Vibration through 'bars on deceleration?

Tornado said:

I'd think position and weight amount will depend on the bar bend, material and even switch gear/other gubbins placement.

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As mentioned, not sure about low frequency thudding, but many, many, many bikes get relief from the weight positioned on the end.
Item 8:

The gearbox might be loose in it's mounts, and the chain adjustments might not be constant. chains often have different amounts of stretch at places along their length. As you back off, you might feel the tight spots in the rear chain..

Bonzo said:

Went to start the bike and found fuel pAssing out of the l/h tickler. Stripped the bowl, checked the float, couldn't see a problem, put it back together again and its fine.

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If it is a stuck float then a few taps with the handle of a screwdriver or similar on the float bowl can free it off.

More likely to be dirt lodged in the float valve so with the fuel turned off and a suitable container positioned under the carb, the drain plug can be removed and the fuel turned on again for a few seconds may clear the float valve and save having to remove the float bowl.

Bonzo said:

I'll bear that in mind Nigel, cheers.

Just took it out and the flooding issue hasn't reappeared, so I won't delve in again until I need to.

EDIT. Actually, I remember checking that (on your recommendation, I think) a while ago - before they went on.

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Keeping a diary of work done and other details is a good way to save guessing in the future

BERT said:

Keeping a diary of work done and other details is a good way to save guessing in the future

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Oh to be that organised

Bonzo said:

Oh to be that organised

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I thought that is what this forum was for? I can search for all my old posts of things I've dealt with.

Tornado said:

I thought that is what this forum was for? I can search for all my old posts of things I've dealt with.

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Old Hobot speak....

Bonzo said:

Well, as it turned out, I didn't get much riding time this weekend (despite it being an unplanned bank holiday), and so my fettling has amounted to precisely bugger all.

Was gonna take a ride out to our eldest's at his new gaff this avvie, but before I did thought I'd check the valves again as the timing side exhaust seemed to be a touch rattly (it needed a tweak). Went to start the bike and found fuel pAssing out of the l/h tickler. Stripped the bowl, checked the float, couldn't see a problem, put it back together again and its fine. New Premier's so can't blame it on any worn parts. Float could've just stuck I suppose. Taking it for its vehicle examination on Wednesday (like a one-time strict MOT), so need it to be bob-on.

I'll take it for a quick run out now because I'm gagging for a ride out on it.

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Could also be the float hanging up on the bowl gasket. Sometimes the ID is a bit generous.

I thought Commandos had rubber-mounted motor and gearbox assemblies. Perhaps your head-steady is too tight ?

acotrel said:

I thought Commandos had rubber-mounted motor and gearbox assemblies. Perhaps your head-steady is too tight ?

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Not really sure how the head steady could be too tight? Please explain

If you are getting bliss out of this bike you have a normally operating Commando. The other Brit bikes of the day did not provide bliss.
Even the Japanese bikes from the period only came close to providing bliss at low speeds, only to lose it in a crescendo of tingling high rpm vibration at highway speed.

Glen

acotrel said:

I thought Commandos had rubber-mounted motor and gearbox assemblies.

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That doesn't mean they are completely vibrationless (as anyone who has ridden a Commando should know).

acotrel said:

Perhaps your head-steady is too tight ?

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The Commando head steady is attached to the frame by rubber mounts.

I would think that when you are experiencing more than usual low frequency vibes on overrun the front ISO is failing. Signs that the rear ISO is failing is the gap between the primary chain case and footrest mounting plate is reducing, off or on the centre stand.

Higher up, there was the suggestion it may be the drive chain. That was my experience. My chain looked ok, but when I removed it there were a number of really stiff links. Noticeably improved with a new chain.

Mart UK said:

Higher up, there was the suggestion it may be the drive chain. That was my experience. My chain looked ok, but when I removed it there were a number of really stiff links. Noticeably improved with a new chain.

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It's a new IWIS chain. I agree there could still be stiff links but I'm not convinced this is the issue.

cash said:

I would think that when you are experiencing more than usual low frequency vibes on overrun the front ISO is failing. Signs that the rear ISO is failing is the gap between the primary chain case and footrest mounting plate is reducing, off or on the centre stand.

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I replaced them with the adjustable kits from AN, and I'm pretty happy that the space between the primary & z-plates are pretty even all the way round.



As soon as I tapped that rear stud through, I was so relieved that that ball ache of a job was done I didn't put enough focus on checking the gap, instead just backing it off a couple of holes from rigid. Hoping to get a look at the Iso's today.

Bonzo said:

Went to start the bike and found fuel pAssing out of the l/h tickler. Stripped the bowl, checked the float, couldn't see a problem, put it back together again and its fine. New Premier's so can't blame it on any worn parts. Float could've just stuck I suppose.

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Fast Eddie said:

Burrs on the float tang, causing it to bind on the needle and prevent proper action is a common ish problem on new Amal’s (Premier and MK2).
Finishing with a fine file and emery is the answer.

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L.A.B. said:

If it is a stuck float then a few taps with the handle of a screwdriver or similar on the float bowl can free it off.

More likely to be dirt lodged in the float valve so with the fuel turned off and a suitable container positioned under the carb, the drain plug can be removed and the fuel turned on again for a few seconds may clear the float valve and save having to remove the float bowl.

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gortnipper said:

Could also be the float hanging up on the bowl gasket. Sometimes the ID is a bit generous.

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I did a check on the front Iso. and found I couldn't get a feeler in there. After I initially set it, I torqued the through bolt up to 30ft lb., but failed to check it afterwards, and so I've now got it set at 0.008".

Lid donned for a test ride, when the l/h carb once again flooded.

Tried all of the above tips, tapping with screwdriver, flushed through drain plug, double checked float tang for burrs (and gave it a once over with a flat needle file), and put a new float bowl gasket on (as @gortnipper mentioned, there could be a little over-lap).

I'm conscious not to overtighten the screws to prevent distorting the bowl. The float looks the perfect height in the bowl (as is identical to its counterpart). The fuel is fresh, and the tank is nice & clean. In the depressed position, the tickler looked more flared than I thought but comparing it with the other one confirms they are identical.

It doesn't flood until tickled is a point worth mentioning.

Tickler doesn't appear to be sticking, I mean it returns quick enough. Do they play up?

Bonzo said:

It's a new IWIS chain. I agree there could still be stiff links but I'm not convinced this is the issue.



I replaced them with the adjustable kits from AN, and I'm pretty happy that the space between the primary & z-plates are pretty even all the way round.



As soon as I tapped that rear stud through, I was so relieved that that ball ache of a job was done I didn't put enough focus on checking the gap, instead just backing it off a couple of holes from rigid. Hoping to get a look at the Iso's today.

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I am fairly new to Norton isolastics as well , and mine need the swingarm checking so while it was out I thought it would be good to do the isos and all the exhaust rubbers etc , mine was , making going through town , very hand numbing , my old isos had back rubber dust from the front inner hole worn 2-3mm and the rear iso had a ripped up shim , I have set mine the same as you tightened up and backed off 2 notches , I lubed my washers , for good or bad I don't know , the top head steady rubbers I got look like a general purpose rubber exhaust mounts , they have a small diameter steel washer where it screws in , so difficult to nip up , this might make them more flexi ? I have only done about 30kms but seems so much better than it was , mirrors are more useful now , I will add some weights and silicon them into my bars I think that might help deaden some more vibs , I know keeping the rear chain adjusted helps to , when I checked my primary chain it was so tight , so I backed that off to spec and run some ATF , now the clutch works .I also replaced the rear drum bearing and wheel bearings feel good . I did change to a 20T front sprocket from 19T , this has lowered my crusing rpm about 300rpm More testing .Cheers.

Bonzo said:

I did a check on the front Iso. and found I couldn't get a feeler in there. After I initially set it, I torqued the through bolt up to 30ft lb., but failed to check it afterwards, and so I've now got it set at 0.008".

Lid donned for a test ride, when the l/h carb once again flooded.

Tried all of the above tips, tapping with screwdriver, flushed through drain plug, double checked float tang for burrs (and gave it a once over with a flat needle file), and put a new float bowl gasket on (as @gortnipper mentioned, there could be a little over-lap).

I'm conscious not to overtighten the screws to prevent distorting the bowl. The float looks the perfect height in the bowl (as is identical to its counterpart). The fuel is fresh, and the tank is nice & clean. In the depressed position, the tickler looked more flared than I thought but comparing it with the other one confirms they are identical.

It doesn't flood until tickled is a point worth mentioning.

Tickler doesn't appear to be sticking, I mean it returns quick enough. Do they play up?

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If your float height/furl level is set too high, it can leak out the tickler since the inlet will never get closed.

Bonzo said:

I did a check on the front Iso. and found I couldn't get a feeler in there. After I initially set it, I torqued the through bolt up to 30ft lb., but failed to check it afterwards, and so I've now got it set at 0.008".

Lid donned for a test ride, when the l/h carb once again flooded.

Tried all of the above tips, tapping with screwdriver, flushed through drain plug, double checked float tang for burrs (and gave it a once over with a flat needle file), and put a new float bowl gasket on (as @gortnipper mentioned, there could be a little over-lap).

I'm conscious not to overtighten the screws to prevent distorting the bowl. The float looks the perfect height in the bowl (as is identical to its counterpart). The fuel is fresh, and the tank is nice & clean. In the depressed position, the tickler looked more flared than I thought but comparing it with the other one confirms they are identical.

It doesn't flood until tickled is a point worth mentioning.

Tickler doesn't appear to be sticking, I mean it returns quick enough. Do they play up?

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“once over with a file” isn’t likely to be sufficient IF this is the issue, in fact, depending on your choice of file, and filing skills, you could make it worse ! You need to polish the tang interface area nicely with some Emery / wet & dry.

Are you sure your tank and fuel is free of debris ? Perhaps time to invest in some in-line filters ?