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Sherpa T 156 Front Fork Woes


sbaussie
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I have a Sherpa T 125 model 156 that has 30 mm forks. I removed fork legs, repacked steering/ ball bearings (what a pain) , put new seals in forks legs (also a pain) and reassembled.

Problem : the fork tubes are tapered at the top and fit up into the top yokes, lower yoke is split with two bolts. The fork tubes only go so far up into the yokes (about 7.5mm down from top ) Both sides are the same . I have gently heated and tightened Stanchion nut to snug them up.

Where the forks fit in the lower yoke (criss crossed markings) there is a definite mark where they fit into the yoke before (slight rust mark from the steel lower yoke) but it is a good 5mm below the lower surface of the yoke. I have the lower yoke openings separated with wedges so its not binding there. It looks like they need to still go up 5 mm but they really don't want to go up into the upper yoke any more!! If I slacken steering tube nut they will go up to previous marks bit all that is happening is upper yoke is moving up the collar of the bearing lock nut and now I have a 5mm gap between the top of the bearing lock nut and the bottom surface of the upper steering yoke and barely any thread showing on the bearing luck nut collar to attach steerer tube nut.

Did I miss something obvious here???post-19685-0-98089700-1398380042_thumb.jpgpost-19685-0-92051500-1398380069_thumb.jpgpost-19685-0-96329100-1398380101_thumb.jpg

post-19685-0-65709000-1398379995_thumb.jpg

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It's possible that one or both of the tubes have a bend, or one of the yokes has a bend, and you might need to experiment a bit to fit the tubes back into the yokes exactly the way they came out.

To work out what is wrong, fit only one tube to the bike at a time and see what you need to do to get it to move fully into the tapered hole.

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The fork tube should slide all the up till it bottoms out on the spigot on the top triple clamp. Assuming the inside bore of the top clamp is clean and free from burrs etc and the fork tube is also clean and free of imperfections, I would use the fork nuts to pull the tube up till it bottoms out on the top clamp,a light smear of oil wouldn't hurt either [leave the springs out while doing this]

Cheers Greg

Oops, sorry just went and checked in the shed and there is no machined spigot in the top clamp[these are on the later non tapered legs]

But I would still use the nuts to pull the tube up as far as it will go into the taper

Edited by sherpa325
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It's possible that one or both of the tubes have a bend, or one of the yokes has a bend, and you might need to experiment a bit to fit the tubes back into the yokes exactly the way they came out.

To work out what is wrong, fit only one tube to the bike at a time and see what you need to do to get it to move fully into the tapered hole.

+1!

I would too recommend to check the stanchions if they are still straight before assembling.

Another hint, for getting the tubes better in / through the holes is to clean the surfaces of the holes of the fork clamps very well, (probably using steel wool).

And if you want to use the upper nuts to pull the stanchions up in the upper yokes be sure you have the nuts at least two or better three threads turned in, (just to avoid pulling threads instead of the stanchion ... )

Edited by pschrauber
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Are you sure all the bearing lock nuts are in the correct position?

And maybe the fork tubes come out of an other (later) model that have a bottom yoke that bends downward towards the bottom fork tube clamping.

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Thanks all for the replies. I have checked the tapered sections and they look clean , ran some 180 over them then some 400 and steel wool. very nice now, A little oil too , a litttle heat but still only go in the same distance . If I snug them in there using Stanchion nut then remove them there is a definite line where the top of the fork tube was, in fact there is a distict ridge where it "cut" into the softer alloy. It is possible that the fork tubes are not original , I am not the original owner and the last owner did quite a nice restoration job. It is obvious that the bike was used for some serious competition or fun as there are a few deep gouges in the fork legs, and some nice after market bits,

Renthal bars, domino throttle etc etc..

Bearing lock nut is good and sitting snug against bearing race.

These forks came out of these yokes . I have tried to snug the the fork leg into just the upper yoke (lower swung out of way ) same result....

So it is quite possible he replaced fork tubes with tubes from some other model?

I did not look closely at the forks where they enter the lower yoke before I removed them so maybe they always were 5 mm off !!.

Anyone out there have a Model 156?? If so what is the distance between the bottom surface of the upper yoke and the Top surface of the lower yoke? ie how much fork tube showing between them ?.

Thanks again Mikepost-19685-0-93864300-1398470959_thumb.jpgpost-19685-0-36308400-1398471036_thumb.jpg

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  • 3 weeks later...

My suggestion is that the forks were assembled incorrectly before you got the bike leaving the marks that you can see. The top lock nut looks to be about that thickness from memory and if it has been under the top yoke instead of on top it would allow the stantions to move up higher in the bottom yoke.

Here's a pic of a 156 showing the same amount of crossmarks/knurling as you have.

post-997-0-66054200-1399803862_thumb.jpg

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No everything is correct with the yokes. It's the top yoke lock nut that is the problem. If you look closely on one of the pictures it shows the whole top yoke assembled wrong.

They are now assembled correctly and that's what is causing the confusion..

Could be wrong....usually am.

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130 mm it is , so I'll assume yokes are correct and spaced properly. Lock nut was definitely above the upper yoke , but may have been assembled the wrong way in a previuos life.

So i'll put it back together, add some oil and head on out.

Thanks for the input everyone..

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Just out of interest, let me know how you go on starting it and how it runs.

I know they aren't the most powerful of bikes, totally gutless to be fair but they are a lovely looking bike with the smaller wheels.

I guess the Lobito which preceded this model was only designed as a small Trail type bike and as such they go very well when you get them moving.

Good luck.

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