FF: Forks Girdraulic eccentric shimming method

[Albervin]

I have been through nearly two months getting my steering head/stem/bearings aligned. It all started when I pulled the front end to pieces and the upper bearing cup was floating around, literally. The lower bearing cup was fastened with half a bottle of loctite. An initial clean up and sleeve still left the steering column FF33AS not centred. I pulled it apart and with the help of a friend a dual diameter mandrel was made and on a large mill the whole thing was centred and line bored. New sleeves pressed in, cups pressed in and finally all is good in the world. You simply cannot change the dimensions of something like the eccentrics to cover up a problem elsewhere.. It is what a lot of Australians call "A British restoration" and it is not a compliment. I now strongly suspect the bike has been involved in a collision at some time BUT it was still running, steering, braking when I bought it. It only goes to show that these bikes will keep going despite the abuse that owners throw at them. Next step is to fit the blades etc. If they don't fit then I may well lose whatever colour I have left in my hair! At least I have most of the rear end fitted now but there is still room for disappointment!

 

[Albervin]

After Simon's post a quick walk into the shed despite the heavy rain. How would I sleep otherwise? From these pictures I hope you see the bushes are all aligned. The top and bottom links don't both touch because there is extra metal on one side (I think).

 

[Albervin]

Here is the O ring replacement for the felt washer on the lower steering head bearing.

 

[Bill Thomas]

I have not done it myself , But I like Oldhavens way of fitting long bars,
Though holes to see if every thing looks right.

 

[oexing]

Well, reacting to the last poster above. As to Spqreddies problems, he´d have to check all components for flaws from accidents or machining faults, all sort of mistakes to be expected. Any girder fork is a challenge to get right, often you get the torch out for "adjustments" and all. One way to check some places is to set the steering stem in the lathe, between centers or so, for getting bearing deats to run true. So then you can check if the bottom spindle is square to the stem and if bottom bracket ends are roughly same distance from center line - which can be shimmed to taste later.
i had to put the Brampton bist under the press to straighten the steering stem and for squareness too. So after I machined the bearing seats a bit for Loctiting oversize bushes on. After I machined bushes top and bottom in line for 34 mm BMW taper bearings.
Story goes on with alu castings on the Girdraulic, but not my fish:
Put some spindles through bores of these castings for checking for twist and squareness and rectify them to suit. I´d fit the bottom brackets first with all bushes set. Only then check the situation for the top bracket and add shims or machine parts to fit the rest. It is not an easy job, for sure.

Vic

 

[Albervin]

Eddie, please go back to basics here. IF something is not right then it is wrong! Fitting shims where they do not belong covers up the problem, it doesn't fix the problem. If the head stem is not centred in the steering head then the eccentrics have nothing to do with it. When I restore a bike I want to be confident in riding it to its potential. I also want the next owner to know I did the best I could to look after the bike. Often this means money has to be spent BUT having survived a nasty high side caused by very poor engineering by the previous owner I cannot in all conscience take short cuts. With my latest problem I was determined to keep my steering head as it has the numbers stamped on it that denote what it is. It was complicated and time consuming but fortunately not expensive. You may want to reconsider your solution.

 

[Spqreddie]

Eddie, The last three posting got in while I was checking. I'm glad it is not one of mine. It is a long way from standard and my guess is that it is badly machined. What is the purpose of the three bolts across the rear of the lower part of the steering head. Have you checked the distance from the centre of the tube to each side of the lower block? If they are out by a thou or two I don't believe you would have the effect you have. I think there must be something a lot further out than that.

Thank you Norman,
it's different from standard, but the design is close, as it retains the eccentrics system. The spindle is just located differently in order to change the fork movement keeping it vertical (not going forward) and keeping the anti-dive characteristic of the standard Girdraulic.
The three bolts are to fix the steering damper arm.
I don't think it is badly machined, but I will definitely measure everything again to understand where the issue is. And as I can read from the previous posts, probably it is not in the stem but in the links.

Gosh its been so long since I did a stock front link/bushes its hard to remember.....Check to see if the trail stop pins are in the exact same place/height.........How did you check the alignment of the lower link.......They are often bent, and only need to be out a bit to show up on assembly. Use a square to see if the column/tube is square to the lower motion block.

Thank you Greg, Will try to measure that way!

If you just have the stem and links together and you don't think it's right,
Maybe the head bearings are not fully home and square ?.

Thanks, but havent tried it on the UFM yet, this is a "dry assembly" not on the bike.
I will dismantle it and put everithing on the UFM without the blades

One of Eddie's picture shows that the cone bearing is fully home on the steering stem. If there is something wrong there then it has to be the cup which is tilted in the lower part of the steering head. Has this been removed or replaced since the bike was last used successfully?

All the components are new, including steering cups balls bearings and fork completely refurbished, so no reference to the past unfortunately.
As mention will try now to assembly everything on the UFM without blades.

Spqreddie
You have exactly the same problem that I had on my Shadow which I mentioned in my post no.9.
Unlike like you I did the assembly of the forks on the bike and mine was also had a standard FF2 lower headstem. What I did was fit the FF1 head clip & FF2 headstem to the bike first. Then I fitted the lower link and excentrics which was already shimmed and then the top link. Finally I fitted the fork legs. When adjusting the spindles to achieve minimum end clearance so the FF10 cups would just rotate what I found on the top link is on one side the cup would jam up but the other side was still rattle loose. The same was seen on the bottom link but on opposite sides. My conclusion was something was putting side thrust and that the top link wasn't in alignment with the bottom link. I initially thought oh bugger the bottom link is bent as they do bend easily, so I dismantled the lot and measured everything.
What I found was the bottom link was perfectly in alignment as well as the headstem and head bearings and the problem was actually the top link.
The top link had not being machined equally on the area where FF6 bronze bushes pressed in. I cannot remember the exact figure but it was approx 30 to 40 though out side to side. Hopefully this photo will explain. Please note this photo is a good top link.


View attachment 40945

Please ignore the parallax error due to the photograph but hopefully it will show what I'm talking about.
Dimension X and Y should be both the same. On mine X was plus and Y was minus but I cannot remember the exact figure. At first I thought the link was bent sideways but when placing another good link on top of the suspect one above the casting was perfect and it was clear the link had being machined with a sideways offset. I ended up making special FF6 bronze bushes with different flange thickness to bring it all back in alignment.
Now the easy way to spot this without measuring is if you look in the areas I have circled and look at the casting and how it has being machined then both sides should look the same. If you look at the photo Spqreddie posted in post 20 you can see the casting looks different side to side as it has been machined wrong and more of the cast web has been removed on one side to the other. I have highlighted this in the photo below. If he had assembled the forks on the bike in the normal sequence this wouldn't have been found until final setting up of the side clearance of the spindles. I'm not saying 100% that this is the problem but I would certainly start by looking at the top link.View attachment 40947

Thank you Simon!!
This probably what's going on indeed!
Will check first symmetricity on the top link as you indicated.

I have been through nearly two months getting my steering head/stem/bearings aligned. It all started when I pulled the front end to pieces and the upper bearing cup was floating around, literally. The lower bearing cup was fastened with half a bottle of loctite. An initial clean up and sleeve still left the steering column FF33AS not centred. I pulled it apart and with the help of a friend a dual diameter mandrel was made and on a large mill the whole thing was centred and line bored. New sleeves pressed in, cups pressed in and finally all is good in the world. You simply cannot change the dimensions of something like the eccentrics to cover up a problem elsewhere.. It is what a lot of Australians call "A British restoration" and it is not a compliment. I now strongly suspect the bike has been involved in a collision at some time BUT it was still running, steering, braking when I bought it. It only goes to show that these bikes will keep going despite the abuse that owners throw at them. Next step is to fit the blades etc. If they don't fit then I may well lose whatever colour I have left in my hair! At least I have most of the rear end fitted now but there is still room for disappointment!

Thank you Albervin,
will go that way! assembling everything on the UFM with no blades and take it form there

After Simon's post a quick walk into the shed despite the heavy rain. How would I sleep otherwise? From these pictures I hope you see the bushes are all aligned. The top and bottom links don't both touch because there is extra metal on one side (I think).

thank you, it's clear. will have a look like this!

I have not done it myself , But I like Oldhavens way of fitting long bars,
Though holes to see if every thing looks right.

indeed, good method, will just need to turn bars to that dimension.

Eddie, please go back to basics here. IF something is not right then it is wrong! Fitting shims where they do not belong covers up the problem, it doesn't fix the problem. If the head stem is not centred in the steering head then the eccentrics have nothing to do with it. When I restore a bike I want to be confident in riding it to its potential. I also want the next owner to know I did the best I could to look after the bike. Often this means money has to be spent BUT having survived a nasty high side caused by very poor engineering by the previous owner I cannot in all conscience take short cuts. With my latest problem I was determined to keep my steering head as it has the numbers stamped on it that denote what it is. It was complicated and time consuming but fortunately not expensive. You may want to reconsider your solution.

Sure I will fix it an make it right! this is why I was seeking suggestions.
Otherwise me too i can not sleep!
Eddie

 

[greg brillus]

Don't stress too much about it all, the forks need the same fettling to get right just like the timing chest. All the stories about worn bushes, and steering head bearings falling out and bla, bla, If any of that causes a "Head shake" then you are just plain unlucky.......all it takes is the wrong combination for this to happen to any bike.........I've seen some pretty bad things on these bikes, things that would make you cringe.......But they still keep going and most times the owners wouldn't have a clue........Just keep working away at it.

 

[greg brillus]

Actually one thing on these bikes that can be quite nasty........I've struck this a few times and the symptoms vary from mild to chronic....... It is possible to install too many ball bearings on assembly of the steering stem.........this will make low speed stability of the front end feel very weird........I've had similar and one in particular was reeeealy bad.........It had me quite worried, because I'd just installed the modified stem kit and all that goes with it. well on many bikes with no issues........This one however had touring guards and when riding the bike, the low speed cornering felt rally scary, very unstable, like the front wheel was sitting on a large ball bearing itself.........It did seem to have a smallish amount of play in the steering head bearings.........I disassembled it, and found the lower steering head race was crooked in the pocket........so one side was lower than the other by about 1 mm or so..........I think this might be more common than you might think, the bearing was not loose at all, and after removal you could see it had broached its way in leaving a steel ridge in the pocket.......I had to dremel this away, and then the bearing race went fully home........After reassembly the bike was an absolute delight to ride........just lovely.........But it sure had me a bit worried. Also this bike had the 19 inch front wheel with a larger width tire.....I think a 3.50 x 19 I felt this may have made the symptom worse than if it had say a 3.00 x 20 with less contact patch on the road surface. If your bike has a low speed odd feeling not unlike if the steering damper is wound on, but in fact it is not........you might find the bearings and their either fit in the pocket, or similar is the culprit, and not easy to spot without looking very carefully...........Cheers all........

 

[timetraveller]

Paul Richardson., page four of the first section on the Front End. "Although each bearing will take twenty-one , not more than 20 may be used in each race"