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#593807 - 04/06/15 5:22 pm New BSA owner ***  
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barreto Offline
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Boise, ID
just picked up a 1972 Thunderbolt over the weekend and need some information that I can't seem to find anywhere.


I want to replace the current exhaust with a stock-looking system. I'd like to use this exhaust this exhaust but it says it's for up to 1970 models. I can't find any reason it wouldn't fit the 72, but I haven't been able to find a definite answer.

I'm planning on just replacing the exhaust, possibly updating the carburetor to a pwk, and then just riding it as is. My dad had a bsa like this in college and I've always wanted one.

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#593825 - 04/06/15 6:25 pm Re: New BSA owner [Re: barreto]  
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LarryLebel Online content
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Canada
Looks nice but do your neighbors a favor and add mufflers.

#593826 - 04/06/15 6:28 pm Re: New BSA owner [Re: barreto]  
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Keane Lucas Online content
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New Jersey
<www.classicbritishmotorcycles.com/bsa/ex...ml?review=write> A 71-72 OIF BSA has different exhaust mounting points than the earlier dry frame models. Please keep in mind that when it comes to pattern(reproduction) parts, that they may need some tweaking to fit.Some are a real ballbuster. The picture of these pipes show the primary (left)side kicking up a bit before the silencer.Do not buy a set of pipes that does not kick up on the primary side.If they are both straight(Armours) the silencers do not sit evenly and the center stand fouls the left silencer. Ask me how I know.There must be some outfit stateside or Canada that has these. This was the first picture I found to best make the point.Get a "Genuine BSA Spares" (parts) catalog for your model and order/inquire using factory part numbers.Reprints are cheap enough and vital for sanity.Considering the description these may be worthwhile. beerchug


1969 BSA A65T w/A70 engine
1970 Royal Enfield Interceptor S ll
#593843 - 04/06/15 9:04 pm Re: New BSA owner [Re: Keane Lucas]  
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barreto Offline
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Boise, ID
Originally Posted By Keane Lucas
<www.classicbritishmotorcycles.com/bsa/ex...ml?review=write> A 71-72 OIF BSA has a different exhaust than the earlier dry frame models. Please keep in mind that when it comes to pattern(reproduction) parts, that they may need some tweaking to fit.Some are a real ballbuster. The picture of these pipes show the primary (left)side kicking up a bit before the silencer.Do not buy a set of pipes that does not kick up on the primary side.If they are both straight the silencers do not sit evenly and the center stand fouls the left silencer. Ask me how I know.There must be some outfit stateside or Canada that has these. This was the first picture I found to help make the point.Get a "Genuine BSA Spares" (parts) catalog for your model and order/inquire using factory part numbers.Reprints are cheap enough and vital for sanity.Considering the description these may be worthwhile. beerchug


Thanks, that's what I was trying to figure out. I assumed I'd have to tweak whatever exhaust I ordered, but I liked the pipes I linked because they didn't have the crossover pipe. Either way I will be adding a set of reverse megaphone mufflers to the pipes I buy.

#593909 - 04/07/15 10:05 am Re: New BSA owner [Re: Keane Lucas]  
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barreto Offline
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Boise, ID
Are the heads different from 70 to 71-72? If I were to buy a set of siamese pipes for a 70, would they fit the head on a 72? I've found siamese pipes in Canada for pre-OIF. I also inquired on a set for OIF bikes in England to see if they would ship to the states. If modifying the mounting point is needed, that is an easy fix.

#593914 - 04/07/15 10:42 am Re: New BSA owner [Re: barreto]  
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KC in S.B. Online content
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Assuming you know that on these forums you will get all opinions:
I like what you have. You might consider having them blasted and coated with that HiHeat silver (Cerma coat?). Cut them just short enough to fit some shorty mufflers, with baffles, and an exit angled away from the shock. Have them coated along with the pipes the Silver sheen. I think it would go nicely with the overall look.


Down to 1 BSA, 2 Triumphs, 2 '56 Chevys
#593916 - 04/07/15 10:55 am Re: New BSA owner [Re: KC in S.B.]  
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barreto Offline
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Originally Posted By KC in S.B.
Assuming you know that on these forums you will get all opinions:
I like what you have. You might consider having them blasted and coated with that HiHeat silver (Cerma coat?). Cut them just short enough to fit some shorty mufflers, with baffles, and an exit angled away from the shock. Have them coated along with the pipes the Silver sheen. I think it would go nicely with the overall look.


I'd be happy to sell them to you grin

I'd like to do away with the high-side pipes either way. I really like the look of the siamese pipes and would prefer to deal with just one muffler. This exhaust is what I would like to order. The seller says that the '72 frame would prevent me from mounting them, but I see little difference or distance between the head and frame on a 70 or a 72.

#593917 - 04/07/15 11:06 am Re: New BSA owner [Re: barreto]  
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DMadigan Offline
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No difference in the exhaust ports that I know of. The valve cover studs were changed to 5/16" in the four corners for the cover mounted head steady. That tab on the lower run will have nothing to mount to and mighht have to be cut off if it fouls the frame. From what I remember of my '70 pipes there were no mounting tabs on the pipe, just the crossover pipe. I think the lower frame at the swing arm is about the same width so the end of the pipe should clear the frame. Ask the seller for details why it would not fit.

#593921 - 04/07/15 11:23 am Re: New BSA owner [Re: DMadigan]  
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barreto Offline
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Boise, ID
"The problem fitting this siamesed exhaust pipe to the OIF 71-72 A65 is the double downtube frame. The frame downtubes impede fitting this great siamese pipe to your bike."

Yours truly,

John Oland
MOTOPARTS INC

I'm not seeing any difference between the downtubes on a 1969 or 1972 though. For $230, I'm tempted to just risk it.

#593923 - 04/07/15 11:26 am Re: New BSA owner [Re: barreto]  
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shel Online content
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If they would fit a 72 they'd be listed for a 72, they make a different part for a reason


When given the choice between two evils I picked the one I haven't tried before
#593924 - 04/07/15 11:38 am Re: New BSA owner [Re: shel]  
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barreto Offline
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Boise, ID
Originally Posted By shel
If they would fit a 72 they'd be listed for a 72, they make a different part for a reason


I realize that. But if the difference between the part numbers is only a mounting tab that I can remove or relocate if needed, that is not a problem.

#593926 - 04/07/15 12:11 pm Re: New BSA owner [Re: barreto]  
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stubbicatt R.I.P. Offline
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Welcome to the asylum.

(Watch out for nurse Ratchet!) wink


Hate is a poison which one consumes hoping for another to die.
#593931 - 04/07/15 12:45 pm Re: New BSA owner [Re: barreto]  
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Rich B Online happy
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Stone Creek OH USA
Dry and wet frames used double down tubes. The dry frames did have tabs on the frame for the pipes to attach. Wet frames used the motor mount bolt (if I remember correctly eek )

Siamese pipe are a bit of a pain to get to fit a dry frame due to tight clearances around the down tubes. The LH pipe runs very close to the down tubes and usually fits the head so-so.

Before you order a set, see if you can find a dry frame locally and measure width of the down tubes just below the exhaust ports and distance from front of head to down tubes and compare to your wet frame. There were some differences in the frames, with the wet frame tending to be a bit more spacious than the dry frame.


Life is too short to drink cheap, bad beer.
#593941 - 04/07/15 2:51 pm Re: New BSA owner [Re: barreto]  
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DMadigan Offline
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I think the seller must not know much about OIF and dry frames. According to Bacon's book the dry frame is 5.4375" between lower engine mounts and the OIF is 5.345" (Clymer). The front downtubes are 18 from vertical on the dry and 22 on the OIF.
Compare the dimensions in Bacon's dry:


With Clymer's OIF:

Note Bacon has an error in the width of the front mount. It cannot be 5.5" between lugs and 5.5" between tube centers at the bend.
It could be the left hand exhaust tube does not come far enough forward to clear the OIF down tube.
Rich, note the distance from swingarm bolt to front engine bolt, 18.490" OIF and 16.969" dry. Probably to account for the less compact Triumph twin.

Last edited by DMadigan; 04/07/15 2:56 pm.
#593943 - 04/07/15 3:31 pm Re: New BSA owner [Re: DMadigan]  
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barreto Offline
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Extremely helpful. Looking at where the downtubes tie into the steering head, the non-oif ties in at the top, whereas the oif ties in at the bottom. This might put the downtubes to far forward on the oif for the exhaust to clear.

#594015 - 04/08/15 10:30 am Re: New BSA owner [Re: DMadigan]  
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barreto Offline
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Boise, ID
With my extremely limited photoshop skills, I tried making one image negative and overlaying one frame over the other. I scaled them as close as I could estimate. I lined them up on the front engine mount, since that point should be a good reference point for where the engine sits.

I have no idea if these pictures are to scale, or how accurate the angles are since they are obviously hand-drawn blueprints, but this is how it looks. The images don't quite line up since I believe the bottom mount should also line up over eachother.



I might get away with the pre-oif pipes if they just slightly clear the downtubes.

Last edited by barreto; 04/08/15 10:34 am.
#594031 - 04/08/15 12:23 pm Re: New BSA owner [Re: barreto]  
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Rich B Online happy
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Stone Creek OH USA


This gives you a good idea how tight the Siamese pipes come across the down tubes. If I can remember, I will get a picture from the LH side tonight to show the actual clearance. It is not much......


Life is too short to drink cheap, bad beer.
#594082 - 04/08/15 7:08 pm Re: New BSA owner [Re: barreto]  
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Roger Gulledge Offline
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Don't mean to step on your toes Rich.

I understand you on wanting to install siamese pipes, of all the different modes I have done it is right up there at the top. I was lucky enough to find a used set on eBay for $100. I think they are used original pipes, the tubing is thicker than re-pops today and they did not have the two little tubes at the top for a threaded rod to connect them so they would stay seated. Also the chrome appears to be heaver. Was not sure what would show up at my door being from eBay but was very pleased with them. No dents and chrome was in pretty good shape.

No problem installing them, they went on much easier than expected after reading what a bitch they could. Might just be the re-pops that are the problem. I just taped each side in the head about 1/2" and then started to fit the left side into the right side, taped them in a bit more, taped the connection together a bit more and just repeated till they were seated.

Clarence is tight on the down tubes, left side is about 1/2" to 5/8", right side would say 1/4". It might be possible to weld on short extension pieces to the ends that slip into the head. If memory serves me I think they slip in about 1" to 1.25" it might even be more than that. Don't know how that would change the geometry of getting the two sides to fit together but I bet it could be done if the extension pieces don't have to be too long.

Good luck with your quest, plus the sound they make is sweet.














Last edited by Roger Gulledge; 04/08/15 7:17 pm.

Roger G
70 Thunderbolt
#594091 - 04/08/15 7:51 pm Re: New BSA owner [Re: Roger Gulledge]  
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Rich B Online happy
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Stone Creek OH USA
You saved me taking pics Roger! So no worries. The pics you took show how tight the fit is on the siamese pipes. I have my doubts the will fit a wet frame, which is a physically larger frame in a lot of places.

You are so right about the sound. An A65 with siamese pipes is so awesome sounding.....

Did roger and I say the pipes sound awesome? laughing


Life is too short to drink cheap, bad beer.
#594104 - 04/08/15 9:31 pm Re: New BSA owner [Re: Roger Gulledge]  
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barreto Offline
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Boise, ID
That is a huge help.

Looking at the set on eBay that I want to buy, they look like they have a bit more room than your pipes. They may not be seated all the way, which might make them look like they have more room.






#594115 - 04/08/15 11:18 pm Re: New BSA owner [Re: barreto]  
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John Goodwin Online content
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Just bear in mind that you are looking at 2 completely different sets of Siamese pipes.
The pictures of Rogers bike don't have the same tie bar set up as used on the bike posted below and must be from another manufacturer and the two sets of pipe may be very different in ease of fit and the amount of clearance.
The lower set up looks very much more like the pipes my 65 A65 had on it with the long threaded stud and nut arrangement with a small bit of tube welded to the underside of each side of the pipes for the stud to run through.


Current: 2 x 1966 A65S, 1 x 1967 A65SA, 1 x 69/70? A65LA space Y, 1 X D14/4 & 1 x B175
Past: 4 x 1976 T160V, 1 74/5 T150V, 83 model GSX 750 ESD, Z650, Katana 1100(Bathurst Model), 79 T140V, 70's TR6, 2 x 1971 BSA 250 Gold Stars, 50's 350 Goldie, A65 Spitfire semi basket case, 1965/6? A65 LC, Tiger 21 350 & a D14/4 Bantam, 175 Bridgestone Twin with Zimmerman discs!
#594122 - 04/09/15 12:50 am Re: New BSA owner [Re: John Goodwin]  
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barreto Offline
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Boise, ID
Originally Posted By John Goodwin
Just bear in mind that you are looking at 2 completely different sets of Siamese pipes.
The pictures of Rogers bike don't have the same tie bar set up as used on the bike posted below and must be from another manufacturer and the two sets of pipe may be very different in ease of fit and the amount of clearance.
The lower set up looks very much more like the pipes my 65 A65 had on it with the long threaded stud and nut arrangement with a small bit of tube welded to the underside of each side of the pipes for the stud to run through.



That was my point. The set I'm looking at buying appears to have a little more clearance and I might be able to get away with them on an OIF bike.

#594158 - 04/09/15 11:38 am Re: New BSA owner [Re: barreto]  
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DMadigan Offline
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Ask the seller a couple of questions he should be able to answer. 1) The distance along the downtube of closest approach of the cross-over pipe to the front side of the downtube down to the front engine bolt, 2) the clearance of the cross-over pipe to the front of the downtube and 3) the perpendicular distance of the front engine mount to the rear side of the downtube.
Measure your #3. The difference in angle of the downtubes is 4 so an approximation of the clearance is:
Dry(2) + Dry(3) - Dry(1)*sin(4) - OIF(3) = clearance

Last edited by DMadigan; 04/09/15 11:39 am.
#594238 - 04/09/15 9:45 pm Re: New BSA owner [Re: barreto]  
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Roger Gulledge Offline
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Going through my pics. yesterday I came across this one. When I first started looking around for siamese pipes someone from Australia (cant remember his name) had an add in the buy and sell forum had a set for sale and sent me this pic. of them. He had a potential buyer ahead of me and ended up selling them to him. They look like they are on a late model A65 head, he wasn't sure where they came from, I believe he said they were SS. I didn't know much about siamese pipes at the time and never noticed the bend in the left side pipe till I looked at them again yesterday while posting.



Then last night a friend sent me some pics. he took at the Barbers Museum on his trip last week. If you more enlightened members have info on it please chime in as to the pipes. Could this type of configuration work on a A65 in a late model frame?
Could this be a possibility for barreto if they make repops for this bike today?



Last edited by Roger Gulledge; 04/09/15 9:56 pm.

Roger G
70 Thunderbolt
#594311 - 04/10/15 11:51 am Re: New BSA owner [Re: Roger Gulledge]  
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barreto Offline
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barreto  Offline
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Boise, ID
Originally Posted By Roger Gulledge
Going through my pics. yesterday I came across this one. When I first started looking around for siamese pipes someone from Australia (cant remember his name) had an add in the buy and sell forum had a set for sale and sent me this pic. of them. He had a potential buyer ahead of me and ended up selling them to him. They look like they are on a late model A65 head, he wasn't sure where they came from, I believe he said they were SS. I didn't know much about siamese pipes at the time and never noticed the bend in the left side pipe till I looked at them again yesterday while posting.



Then last night a friend sent me some pics. he took at the Barbers Museum on his trip last week. If you more enlightened members have info on it please chime in as to the pipes. Could this type of configuration work on a A65 in a late model frame?
Could this be a possibility for barreto if they make repops for this bike today?




I also found these pictures. I was not able to find another set that looked like this for sale. If someone knows where to find one, I'd appreciate it.

I went ahead and ordered a set of reproduction stock pipes, but would still like to pick up a set of siamese pipes that work with my bike. I studied the eBay set I posted and figured out that the pipes were not seated all the way, and would probably not fit my frame if they had to move any closer to it.

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