Amal's - first kick and 3500rpm!

Greetings Guru's!

And there was I, all chuffed and smug at rebuilding my Amal's - even posted a picture of their new matt "shininess"! - until I kicked my Yellow Peril over for the first time ...

I have a 3500rpm tickover!

No worries for me about cold starting. Backed the pilot air screw all the way out, to no avail. Checked the cables for tightness, all is good on the bondage front.

So it's time to remove the float bowls and re-check the float height. I had followed Bushman's advice and set them at 2mm below flange and I'm thinking this is too high, setting a very rich mixture (did I mention I don't need the pilot air screws for this ...)

A little research had me coming to the conclusion that a 2mm float height is good for Triumphs but not Commandos due to the difference in engine incline, carburetor alignment and hence relative float angle, leading to float height.

It seems I should be setting the float height at between 4.33mm to 6.35mm (0.017” to 0.25”) from the top of the bowl.

What are guys thinking?

As ever, please enlighten this poor Norton Adherent ...

for now leave the air screws at the recommended one and a quarter turns out from seated

Given your immediate rise to 3500rpm after starting, I would first guess that the slides are hung up.

Looking into the back of your carbs with the air filters off, engine off, can you verify that the slides are very close
to being fully down, like maybe a 1/16 of an inch air gap?

raise the slides with the throttle and then release the throttle while looking in the back of the carbs, do the slides slam fully down with authority? They should.

If all that is ok, how about your choke slides? You do have them in fully off and not on position?
That can enrich the mixture but certainly not enough to rip right up to 3500rpm.

I doubt the problem is jetting at this point, so how about throttle cable slack? Make sure you can turn the throttle a good 1/8 of an inch without the slides rising, and then I would take the tank off and verify carefully that you have the throttle to lower cables properly configured, you may well have a lower cable hung up inside the junction box

If you didn't keep track of which slide went with which carb when you took them apart, that could be your problem. From what I learned at N-V, the slides are individually lapped to the carb bodies and are not interchangeable.

My works hack 650SS was used for a single carb trial and when I got it back, I just reassembled the twin carb set and installed it. Going home that night, I did a quick full-throttle pass round a slow moving car and tucked in behind a double-decker bus. When I rolled the grip closed, the power stayed up. It was only a quick thumb on the kill button saved me from an embarassing wreck. It wouldn't have looked good if an N-V test engineer on a company bike had plowed into the back of a bus!

I don't think the floats are it. Try turning off the Taps to see if RPM's decline with the Bowl levels.
Did you over tighten the flange bolts? Spray some WD40 around the gaskets. Any change?
Did I read rightthat you pulled the air screws? Or was it the idle screws?

shrugger said:

Did you over tighten the flange bolts?

Click to expand...

Thank you Shrugger!

It's an overtightened flange!! Darn it! Just tooooo keen to get everything bolted back up. Time to pull the carbs and true out the flanges ...

It does say in the manual not to over tighten, just enough to flatten out the lock rings.

Ahhh, blissful joy, more time to commune with my ohhhhh so sweet and immeasurably patient Yellow Peril ...

I am learning that the true definition of a Norton Adherent is to practice, practice, and then to practice some more.

- Nells

Nells,

The fuel level heights I mentioned are not to be confused with the actual float height setting. As you have established the float levels are not the issue here, but you are right the Commando float levels should be set higher than Triumph or non down drafted mountings. The floats can be set level to the flange for Commando, or you can get more anal, like me, and go to the trouble to set the actual fuel levels. I did this because I got some fancy stay up floats, these make setting the floats easier, than original. Leave this process to latter on if you are not entirely happy with the idle.
Hope you can get the flange and carb un distorted?

Cheers Richard

Float level base line to feed the rest of the circuit is spot on when best idle obtained by 1.5 air screws out, the measuring level is just ballpark to get started, but close enough for most. There's definite risk of loosing and loosening of proper light tightening of carb fasteners and found some RTV works well w/o the strain to remove with loctite especially on the float screws which I found almost stripped the slots d/t the force and skewed angle of approach down under, same with the caps, no more loctite there for me. Carbs flanges can be distorted new out the box. I gave up on oil rings for rubber like gasket so can nip up good w/o bowing the flanges. Not a bad ID to carry a spare carb screw or two in kit. I made it to Texas and back 1000 miles no problemo till a local ride with friends embarrassing me on my hard starts and rising idle speeds, till a gas stop had fuel leaking out to see a float bowl hanging by one screw. Its not a bad habit to give bowl bottoms a tug test before tickling to go.