Misc: Carburettors Comet 229F/1DV Carburation Issue

[Bradley Burt]

I'm having a few issues with the tuning of a standard 1-1/8 inch carburettor on the comet. This is the first time that this carburettor has been fitted to the bike. The comet will not run between 1/4-3/4 throttle position. It will bog down (starving of fuel) here. Turning the choke on helps. The comet starts and idles easy, and is fine on full throttle but nothing inbetween. This is a fuel problem, not electrical in this case.

106 needle jet, 29/3 slide, needle in middle notch.

The total overall needle length is 3.46 inches (88mm). Is this the correct overall length? When the throttle is completely shut the needle sits approximately 1.5 inches into the needle jet.

On this forum I found an article by E.M.G Stevens (MPH 191, page 22). He states that the needle type fitted to the 1-1/8in. carburettor is "1.7/8in. overall” in length. But isn't this way too short?? At full throttle the needle would come completely out of the needle jet I would think.

Any thoughts would be greatly appreciated.
Thank you,
Brad.

 

[passenger0_0]

Hi Brad, I have found some new replacement throttle slide needles have the wrong taper profile which gives exactly the symptoms you describe. Cheers David

 

[Bradley Burt]

Hi Brad, I have found some new replacement throttle slide needles have the wrong taper profile which gives exactly the symptoms you describe. Cheers David

Hi David,
See the attached photo showing what I've got.
Thank you,
Brad.

 

[Chris Launders]

Rather than moving the needle one notch at a time try the next size jet first, as in try a bigger step to begin with, you can always work back but at least you will have more of an idea where you want to be going.

 

[passenger0_0]

Hi Brad, you can't see this error by eye, and not the length. It's the taper profile that's important.
I suggest you get an old needle from another source and compare the lengths when engaged into a small diameter hole - like a taper gauge.

 

[bmetcalf]

John Healey at Coventry Spares had a bunch of bad needles a few years ago and invested in a gauge to measure all he gets in stock. He told me maybe 3 years ago that at that point, he hadn't had any bad ones for a bit, but he still checked them. I would get a new needle from your best supplier.

 

[chankly bore]

I've just been down to visit John Parker the local AMAL man. The needle seems the correct length, but the needle jet may be the wrong part. Even though the listing in "Richardson" says "Standard" for both 276 and 229 instruments, they are different part numbers; 4/061 and 29/076 respectively. John says they differ in length by 1/4". I therefore assume that "standard" in this case refers to the flow rate; 106 c.c. per minute.

 

[Chris Launders]

Yes Amal standard was a 106 and at one time originally they were unmarked.

 

[Bradley Burt]

I've just been down to visit John Parker the local AMAL man. The needle seems the correct length, but the needle jet may be the wrong part. Even though the listing in "Richardson" says "Standard" for both 276 and 229 instruments, they are different part numbers; 4/061 and 29/076 respectively. John says they differ in length by 1/4". I therefore assume that "standard" in this case refers to the flow rate; 106 c.c. per minute.

Hi Charlie,
Spoke to John. Both needle jet and needle are correct lengths (shown in post #3). Pulled the body apart again and put back together. Raised the needle to the bottom slot and ran much better. The BP8ES spark plug looking good... not rich.

Thank you all,
Brad.

 

[chankly bore]

BP8ES is a little on the cold side. B6ES is equivalent to K.L.G. FE70 and even the "Comet on Steroids" only gets BP7ES. Glad your problem is sorted, anyhow.