Author Topic: silentbloc bushes.  (Read 620 times)

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Offline Roys rider

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silentbloc bushes.
« on: 10 Nov 2017 at 14:43 »
Hi
I have been putting the D/fly forks together from NOS parts. Trying to put the bolt through I found that one of the Silentblocs had been badly made and the inner tube was offset about half way across at the middle (and at the open end), so it is going to have to come out. Without damaging the new paint, which burning would do, how do I do it? I know I should have checked first.
Cheers
Peter

Offline eddie

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Re: silentbloc bushes.
« Reply #1 on: 11 Nov 2017 at 08:02 »
Hi Peter,
             I presume, from your description, that the silentbloc bush has been poorly manufactured so that the outside is eccentric to the inner - in which case it will be of no further use.
   The only way I can suggest of removing the offending item would be: - carefully scrape away the paint from the ends of one of the bosses for the front wheel spindle (so that you can clamp the swinging arm securely in the vice without bursting the paint from the boss). Then repeatedly attack the rubber of the bush with a small drill (about 1/8") until you can break out the centre tube. With the centre tube removed, attack the outer tube with a rotary file until it collapses and can be removed.
  Unless you have a replacement, your biggest problem will be finding another silentbloc. I believe there are similar bushes available but they have a 12mm bore instead of ". Also, you will need to make up a spacer, as the centre on the genuine article is extended to abut the opposite silentbloc.

  Hope this is some help,
                                     Regards,
                                                   Eddie.

Offline Roys rider

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Re: silentbloc bushes.
« Reply #2 on: 11 Nov 2017 at 21:19 »
Thanks Eddie I was hoping you would come up with something. It is a manufacturing fault with the inner tube at an angle. Dick (at LDMCC spares for those who don't know) has some but didn't have them in part number order. I have given him the size I need and have my fingers crossed. 
I will re-post when I have something more to tell. In the meantime I have fitted the rear wheel.
Peter

Offline Roys rider

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Re: silentbloc bushes.
« Reply #3 on: 17 Nov 2017 at 11:16 »
Hi
Dick at LDMCC spares sold the last front pair a month ago. There are some manufacturers however they are metric. I am trying to phone someone (Superflex) who does replacements for classic car bushes. I'll post when I know more.
Peter

Offline Roys rider

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Re: silentbloc bushes.
« Reply #4 on: 18 Nov 2017 at 20:50 »
Hi
Further to my search for D/f front swing arm bushes, Silent-bloc, I have found some suppliers but I am stuck for the measurements. I know they are roughly 1" OD, 1/2" ID, and 4" with the extension. Can someone give me accurate figures, preferably in metric? I need OD of big tube, ID of small tube, length of big tube and length of small tube.

If I find one that works the club will probably restock.

Thanks in advance.
Peter

Offline eddie

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Re: silentbloc bushes.
« Reply #5 on: 18 Nov 2017 at 21:15 »
Peter,
          Surely, you can get those dimensions from the faulty silentbloc that you are removing from your swinging arm.

 Eddie.

Offline Roys rider

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Re: silentbloc bushes.
« Reply #6 on: 23 Nov 2017 at 17:40 »
Hi,
Yes but I am loathed to remove it until I have a replacement. Catch 22. It would be just possible to use the faulty one. It covers almost half the bore in the center of the swing arm however a bullet shaped leader pushes it aside. No-one has come up with sizes so I am going to guess that the external diameter is 1". The inside is 12.7mm. There seem to be some that size.

I have been working on another problem. Whilst I was waiting, I put the engine in but now the kickstart wont work. The gearbox is free, as is the crankshaft. The kickstart gear doesn't seem to pick up the k/s pinion. Any ideas? It worked before I put the engine and g/box together. 
Thanks in advance.
Peter

Offline Pensioner73

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Re: silentbloc bushes.
« Reply #7 on: 23 Nov 2017 at 22:45 »
You might find something here, and I would think they will be imperial.
https://www.moss-europe.co.uk/bush-silentbloc-081752.html

Offline eddie

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Re: silentbloc bushes.
« Reply #8 on: 24 Nov 2017 at 07:23 »
Peter,
          Your original posting inferred that the silentbloc was faulty because the inner was not concentric with the outer, you now seem to be saying that the rubber might just be deformed by - say - poor storage. If you can push the pivot bolt through the 2 bushes and the ends of the bushes look to be concentric, leave well enough alone. One of the ends would need to be noticeably off centre for it to seriously affect the handling. About 12  years ago, I converted a front swinging arm to bronze bushes and remember the OD being something odd - like 1 1/32" or 1 3/32" (bear in mind that the bike was built in 1955, so the dimensions then would have been imperial, not metric).
   Regarding the kickstart problem - if both the engine and gearbox can be turned as separate units, the problem probably lies with the mating up of the 2 units. Try undoing the front engine mount, then undo each of the bellhousing allen screws one turn to see if that improves matters - if it does, there is probably something amiss in the bellhousing (maybe an over thick washer on the gearbox main shaft, or the crankshaft split pin only bent lazily over the end of the shaft and bearing on the gearbox mainshaft) that is creating an end load on the shafts. If the kick start wont turn, don't force it! The weak point in the Dragonfly gearbox is the kickstart auxiliary shaft. The round cover at the back of the gearbox has a slot in it for the auxiliary shaft locating pin - this breaks out, also causing damage to the main casing where it supports the other end of the shaft. I prefer to have the slot welded up, and remove the locating pin - after all, the shaft will only turn while the kickstart is being operated - during normal running, the kickstart is stationary!

  Regards,
                Eddie.

Offline Roys rider

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Re: silentbloc bushes.
« Reply #9 on: 24 Nov 2017 at 11:14 »
Hi
Thanks Eddie and  Pensioner
I have phoned Moss who only do MG bits by part number. I have also tried Superflex:- www.superflex.co.uk  who make polyurethane ones (used on modern bikes) but I can't find a fit however it might be possible to drill one, not sure. Also contacted Robush :- robush.com (their catalog was too big to attach)  who are big in vibration mounts, sales guy was helpful and is checking what they have in 1 1/32" by 1/2" (I did give him metric as well). Eddie: your memory and my measurement. Sorry to confuse you; the bush inner tube is at a bit of an angle. Pushing the bolt cannot be done by hand and doesn't do the threads any flavors. I'm going to have to get/make a new bolt, which is the reason I am trying to find a new bush. I will use the old inner to make an extension.
Back to the k/start this pm.
Cheers and thanks
Peter

Offline Roys rider

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Re: silentbloc bushes.
« Reply #10 on: 27 Nov 2017 at 08:51 »
Hi
I thought I should give a little follow up on the kickstart. As Eddie suggested, I slackened the gearbox/crankcase screws and it made no difference, I even checked the clutch worked, but then I got to thinking - this is a brand new engine and it is a bit tight. I checked the torque to turn it on the crankshaft nut - less that 10 ft.lb (below the lowest on my wrench) so not too bad.  The k/start is a lot more than that but that has a lot of gearing involved.  One kick must do a full turn of the crank whereas the crank nut is 360 degrees for one turn.  I have filled the crank with oil, turned the engine, no c/heads, over a few times and can now push the k/start down (bikes on a jackstand so not easy to kick - part of the problem?). So unless someone can come up with a better idea, I'll bolt the heads on and try it again.

Thanks
Peter

 

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