Anyone good with carbs ?

[gifdy]

I’ve got a problem with my SU carbs that I can’t seem to sort, and the engine won’t start. The engine has good compression but in the carbs, the fuel is not atomising. I assume this is lack of vacuum but not sure why. I can’t find any leaks.

This is what happens when cranking. SU carb

You can see fuel seeps out but doesn’t atomise. I’ve tried the jet set ant various heights but get the same. Any ideas ?

[tapkaJohnD]

The Carb piston isn't moving.

The needle that is seen in the video (very well done, by the way!) should be pulled up out of the jet as the piston rises as the throttle opens. Towards the needle's point it narrows, so the the annulus, the space around it in the jet, gets wider and admits more fuel. Yours isn't doing this as it should as the throttle butterfly opens.

Diagnosis: Stuck piston, if an SU carb. If Stromberg, split diaphragm.

John

Edited by tapkaJohnD on Sunday 10th September 19:25

[gifdy]

Thanks, I’ll take a look at that !

[gifdy]

It runs !

I'm not exactly sure what the issue was, but maybe lots of little things. The fuel level in the dashpots was very high, so I adjusted the floats. I also took out the pistons and polished the surfaces so they wouldn't stick. They passed the 'drop test' afterwards. I then set up the jet heights & idle screws to default.

I also swapped the distributor and put fresh fuel in it which may have helped. Anyway, it starts nicely now. Just need to go through the tuning procedure. Thanks for the help !

[ARHarh]

Just a quick tip to anyone who has similar issues. When trying to start, unscrew the piston oil filler cap and use the damper to manually lift the piston, it will instantly unstick a piston which has been siting for a while.