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I found that the exhaust port angle changed in 1966, so different pipes are needed for the early heads.

Regards


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Originally Posted by Allan G
It’s a year on year thing. The headers with the balance pipe came
In around 69/70 (purely for noise reduction)

66? 67/68 would have had the tie bar (so a stub under each header)

Years prior to that had no tie bar or balance pipe.

'67 had a flat brace instead of a round tie bar. But right, no tie was pre-'67 or pre-'66.

Andy: "# 2 which BSA,s only used 2 single twin headers pipes."

Not sure what you mean here. Do you mean as opposed to a 2-into-1 or high exhaust? All unit twins had a single pipe on each side except for the Clubman and '69-'72 Firebird Scramblers, which had Siamesed, or 2-into-one, pipes. Hornets, Wasps, and the '68 Firebird Scrambler had single pipes, but they were up high.

So ideally, you want 1967 header pipes, but '68 or '69 would do. I would stay away from the ones with the balance pipe, as they are a PITA to mount and dismount, in my opinion. But don't count on the aftermarket pipes fitting correctly; they often do not (see previous replies about this). Take whatever steps are needed to ensure that they fit well - the damage to your present pipe was likely caused by its being mounted under stress.

FWIW, it's correct that one pipe is longer than the other.


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Didn’t read the entire thread,…. But: would it be possible to cut some of the inlet off, so the pipe moves aft? Maybe not, Dunno..


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Originally Posted by Mark Z
Originally Posted by Allan G
It’s a year on year thing. The headers with the balance pipe came
In around 69/70 (purely for noise reduction)

66? 67/68 would have had the tie bar (so a stub under each header)

Years prior to that had no tie bar or balance pipe.

'67 had a flat brace instead of a round tie bar. But right, no tie was pre-'67 or pre-'66.

Andy: "# 2 which BSA,s only used 2 single twin headers pipes."

Not sure what you mean here. Do you mean as opposed to a 2-into-1 or high exhaust? All unit twins had a single pipe on each side except for the Clubman and '69-'72 Firebird Scramblers, which had Siamesed, or 2-into-one, pipes. Hornets, Wasps, and the '68 Firebird Scrambler had single pipes, but they were up high.

So ideally, you want 1967 header pipes, but '68 or '69 would do. I would stay away from the ones with the balance pipe, as they are a PITA to mount and dismount, in my opinion. But don't count on the aftermarket pipes fitting correctly; they often do not (see previous replies about this). Take whatever steps are needed to ensure that they fit well - the damage to your present pipe was likely caused by its being mounted under stress.

FWIW, it's correct that one pipe is longer than the other.

I don’t believe any of the bikes used a tubular threaded rod like some repo items, the flat brace you refer to is what I would call a bar (or flat bar) typically anything different I’d call a threaded rod. The pre 67 models had no additional support apart from the mountings under the frame. The Siamese is a different thing altogether as it is held together by the pipes joining together, though a threaded rod does help to keep these tight in the head. Essentially also yes I’m ignoring fancy pipe work like high level, TT Pipes, Siamese or anything that isn’t the conventional 2- downpipes leading to low mount silencers. I didn’t think it was worth mentioning those as it adds to confusion…


Also who is Andy? 😉


Now let’s all have a beer beerchug

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71’ A65 823 Thunderbolt (now rebuilt)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

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Originally Posted by andyame1974
This thread is a bit old but yet as my search seemed to be relevant without any hijacks, maybe fellow members can relate, After rebuild/restore after 40 plus years in storage of a 1969 royal star with a 1967 650 engine, presently in the process of reinstalling the engine header pipes. These pipes have neither the balanced tubes or straps, just the tab which bolts to the lower frame tabs. There was as i recall some parts trading with a buddy that aquired the same model of bike and parts back then.

Anyways after all these years i find that the L/H header pipe mounting bracket has been pushed forward and has been indented into the header pipe radius about 1/8th of a inch with a cracked weld with the same, Most likely from a back slide one night back then with also good scrapes into the chrome exterior of the pipe.

When i set both pipes side by side the R/H is 1 1/2 longer then the L/H side, Hopeing this will not affect muffler mounting,

My Question is, 1, Which BSA 650.s only used twin header pipes without the balance pipes and also and the straps between the pipes.
# 2 which BSA,s only used 2 single twin headers pipes.

Any good suggestions for good proper replacements for type much appreciated

Allan, here's the post from "andy". My description of the various exhaust configurations was in answer to his question #2 (i.e., not anything you wrote).

BTW, I made an error in writing that the '69-'72 Firebird pipes were "Siamesed"; they were two separate pipes up along the left side. So I guess the only Saimesed pipes were on the Lightning Clubman.

I have seen round cross-braces and I had assumed that they were stock in some year(s), but perhaps they were aftermarket (or homemade).


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Just reread this post, The #2 Q was badly written, I was trying to determine if the Bsa 500,s in 1969 came with headers without balance tubes or straps, Which was what the bike was originally when i purchased it, with the original 500 engine and 2 650, engines along many extra parts. Sorry for not proof reading and confusion.

Thanks for reply Mark, Allen for education and advise with aftermarket spares fitments. I am still considering trying to find new pipes without the balance tubes or straps to replace my scraped up l/h header and welcome any recomendations for suppliers.

After reading from Mark that the pipes are often different lenghts at the muffles ends, I examined the pipe/frame brackets mounting again and find that even though the bracket tab was what appeared to be bent forward, It gives the head port connection a tighter fit, So if i had got a muffles shop to heat the pipe tab up and bend it back to the rear that i would then loose the tight connection into the head port. I was too concerned about the stagger with the rear end connection of 1 1/2 inch with the mufflers.

What i thought was a cracked weld was just dirt in the seam. Although it does not look like right that the tab has been bent forward, It seems to been done on for a reason.

Thanks again guys, , Andy

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Originally Posted by Mark Z
Originally Posted by andyame1974
This thread is a bit old but yet as my search seemed to be relevant without any hijacks, maybe fellow members can relate, After rebuild/restore after 40 plus years in storage of a 1969 royal star with a 1967 650 engine, presently in the process of reinstalling the engine header pipes. These pipes have neither the balanced tubes or straps, just the tab which bolts to the lower frame tabs. There was as i recall some parts trading with a buddy that aquired the same model of bike and parts back then.

Anyways after all these years i find that the L/H header pipe mounting bracket has been pushed forward and has been indented into the header pipe radius about 1/8th of a inch with a cracked weld with the same, Most likely from a back slide one night back then with also good scrapes into the chrome exterior of the pipe.

When i set both pipes side by side the R/H is 1 1/2 longer then the L/H side, Hopeing this will not affect muffler mounting,

My Question is, 1, Which BSA 650.s only used twin header pipes without the balance pipes and also and the straps between the pipes.
# 2 which BSA,s only used 2 single twin headers pipes.

Any good suggestions for good proper replacements for type much appreciated

Allan, here's the post from "andy".


Ahh, that makes sense, Despite being called Allan I often get called Andy (god knows why?) I thought it was one of those moments.


Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (now rebuilt)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

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