bbenxe's B50T flat/street tracker

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bbenxe's B50T flat/street tracker

Post by bbenxe » Wed May 24, 2017 3:43 pm

Hullo!

Picked up a semi-running (MOT'd but not very healthy...) B50T a few months ago which would run a for a while and then start misfiring. That all turned out to be related to an ignition coil shorting out when warm because of it's clamp done up far too tight. Found this warning in some Boyer Bransden literature (even though I'm using a Wassel) after the misfiring was fixed by replacing the coil, but then started to come back 150 miles or so later.

Here's the bike as bought with the awful supertrapp that kept falling apart.

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Since then I've put a silencer that works (OK, stays on but doesn't necessarily silence very much... fine with me), replaced 32mm Amal with 30mm as the port hadn't been opened up to match, fitted a reed valve to the crankcase breather which I've strung underneath the tank, added the PES braided oil feed instead of the original hose, and made up a sumpguard. Oh, and very importantly, added some decals to the tank.
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I've also added the PES finned and magnetic plugged sump, but in doing so disturbed the non-return valve by poking up the scavenge tube so have new bits on order to stop it wet sumping now.

Current plans, in rough order are:

-Swap the awful gold bars for some black flat track bars.
-Put on a larger front drive sprocket as have been running out of revs at about 55mph at the moment. Think it's a 17T I've ordered.
-Smarten up the sidepanels.
-Either get rid of of the front mudguard and make up a brace or keep it and polish up the alloy.
Get rid of the red stripes on the rear mudguard.
-Get some paint on the tank.
-Oil filter.
-Fit MX cam.
-Open up the inlet to 32mm
-Get the frame stripped and repainted. It's been painted a metallic blue at some point and done pretty well, then sprayed black over the top which rubbing off in all sorts of places now.

Really enjoying the big single. I've got a little one (Matchless 250) and another big one (S*zuki DR600) but this thing is just so much fun on the road, and I've been very impressed with the 8" TLS front brake thus far.
'66 Matchless G2 CSR scrambler, '71 BSA B50 street scrambler, '75 Bultaco 250 flat tracker, '81 Montesa 200

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Re: bbenxe's B50T flat/street tracker

Post by minetymenace » Wed May 24, 2017 5:12 pm

:ok
There is no evidence to support the notion that life is serious.
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Re: bbenxe's B50T flat/street tracker

Post by bbenxe » Tue Jun 06, 2017 2:01 pm

Been putting lots of miles on recently, rides out with friends, the VMCC, and the AJSMOC. Running very well, but really feeling the need for more teeth on drive sprocket. Fortunately Mr Hingley is letting me borrow his pullers if he can find them in his garage so I can put on a 17T sprocket.
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New handlebars look great, and I've made up a fork brace now that I've yanked the front mudguard. Might be going to a 19" rim at some point so left a bit of room for that.
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All the black paint is slowly rubbing off revealing a more successful coat of blue underneath...
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And when I had the front wheel out I noticed the stud for the 'torque arm' (well, that goes into the notch on the forks) has barely enough thread for the nylock that's being used to hold on to. The nut only gets about halfway on before it runs out of stud.
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So two questions:

1) Does that stud look too short? There's a washer between the disc and fork, and then another between fork and nut that could be creating clearance issues but it all slides together nicely at the moment. I'll order another stud to compare.

2) Any suggestions on a product that might help me rub off the rest of the amateur black paint to reveal the blue underneath? Wasn't sure at first but the bike looks a bit tatty, and then I saw this bike and am now tempted...
IMG_20170606_135908 copy.jpg
'66 Matchless G2 CSR scrambler, '71 BSA B50 street scrambler, '75 Bultaco 250 flat tracker, '81 Montesa 200

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Re: bbenxe's B50T flat/street tracker

Post by bbenxe » Tue Aug 15, 2017 8:12 pm

Well, my BSA is going very well, fractured the kickstart return spring and then vibrated off the gear lever when I forgot to loctite it back on after replacing the spring (fortunately found it on the roundabout right by my office...) recently but really enjoying riding it almost every day apart from that!

Found that a rub down with some paint thinners has revealed the coat of blue underneath. This bike was dispatched to Duarte, California in 1971 and the blue seems a very good quality job. Did any bikes come out of the factory blue...?
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Haven't got around to putting on the 17T gearbox sprocket yet so still feels quite undergeared, but after reading this thread http://b50.org/phpBB2/viewtopic.php?f=3&t=7733 I'm even contemplating a 19T... :thumb
'66 Matchless G2 CSR scrambler, '71 BSA B50 street scrambler, '75 Bultaco 250 flat tracker, '81 Montesa 200

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Re: bbenxe's B50T flat/street tracker

Post by midgie » Sun Aug 20, 2017 2:58 pm

No bikes left the factory blue to my knowledge. I think a 19t gearbox sprocket is making it overgeared, I run a 17t and 52t rear which I find gives good all round performance. but your choice of course.

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Re: bbenxe's B50T flat/street tracker

Post by bbenxe » Mon Sep 25, 2017 8:29 pm

B50 continues to be a great ride, although it took me down to the wire as a simple head gasket replacement nearly lead to me missing the Bristol Distinguished Gentleman's Ride as I found one of the domed nuts holding on the head's oil supply had stripped with very little time to get a new one in the post.

Many thanks to Ian Hingley for offering to take one off his Victor to help me out before the postman came through in my hour of need!
DGR_Ben_5288.jpg
'66 Matchless G2 CSR scrambler, '71 BSA B50 street scrambler, '75 Bultaco 250 flat tracker, '81 Montesa 200

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Re: bbenxe's B50T flat/street tracker

Post by bbenxe » Mon May 21, 2018 6:33 pm

Been putting lots of miles on the bike recently around Bristol and surrounding countryside, most recently on the VMCC SW Coast run, and out to the Redhill Classic Car and Bike shows.

Here's a recent photo of the bike, frame all stripped back to blue now, MX panels fitted but not yet painted, and new polished alloy mudguards front and back using a Sammy Miller brace.

In terms of gearing, I've gone from to 14-47 to 17-47 gearing on the drive chain. Huge improvement for the sort of riding I do, but first still feels quite short and top still very buzzy on A-roads with my mate on his plunger A10... I've picked up a 19T from Mark so hoping that'll be the final word in the matter.
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Next thing I'm keen to do is fit a 33mm pumper flatslide carb (Mikuni TM) to match the MX cam when I put that in. I don't enjoy not being able to rev the engine quickly without it bogging and going lean, and need to go up to at least 32mm to match the cam anyway.

The first question that needed to be answered was will it fit. To which the answer is almost... Will need studs replacing with bolts, and the mounting face recessed by about 9mm (which it looks there's plenty of room for) on the head to account for the spigot mount.

I'm unlikely to start undertaking the head modifications until winter since I'm enjoying riding the bike so much almost everyday to work and at the weekend currently!
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'66 Matchless G2 CSR scrambler, '71 BSA B50 street scrambler, '75 Bultaco 250 flat tracker, '81 Montesa 200

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Re: bbenxe's B50T flat/street tracker

Post by bbenxe » Thu May 31, 2018 3:28 pm

Got some proper tyres on as I'm going trail riding on the TET this weekend.

Bike's going well. Rubber mounted all the mudguards, but that gave them enough slack to move around just a little, but little was enough to start clattering into the chain and giving me a hell of a fright... Resolved now.
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'66 Matchless G2 CSR scrambler, '71 BSA B50 street scrambler, '75 Bultaco 250 flat tracker, '81 Montesa 200

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Re: bbenxe's B50T flat/street tracker

Post by bbenxe » Mon Jun 04, 2018 7:32 pm

What a day out! B50 went fantastically well. Broke a clutch lever slipping in a cowpat... But jury rigged a pivot with a zip tie to get some more lanes done before heading home.

Video of the river crossing here: https://www.youtube.com/watch?v=-AvqUGvKlR0
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'66 Matchless G2 CSR scrambler, '71 BSA B50 street scrambler, '75 Bultaco 250 flat tracker, '81 Montesa 200

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Re: bbenxe's B50T flat/street tracker

Post by Ian Hingley » Mon Jun 04, 2018 10:46 pm

So it's OK to borrow my tools, but then you forget to invite me out for some local trail riding?
How does that work then??

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Re: bbenxe's B50T flat/street tracker

Post by bbenxe » Tue Jun 05, 2018 8:12 am

:laugh

Now can't decide whether I do want to use them to put that 19T sprocket on! Still wanted a taller gear riding home, but I wonder whether it would have made first too tall for the some of those trails...

We'll test it together in the South Wales section :thumb
'66 Matchless G2 CSR scrambler, '71 BSA B50 street scrambler, '75 Bultaco 250 flat tracker, '81 Montesa 200

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Re: bbenxe's B50T flat/street tracker

Post by bbenxe » Wed Oct 02, 2019 8:56 pm

A quick update on my B50 since it's been a while. Not much of street tracker anymore...
IMG_20180616_152622_773.jpg
Many more happy miles in it's latest scrambler guise, including a razz up the hill at Prescott
( see here: https://www.youtube.com/watch?v=NjoeBWH31fk )
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I snapped the con-rod riding around Cornwall. Wasn't even revving it! Had just set off in the morning to head back to Bristol and was about 200m down the road pulling away from a junction when BANG and the rear wheel locked. Grabbed the clutch quick enough to not throw me off but internal devastation had occurred.
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All the usual damage, but fortunately didn't blow a hole in the cases. While it was out of action I also got into some actual flat-track and have been competing in the Rookie and Vintage classes of the DTRA in the UK this season on a bike I built based on a Bultaco Pursang 250
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Sent off the B50 to RTS for a rebuild and replacement of all the tired old engine and gearbox bits, plus:
-MX Cam
-Inlet opened up to 32mm and head gas-flowed
-pressure side filter adaptation
-lightened and polished rockers
-spigot welded on to take modern carb
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I originally wanted to put a pumper-flatslide carb on, a whopping great big Keihin TMR, but couldn't make it fit. Settled on a 32mm PWK, still a flat-slide, and I've been very happy with it so far.

Still running in, and I probably haven't passed 1/2 throttle or 4000rpm but it certainly feels urgent. Had a potentially disastrous moment on the DGR this Sunday where my rocker feed fractured from pressing against the tank and was dumping oil, but I noticed before the tank ran dry and vanned it home. I've since switched over to the CCM style rocker feed with a PES braided hose and taking the tee from behind my filter.
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Many more plans, first up some trail riding down in Devon mid-October.

I'm also on the hunt for a single seat after helping a friend get his B50MX back together and road registered, plus a tidy tool-bag to fit behind the single seat, ideally a Malcolm Smith bag like Rookster's on his Hammer of the Gods B50SS https://www.b50.org/phpBB2/viewtopic.php?f=14&t=7774
'66 Matchless G2 CSR scrambler, '71 BSA B50 street scrambler, '75 Bultaco 250 flat tracker, '81 Montesa 200

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Re: bbenxe's B50T flat/street tracker

Post by beat » Thu Oct 03, 2019 3:21 pm

what is the needle identification in your flatslide carb ??

beat

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Re: bbenxe's B50T flat/street tracker

Post by midgie » Fri Oct 04, 2019 12:56 pm

Typical std b50 rod trick, breaks there every time, you were very lucky not to destroy the cases.

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Re: bbenxe's B50T flat/street tracker

Post by bbenxe » Sun Oct 06, 2019 9:06 am

beat wrote:
Thu Oct 03, 2019 3:21 pm
what is the needle identification in your flatslide carb ??

beat
Hi Beat, my needle is marked JJH and is in P3. It's a 32mm "JRC PWK" that I sourced from BrillBikeParts in the UK.
'66 Matchless G2 CSR scrambler, '71 BSA B50 street scrambler, '75 Bultaco 250 flat tracker, '81 Montesa 200

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Re: bbenxe's B50T flat/street tracker

Post by B44Claus » Mon Oct 07, 2019 4:04 pm

Hi,
I'm building on a B44 engined project with a similar carburetor. Can you disclose what main jet, idle/slow running jet & slide you have on your bike?

Thanks,
Claus
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Re: bbenxe's B50T flat/street tracker

Post by bbenxe » Mon Oct 07, 2019 9:13 pm

B44Claus wrote:
Mon Oct 07, 2019 4:04 pm
Can you disclose what main jet, idle/slow running jet & slide you have on your bike?
Hi Claus,

the technical data for the JRC PWK from Brill can be found on their site:

http://brillbikeparts.co.uk/images/jets.gif

for a B44 they recommend a 30mm body, 30 pilot and a 135 main with needle on the "center" position.
for a B50MX they recommend a 30mm body, 35 pilot and a 140 main with needle in the "bottom" position (although it's unclear whether they mean the clip in bottom ring or needle as low as possible. Presumably the former...)

In my ported B50 with MX cam I'm using a 32mm body, 38 pilot and 140 main and needle in the centre position which is a slight deviation from the recommended for a B50MX but is what the 32mm comes with as standard. They sent me a few other jets to try but so far the 38 pilot with the screw out a turn and half and needle in the centre have been free from trouble. I haven't ventured far into main jet territory yet as am still running in.

I'm afraid I can't comment on the slide - mine is unmarked.

Ben
'66 Matchless G2 CSR scrambler, '71 BSA B50 street scrambler, '75 Bultaco 250 flat tracker, '81 Montesa 200

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Re: bbenxe's B50T flat/street tracker

Post by B44Claus » Tue Oct 08, 2019 3:53 pm

Hi Ben,

Thanks for the response! There might not even be a choice of slides, - anyone knows?

Brgds,
Claus
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Re: bbenxe's B50T flat/street tracker

Post by beat » Tue Oct 08, 2019 8:50 pm

B44Claus wrote:
Tue Oct 08, 2019 3:53 pm
There might not even be a choice of slides,
by the Mikuni TM Flatslide it s so : no choice for a other slide than the 4.5 ... ( or self made )

I don't know the JRC.
bbenxe wrote:
Sun Oct 06, 2019 9:06 am
my needle is marked JJH
can not find this needle Nr in the Mikuni book,- seams to be not comparable.

beat

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Re: bbenxe's B50T flat/street tracker

Post by bbenxe » Wed Oct 09, 2019 11:56 am

beat wrote:
Tue Oct 08, 2019 8:50 pm
can not find this needle Nr in the Mikuni book,- seams to be not comparable.

beat
Not surprised you can't find it in the Mikuni book Beat, you might have better luck in the Keihin though!

I'm not sure whether it's N427-46 or the N427-48 needle in my 32mm PWK, I'll measure it tonight to check though.

Once that's determined then the JJH spec can be read from either here:
http://www.allensperformance.co.uk/keih ... t-needles/

...or here:
http://www.allensperformance.co.uk/keih ... t-needles/
'66 Matchless G2 CSR scrambler, '71 BSA B50 street scrambler, '75 Bultaco 250 flat tracker, '81 Montesa 200

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Re: bbenxe's B50T flat/street tracker

Post by bbenxe » Wed Oct 09, 2019 12:02 pm

I should also share this exceptionally useful tool I found recently that lets you see the effect of changing jets, needle and needle position in the Keihin Carbs

http://www.kyajet.de/index.php?lang=en

You can choose the needle type (N427-46 or N427-48) and then changing the spec (e.g. JJH vs JJG) let's you see the % change on mixture at different throttle positions.
'66 Matchless G2 CSR scrambler, '71 BSA B50 street scrambler, '75 Bultaco 250 flat tracker, '81 Montesa 200

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Re: bbenxe's B50T flat/street tracker

Post by B44Claus » Wed Oct 09, 2019 12:28 pm

Thanks Ben,

The slide in my pwk is also unmarked so perhaps there is only that slide.

The most significant differences between the N427-46 & the N427-48 needles is the diameter which means that the needle jet also has to be different. The length is different too, - but perhaps that is depending on the carb size: The larger carb the longer needle?

Brgds,
Claus
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Re: bbenxe's B50T flat/street tracker

Post by johnu » Thu Oct 10, 2019 5:00 pm

A great looking bike that gets well used I love it!

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Re: bbenxe's B50T flat/street tracker

Post by FGF » Fri Jan 24, 2020 11:08 am

Hello Bbenxe ,

i 'm looking for a sample work on my B50 SS.

did you finish the fitting with the JRC carb ?

and are you satisfied of your choice ?

thanks
francois

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