1960 Gold Flash only runs correctly on choke

[cdsdorset]

Just fire the bike up and spray some wd40 or easy start on the carb to manifold joint. Any change in engine note means you have a leak.

[Seamus]

Thanks again gentlemen. Some good ideas there.
Hope to get round when I get a couple of negative tests. Luckily. I don't feel really bad. Bit like a cold.
Cheers all

[Seamus]

Resurecting this thread as I had a bit of time and a suitable day to test. Carb stripped again, it has no number stamped on the flange, but I measured it at 1 1/16 choke size, guess a 376 ype as fitted to 55 to 59 gold flash. This is a 60/61 bike and should have an 1 1/8 carb. I have assumed if the jets are correct for the earlier carb, it should run ok. The carb has been stripped again, poked and prodded, washed out with carb cleaner and everything appears to flow fine.
All reassembled and a pancake air filter fitted.
Running the bike, it idles well and revs fine on choke. Off choke, it will idle and when trying to rev, it missfires and seems to be running on one cylinder. Difficult to see which cylinder it is not running on as both exhausts are hot by then.
Will try starting on choke to warm up a bit, then remove one ht lead and start on choke, take off choke and see how it runs, then swap over. At least it will eliminate the ignition side.
Should have more time to play with it as th weather is getting warmer

[Spaceman]

The earlier A10 was fitted with a 376 carb with 240 main jet whereas the 60-61 A10 was fitted with a 389 carb and 250 main jet. Assuming it's got a 60-61 head on then it probably should be run with the 250 main jet also assuming it's got an air filter attached. If not, an even bigger main jet is required.

The fact that it revs with the choke on would indicate that it's running very weak. Assuming that the main jet is the right size, a possible reason for it running weak can be a worn throttle slide or throttle body allowing air to enter past the slide. The slide should be a snug fit as you move it up and down in the body with no free play discernable. If there is significant free play, a new slide might be enough to cure the problem otherwise, unfortunately, the carb may be worn out.

[idie]

The other problem may be a weak spark. A weak magneto will fire a rich mixture but when weakened and the engine reved it will tend to blow out the spark. Had this problem a few years ago with a Shooting Star. Worth checking how far the spark will jump.

[DAVE BRADY]

Hi Seamus,

Can you confirm the colour of the plugs after idling and revving with the choke slide in the lowered 'on' position.  Then after cleaning, the colour with the choke slide raised in the 'off' position after idling and then trying to rev.

Also, how much are you opening the throttle to get it to rev?  Have you tried opening the throttle to about 3/4 + to see what happens?

Dave.

[Seamus]

Thanks again for the suggestions. Unfortunately, my mate is off on holiday for a couple of weeks so I will not have access to the bike.
Found a working colourtune plug in my box of bits and will try that in one cylinder at a time and see if I can judge the mixture from that.
Rechecked the jets and founf pilot 25, main 250 and needle at 106, so should be in the right ballpark. Carb flange is flat (checked on a surface table) O ring is new and squirting carb cleaner through the pilot holes, comes our in a good flow.
See what happens and will report back

[Mike Farmer]

 

Hi

Coca Cola doesn't work---honest

Mike

[DAVE BRADY]

Hi,

'Colortune' is a great tool.  Although the engine will not be under load, the full range of throttle openings can be assessed.  Also the affect of quickly opening the throttle can be seen as well as the affect of using the choke.

Dave.

[Jhg1958]

Seamus

How are you getting on. My friend's T100 problem was cured with screwing in the air screw fully then out by 1 1/4 turns. Started and ran ok without choke!  Adjusted the air screw following Amal instructions.

Too simple?  Perhaps just my ignorance.

John