Exhaust downpipes with twin balance pipes, on R75/6 ?

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Restless
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Exhaust downpipes with twin balance pipes, on R75/6 ?

Postby Restless » Wed Apr 07, 2021 2:12 pm

The downpipes on my R75/6 are chrome but have seen better days, although they are completely serviceable. The bike has Keihan silencers, which look excellent, and I have a spare set of used stainless steel downpipes handed to me by the previous owner. The S/S downpipes look as if they will clean up quite well although I have not scrutinised them to see whether there are any manufacturer details. I've measured all the pipes as being 38mm in diameter, as I'd expect. I have however noted that the original pipes have a single balance pipe at the front of the engine, as they should, but the S/S set have a second one at the rear (so they were made for a later model I assume). Because I have removed the exhaust ring nuts to clean the threads, I'm wondering whether to spend a little more time and to remove the headers and to have a go at fitting the S/S ones. However, if it's going to be a pointless exercise, it would be useful to know in advance! I'm wondering whether anyone can comment on:

- Is there likely to be a problem with centre stand retraction on the R75/6, if the second balance pipe is there?

- Could adding the second balance pipe have any negative effect when running? Nothing I have read suggests that it would be likely to make much difference.

Roy Gavin
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Re: Exhaust downpipes with twin balance pipes, on R75/6 ?

Postby Roy Gavin » Thu Apr 08, 2021 6:03 am

Try them and let us know what you find.
But what you have read is what folk who have tested on a dyno usually find, on a legally silenced bike one if fine, and the location or adding a second makes no measurable difference.

John Marshall
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Re: Exhaust downpipes with twin balance pipes, on R75/6 ?

Postby John Marshall » Thu Apr 08, 2021 8:11 am

If it fits without stressing or impeding anything fine. If not you will need to source a pair of the correct pipes ideally in SS to match. Maybe second hand available to reduce £ ?
John

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Rob Frankhamr
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Re: Exhaust downpipes with twin balance pipes, on R75/6 ?

Postby Rob Frankhamr » Thu Apr 08, 2021 9:30 am

I think you'll find that the second crossover will foul the main stand which is why the stand was changed in 1981 replacing a pretty good stand with one that is barely adequate and subject to wear. The second crossover will make a small difference to the power curve but whether, it is a detriment or an improvement and whether it will be noticeable in normal use is open to doubt.

Rob
Last edited by Rob Frankhamr on Fri Apr 09, 2021 9:46 pm, edited 1 time in total.
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Restless
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Re: Exhaust downpipes with twin balance pipes, on R75/6 ?

Postby Restless » Fri Apr 09, 2021 3:06 pm

Thanks for the replies - very helpful. I've taken a closer look and I can see that the rear balance pipe would indeed conflict with the centre stand, so I think I'll now start by removing the original pipes and see if I can clean them up to an acceptable state. If not then I could be in the market for some 2nd hand stainless headers of the right type, and of course I might be putting the wrong type up for sale, although I'll examine them again and see if I can identify the maker first. It occurs to me that it could perhaps be possible to saw off the second balance pipe on the S/S set and have someone weld blanking plates over the resulting holes to blank them off; the scars shouldn't be visible but I suspect that the cost/trouble might not be worthwhile.

Richard


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