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Tricks to starting a 1971 BSA B50SS (500cc single)?

27K views 34 replies 21 participants last post by  baron_beeza  
#1 · (Edited)
I am looking for the input of people who have owned, or worked on, the 1971-2 BSA B50SS, and that have the "knack" for consistently starting these machines. Hopefully a few of you could share the sequence of actions or subtleties with me, on getting this machine on the road. I got it running yesterday, and it actually ran really well, but I have not been able to get the sequence for consistent results starting it.

Timing, ignition, proper mechanical condition, carburetion and electrical are all sorted, so at this time I don't need troubleshooting advice, just what you have found works to consistently start these thumpers most every time. This bike kicked the holy crap out of me the last time I started it several years ago and I'd rather not be crippled for three weeks again.:D

Thanks in advance, Dan.
 
#5 ·
#4 ·
Tony's advice is pretty good. I've had a few bikes really muck up my foot and ankle from the kick.

Couple of non-traditional thoughts on the subject:

1. Valve Lash - I've discovered a motor with lash set a tad tight (tight fit on the feeler gauge) seems to spin a little more easily. I attribute this to compression bleed-off from extension of the cam duration - some of the opening ramp is used. Motor's a little quieter, too. This is a very subjective thing, and I don't advise it unless you know what you're doing.

2. Discovered this one by accident - if the clutch spring basket is adjusted to the lightest tension possible which still holds, the clutch will 'give' a little on kickback, saving your leg. Just had this happen yesterday on an A65. I'm glad it gave - last time one kicked back, I limped for two weeks.

I HATE kickback. Ankle and bottom of my foot have been black and blue more than once, and at my advanced age, I don't heal as quickly as I did before.

Hope this helps.
 
#7 ·
^^Thanks!^^

So, there is no need to use, what I am assuming is, the compression-release lever on the left side of the handle bar? I'd love to get rid of that lever if it's not needed.
Cheers, dan.
 
#10 ·
^^Thanks!^^

So, there is no need to use, what I am assuming is, the compression-release lever on the left side of the handle bar? I'd love to get rid of that lever if it's not needed.
Cheers, dan.
With all singles the compression release lever is your friend. Love it, caress it, wear it proudly on your bars. The trick is to bring the piston up on compression. Use the compression release to ease it over compression. Just past TDC. You will learn that in time. The whole idea is to give the flywheels and piston a running start at the next compression stroke. Inertia if you like. If you have an ignition retard lever, retard it a hair. But I think you may have an auto retard. Depending on the carb and weather, choke it or if you have an Amal, tickle it. Obviously the choke won't be needed if the engine is warm.

Give it a good kick. Try not to lock your knee at the bottom of the kick. That way if it kicks back your knee can flex and your hip doesn't wind up just under your armpit. Once you figure it out you'll have a one or two kick bike. Plus you'll be able to make a few bucks at the local bar by betting people they can't start your bike in 3 kicks or less.
 
#13 ·
Super -

One more thing...You'll learn that a kicker bike always runs better than an e-start, as no one riding a kicker wants to beat themselves up starting it. You'll probably figure out how to tweak it to run even better.

I just had to kick my A65 over four times this AM - discovered the idle circuit was a half-turn rich. Kickers make you listen to your bike.

Finally - never attempt to start one with a bunch of women watching. Kicker bikes know when wimmen are around, and they get their jollies by tossing you over the bars.

Enjoy.
 
#14 · (Edited)
Thanks for the help. All I build and ride are kick-start bikes, specifically Triumph twins. They are tuned to be one or occasionally two kick bikes, that is why this single had me so frustrated. The only times my '56 Trump has failed to start is when I forgot to switch on the magneto. :eek:
 
#16 ·
I have a Weslake 500 single in my Norton. I used to kick start it but when I got it to 14:1 comp., 36 deg. fixed advance and no compression release I had to build an electric starter that runs off the crank. Couldn't kick it anymore.
 
#17 ·
My experience from 441's

Tickle the carb about 4 seconds, until a little fuel gets on your tickling finger.

Pull the decomp lever in and pull the fuel into the cylinder with 3 "dry" kicks, applying about 1/4 throttle.

Slowly kick it to TDC, and crack the decomp lever to let it past TDC.

Turn the handlebars a little to the left, just in case a kickback wants to send your knee into your thumb underneath the throttle.

Kick with authoritIIII, closed throttle but ready for that lil twist she might want to get urged into life.
 
#34 ·
Exactly...this how I started my 441s and my Velo. One thing I learned with the Velo and wish I had realized it when I had the Victors, was I straddled the bike and kicked outward so my foot came off the pedal at the bottom of the stroke and out of the way when it did inevitably did kick back. Learned this trick watching a guy start a Goldstar.
 
#20 ·
Hoof's and the other's remarks on using the compression release are on the money. Keep in mind, the whole kicker mechanism on these bikes was originally designed to start a 250. Doing away with the compression release on the bigger singles and just kicking your ass off will take it's toll on the kicker parts, not just your body.
 
#21 ·
with my experiance on big british singles, i agree and recommend using the decompression for starting in the method descrbed above, the decompression (jake brake) is your friend for starting. kick it till you feel tdc then use the the decompression to get it a few degrees past tdc and give it a good kick. they always start that way and safer for your foot or knee.
big british singles are one of my favourite motocycles.
if your b50 is an off road bike the decompression is also great for slowing down in the trails or track.
 
#22 ·
Lower the compression — easier to start, idles better, vibrates less and is all around more comfortable to ride. A lower compression piston that retains a good squish is best, but you can also make a thicker head gasket or base gasket (out of copper or alu).
 
#25 · (Edited)
Lower the compression - easier to start, idles better, vibrates less and is all around more comfortable to ride. A lower compression piston that retains a good squish is best, but you can also make a thicker head gasket or base gasket (out of copper or alu).
Glider is right, with today's crap gas lower compression is very helpful. I have a 70 Bonneville with a piece of .080 aluminum below the jugs and it is a wonderfully smooth torqey bike to ride.

By the way I hear there is a group of guys at Willowsprings raceway that love the B50's as a roadrace bike, they are torque monsters that just power through the turns without running through a bunch of gears.
 
#24 ·
Many thanks go out to the friendly responses to my question. I followed the direction on kicking AFTER TDC and BAM! This thing lights up every time now, no struggling, no kick-back, and not too much more effort than starting a 650 twin.

THANKS again! Dan.
 
#28 ·
Some of you guys are right. But! The B50 is a easy starter, it´s all about the technique. So wooshdave have the right answer. Don´t remove the decompression, it will destroy the cogs on the kickstart ratchet.
Hoofhearted comments are spot on. I would probably start my B50 by hand if I only dare.

And please don´t compare a B50 with a B33 on starting.


Rickard
 
#29 ·
I can't kick start my sidecar because of where the sidecar is. This makes life a peach.

 
#32 ·
Well, none worth sharing. I haven't had time to mess with that beast, commission builds take priority. It looks like its going to be a while longer too. There were three bikes scheduled after the Aussie bike (just finished), but I just got a contract and deposit on a bike for a client in Japan today. That thumper may never see the road at my hand.
Cheers, Dan.
 
#31 ·
Hey Tony,

I seem to kinda remember a mod to the B50MX to help starting. I believe it was a cam swap or maybe like you were talking about thicker base and/or head gasket. All about reducing compression ratio I believe. And the use of a C/R clearly points to LOWERING the initial C/R on start up.

Sorry to be so un-clear just don't remember the specifics.....but there ARE specifics concerning this problem. Try the GAMBA site and/or BB.com

Dale