OzVMX Forum
Marque Remarks => British (BSA, Greeves, Triumph etc) => Topic started by: big mac on February 16, 2014, 06:08:31 pm
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So if you were building the best BSA B50MX you could what mods would you make. i,e
Frame mods
Forks to use
shocks
Tank seat combo
Wheels
Plus the engine mods
I would like to get some ideas before I start on a project.
Rory
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The B50mx are a beautiful looking bike in stock trim, lets see best mod for competition use ? Ever heard of Clews Competition Machinery aka CCM. ;)
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Yes I know I was looking for ideas for building one up from bits that can be brought from around the traps.
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Send firko and bazza a pm on here they may help , I know bazza is having a break on here firko might be to.
they may reply to you buy pm ;)
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Seriously do a search of the UK BSA clubs. There used to be one specialty site that had heaps of info with great photos and diagrams of mods for the B50 and B25.
Will post a link if I can find it and it is still there.
Would not even think about changing that gorgeous tank ever.
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Big mac
Id be asking forum members geoff,flower pot racing or HVA61 :)
cheers
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http://b50.org/index2.htm
gets you into Rickard's site which is 100% unit single stuff.
I've found that B50s benefit from eliminating as many stock parts as possible. Ditch the chassis, clutch, transmission, ignition and you start to have a much nicer bike.
:)
cheers,
Michael
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Thanks gentlemen gained some useful info from Richard site.
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Hi mac ! the first thing to get is Rupert Ratio's book/manual on unit singles - will give you a great insight on what t hey need ! good luck with the build and keep us all updated ! luv the unit singles , look and sound great with heaps of character ;)
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That is one I was on about http://b50.org/index2.htm ;)
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Send firko and bazza a pm on here they may help , I know bazza is having a break on here firko might be to
Bazza's having a break but I'm just cutting back a wee bit by avoiding anything that looks like a scrutineering or rule thread or any shit fighting. This is what we need more of on the forum.
Anyway.....With the old B50 the KISS principle is the best plan. In stock trim they're a beautiful bike and it'd be a shame to change its appearance so much that it looks like a Cheney or CCM wannabe or worse. Not that those bikes are ugly, far from it. It's just that they have their own particular look so why turn a B50 into something it ain't.
If I had a B50 I'd concentrate most of my chassis effort on the forks and shocks. First up I'd change the 20" front wheel to a 21" Rickman or REH off a Rickman Zundapp or Monty which is both a better brake and lighter. They're pretty cheap on USA eBay and it keeps it all British. The BSA forks aren't that wonderful so fitting cartridge emulators from YSS, Racetech and others is a positive move. Many B50 racers replace the forks with either Betor ( Bultaco, OSSA, Montesa, Rickman and many more) or more expensive but not that different Cerianis. Shocks are pretty much down to whatever you can afford....You can get the best Ohlin, YSS, Reiger and others for $1000 give or take or you can do it on a budget with Works Performance, Progressive and any others for around $500. Of course you can buy second hand quality shocks for beer money and rebuild them yourself (Works are especially amateur rebuilder friendly).
The BSA B50 motor is one of the most durable and hot rodded in the sport....it's the small block Chevy of VMX. There are plenty of sites explaining B50 mods but like Huskibul said, don't even start until you get a copy of Rupert Ratio's BSA singles book. It's brilliant and in simpleton English...even I understand it ;).
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don't even start until you get a copy of Rupert Ratio's BSA singles book.
Readily available ~ too easy :)
http://www.amazon.com/Rupert-Ratio-Single-Engine-Manual/dp/0953509818
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(http://i951.photobucket.com/albums/ad360/tdee754/MotorcyclePicturesBSA.jpg) (http://s951.photobucket.com/user/tdee754/media/MotorcyclePicturesBSA.jpg.html)
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Thanks for the input I have Ruperts book it will be my guide for the motor. I was wondering about the frame would it benifit from de-raking a few degrees.
Thanks Rory
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I was wondering about the frame would it benifit from de-raking a few degrees
Maybe if you're intending to use it for dirt track but I wouldn't bother otherwise. Perhaps experiment with less offset triple clamps if you're looking for faster steering.
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I believe this is an original factory photo I have here, Dated by Kodak on the back (OCT '70)
More photos to come of the first import arriving into NZ.
(http://remotepc.com.au/images/BSA_Victor_1971_Factory.jpeg)
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Arrival & Road Test @ Ruapuna, ChCh, Canterbury, NZ (Aug '71):
(http://remotepc.com.au/images/BSA_Victor_1971_ChCh.jpg)
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Fully sponsored and ready to race (Kaiapoi, ChCh, NZ, 1971):
(http://remotepc.com.au/images/BSA_Victor_1971_ChCh2.jpg)
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(http://remotepc.com.au/images/BSA_Victor_1971_ChCh3.jpg)
A Sabiston, Kaiapoi, Canterbury, NZ, August 1971, 499cc BSA. Followed by Paul Doecke on a 380 CZ.
(http://remotepc.com.au/images/BSA_Victor_1971_ChCh4.jpg)
A Sabiston, Clarkville, Canterbury, NZ, Sept 1971, 499cc BSA.
(http://remotepc.com.au/images/BSA_Victor_1971_ChCh5.jpeg)
A Sabiston, Halswell, Canterbury, NZ, Oct' 1971, 499cc BSA
(http://remotepc.com.au/images/BSA_Victor_1971_ChCh6.jpg)
A Sabiston, Kaiapoi, Canterbury, NZ, Dec' 1971, 499cc BSA
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I love my B50. What is your budget? You can go completely bananas if you wish......
Stock wheels weigh an absolute ton. Loose them. Forks are short and there are better available. Shocks, straight in the bin.
Motor will make you smile in std trim, but the sky is the limit if you want F1 technology. A modern style clutch will work wonders and is a good upgrade, but the first thing I would do is change the ignition. Basic electronic is fine, but you can spend big bucks on Interspan if you wish.
Frame is heavy, loose that, replace with a faber works B50 one or a cheney, or a CCM frame, hang on a minute where did the B50 go.....
If I could only do one thing it would be to fit electronic ignition. Got and forget. I run PVL which is fine, fires the bike up easily and has never let me down......
Don't for get to add a drop of Castrol R in the fuel, then it'll even smell good to!
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So Ben replace everything except the seat,handlebars and tank? :) J
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Thanks for the great pics and advice. ignition was high on the list as I like my bikes to start off the kicker.
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I love my B50. It's a pleasure to ride and gives the 2 stroke pre75's a run for their money. Mine is pretty stock in the motor department, apart from an Electrex ignition and a bit of head/barrel fin removal. Bigger diameter header pipe. Pay close attention to cam timing and tappet adjustment to make sure they are both spot on. They also need to breathe so there are extra breathers on it. I saved nearly 1.5kg of unnecessary weight from the fin trimming. It runs the standard B50MX cam which by all accounts is the best of the cams. Carby is a Mikuni 34mm. Ditch the Amal carb.
The frame back bone has been shortened and a new rear loop has been made to meet the back bone. That mod saved another 2.5KG! Shock mounts are in the standard position. It runs a '74 CCM airbox with a decent size filter.
Aluminum rims. 21" front and 18" rear. Front hub/brake is '74 Honda XL350 mated to Betor forks. Rear hub/brake is '73 Bultaco. Rear shocks are 14.25 eye to eye Betor's. The longer shock gives a sharper steering angle while staying within the 4" travel limit. Honestly, there is no need to alter the rake of the headstem. The B50 turns exceptionally well and goes where you point it.
I will post a few pics when I get the time.
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So Ben replace everything except the seat,handlebars and tank? :) J
Depends how far you want to take it..... They are a good bike in std trim. A bit of Castrol R in the fuel could be the easiest way to have more fun as it will smell nicer.
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(http://remotepc.com.au/images/BSA_Victor_1971_ChCh3.jpg)
A Sabiston, Kaiapoi, Canterbury, NZ, August 1971, 499cc BSA. Followed by Paul Doecke on a 380 CZ.
Paul is still going strong on a CZ250, not an easy rider to finish ahead of even at his advanced age
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Hi, if you look closely you can see me stuck in the Gorse bush , one lap behind of course,
cheers
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Am interested in the specs for a 34mm mikuni did you get it from the USA with an inlet manifold. How did it effect the performance was there still plenty of grunt.
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Am interested in the specs for a 34mm mikuni did you get it from the USA with an inlet manifold. How did it effect the performance was there still plenty of grunt.
No, I didn't get the carb from the USA with an inlet manifold. the original port inlet was cut and shut to allow a hose type fitting to connect the carby. There is way more useable power with the Mikuni. basically the bike pulls from zero to hold on with very little noticeable hesitation. ;D
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I've got some B50 info on a page of my website
http://www.eurospares.com/bsaunit.htm
including some detail photos of Cycle Factory and Dick Mann-framed bikes. I got to race the DM bike though unfortunately the whole day was a case of "bastard stopped again" and I was lucky to get 3 laps in a race, it never ran long enough to complete any of them. The DM frame was friendly and didn't want to push the front end the way my B50MX did.
I never had much luck with starting with the ET magneto installed. Converting to regular points/coil/full-circle stator as in the T or SS gets you almost double the amount of static retard, and as mentioned above a Rita or other electronic ignition makes things very nice.
I recommend the rearset footpegs like Dick Mann used to sell. You can also use the pegs off of a TR5T Triumph 500 as they bolt on and are more rearset than the single parts.
The 932 Amal worked fine but you need to have one that isn't worn out, and they start wearing out as soon as you use them. I sent mine out to have the body bored and fitted with a hard-chromed brass Mikuni slide, which should fix the wear issues.
The kick starter flops backwards over jumps and tries to engage and also gets in the way of your leg. Getting a bottom-pivot lever is a big improvement and removes a significant distraction.
I've got a long Carillo rod/JE Piston installed and I['m looking forward to getting the engine built with that and a PES/CCM-UK clutch and an NEB 3 speed.
cheers,
Michael
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I have used a Dellorto 34mm at PES recommendation, and im very happy with it. Im getting life within a couple of kicks with a HPI ignition. Have gone down 3 speed, PES splined clutch route.
The clutch totally disengages if you push in gear, and using one of ballards yam. clutch levers the pull is like a modern bike
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I've got the PES outrigger plate on mine as well. The BSA unit singles have a problem with the outrigger plate coming loose and the bolts then locking up the clutch. A simple way to cure it is to use some shim metal to build up the circumference of the outrigger flange so that it becomes a press fit into the engine case. I also tapped out the bolt holes to 6mm*1pt and used machine head counter sunk bolts with loctite. Hasn't come loose in 2 seasons ;D
I've nearly gone for a big flying W when the kickstart lever engaged landing off a small jump...lucky it was a well watered and slippery track so the rear wheel just slid instead of biting to a halt. Who ever designed the lever at BSA got paid too much for their time! I just use the rubber strap method of retaining the lever now but I wouldn't mind a new lever that pivots at the shaft end and doesn't stick into my leg...
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I've done some drawings of the stock BSA kick lever base and some other bottom-swivel levers I had sitting around to try and come up with a base that would go between the BSA shaft and some readily available OEM Japanese lever (like RD350, etc). I haven't looked at those for quite a while but I'll dig them out and see if they are far enough along to post if anyone wants to play with them. I figure making the base out of 4140HT (about 30-32Rc) would give plenty of strength and still be fairly easy to machine. The base should not be a super-challenging DIY machining job.
In my unit single folder
http://www.eurospares.com/graphics/BSAunitsingle/
you'll find an article on a modifed Rickman unit single with a rear-set kick lever:
http://www.eurospares.com/graphics/BSAunitsingle/B44Rickman2MC061972.jpg
which would be something to consider. I think Mike Bungay's Cycle Factory has a modified kick shaft that has splines to match a Japanese lever:
http://www.eurospares.com/graphics/BSAunitsingle/BungayB506.jpg
My engine will also get the PES outrigger plate.
cheers,
Michael
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Somebody went to the trouble of making a Ti kickstart on my motor, it seems to have no problems with the pivot and feels like its made of plastic when holding it (light) . And having played around cutting threads on Ti round bar, its a a material that's demands to be kept cool! or eat your tools!
Ill be forever grateful to whoever made it!
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(http://remotepc.com.au/images/BSA_Victor_1971_ChCh3.jpg)
A Sabiston, Kaiapoi, Canterbury, NZ, August 1971, 499cc BSA. Followed by Paul Doecke on a 380 CZ.
Paul is still going strong on a CZ250, not an easy rider to finish ahead of even at his advanced age
No way? That's amazing!
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Thanks for the links Micheal. Very helpful.
Cheers,
Mark