Swing arm mounting bolts

[jamestnewsonr65]

I have every ready to go for the rear end to be buildup again except that the bolts for the attachment of the swing arm just won't screw in without deforming the threads.

I think the powder coating might have got into the threads on the frame and it is a difficult area to remove it from.

I have tried a wire brush, but think the threads on one side are not deformed slightly. I did buy some new bolts as there are some flattish threads on the old ones, but no joy.

I am thinking that I might need to re-tap the threads but haven't idea how to determine what size I would need. Foes anyone know this information or have any other suggestions.

Thanks

[nhmaf]

I have used a thread file to clean up some exhaust port threads that were mildly mangled, but the file seems to work best on external threads and not so much on internal threads.

Any chance you can get a digital camera on macro mode picture setting to show us a pic of the offending area?

[Bob_Roller]

Would heating it, cause the powder coat to soften up to where you may be able to scrape it off

Maybe a heat gun with a reducer nozzle to keep the heat where you want I .

Or, if you are brave a propane torch .

[montmil]

... Or, if you are brave a propane torch.

I have used a small, butane gas, pencil torch for a variety of chores. Small flame is easily controlled.

[Barry]

If you mean the swing arm bearing pin threads then someone on a UK forum recently had the same problem with powder coating and got them stuck fast. They couldn't be removed without with major trauma so don't try and force them in.  The correct tap size is M20 x 1.5mm.

Read all about it here http://www.bmbikes.org.uk/Forum/viewtopic.php?f=15&t=19095&start=150

[montmil]

From experience, do not expect your powder coat contractor of choice to locate / seal / protect every threaded opening that will be critical to the reassembly process. Ground wire locations may even need a small square of tape to maintain exposed metal which will provide a good electrical connection. Bearing races are another frequent source of frustration.

[jamestnewsonr65]

I did tell the powder coaters to steer clear of the threads, but hey. I think my problem is definitely with worn threads rather than debris from the coasters now, although at the beginning if was a mix of the two.

Do you know if the M20 x 1.5 is applicable to all models and years? I would hate to order one and find its not useable.

Thanks for the replies though, a big help.

[Barry]

Do you know if the M20 x 1.5 is applicable to all models and years? I would hate to order one and find its not useable.
 

I'd be fairly confident the swinging arms bearing arrangement is the same for all contemporary airheads. There are a number of things you could do to confirm it's correct.

Check the online parts fiches to see if the bearing pin is the same part No. for all airheads.

Measure the bearing pins that you have.  The OD should be a fraction under 20mm something like 19.8mm. Then measure the thread pitch. You don't have to be too accurate with this as M20 Coarse is 2.5 mm pitch and M20 fine is 2.0 or 1.5 mm pitch. It should be easy to distinguish between them by counting how many threads in 20mm length.

Procure an M20 x 1.5mm bolt and compare it with your bearing pins.

[jamestnewsonr65]

I ordered an M20 x1.5 which arrived today. Tried it out this evening and loads of metal/sand blast/ powdercoating came out of there but now all is smooth and on with the install of the rear.

Thanks for the help as ever.

[Tony Smith]

From experience, do not expect your powder coat contractor of choice to locate / seal / protect every threaded opening that will be critical to the reassembly process. .

One of the two main reasons I dislike powder coating, the other being the ability of very significant rust to form and give no indication of its presence prior to frame failure.