Are your yokes/trip trees straight? (2013)

It wasn't until I got on the project bike and rode it for the first time that I noticed the handlebars were not perpendicular by about 5 degrease. loosening all the pinch bolts and twisting everything straight just reverted back to the same position when everything was re-tightened. I knew the yokes were probably bent, after all, the top tube had needed straightening from a front impact.
I am fortunate to have a frame specialist just south of Seattle http://www.wascoframe.com/ . Richard the owner is one of those old school professionals that I try and soak up as much knowledge as he will divulge. He showed me how to check triple trees and I thought I'd pass it on to whoever doesn't know this already. It would have saved me the task of rebuilding the front end again this winter.

Take a perfectly flat plate, this 2x4 is a poor example, Richard used a 6"x12"x1" steel plate. lay it across your fork tubes just below the trees. if it wobbles, something is bent.


It's hard to see but that's about a .125" gap. That translates to about .5" or more by the time you get to the front axle. Richard explained that the reason this is critical to fix is not because your handlebars look crooked, it's because your forks are not parallel, therefore they bind in opposite directions when they move up and down, making my front suspension all but useless and eventually deforming sliders and oil seals.
I'm looking forward to the improved handling once the yokes are straightened and feel fortunate to have Richard as a resource.

Good to know. Others have said to roll each tube gently by hand on a perfectly flat surface such as plate glass. Any bendage will become eyeball -revealed. Another thingy that is a factor is proper re-assembly. Both Top nuts ,then the lower stem nut,then the Allen pinch bolts,then spindle nut, then pinch bolt. All procedures listed have torque values attached. Oh yes, the steering head bearings must be critically spun/examined after any love-tap. :!:

Thank's roadrash for re-kindling this topic, very close to my heart :!: www.lansdowne-engineering.com

I think the test is to check the yolk's are twisted :?:

Torontonian said:

Good to know. Others have said to roll each tube gently by hand on a perfectly flat surface such as plate glass. Any bendage will become eyeball -revealed. Another thingy that is a factor is proper re-assembly. Both Top nuts ,then the lower stem nut,then the Allen pinch bolts,then spindle nut, then pinch bolt. All procedures listed have torque values attached. Oh yes, the steering head bearings must be critically spun/examined after any love-tap. :!:

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Is that a pressure treated straightedge? Or kiln dried spruce?

The 2x4 was just for the pictures. He said you'd need a proper straightedge for actual work.

That is useful information - never thought about it.

Indeed - some years back I acquired a basketcase crashed Commando - the front wheel was twisted sideways probably 30 degrees.
Stripping everything down, the fork yokes were bent/twisted.
But when measured, the twist was barely even visible with a straight edge across them (in place of that piece of wood !).
Only what seemed a few thou of twist - and the front wheel was soooo far out of line.
Replaced yokes, rather than attempt to straighten them.

Still have the bent ones - show them to folks and ask if they can see the twist in them..
Certainly not by eye. Even with a straight edge take some convincing.
Measure carefully....

Small mirrors with optical flat glass are easiest to find in handy size. A slick and easy sure way is rolling both stanchions against each other so Any gap is obvious while rather hard to tell on just flat surface which also only shows one legs worth of out of true at once. It takes a fairly out of true restricted system to be detectable to me. I absolutely could not get RGM fork brace to work even after much sanding of clearances to finally give up after rolling stanchions together. On the Other Hand I took Trixie's deer strike tubes and Peel's many times crashed on tubes to a machinist to try to fix and used the best two of those on current Trixie last 7ish years no problemo with a few thoughsandth's off on each one. Refine as much as possible but don't expect too much a miracle as don't take much "actual road going" fork travel or stem swing striction to be too dramatically obvious to ride any further than creep back to shop, which will not be far away either. So if not afraid to ride then not stricting enough to ruin the ride but still may onset some BS handling too soon and wear stuff out to seal as mentioned.

concours said:

Is that a pressure treated straightedge? Or kiln dried spruce?

Click to expand...

It's my trusty #1 grade hemlock multi tool. Essential in Norton restorations I have found.

hobot said:

Small mirrors with optical flat glass are easiest to find in handy size. A slick and easy sure way is rolling both stanchions against each other so Any gap is obvious while rather hard to tell on just flat surface which also only shows one legs worth of out of true at once. It takes a fairly out of true restricted system to be detectable to me. I absolutely could not get RGM fork brace to work even after much sanding of clearances to finally give up after rolling stanchions together. On the Other Hand I took Trixie's deer strike tubes and Peel's many times crashed on tubes to a machinist to try to fix and used the best two of those on current Trixie last 7ish years no problemo with a few thoughsandth's off on each one. Refine as much as possible but don't expect too much a miracle as don't take much "actual road going" fork travel or stem swing striction to be too dramatically obvious to ride any further than creep back to shop, which will not be far away either. So if not afraid to ride then not stricting enough to ruin the ride but still may onset some BS handling too soon and wear stuff out to seal as mentioned.

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You are talking about the fork tubes, NOT the yokes being bent or twisted.

Fork tubes rolled on a flat table will soon show if they have any bend to them.
Or just put in a pair of v-blocks, and spin them - by hand.

BTW, the fork tubes were still straight in these bent yokes I met...

That twist depicted in the photo, that is, the fork stanchion tubes being not in a perfectly parallel condition, can be achieved (and thus easily solved) when the front wheel is "twisted", you know the kind where you just stick the front tire in between two trees, turn the bars back and keep checking until straight. The frame straightener guy's comment of "something's bent" is presumptuous, "something MAY be bent, we need to take more measurements" would be more accurate.

concours said:

That twist depicted in the photo, that is, the fork stanchion tubes being not in a perfectly parallel condition, can be achieved (and thus easily solved) when the front wheel is "twisted", you know the kind where you just stick the front tire in between two trees, turn the bars back and keep checking until straight..

Click to expand...

Don't bet on it....

This pair of yokes came off a (lightly) crashed bike.
The front wheel was kicked sideways about 30 degrees.

A very careful measurement showed the top yoke was very slightly twisted.
A few degrees up top makes a big difference down at the front wheel.
Replacing them fixed the problem - along with a new front axle - nothing else was bent

They could possibly be straightened ?
But tweaking all 4 corners, with tons of force each to get them right would take some skill.
And would you want to trust them after that.

Inspect carefully if all is not right...

well the early Commando , Atlas type yokes are weaker again, especially the bottom yoke, they look strong but that heavy looking steel casting is hollow, I've straightened heaps of them in a vise, they are the weakest bottom yoke I have ever seen on any motorcycle, beats me why they considered them
in high regard. check the thickness at the bottom near the stem compared to one of my alloy yokes.

Useful way to check parallel of tubes on bike. If a twist is evident then, as suggested, rolling tubes on a known flat datum, thick plate glass is a cheaper alternative to a surface table, check for bends. Once tubes are straight reassemble into bottom yokes only and then check on your flat surface that tubes are parallel. If not yokes need attention. When parallel assemble with top yoke as well and re check tubes are parallel.

^Twisting a wheel between two tree's " ? this action , if two trees are used to" bend" or attempt to TWIST, BEND the fork assembly is just evidence that the yolks are dammaged and they should be replaced.
I agree that a tiny and i mean "Tiny" error can re- aligned by this action [between your knees]...but if this cannot be done with the slightest of force ..then scrap the yolks, brutal force is not the answer :!:
When one stanchion is fitted , that means the stanchion tube top taper is "Snugged up" in the top yolk and the lower is nipped up...the other stanchion should slide into the other side, if the tube top taper does not engage the yolk taper without any mis-alignment..and this can be easyly checked by appling engineers Blue then suspect damage.
A 1/4 mm at the top can be 5mm at the wheel, that amount will cause a poor fork action...issue's like bent yolks are common, cannot be seen easly by eye and go un-corrected, twisting into alignment seems the cheap way out. :twisted: this mis-alignment is often the cause of stiction in the sliders.

Rohan said:

concours said:

That twist depicted in the photo, that is, the fork stanchion tubes being not in a perfectly parallel condition, can be achieved (and thus easily solved) when the front wheel is "twisted", you know the kind where you just stick the front tire in between two trees, turn the bars back and keep checking until straight..

Click to expand...

Don't bet on it....

This pair of yokes came off a (lightly) crashed bike.
The front wheel was kicked sideways about 30 degrees.

A very careful measurement showed the top yoke was very slightly twisted.
A few degrees up top makes a big difference down at the front wheel.
Replacing them fixed the problem - along with a new front axle - nothing else was bent

They could possibly be straightened ?
But tweaking all 4 corners, with tons of force each to get them right would take some skill.
And would you want to trust them after that.

Inspect carefully if all is not right...

Click to expand...

hobot said:

Small mirrors with optical flat glass are easiest to find in handy size. A slick and easy sure way is rolling both stanchions against each other so Any gap is obvious while rather hard to tell on just flat surface which also only shows one legs worth of out of true at once. It takes a fairly out of true restricted system to be detectable to me. I absolutely could not get RGM fork brace to work even after much sanding of clearances to finally give up after rolling stanchions together. On the Other Hand I took Trixie's deer strike tubes and Peel's many times crashed on tubes to a machinist to try to fix and used the best two of those on current Trixie last 7ish years no problemo with a few thoughsandth's off on each one. Refine as much as possible but don't expect too much a miracle as don't take much "actual road going" fork travel or stem swing striction to be too dramatically obvious to ride any further than creep back to shop, which will not be far away either. So if not afraid to ride then not stricting enough to ruin the ride but still may onset some BS handling too soon and wear stuff out to seal as mentioned.

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Sorry but you have completely missed the point , ................... The yokes are twisted................ and at the axle are 1/2 inch on the piss!!!!

swooshdave said:

The 2x4 was just for the pictures. He said you'd need a proper straightedge for actual work.

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I understand what you say but Just standing back and "looking" too see if the forks are paralell would be an easy start.......

Sorry but you have completely missed the point , ................... The yokes are twisted................ and at the axle are 1/2 inch on the piss!!!!

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Right I only found tubes bent not the yokes so I'd be pissed too. Will ya attempt the brutal correction or just replace? If ya use a mirror and break it - 7 more years of you know what. One thing I found that may save some swearing was a couple new sets of bushes would not slide on the stanchions - till i realized none of them came round so used light hammer taps with bush on tube till they slid as intended. Then found the new ones were a looser fit than the decades old - 10's of 1000's rough mileage set, so put old ones back in with the wasted time getting me smarter on Commando parts decision points.

What others have run into or done when Uri Geller couldn't straighten but just make worse.
https://www.google.com/#psj=1&q=bending ... ycle+yokes

I gotta say that I have never seen a bent triple tree.
Sure, I suppose It's possible, but I can only think that it would take one hell of a crash to bend one out of shape like the pic shown.
I have encountered many front ends knocked out of alignment, bent tubes and even entire steering heads broken off of the frame,
just not bent yolks.