out of balance crank

My APR 69 production date S model had baffles in the very end of the silencer, right at the widest part of the peashooter. There were no holes in them as I remember, but I have the pictures somewhere if you care to see them, lighted from the inside so you can see what's in there. I didn't have any issues with vibration. Actually my vibration came after I got newer 'donuts' for the isos which I assume were stiffer than the originals.

Ugh, first Commandos isolated below 2000 but new cushions stiffer than designed so I bench grinder bevel fronts to 1/4" rim left for sweet flying carpet sense about 2000ish w/o much/any loss of handling to wiggle worm threshold that's always innately lurking in non tamed-linked/swash plated Commandos. Head steady alone is not able to prevent this only delay a bit for even worst speed/loads terror onset, yiKES. Still even newer stiffer cushions eventually isolate below 3000 so we still don't know why yours was so annoying to help us logically avoid similar.

I replaced my muffler support rubbers with four from McMaster-Carr, but was unsure of what the durometer should be. I started with 60A's based on their weight-carrying capacity, but they were noticeably stiffer than the stock items. Yes, they definitely increased vibration throughout the rpm range. 'Tried 50A's. While it helped, it still vibrated more than stock. I since went with 40A's, but might go even as low as 30A. Each successive drop in durometer has decreased the vibes an equal amount.

Nathan

I always get my "lord fittings" blessed by andover Norton themselves from Old Britts. Did not realize there were options in stiffness. Several people claim the lord fittings have a big effect on vibration...don't see how really but if many people come up with the same conclusion, it's worth investigating. If you are talking about using softer ones in the head steady I can see that.
I suspect the baffles in the muffler was giving an odd back pressure which made it shake which vibrated the single Mikuni something awful and further upset the carburation which caused more shake etc,etc,

Nater_Potater said:

I replaced my muffler support rubbers with four from McMaster-Carr, but was unsure of what the durometer should be. I started with 60A's based on their weight-carrying capacity, but they were noticeably stiffer than the stock items. Yes, they definitely increased vibration throughout the rpm range. 'Tried 50A's. While it helped, it still vibrated more than stock. I since went with 40A's, but might go even as low as 30A. Each successive drop in durometer has decreased the vibes an equal amount.

Nathan

Click to expand...

Previously a new set of AN isos were found to have a Shore A durometer in the 45-50 range, so similar to your observation.

https://www.accessnorton.com/NortonCommando/shore-hardness.17329/#post-255793

I've been through a slew of various stubby Lord's mounts to find them either too weak to control sag & bouncing then fracture fairly soon or too robust-stiff to cushion much, especially if the muffler clamped tight on header. Longest lasting/stiffest were from Harley so used hacksaw blade to slice a slot around rim til compliant enough to tolerate but of course shortens their life. Over time, on 2 Combats THE Gravel paths beat muffler clamps and header ends to fail to clamp solidly, for a slip on/off fit, to find the mounts lasted longer and nil vibes, though some carbon blast deposits appear around seam. Its nerve racking to get on home after muffler mounts fracture - hearing seeing the muffler flailing about shortening life of header bends. I gave up Lords on Peel 2-1-long megaphone, so rigged spring mounts, which solved the up/dn bounce and support but was hard to arrange the 2 springs angles to also control sideways oscillation, ugh.

Only real solution I can think of is making the mounts ~45' angles to help support via compression rather than pure shear loads.

seattle##gs said:

I always get my "lord fittings" blessed by andover Norton themselves from Old Britts. Did not realize there were options in stiffness. Several people claim the lord fittings have a big effect on vibration...don't see how really but if many people come up with the same conclusion, it's worth investigating. If you are talking about using softer ones in the head steady I can see that.
I suspect the baffles in the muffler was giving an odd back pressure which made it shake which vibrated the single Mikuni something awful and further upset the carburation which caused more shake etc,etc,

Click to expand...

I will submit that changing the silencers can have a large effect on vibration, not so much due to the muffler itself (although that's possible, according to how they are made) but rather due to the way they are mounted, and specifically the degree to which the clamps at the join to the headers are tightened. ( I think this is what Hobot was alluding to?)

The header pipes are gonna shake with the motor. At the other end, you have 15 inches of unsupported weight (the heavy end) wagging around behind the lords. If the headers and mufflers are rigidly clamped, all of the header pipe vibe is sent through for the lords to deal with. I was able to "tune out" some vibe by judicious loosening and tightening of the left clamp today, and as soon as it warms up a little, I'm gonna get more involved.

I may also pop for the CNW head steady, try to lose some of the side-to-side motion up front.
Any reviews on this expensive "upgrade"?
Any opinions about whether I can lose that nasty "suspensor" spring if I mount the CNW item?

I think the cNw head steady is a must have. It’s such a logical approach, and compared to others on the market, is so well made and robust.

‘Spring or no spring’ is another debate etntirely, with or without the cNw head steady. Personally I do not use a spring. Others feel them to be very necessary. Maybe the heavier MK3 benefits from the extra support? But my own set up seems fine sans spring.

Drunk rednecks , why not put you bikes on a dyno (test tool) to find out the best mufflers to use and get the best results.
I cut the small end of of a set of peashooters close to where the headers connect, removed the baffles, welded the small ends back on again and then tested again on a dyno.
Huge midrange gains with both power and torque.
This test was done on both a race motor and a standard motor.
Gains on both.
Also lightens the load on the headers, therefore less vibration
Regards Mike
PS Im sure I saw that same video 5 years ago!!!!

Brooking 850 said:

Drunk rednecks , why not put you bikes on a dyno (test tool) to find out the best mufflers to use and get the best results.
I cut the small end of of a set of peashooters close to where the headers connect, removed the baffles, welded the small ends back on again and then tested again on a dyno.
Huge midrange gains with both power and torque.
This test was done on both a race motor and a standard motor.
Gains on both.
Also lightens the load on the headers, therefore less vibration
Regards Mike
PS Im sure I saw that same video 5 years ago!!!!

Click to expand...

Interesting about the removal of baffles. Would like to see full range output of dyno test. Wonder if close to same results could be had with adjustments on carb end -- intake length, needle, etc. Or was mid-range level maxed out with carb adjustments at that point? Maybe baffle removal acted in a more direct way on mid-range than other points of adjustmement. I remember an old VW beetle with about the last and most complicated carbureter they put on it. Two different vacuum lines to the distributer. All who attempted to adjust it were frustrated and the aftermarket manuals only went so far. "Get rid of it!" was the common wisdom. But I found the factory manual (in German which my wife translated) and followed it in all it's complicated adjustments and measurements. It wasn't That bad, really. And then it ran more sweetly than any other. Garage mechanics would have been chastised severly by their bosses if they had taken all that time to adjust a carb. So it was always done in a half-baked way. All that was to say these adjustments are not isolated in an end to end system. I know all here know that. But the correct end to end sequence of tweaks and changes is much of a mystery to me; a dark art that gets revealed in bits and pieces. So (after all that rambling). How was the dB level increase?

I've done an operation in the past on some of these mufflers. There was a time in the mid 70's when Norton was supplying them as replacements. You can knock out the plate with the small hole using a large iron stake and a big hammer. Insert stake into conical end and stand muffler up vertically on a piece of wood. The actual louvered baffles are not affected - just the restrictive plate.