The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: Billmc on October 13, 2016, 09:26:26 AM
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If I replace the crapped out, California required catalytic converter on my '87 with new longer, dual wall exhaust pipes that hook directly up to the stock mufflers, will I have to re-jet the Bings?
They new ones still have the front crossover.
I'm trying to clean up the flow and look and get rid of the heat generated by that CAT.
Thanks, Bill
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I'm not sure about which pieces of the exhaust system you're referring to. My '86 has never had a catalytic converter. Do you mean the exhaust box the headers run into? (or am I ignorant and that box is the catalytic converter?)
To my mind exhaust pipes (headers) come before mufflers. Are you wanting to replace last piece of the system, or the first part?
In general, if you stay close to stock you won't have to rejet. I did not notice any difference when I switched from the stock mufflers to the stainless steel Keihans.
I'm intrigued by the thought of dual wall exhaust headers but suspect they won't fit the exhaust nuts. What parts are you intending to put on the bike?
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Realoem.com calls it a "FRONT MUFFLER"
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Yes, The exhaust pipes are the 1st part and are attached on the exhaust ports. The mufflers are the 2nd part and are at the rear attached to the exhaust pipes. In between is a large, heavy, hot catalytic converter that I believe was only on California destined bikes.
The new set is from MAC Performance and are listed as 35mm exhaust header head pipes. They are longer by the length of the CAT and are supposed to be direct fit to the mufflers at their factory mounting locations.
There shouldn't be a change in the jetting as the overall length stays the same, but I needed a little bit of experience to confirm. Thanks!
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I would not worry about jetting with replacing the headers, presuming they are the same size. However, I would triple check, perhaps even to the point of measuring the existing headers, because I think there is a 38mm header and a 35 mm header.
Although my '86 headers fit the '84 motor just fine... Perhaps I"m thinking of the outlets the mufflers attach to.
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Monte I'm too new to this BMW R65 world to know that answer.
When I took it off to patch the holes and to clean it up it just felt too heavy to just be a "muffler", (even though it was chromed) and when I tapped it to clean out the inside and a bunch of carbon came out, I just naturally thought it was.
Whatever it is it's ugly, heavy, hot and needs to go!
BMW did this to satisfy a law and external requirement, not because they liked it. Look how clean and open the prier years are without it.
That's what I want!
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The parts fiche lists that front muffler at $519.89. You would think it was made of precious metal at that price. The question is academic at such a high price and I can understand you wanting to get rid of it.
I can't imagine re-jetting would be needed.
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It is made of precious metal, platinum just like automotive catalytic converters .
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If that is a CAT it may be worth something at the scrap yard ;D
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MY 88 R100RT, which never went west of the Mississippi, had the same box. There are some claims that it does help the tuning with the stock jetting for improving mid-range torque, as the lower compression late 80s airheads were significantly down on peak HP than the late 70s/early 80s models, but - in my experience anyway, the late 80s models actually ran more smoothly at reasonable road speeds (anything under 80 MPH). But, YMMV - you'll never know what happens til you try it - but I wouldn't throw out that 'collector box' as it was sometimes called - someone (possibly you) might really need one someday..
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I'm not going to throw it away, just want it off!
Not sure about doing the dual wall pipes its just that those are what popped up when I did a search. I have no problem with the bluing of the pipes, its the rusted, pitted corroded front crossover and similar condition of the 'front muffler' as its called. If I could find a good exhaust shop that could bend me a pair of short, polished stainless steel replacements for the 'box' I would do that and live with the ugly parts.
That would make it a 3 pipe system instead of 2 but that would be ok.
I'll keep you updated as I progress with this and THANKS for y'all's input, mucho appreciatado !
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Exhaust pipe wrapping is supposed to be a good thing from a performance point of view. Exhaust gases slow down as they cool so the wrap helps keep the exhaust gas velocity up.
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Barry, what 'fiberglass tape' did you use, specifically for exhausts or just bought at the boat supply store variety?
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Bill,
I imagine it's proper exhaust wrap but Monte is the man with the taped exhausts.
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Bill,
I imagine it's proper exhaust wrap but Monte is the man with the taped exhausts.
Right, sorry Barry.
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I wish this post was made a week ago - that is when I wrapped mine, without gloves - without soaking them. It was a decent job but made my arms and hands itchy. I used SunPlus Titanium tape 2".
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I used 1" tape when I wrapped mine. Someone told me it would allow a tighter wrap in the headpipe bends. I did but it took forever to wrap. Plus it took about 35' per side to complete the wrap back to the start of the muffler (so 2 rolls needed).
Soaked in water to wrap and went out for a ride after I was done to dry it out. Every time I came to a stop I was encased in my own personal fog bank. People kept honking and yelling ,"Hey man, I think your on fire!"