grind the rust away and either weld the flanges to the pipe or make up collets to hold the flange against the lip on the end of the pipe. I'd be grateful for some information about what they were like when new. Should the flanges 'float' on the pipe so they can be aligned with the studs or were they originally welded up solid? And are they just that bit of flat 5mm plate or did they incorporate a sleeve that's rusted onto the pipe on mine?
Corroded exhaust header flanges on 16v Y4m556byVNAifVIjTdOhE-T2hl3vskEdiq2HYAbnZcNhVYhIjSEouUWaPT9ZbJfXrt3X9LJT6iPhWqp7yPMqhHzkRdMuYG8GBZqaiWctO6uaW86PPV9IHAnp1sJEbpRP3B2lBj-MB8MHFUj0jFhNs-Wok85nqiLruEaDZ9rIV7aexKm_dc_O8Vu0CY0-bm7-W_JsbGPEZFDD5ruRgKluZ61PA?width=576&height=1024&cropmode=none

All the nuts were rusted on so the studs have come out. (and been thrown in the bin). As you can see in this pic, one stud on #2 brought an insert out with it. Looks a little diffrent from your run-of-the-mill helicoil. Do all the studs holes in the head have inserts or is this a repair?
Corroded exhaust header flanges on 16v Y4mAvIPNdZyS4yad5r0t5jElzxWlBLXPpwQhDgT0qBdZgBlKFPOGx8WsmnZzdSKnsE_mdyxThMr4xyb3DT__9OkywzOIN_fpHTAof68QFI4EWG1haji0VnwCjs1S186D2Gp95qtOVVENc8c-nMJuERCTxk_cfc3py-HcxLQpzY_F6cTYb45DxZyHDeCHW_dMcT8ziwS7QAYO49uqrnekUCsaA?width=1024&height=575&cropmode=none

    

Dai

Dai
Life time member
Life time member
https://www.ebay.co.uk/itm/BMW-K100-exhaust-headers-and-collars/153847943390?hash=item23d20d50de:g:daMAAOSw1T1eLbQc

I'd jump: that's a good price for decent set of exhaust pipes.

Pic.2: That looks like a timesert/nutsert. It's a repair, but unlike a helicoil it has a thread rolled down a solid tube. I'd try and wind it back in. Normally I reserve ***serts as a last-chance-saloon repair for the simple reason that (e.g. off the top of my head and IIRC) a 6mm helicoil requires a 6.2mm drill and 7.0mm tap, but a 6mm ****sert requires a 6.5mm drill and an 8mm tap. It takes a much bigger hole to fit.

Oh yes - you haven't pinged out the old gaskets yet as I can still see them. Highly recommended tool for doing just that:

https://www.ebay.co.uk/itm/Draper-Automotive-Universial-O-Ring-Oil-Seal-Puller-Remover-Tool-Hook-37439/302147640823?epid=1205673631&hash=item4659671df7:g:yksAAOSwHMJYNx67


__________________________________________________
1983 K100 upgraded to K100RS spec, 1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

stanthomas

stanthomas
Silver member
Silver member
@Dai wrote:https://www.ebay.co.uk/itm/BMW-K100-exhaust-headers-and-collars/153847943390

I'd jump: that's a good price for decent set of exhaust pipes.
...
They're for an 8V. I suppose I could saw the header pipes off mine, leaving a length of straight pipe sticking out of the silencer, and sleeve the 8V headers on to them. Might stop them cracking at the welds too.

Something to think about. Thanks.

    

Dai

Dai
Life time member
Life time member
Nothing to stop you mounting a square silencer on the RS. You'll need to fiddle a bit around the mounting point, but it's not insurmountable. Otherwise, if you source another 16v pipe, fit a jubilee clip around all four pipes and about three inches forward of the welds. It shifts the resonant frequency of the exhaust and greatly reduces the probability of the welds cracking.


__________________________________________________
1983 K100 upgraded to K100RS spec, 1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

stanthomas

stanthomas
Silver member
Silver member
I quite like the square silencer now, has a certain quirky charm. Although I was rather rude about them 35 years ago. But I'd have to buy one of those too and this bike is in a mend and make do phase.

Is the only difference between 8v and 16V headers that the flange is loose on the 8V and welded in situ on the 16V? Or is there something more subtle going on?

And, on a more general point: the headers look to be quite different lengths going into the collector although they should ideally be the same length. They do bend all over the place but I don't think there's enough to equalise the lengths. Is this something the aftermarket exhausts try to address?

    

6Back to top Go down   Corroded exhaust header flanges on 16v Empty Exhaust on Sun Mar 08, 2020 7:15 pm

daveyson

daveyson
Life time member
Life time member
I'm thinking the newer exhaust is made to look smaller for looks. 

Another way of looking at it is if cylinder four header, for example, goes further into the muffler, it's overall length is more equal to the others, for a more balanced performance. I've noticed that on my bike too.


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
    

7Back to top Go down   Corroded exhaust header flanges on 16v Empty Re: Corroded exhaust header flanges on 16v on Sun Mar 08, 2020 10:20 pm

Point-Seven-five

Point-Seven-five
Life time member
Life time member
The two valve exhaust can fairly easily be fitted to a 16 valve K100.  Took me an afternoon, mostly fiddling with the centerstand and lining up the hanger with the mount.  No perceptible difference in performance or sound. 

A very minor loss of cornering clearance on left turns, but I ride like an old man, not wanting to scratch up the luggage in a low side.


__________________________________________________
Present:
1994 K75RT
1991 K100RS
1988 K100RS SE

Past:
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

Dai

Dai
Life time member
Life time member
If you do go for a square pipe, I'd leave the exhaust-to-silencer clamps off. They're a bastard to get lined up so that you can tighten them up individually and the inner one inevitably corrodes so badly that you can't unscrew it again. Low Flying Brick has no clamps on and there's no increase in noise, nor is there any trace of carbon around the joints.


__________________________________________________
1983 K100 upgraded to K100RS spec, 1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

9Back to top Go down   Corroded exhaust header flanges on 16v Empty Re: Corroded exhaust header flanges on 16v on Mon Mar 09, 2020 11:41 am

Point-Seven-five

Point-Seven-five
Life time member
Life time member
@Dai wrote:If you do go for a square pipe, I'd leave the exhaust-to-silencer clamps off. They're a bastard to get lined up so that you can tighten them up individually and the inner one inevitably corrodes so badly that you can't unscrew it again. Low Flying Brick has no clamps on and there's no increase in noise, nor is there any trace of carbon around the joints.
Any backfire issues?


__________________________________________________
Present:
1994 K75RT
1991 K100RS
1988 K100RS SE

Past:
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

10Back to top Go down   Corroded exhaust header flanges on 16v Empty Re: Corroded exhaust header flanges on 16v on Mon Mar 09, 2020 11:54 am

Dai

Dai
Life time member
Life time member
None whatsoever.


__________________________________________________
1983 K100 upgraded to K100RS spec, 1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

11Back to top Go down   Corroded exhaust header flanges on 16v Empty Re: Corroded exhaust header flanges on 16v on Tue Apr 14, 2020 11:35 pm

lion1453

lion1453
active member
active member
Cobraexhaust have

    

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