ST1100 - Determine If Front Forks/Triple Tree Bent

[Uncle Phil]

Other than visual, any ideas of determining whether the front forks and the triple tree are bent/out of line (riding it is not an option right now! )?
I finally was able to wheel Redbird into my shop today so I could take a look.
I thought originally that her forks were bent but I've not felt well enough to take a better look until now.
She took a hard lick on her front but I don't think she hit anything but the asphalt like me.
Without a real close inspection or measurements, her forks/triple tree 'look' to be fine.
If they are, I am considering 'reviving' her.
If not, she will become a parts bike.
Your ideas for making the forks/triple tree determination are appreciated.
Not meaning to be rude, but please don't turn this thread into whether I should revive her or not.
Thank you very much.

 

[dbst1300]

I have the Motion Pro fork aligment tool ….. tells you if things are square.

ForkTru™ - Fork Alignment Tool - Motion Pro

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www.motionpro.com

 

[Firstpeke]

After I had my accident in 2010 on my ST1100, which the insurer wrote off.... I was contacted by a guy who bought the remians.... this was my first ST not my blue one!

The forks were clearly bent just under the lower yoke, but according to this fellow who bought and sold many ST1100's, it takes a very serious accident to damage the front end.

He intimated that my bike was rebuildable and was about to do so, requiring forks and probably a wheel, but simply loosening and re-aligning the triple tree was probably sufficient given the overall strength of the frame.

Clearly to be safe an alignment check would be recommended, but if you haven't had a substantial front end impact, I would guess that a simple loosen and re-align would be more than enough to correct any minor wanderings....

HTH/YEMV

 

[Larry Fine]

He intimated that my bike was rebuildable and was about to do so, requiring forks and probably a wheel, but simply loosening and re-aligning the triple tree was probably sufficient given the overall strength of the frame.

He probably turned the tubes around so the front wheel stuck out like a chopper.

 

[sirbike]

This ought to be a close enough way to check it without measuring tools and fork disassembly.

Remove front wheel, fender, on abs that bridge and anything else connecting the two sides between the forks.

Spin the upper tubes 90 degrees each in opposite directions.

If one or both are bent, the fit of the fender/ bridge between the forks will change. Maybe a gap or maybe a tight fit.

I inadvertently discovered bent tubes on one of my ST1300s when I randomly reinstalled forks after servicing them. The fender didn’t fit afterwards.
That bike had been riding perfectly straight hands off.
The fender had been fitting fine as well.

About $300 later the forks were straightened.

 

[SMSW]

Depending how much disassembly is called for, I think the usual way is to pull the forks apart and place the tube on a flat surface and roll it. Alternatively, you could place a machinist's straight edge along one side of the top tube (again, once it is on the bench).

I like Frank's method if you don't need to pull the front apart. A slight modification - pull the wheel. fender, etc, measure the gap between the inside faces of the lower fork tubes at the axle and rotate each of the upper tubes in 90º increments. There should be no change in that distance.

 

[Erdoc48]

I was just wondering if the original accident was a low speed lowside, unless the front of the bike hit another object, I would assume (maybe wrongly) that the forks would be intact.

 

[bdalameda]

I would use a string to check alignment of the front and rear wheels. Put the bike on the center stand and take a string around the rear wheel leading to the front of the bike. Get in the front of the bike on your stomach or knees and pull the string and sight down the string and align it so that it just touches the front and back tire beads on the rear tire and pull it tight so that it is straight and will be aligned next to your front wheel. You may need to get someone to keep you forks straight. The line of the string will be wider than your front tire because the rear tire is wider than the front tire, but you can turn the front forks so that the spacing between the front tire front and rear beads and the straight string is the same. When it is you will see if your handlebars are straight or not. You can also measure the distance from the straight string to the tire bead and then do the same thing on the opposite side of the bike. This will tell you if your front and rear tires are running true to each other and if the handlebars and clamps are twisted. You may be able to get the wheels aligned by loosening the fork clamps and giving the tire a hit and rechecking for proper alignment. If the distance from the tight string to the front bead is not the same from side to side you may have a bent fork or t-stem or frame. Very few bikes are perfectly aligned so minor differences are common. Old Kawasakis had terrible front and rear wheel alignment and the chain adjusters were terrible for aligning the wheels. Hondas tend to be fairly straight, at least in the old days.

 

[Uncle Phil]

I finally got the fairing stay, the remains of the front cowlings and the front fender off (a little tough working pretty much lefthanded, one armed .
The fairing stay appears to have taken the brunt of the blow and it broke off one of the handlebar weights.
The radiator is pushed back a little bit (tab appears to be bent) and the center fairing stay tab is bent slightly.
What I can't figure out is I went off on the right side (where my damage is) but most of the damage is on the left side of the bike.

Great ideas - especially turning the forks and the string business.
As I said, if the forks and triple tree are okay, I've got most of the other parts so a restore would be more time than money.
But sourcing ABSII forks and triple tree are quite difficult (BTDTGTTS)!

 

[Uncle Phil]

I would use a string to check alignment of the front and rear wheels. Put the bike on the center stand and take a string around the rear wheel leading to the front of the bike. Get in the front of the bike on your stomach or knees and pull the string and sight down the string and align it so that it just touches the front and back tire beads on the rear tire and pull it tight so that it is straight and will be aligned next to your front wheel. You may need to get someone to keep you forks straight. The line of the string will be wider than your front tire because the rear tire is wider than the front tire, but you can turn the front forks so that the spacing between the front tire front and rear beads and the straight string is the same. When it is you will see if your handlebars are straight or not. You can also measure the distance from the straight string to the tire bead and then do the same thing on the opposite side of the bike. This will tell you if your front and rear tires are running true to each other and if the handlebars and clamps are twisted. You may be able to get the wheels aligned by loosening the fork clamps and giving the tire a hit and rechecking for proper alignment. If the distance from the tight string to the front bead is not the same from side to side you may have a bent fork or t-stem or frame. Very few bikes are perfectly aligned so minor differences are common. Old Kawasakis had terrible front and rear wheel alignment and the chain adjusters were terrible for aligning the wheels. Hondas tend to be fairly straight, at least in the old days.

I wonder if a long enough straight edge (like multiple yardsticks or levels) would work as well as string?

 

[bdalameda]

I wonder if a long enough straight edge (like multiple yardsticks or levels) would work as well as string?

A long straight edge can be used if it is stiff enough. In my old road racing days I had a long aluminum straight edge to used for this.

 

[Nashcat]

UP, The forks need to be disassembled and the tubes put in two vee blocks, where they can be rotated and checked for runout with a dial indicator. 50 years ago, there was a machine shop in Florence, AL that would check and straighten for $5. I have vee blocks and indicators, if needed to check.

A 8ft fluorescent lamp makes a good straight edge.

John

 

[bdalameda]

UP, The forks need to be disassembled and the tubes put in two vee blocks, where they can be rotated and checked for runout with a dial indicator. 50 years ago, there was a machine shop in Florence, AL that would check and straighten for $5. I have vee blocks and indicators, if needed to check.

A 8ft fluorescent lamp makes a good straight edge.

John

I have a set of soft brass V-blocks just for straightening forks on my press. I use a lathe for checking runout. It is surprisingly easy to straighten fork tubes with a little patience and to make sure that the tubes are not kinked. I'll bet it's been 30 years since I have straightened fork tubes. It used to be pretty common to have to straighten fork tubes on dirt bikes.

 

[dwalby]

I'd disassemble and roll on a flat surface like a glass table top or granite table top. Dial indicator is also a good idea if you have one, but it sounds like Nashcat may be able to help you out with that and he's nearby.

 

[Uncle Phil]

UP, The forks need to be disassembled and the tubes put in two vee blocks, where they can be rotated and checked for runout with a dial indicator. 50 years ago, there was a machine shop in Florence, AL that would check and straighten for $5. I have vee blocks and indicators, if needed to check.

A 8ft fluorescent lamp makes a good straight edge.

John

John - Could we do this without removing the fork lowers from the tubes?
That would mean all I would have to do is remove the front wheel/fenders/braces and drop the forks out of the triple tree.
And I know the way to your house already ...

 

[dbst1300]

If you drop both fork assemblies and manually compress the inner tubes into the lowers they will stick or bind in the lowers if bent to any degree.

 

[W0QNX]

John - Could we do this without removing the fork lowers from the tubes?
That would mean all I would have to do is remove the front wheel/fenders/braces and drop the forks out of the triple tree.
And I know the way to your house already ...

You could that without the dial indicators or anything. Remove the fork assembled, clamp the lower end down with C clamps or wood clamps to a solid work table along the table top not off the edge and rotate the tube in the lower. Watch for up and down on the little end as you rotate. If it is bent any it will move up off the table farther. if it is straight the tube will not go up or down.

 

[W0QNX]

The only way to check the frame stem tube that I can think of is install a long straight bar and visually check if it looks like it is centered looking from the front about the bikes centerline. Or a laser down the stem tube to show left right at the floor. thinking out loud here, a fishing pole held in the stem tube? A small straight piece of angle iron held in the stem tube? Small straight square tubing. A lightweight straight curtain rod? Anything stuck in the stem tube to show left right. Set a chair in front for visual references.

If you know the headstem angle use a protractor (phone) on what ever the angles are referenced from. Frame bottom tube to fork head stem angle? most phones have an app for angles on the phone.

 

[Nashcat]

Could we do this without removing the fork lowers from the tubes?

Phil, There’s several ways to check them. Easiest way for me is Vee blocks and indicator, just because I have them handy. It depends where the bend is, as to whether or not you need to remove fork lowers.

John

 

[sirbike]

You could that without the dial indicators or anything. Remove the fork assembled, clamp the lower end down with C clamps or wood clamps to a solid work table along the table top not off the edge and rotate the tube in the lower. Watch for up and down on the little end as you rotate. If it is bent any it will move up off the table farther. if it is straight the tube will not go up or down.

For a couple minutes past my described level of disassembly, I like this idea more.