Motor speed seems to "hunt" at idle.

I recently had my Amals sleeved and installed them with new gaskets and internal parts. I can't seem to get a good idle as the motor speed goes up and down, a little, as I try to dial it in. I'm going to yank them, and try replacing/sealing the gaskets to make sure I don't have a vacuum leak, but I'm wondering if air could be seeping past the slides. The slides are tighter in the bores than they were before, but I am not sure what the clearance should be. Any help or suggestions on where to look for the problem would be appreciated. Thank you.

What kind of ignition? I found after installing new anodized slides, it was better, but it just took me a while to get the pilot screw adjusted a bit on the rich side (in) and then it settled down. If you have the AAU, it may be worn, if not, keep fettling.

Dave
69S

Those newly bored out bodys are now thinner and more susceptable to overtightening of the carb to manifold locknuts. 4 lb. torque max. You can't go back if overtightened. Float bowl posiscrews could have been overtightened too allowing air in past the bowl gaskets. Never eat wheaties for breakfast then work on your Amals.

well, someone has to say it: "90% of what are seemingly carb problems are revolved with electrical solutions"

I gotta ask, James, what kind of ignition are you running, points and spring loaded auto advance or an electronic ignition?

A good micro digital, as compared to analog, EI cured ALL my idle issues, with my Amals, my Mikuni and continuing on with my JSmotorsport flat sldies.

Hey James,
Firstly check for air leaks in the manifolds, and blockage in idle circuit...
Hunting, or, gaining revs then dropping again, can be a problem caused by fuel mixture,.. amongst other things, (weak ignition)
Generally, lean at idle, can cause an engine to hunt.
If there are no air leaks or blockages......
As you have just rebiult your carbs includeing sleeving, it's probabaly not an issue of air leaking past the slides
creating a "leaness", so may need to look towards checking the float level, it may be a tad low making it more
difficult to suck fuel up at idle vaccumn pressures.
If you fitted 'stayup floats' the task is made easier.
Tight slides, should mean richer than before, at idle, but means nothing if the motor can't suck fuel up.
New Neddle jets and Needles may be leaner than before at 1/4 to 3/4 throttle, and main jet probably hasn't been affected.
Try to adjust the problem out with the mixture srew, if not possible...
Look at the float level.
PS... Measure the the Cuttaway on the slides and check both are the same, and not been altered or damaged during sleeveing.
Then again, my ignition some how changed recently, while sitting in the shed, so, who knows...
AC.

james
I'm thinking float level might not be right as AussieCombat mentioned. Test the 1 1/2 turns out from fully in. This should be real close. If not adjust float level seat. I Like the new stay up floats. These should make your life alot easier. Air leaks will create backfire on overrun when you back throttle off.
CNN

Yes, love my new "stay up" floats too but don't screw it all up by overtightening those 4 posidrive screws.

My resleeving job of years ago was a hair on the loose side in terms of slide-to-body clearance.

When the idle is hunting, try turning the throttle just enough to put light tension on the cables without even suggesting the slides actually lift.

Slightly loose slides often shake in the bore and leak air, causing the engine to hunt. The tension on the cables will stop them from shaking and the idle settles.

Worth a shot.

And like the others said, worn AAU if you have one can cause similar.

Mark

Some of the more expensive electronic ignitions have an idle compensation feature around 1000 rpm. When the idle wants to rise it retards slightly and brings it back down and when the idle wants to slow down it advances to bring it back up. I'm using a Pazon Altair which has this but I believe the Boyer digital (not the Mk III or Mk IV analog one) also has it, as well as the TriSpark. It seems to work very well on my combat. I can sit at a light now - no hands - without worrying about the engine dying.

Also there is a great device for synching carbs now. Someone posted a link last December and I bought one. It is called the Harmonizer. See this link on advrider -- http://advrider.com/forums/showthread.php?t=701625.

Wow, thanks for all the great suggestions. To those that asked about my ignition, its a Boyer, I believe Mark 3. I checked with the sleever and he assured me that the slides are tight, although I haven't measured them. I did yank the carbs and replaced the manifold gaskets and used a straight edge to check that neither head or manifold surfaces were warped. I also checked that I had not overtightened the carb to manifold bolts causing more problems. I think now its an idle tuning problem and will fire it again soon to see if I can do a better job in that regard. I would like to say that this forum is a great resource. I have been helped more than once by its members and I know I can count on more help in the future. This alone is a good reason to own a Norton.

Batrider has it right. If you're concerned with a stable idle and performance at take-off, get an idle-stabilized EI. Not only will the idle remain steady over all engine temperatures, but the advance curves follow more closely that of the AAU, and take-off is much more spirited. TriSpark and the Pazon Altair have nearly identical advance curves and many happy users. Boyer's MicroDigital has a more aggressive stabilization curve and remains more retarded at take-off. The last time I looked, the Altair was the best deal at $250 USD. Installing one of these units will save you many hours futzing around with your carbs.

My Altair-equipped Mk3 sat alone here in Seattle over the winter while I was enjoying Austin. When I returned last week, I drained the sump (1100 mls, BTW), removed the tender, pulled in the choke, and pressed the magic green button. Two minutes later, choke removed, the old girl was purring at 1000 rpm, just where I left her 7 months ago. I only wish I ran this smoothly.