Re-built, but wont start

[ttrand]

Last year I bought a mostly complete 1951 plunger GF. It had been rebuilt about 10 years ago, but never ran. Upon inspection I found many loose or missing parts. I rebuilt the gearbox, oil pump, re-wired the bike and added a brake light switch. New battery, inspected and timed the points, checked valve clearances. It appears to have good even compression. I get nice fat blue sparks too. I finally stopped most of the oil leaks, and all the gas leaks. Carb (Amal 276) cleaned and set to spec (although it has a 180 main jet, spec is 170). I figured it should still run, so The Great Day came… and went, without any sign of it starting or firing!

I tried pouring a little fuel in the plug holes, still no luck.

How can I test the carb? I should confess I didn’t separate the Jet block from the body of the carb, as it didn’t want to let go easily.. I sprayed with lots of carb cleaner and blew it out the best I could.
I tried tickling it a lot, and a little. Choke and no choke. Zero!

I’m pretty certain the timing is good too. Equal points gap @ 12 thou. New plugs@ 18thou. Strong sparks.

I’m unsure what to try next. Suggestions?

[Rex]

Maybe you've done something most of us have done, and got the plug leads reversed?

[Greybeard]

Rex beat me to it👍

One tiny detail I noticed is the kick start cotter pin is in the wrong way around. If you have the nut on top you get a more upright lever and a better kick-over.

[KiwiGF]

Some only start on 1/4 throttle, some on closed throttle, but for a newly built bike the closed throttle setting (idle speed) may not be right, which can make things tricky.
However, you should get the odd fire regardless of where the throttle (slide) is, so plug leads swapped is most likely, as per prior post.
“Start yr bastard” (ether) can help, it ignites without a spark so can get a reluctant engine spinning faster and more likely to fire and keep going. A mate can help by spraying it down the carb until the engine gets going properly.

[Slymo]

viewing mine for the first time before buying I turned up at the sellers place and found the bike there but the seller delayed. He'd said start it up and have a ride (first possible second not) so I kicked it for nearly 15 minutes without even getting it to fire. Being used to singles I hadn't considered opening the throttle but as soon as I did it went VROOOOOM!

[CheeserBeezer]

Are the plugs getting wet? If not, the carb ain't working.

[trevinoz]

If the pilot is blocked it won't start. Sometimes they will start with fuel squirted in but won't run.
The pilot orifice is in the jet block.

[Richard Hinton]

I rebuilt my A10 and finally finished it last year, but to start was always a pain, The settings finally were plugs 15, inlet valves 12 exhaust 16 and points 0.15 on full cam. this got me an easy start but running was still rubbish then after all the adjustments that can be made to the carb, i bought a new one but concentric.

Some thing to check disconnect the earth wire from the back of the mag, if this has a short to frame you will never start it. the wipac switches aren't that good and sometimes earth out.

[Rex]

He said it's sparking well?

[Swarfcut]

 That's a good looking effort and after the work already posted it is still playing hard to get. There is  always a bit of detective work needed when it's been rebuilt but never ran. The assumption is that all the right bits are in there, set up correctly.  With sparks and good compression as noted it should at least fire. Still no luck after all the recommended checks, I'd get the inner timing cover off and have a look closely at the timing gears. Are they the right ones? All set up correctly? Is there a woodruff key on the crank? Or has it sheared off as has been known. Plenty of information on the forum as well as web images as to what's right. If the sparks are making their guest appearance at the right time and place with good compression it should fire for a few seconds on full throttle and a dose of spray.

 Once you have signs of life the rest is easy. It can only be mechanical, ignition, carb......

  Removal of the jet block from a 276 carb is a whole lot easier if the body is warmed up by a short spell in the oven or a go with the heat gun. Smacking it with the hammer to drive it out cold risks damage big time.  The voice of experience.

 Swarfy.

[ttrand]

I rebuilt my A10 and finally finished it last year, but to start was always a pain, The settings finally were plugs 15, inlet valves 12 exhaust 16 and points 0.15 on full cam. this got me an easy start but running was still rubbish then after all the adjustments that can be made to the carb, i bought a new one but concentric.

Some thing to check disconnect the earth wire from the back of the mag, if this has a short to frame you will never start it. the wipac switches aren't that good and sometimes earth out.

Mag has a push button end cap…which scares me. What if throttle sticks? Anyone know if I can retro-fit a different end cap so I can run a kill switch on the handlebar? Model is K2F

[ttrand]

If the pilot is blocked it won't start. Sometimes they will start with fuel squirted in but won't run.
The pilot orifice is in the jet block.

This is very helpful. Thank you!

[groily]

Mag has a push button end cap…which scares me. What if throttle sticks? Anyone know if I can retro-fit a different end cap so I can run a kill switch on the handlebar? Model is K2F

Changing just the end cap (rather than the complete housing AND end cap) can be a fiddle owing to the fasteners used for the alloy dome type.

The plastic clip-retained caps with wire off can, however, serve if the mag body & cb housing has a short fastener on a third corner, (or even on all four) which can be used for a pillar and clip of appropriate height to retain the cap. The caps are easily available. But you then need to find suitable 2BA screws to retain the housing, without the hex section mid-point and extended thread for the dome, which may require countersinking or counterboring the housing to get the screw heads flush.

It is probably easier to modify the dome by removing the metal button & spring, slightly enlarging the hole to take a nylon insulating sleeve, up which you fit a standard 5mm brush and spring, seating on the head of a small bolt which passes through to the outside world and to which you then attach a wire.

(This is what I have done a time or three - I like the alloy domed sort myself because they hold the camring nicely in position axially, and I think they look better too. Here's a pic of one off one of mine, complete with QD knurled brass 'nuts')

[Swarfcut]

 Just viewed that lovely machine again. Just a couple of thoughts... The lifting handle is more usually fitted on the left side. The stand kick down peg is on this side, a throwback from us Limeys driving on the left and not wishing to be wiped away by some close pass by a truck as we put it on the stand. I may be wrong, but I reckon export bikes used the same stand as home market models and left side stand operation was the norm. I have also seen mirror image lifting handles fitted to the right side, but not seen as an official part in my UK parts catalogues.

 Frame is missing the through stud at the top of the frame seat pillar. This is not a seat mounting point, it is an important frame fixing that needs to be secure. Part no is 66 4175, it's a plain  7/16" bar threaded at each end.

 Swarfy.

 

[chaterlea25]

Hi All,
Sometimes no matter how much kicking you give a reluctant new built or long time standing BSA they refuse to fire up
A run down a decent hill or a paddock starter can be the only way to get the bastards started
I live at the top of a decent hill ,, If they don't start going down that I can chuck them in the tide at the bottom 

John