YASP - Series 90 failing to start

[gaffers]

I had a good chat with Charles this afternoon, a thoroughly helpful chap.

I have done everything possible now:

-Cleaned tap filter
-Cleaned fuel line
-Cleaned carb with carb cleaner
-Cleaned filter behind banjo
-Checked float operation; all good when float in the down position a steady trickle of fuel comes out
-Checked fuel needle valve does not stick
-Checked main jet
-Check fuel needle is clean

and still it will only operate ok on choke, but not without (ie running lean)

I have run out of ideas now, what next?

[Horsley-Anarak]

It might be a crankcase leak, as it will only pull in enough fuel whilst choked.

What are the main bearings like?

H-A

[gaffers]

no idea, how do I check?

[Horsley-Anarak]

Take the recoil starter off (two small screws) then try and move the rope pull that is mounted on the crank.

You should not be able to see any movement.

Also check that the two crankcase halves are tight together and that the cylinder is tightiy fixed to the crankcase.

Have you had the crankcase apart ?

H-A

[gaffers]

I havent touched the head, crackcase or crankshaft.

But I cant comment for the previous owner

[Charles uk]

If the needle valve has a groove in it like a circlip groove at the float end, it is a retained needle & there should be a slot in the float where the needle is retained.

If the needle is not held in this groove the float will be held in a lower position & will not permit the needle to fall, giving a level too low in the float bowl.

On a model 90 I think you should have an Amal 416 1A carb which has the grooved retained needle, can you post a picture of your float & needle?

[Hugz]

Hi, when you get it running, full choke or otherwise try squirting WD40 around the joins (crankcase, barrel etc) and if there are any leaks the revs will change.

[gaffers]

Sorry Charles, I forgot to mention that although there is a groove in the needle there is no slot in the float at all. The float test showed it worked perfectly as well.

I'll try the wd40 trick and the crank bearing test tomorrow afternoon, once I have got rid of the vultures at work

[Charles uk]

I think you will find that, that needle is too long for the standard float.

I can't make my camera take a macro image of the float & needle to show what the correct matching components should look like.

Can you take a picture of yours H A?

[Horsley-Anarak]

Dont think it is the float.

Here are two different types of float needle arrangement

Where do you live Gaffers?

H-A

[gaffers]

I live near farnborough, hampshire.

My float arrangement is identical to the one on the right of that image.

[Charles uk]

H A can you post a pic of the side elevation of your carbs to show the closed needle valve/ float height main jet relationship.

[gaffers]

I will this afternoon, many thanks.

[charlesp]

A question - when you remove the float bowl after your various attempts to start the motor is it full?

[Charles uk]

Do you have the grooved needle?