Dancing Commandos

From another thread:

daveh said:

By the way, I watched your video of your Commando idling on another thread. I noticed it wasn't jumping about on tickover. In which case, I'm envious!

Click to expand...

Just how much does your Commando dance at idle on the centerstand? If it does, is it from too tight of isolastics or too loose?

Mine doesn't move unless you goose the throttle on a concrete garage floor then she'll moon walk for you.
Iso's adjusted a year ago at .10 on both sides front and rear.
New PTFE washers and dust boots. Orig. bushings still inside the mounts.
Slight buzz at bars below 3 grand after that all gone :mrgreen:
Marshal

The new one doesn't move much period since it doesn't run and old reliable does not jump or dance at all on idle. It's pretty much a nice smooth idle at about 1000 rpm's. Iso's adjusted about the same as marshal's. Vibes go away at about 2500 now

No dancing done by normal operating idling Cdo's on either stand. They should resonate a mirror then fender then mufflers then bars in cycles but stay planted until blip ups beyond 2500 on a fairly even hard surface. Couple fold thickness of a rug, carpet or door mat holds em back nicely. If walking away at 1000 rpm then something ain't right yet.

swooshdave said:

Just how much does your Commando dance at idle on the centerstand? If it does, is it from too tight of isolastics or too loose?

Click to expand...

I generally idle my bike on a rubber-backed carpet and it stays put. Vibrations are pretty noticeable at idle though. I don't think the isos make much difference at idle nor will you be able to adjust your isos without test rides. Start out with fairly tight tolerances (0.010 is factory spec - some folks run tighter but you do need some clearance or your frame will break) and see how much vibration you feel and at what rpms it is noticeable. On my bike there is a spot around 2500 rpm where vibration is noticeable on acceleration and deceleration. I assume that this has something to do with how isos are set and balance factor of the crank. Very smooth above and below that. I have the vernier type adjusters on my bike and have played around with them a bit. I am currently at 4 holes out on the front and 3 holes on the rear. If one whole turn = 0.050, and each hole equals 30 degrees, I am theoretically at about 0.012 rear and 0.017 front. There are all sorts of recommendations out there both tighter and looser than this but you need to figure it out for yourself and find the sweet spot between good handling and tolerable vibration for your bike. Start out fairly tight and work up.

I am pretty much sure it is all about balance factors I recall John Hudson telling me that when Norton moved to plumstead
Georges Udall changed the balance factor to 55% (I think from memory)
We found that out when taking a commando crank out of an engine to have it rebalanced to be fitted solid in a race frame it did not need to be rebalanced .This engine was definitely not pampered with before so the balance factor was not 55 but more like 65 I must have notes about this somewhere .I will look if i can find them and post them

Mine stays put at idle. At 4000 rpm checking timing however, she'll buzz around the floor.

maylar said:

Mine stays put at idle. At 4000 rpm checking timing however, she'll buzz around the floor.

Click to expand...

When my bike first started up we tried to time it. At 5k rpm with me sitting on the bike it just RAN backwards on the centerstand.

I never use the center stand to set the timing. Use the sidestand (with maybe a piece of 2X6 under it to make it more upright) or place a jackstand under each footpeg. Resting on the tires and letting the isolastics work will keep it from dancing around.

Ron L said:

I never use the center stand to set the timing. Use the sidestand (with maybe a piece of 2X6 under it to make it more upright) or place a jackstand under each footpeg. Resting on the tires and letting the isolastics work will keep it from dancing around.

Click to expand...

Since there were two of us I thought that would be the easiest way but I was having a hard enough time getting the thing started as it was (see video :mrgreen: ). Now that it start with maybe two kicks it would be easier but I've lost my timing assistant. So I'll have to see if I can do it myself.