Rear suspension pivot pin...

[MrWright]

How does one remove the rear suspension pivot pin?  I have removed the locking pin and have aggressively hit the pivot pin from the side of the frame, expecting the pin to slide out from the frame.  This has not happened.  I have ordered a copy of a T35 service manual, but it has not arrived yet.  Any advice?

Thanks



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[Daren W Australia]

Hi
I think we have all tried this it needs to be extracted or pushed out from the center of the frame there in a thread in side it use a tube washer and long bolt as it has a step in it. I pushed mine out by lying the bike on its side and pushing it out with a bottle jack after removing the small push in cover
Regards Daren

[Doug]

They can be very, very tight. I made up a bolt to thread in the outboard end (where the grease fitting goes) that screwed on to a slap-hammer (dent puller.) I got mine out that way, without disturbing the tin dust-covers on the inboard end.
-Doug

[KiwiJohn]

Mine were very tight too and I did not want to risk distoring the frame by using a jack between the frame members.  I ended up cutting a piece of water pipe and using a bolt as a puller via the greaser's thread.

Bronze expands faster that steel with increase in temperature but I am loath to suggest anyone apply flame heat to their brazed frame lug however, pouring boiling hot water over the lug while you apply pressure via the bold  may help things along(?)

In any event I did not need to apply heat but I did fear for the strength of those threads as I applied all the pressure I could muster to my spanner and gave the head of the bolt a rather assertive blow with a hammer at intervals during the  initial tightening.

[MrWright]

You guys are great!  Good info, and sound advice.  I am still debating the value of a full dis-assembly, the media-blasting company can mask, and I am spraying the frame with paint (not powder-coat)

[Doug]

No matter how well you mask, abrasive blast media WILL get in the joints. The broken down media, the fines, will also pack in there so tight as to 'seize' the joint. Its ability to do so is just short of amazing. If they say they can mask it well enough to avoid that, suspect their credibility! I mask and blast my own stuff and it is nigh impossible to keep the media out of where it does not belong, except with the most diligent care and elaborate masking. You might as well just take it apart now and be done with it; you will just have to take it apart later otherwise to clean it.

It will also be a lot easier to do a good job painting with the swingarm out. The swingarm just gets in the way, and have you noticed how much weight it contributes to the frame?

-Doug

[MrWright]

Yes Doug, you are right.  I just needed to be reminded that the longest distance between two points is a short cut.

Dave

[ChrisS]

Mark frames are notorious for cracking in the tubing forward of the lug which carries the rear fork. If the fork is tight on the pivot pin then a large turning moment is developed on the lug and this may be one of the causes of frame failures. I think it's imperative that you check the pins and bushes for which you must take them out.
A point  to note is the bottom frame tube does not go right through the lug, the tube that the lever arm bush mounts on is just a short section fitted into the lug from the rear.
ChrisS

[MrWright]

Ok, so I am determined to remove the pins, after all the advice, it is the right way to blast the frame.  The company I am using does offer a plastic media blast, which will not hurt bearings, and even dissolve on contact with grease/oil, but as noted by Doug, the paint job will be MUCH easier with the swing-arm out.  Now here is my question: what is the thread size on the ID of the pin?  It appears to be a 1/2 inch nominally, and we, in the US, have two standards UNC (1/2-13,) and UNF (1/2-20).  It appears to be something in-between.  Any advice?

Dave

[MrWright]

I may have found the answer at...

http://www.efunda.com/DesignStandards/screws/unified.cfm?start=64&finish=147
I will post the thrad pitch after I measure with a thread gauge..
Dave

[Chris]

Douglas did not use UNC/UNF threads. Much too modern. If the thread is between 13 and 20 threads per inch it is almost certain to be British Standard Fine (BSF) thread which is to the Whitworth form (55 degees angle). The 1/2" size has 16 threads to the inch.

[MrWright]

Ok, so if you read my last message, you must have thought “what is this guy talking about?”  I was confused, as I did not know that the tap hole for the pin went through, thus I thought that I must screw a “pull bolt” into the pin.  I fed a bolt through from in the inside of the frame and used an impact wrench which made the extraction quick and effortless.  As for the actual thread size of the pin, I will report, after measuring, just for grins.  As for the UNF/UCN, yes Chris, the BSF standard is a safe bet for the year and OEM point of origin.

Dave



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