In search of solutions (and sympathy)
Yesterday, I went out on the B31 twice.
Once was about 30 miles of problem free riding.
The 2nd time, after about 6 miles it died whilst moving and wouldn't start for about 15 minutes of manic kicking, with the decompression lever pulled in and then released once spinning fast. - it then did this trick every 500 yards or so (and sometimes it does it as soon as any "drive" is felt from releasing the clutch.
I got to my destination eventually, exhausted and soaking with sweat after all the kicking, 10 miles in 2 hours !
The journey home was without any issues, about an hour later.
Today, I did a 10 mile run with no issues.
Stopped for a couple of hours then attempted the scenic ride back (charity run) but after the first mile or so, it died again.
It will eventually start again after tons of kicking and the fuel tap turned off.
Whilst kicking, it explodes from the exhaust like a bomb going off, about 3 times and then it will start.
It won't stay running if I give any throttle or try to set off riding, it dies again and the process repeats.
Whilst it is moving, I can feel a "surge" in the power, which I think could be electrical misfire or dirty Carb and I have to Rev it rather than use the torque or it'll die again.
Any suggestions please?
It's got new plug, HT lead and cap
Thanks
Could be a problem with the fuel supply ,Check from the tank first .Or if you are still running a mag. they can sometimes get a little moody when they are getting on a bit. they perk up again when they cool down until the next time ..Good luck !
Nightmare! Have you checked the plug at any time during this? Does it have magneto or electronic ignition?
Sounds carb related if it started better with the fuel off.
Interesting you say you drop the valve lifter once it's spinning fast. That seems more of a diesel starting technique like on boats/dumper trucks etc. I have a B31 and just use mine to ease over compression slowly, let go of the lifter, bring the kickstart lever back to the top, switch the ignition on (electronic) then give it a firm push down on the kicker.
If it was me I'd check the plug, check for spark, give the carb a strip and blow out with some carb cleaner then do several long rides staying close to home with a plug spanner and spare plug in the toolbox and see what happens.
Intermittent faults like this are a nightmare!
First thing is empty your petrol tank fully and see what comes out. If it has been standing over winter with Ethanol fuel it will a) be poorer quality due to evaporation (but B31 will run on anything!) and probably lots of fine rust.
Clean your tank filters on the taps and flush out the carb properly.
If your tank filters are not perfect and the carb filter is sludgy you may need to put a commercial (any car shop) in line filter.
Having said that have you checked your ignition timing and plug setting (18thou) points 12-15thou
Use a non- resistor plug, plain copper wire HT lead and non-suppressed plug cap.
Then move on to your magneto. If original and non-serviced the paper type capacitors in the end cap of the armature start to fail when hot giving rise to popping and banging like the timing is off.
Solution is rebuild with removal of old cap and replacement with high quality internal or a surface mount type from EasyCap (see the website) now in France.
Maybe let us know where you live. Someone local to you could help out.
I'm in Sheffield.
Thanks for everyone's suggestions.
It's not got electronic ignition and I had cleaned out the fuel tank and checked the filter a couple of months ago.
I'll try a new plug. The HT lead and non-resistor cap are new.
Totally stripped & cleaned the Carb.
New plug, HT lead & cap
Still occasionally stalling.
Narrowed down to "fuel starvation" because as it's dieing, if I tickle the Carb, it recovers and continues running.
See my next post / topic on "How do I set the float height"
If it is a monobloc carb try changing the float needle. I had the same problem with my Shooting Star. If worn the needle tilts and sticks in the seat shutting of the fuel.
My b33 farted and coughed , one day and couldn't handle much throttle , I just made it to my gate and it died , I checked for spark , No spark , I thought the mag was stuffed , I pulled it apart , but found oil on the slip ring and the carbon was stuck in the HT pick up . I think mine is missing the top seal for the mag as oil comes out , I've got one on order. Cheers
Cleaned out the Carb again and played about with mixture screw / tick-over and for some reason, I've done 2 x 30 mile "test runs" without issue (thankfully)
I don't need to tickle the Carb to start her, even when been standing for a week with a drained Carb.
The mixture screw is only half a turn "out" but she ticks over nicely.
Fairly fast tick-over when advanced but will allow retarding to half-way and still tick over nice and slowly.
Is that "job done?" Or am I masking a problem?
Either way, she's a delight to ride (when I can select a gear and not a false neutral ::) )
Nice to hear Franz,
One thing about gearbox - enjoy it with confidence ....I used to have the same issue with false neutral when changing bike from Honda to Royal Enfield. I was far too gentle....
My B31 gearbox is full of false neutrals too. I've found the trick is getting the clutch adjusted nicely and being slow with up changes, keeping pressure on the pedal until I feel it click into gear. If I rush, I think it's in gear but end up in a false neutral. A couple of throttle blips always seem to help a down change.
It's worth checking that the selector detent plunger is adjusted correctly.
The s/a boxes need to have correct endfloat on the layshaft (10thou) which is quite important.
Quote from: neil1964 on 17 Apr, 2024, 21:24
It's worth checking that the selector detent plunger is adjusted correctly.
The s/a boxes need to have correct endfloat on the layshaft (10thou) which is quite important.
That's good info. What is an s/a box? Must admit I'm trying to live with my gearbox until the winter ::)
s/a = swinging arm. Different (better) gearbox from the plunger and rigid models.
Quote from: Derek996 on 18 Apr, 2024, 09:59
s/a = swinging arm. Different (better) gearbox from the plunger and rigid models.
Thanks for that - mine is a plunger ::)
Quote from: Derek996 on 18 Apr, 2024, 09:59
s/a = swinging arm. Different (better) gearbox from the plunger and rigid models.
In what way better?
On the difficulty to start when hot. Have you checked that the points gap is still there. Also do you still have any tappet clearance..?
Both of these could reduce to less than zero, when the engine becomes hot.
Best of luck..
Quote from: V500 on 18 Apr, 2024, 22:43
Quote from: Derek996 on 18 Apr, 2024, 09:59
s/a = swinging arm. Different (better) gearbox from the plunger and rigid models.
In what way better?
Better faster and more positive gear changes. Also more robust and reliable.
I've ridden both and still have two plunger gearboxes, one on the Star Twin and the other on a Goldie, and I can't say there's any noticeable difference. The one on the ST is particularly sweet-changing.
Both have lasted for 73 years and counting, so maybe reliability isn't so much of an issue either.. ;)
The Star Twin gearbox bolts onto the back of the crankcase and is basically the same as the swinging arm gearbox but in a different housing.