The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Frame => Topic started by: AnthonyA on 12.12. 2019 18:38
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Hello my friends,
In order to streamline the machine, in want my handlebars to be attached just above the fork tubes, aligning the whole thing when you look from the side.
Because with the standard top yoke, the handlebar is attached way back, and IMO, it's not very pretty. It didn't notice it on a full stock bike, but I want to change the handlebar (something a tad more high, with more curves), and... that's just plain ugly now.
So, I was wondering if some of you know about top yokes that fit in place of the standard one.
Some guy said it had already done such thing, but it was a Triumph one a friend of him had laying around and thus don't know where it comes from.
I just want it to work, doesn't matter if not BSA.
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Here it is:
https://www.ebay.de/itm/Vintage-Taylor-Dow-Superleggera-polished-aluminium-top-yolk-BSA-650cc/274137086409?hash=item3fd3d7f9c9:g:LSQAAOSwnd9d8Bgf
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Nice yoke but that's if you want clip-on handlebars.
I'm search for something that you'd find on any standard bike, but apparently not on BSA's ; mounting points for the handlebar in the middle of the top triple tree, not at the back.
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Not much options I guess.
Either modifying an original yoke ( Make sure that it’s well done. You wouldn’t want it to snap at 250 mph *smile* ) or else making another front fork to fit. Has been done by a forum member I think. If the old memory don’t let me down I think it was a Suzuki fork with disc brake and all...
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morris - you mean 'the project'? I used the Suzi top & bottom yokes and made cupped sleeves to take the Suzi tapered headstock brgs. Then there's Suzi fork shrouds to modify (BSA won't fit) etc. Lot of work if you just want want to move the bars. I'd cut and weld if I was doing it. Or even bolt up some lugs from underneath as my Yamaha / Weslake is, though i'd feel more comfortable with weld.
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'71-'73 OIF/Conical fork yokes might have what you be looking for....depends what legs and wheel/axle you use though with regard to diameter and distance between centres. I think they are 1,3/8" dia. I have one my Plunger (complete set)
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For those interested in the matter, someone on the French forum told me 1st gen A65 top yoke do the trick.
If someone has one laying around...
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G'day Ant.
I was just looking at one of those here https://tinyurl.com/ttzxqks. I think one problem is the distance between top and bottom yoke so the fork shrouds won't fit. It also uses shorter stanchions.
Cheers
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morris - you mean 'the project'? I used the Suzi top & bottom yokes and made cupped sleeves to take the Suzi tapered headstock brgs.
May well be. I knew it was something recently mentioned but didn’t have the time to look it up.
I am currently looking out for an A10 or A65 frame with engine. Feel a bit bored lately so I’m thinking about building some kind of street scrambler with modern forks. That’s why I remembered.
We’ll see what comes up.
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I *think* that BSA have a different taper on the top of the tubes to Trihards , but may be wrong....
That example of muskys looks like what you're after - I've a spare OIF set I can take a pic of when I find them, for comparison
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Thank you guys for the pictures and knowledge !
I don't mind cutting into the fork shrouds for them to fit, they're no concours parts anymore. I want to keep them though.
So, if I do this (top yoke A65 but stock bottom and steering + cutting into the shrouds), it will work ?
Cause I found one used online, and I don't know if I buy it or not... *conf*
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Anthony - sounds a neat way of achieving what you want - but be sure to check the distance between tubes, tube diameter and taper at top are the same. I've no idea, but someone else may be able to confirm / deny. Good luck.
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Anyone can do said measurement ? I have no way to tell myself, and it would be of tremendous help. *respect*
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Anyone can do said measurement ? I have no way to tell myself, and it would be of tremendous help. *respect*
Easy enough- Unless I'm reading you wrong, just measure outside to outside and inside to inside and split the difference (subtract inner measurement from outer)
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I can send you pictures and measurements tonight. (Been off line due to surgery, but up & walking again)
last summer I sorted and organized the land O' forks and trees in storage. (Motorcycle hoarder).
BSA stuff gave me fits and massive confusion. Still have a few mystery parts, but I narrowed 98% of it down for years-makes-models.
Here is the quick version, be happy to post up a BSA Tree tech post for ID.
Based off the top of my head here is what I found:
BSA Preunit singles some years were narrower than the twins,. # part numbers pending
BSA Preunit twins there was some variables for compy models but most were pretty std (Lugs, steering locks, speedo/tach mount and taper for the forks
BSA Unit Singles are their own animal by them selves but are tell tale with a reverse pitch risers,
BSA unit twins. there is 3.5 variants. # part numbers pending. There is a variation similar to the Preunit twins but 2 versions of fork locks. There is an early casting number, a Dual part number, THEN there is the oddball 64-65 Mustache trees (pictured above in this discussion) These are harder to find and I am not clear what all the models they used them on. (Parts books sometimes show for all models, sometimes only certain ones like Hornet) Then Inexplicably they went back to the Preunit style trees again with a variation in fork locks. And finally was the head scratcher that took a lot of investigation. There was some mystery trees and what they are is somewhat resembling the preunit style but had small details different in their castings top and bottom trees. What I discovered is these are factory service replacement trees intended to be one size fits all for unit Twins.
Then ** Some fork parts interchanged with Triumphs for 68-70 with the 2LS brakes, and the noticable difference on the fork legs is the Fork oil seal holder/Spring abutment is LONGER on the BSA and Shorter for Triumph but the top trees differ between Triumph-BSA as well as wider to accomodate the 2LS brake after the first year. (late 67-early 68 trees are oddballs). Also, the brake actuator levers on the brakes differ between BSA-Triumph but the brake plate is the same for TLS.
OIF 1971-> Smaller stem and different spacing and does away with the BSA fork tube taper. Also steering locks
Triples- BSA & Triumph, look similar to the 68-70 trees but have tell tale tabs for brake lines.
OIF unit singles- These are alloy and similar but not exactly the same as Cerrani-Betors. The forks are the same but generally longer on scramblers, but same length on roadsters as OIF Twins. But the forks and trees were largely copied from Cerrani and similar forks. (Quite good actually if you switch to progressive springs)
**I spent HOURS accumulating part numbers and measuring, lots of study of many years parts books.
I also have a vintage bike magazine review-interview of early Rickmans with Bud & Dave Ekins of LA fame. They set up a lot of these (For McQueen and James Garner, as well as quite a few others) So they took BSA Trees, and modified them, cut the fork tube holes, machined out the tapers and welded on pinch bolts to allow the forks to be slid up or down into the trees to set up the bike for off road, the reason was in some cases a nose down attitude was helpful. Its also reprinted in a cycle world compilation. Ill post the dates, & if interest I can scan the article.
** As noted, the fork ears for units were a different length than Preunits, and some variations in that as well. Might be easier to just ALSO use the matching fork ears for the trees being used.
*** I am also matching trees up to projects (Triumph-BSA-Norton) and will be selling off extras soon.
In the interim, enjoy these pix of some Rickman bodywork pinstriped by the famous Von Dutch (Kenny Howard) who often was at Ekins shop. ( ** I have been exchanging emails with a former local club member who was a regular down at their shop and has some interesting pictures and stories)
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......OIF 1971-> ............ and does away with the BSA fork tube taper........
You sure about that ?
I bought my NOS Conical/OIF forks from the US and they have taper tops, as do any others I've seen- which isn't a lot
I'll extra double check later though.....
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Well Sluggo that's some crazy work. Mind-blowing actually, and the fact that back then they went all over the place. No wonder they went bankrupt haha !
I don't plan to use fork ears, as the standard headlight and its fairing will go away, replaced by a more discreet lamp with a smaller diameter, and no fairing. I find the whole thing very heavy looking (and simply heavy !).
Anyway, I'm kind of clueless now...
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Anthony. Have a look at Yamaha XS Series yokes. These have pinch bolts to suit plain tube legs and a more forward handlebar mount. Bit of a knife and fork job, but may be more to the style required. But as usual, a whole lot of extra work to mix and match.
Swarfy.
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I dug my spare Comical/OIF yokes out;
kinda ~'bout 6,3/4" between centres of tubes, Taper on top yoke= 1,3/8" (tube diameter) down to 1,14" over 3/4" thick
Handlebar risers are rear of the tubes by about ~kinda 1/4' max, and ~kinda 'bout 40mm forward of the stem ** handy if you want to add higher risers
incredibly over-precise measurements I know, but I wouldn't want to mislead anyone *eek*
Pic coming from phone sho®tly
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Thank you guys for the pictures and knowledge !
I don't mind cutting into the fork shrouds for them to fit, they're no concours parts anymore. I want to keep them though.
So, if I do this (top yoke A65 but stock bottom and steering + cutting into the shrouds), it will work ?
Cause I found one used online, and I don't know if I buy it or not... *conf*
Anthony,
My A10 has the '62-'65 A50/A65 "moustache" top yoke with an A10 bottom yoke, so, width is correct. (The range of years is as close as I can tell from brief research.) I have headlight ears, not shrouds, and, yes, they are almost exactly 1" shorter than A10 ears. I also have A10 stanchions and they work just fine. I don't know if they are longer than A50/A65 for that yoke and don't really care. The story of why I have this combination is too tedious for this post. I've included some photos taken in a cramped space in my garage.
Richard L.
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Thank you Richard, it looks perfect, this is exactly what I want to do !
Side note, the color of your bike is gorgeous, and the shape/size of the tank is what I'm looking for.
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G'day Ant.
I doubt if you will be able to cut down your fork shrouds. The top is tapered to fit the staunchion, if shortened it will be very loose and the headlight ears will be too high. The ones on Richards bike look like early A50/65. 68-5059 and 68-5060.
Cheers
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...and, yes, they are. Here is a quick shot at the story, now that I'm not thumb typing.
Bought the bike in '73 for $50. At the time it had an A50/A65 moustache top yoke, but I didn't know a damn thing about original parts. Put $3K of '70s money into having a shop restore the bike. In Novermber of '79, on my way home after a beautiful day at Malibu Beach, a kid made a left turn in front of a rather novice rider making a legal, but dumb, passage through a green light. After sitting in storage (mostly outside, the bike, not me) for 23 years, I decided to give restoration a try. Still not knowing anything about original parts, I bought A10 top and bottom yokes on eBay. I also pounded out some dents and had my headlight ears re-chromed. Lo and behold, my beautifully chromed headlight ears were not long enough when I went to reassemble the front end. After doing the research, I decided to buy a replacement A50/A65 top yoke rather than new ears and new chrome. Much cheaper, and faster to the finish. Rebuild took around three years at my slow pace. Rode her around 60 miles before lack-o-sludge-trap-knowledge gave me another opportunity to rebuild the engine.
One thing you might notice with the A50/A65 yoke is the steering lock on centerline. A10 steering locks are off center. My answer was to attach a metal plate to the landing on the steering head where the A10 locking hole is found, then, make a new hole in the new plate. Works fine, since steering locks are just mild discouragers anyway.
Richard L.
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One more thing, as if that wasn't long enough. Don't forget that not all A50/A65 top yokes were the "moustache" type with centered handlebars.
Richard L.
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Tremendous help Richard !
And thanks for the story time, I always appreciate a little background.
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I am sorry I was not more timely, I had surgery recently and really behind the curve, as well as an impending weather crisis now unfolding. (lots of excuses)
I went down and started doing photos and measurements. I will hold off on the expansive "Comprehensive interchange and triple tree & Fork/stanchion ID" thread because I am not satisfied with the photos, lighting and need to do a better job of ID. Admins have been generous in allowing Sticky Tech threads & worth doing properly so its useful. I HAVE most every variation and some mystery ones to do it. But a crusty poorly photo illustrated one that jumps around the years is not helpful.
But to respond specifically The Mustache mid 60s trees would be your best bet. Its POSSIBLE you could use the 68-70 style Triumph ones that use P clamp risers, but not everything will line up. I also photo'ed some of the ALLOY BSA B50 OIF variants and the 1971 and up Triumph-BSA OIF variants as well as the the T150/T160 and T140 Disc brake variants that ALSO use the P clamp risers.
I also did some surveys on fork tubes. When I mentioned the taper, I slightly mis-spoke (The dangers of reliance on memory). So heres the deal.
TAPER and Fork OD and Tree ID's vary. SOME, but I am not sure which years but SOME BSAs used a stepped Tube OD and that presents problems in many ways. REPOP tubes frequently dont have that stepped OD.
Secondly, the tapers on the ends Differ. On some early 60s BSA unit twin A65 forks I meaured the taper is gradual and then increases towards the end of the tube, but it appears the taper starts aprox 2" down,
But a 1971-72 BSA OIF tube no such long taper and it clearly is visible about 0.820 from the end and I would have to measure with a taper gauge or angle finder but its way different than pre 71 BSA.
The stems, also differ in length and in some cases the threads and OD. The Mustache style stems seem to average around 7 & 5/8ths total from tree to top including lower bearing race.
The OIF stems are small in OD, approx 0.75-0.76 and the alloy trees for the BSA B50-B44-B25 have an odd threaded stem with fine thread at the top and a course thread THRU the bottoms. Overall length total was just a hair under 7" but from the tree to tip was 6".
I also found 2 different thread forms to the tops of OIF stems, a medium course and a fine thread.
I have some pictures I will post tonight but, also keep in mind I need to recheck measurements because it was below freezing here, and my calipers were acting up. **Approx.
More soon.
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Better pictures coming as long as we dont lose power, Storm, its a' comin!
Mustache style trees, I will post up years and part numbers as well,. Got a long spread sheet and pages of notes.
Threads and land of Trees and parts current sorting. *** IF ANYONE HAS ANY EARLY TRIUMPH TREES FOR A 48 AND 52 (pre-nacelle on the 48 AND nacelle on 52) i AM NEED OF SEVERAL SETS. TRADE OR CASH.
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Alloy style typically used on BSA-Triumph scramblers. (Unit 500 twins Triumph hybrids, Unit Single B50s-B44-B25, *Note I have a late B50 that was sold and titled as a Triumph 500 single, sold in 1974 and have original receipt)
Land O' Trees and my current mess in storage. (Feel free to come by and lend a hand, There is a bar next door, Also all the coffee you can drink, and Mrs Sluggos cooking.)
Close up of Taper, I can do better, but thats what I could manage under the circumstances.
The Pre OIF unit single style trees. I *BELIEVE* but will confirm there is 3 variants of these but might be a viable option, They have a reverse lean for the cast in risers and might be an option. These were used on C15s, C25, B25, B40, B44, and the Triumph T25 variant.