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Fork Run out, BENT FORKS

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gavcarter
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PostPosted: 19:50 - 29 Jun 2014    Post subject: Fork Run out, BENT FORKS Reply with quote

Any one know what the run-out spec is for a cbr600fv its the 97 F3
Or just a general acceptable tolerance would be cool.....

Ive spent about 8 hours today stripping one fork and making a monstrosity of a bending jig to take a slight bend out.....

Other leg tomorrow but need to know if im getting them close enough...

I took the right leg today from 1.73mm out of true ( just below bottom yoke so roughly the middle of the stanchion) to 0.09-0.10mm

Took me nearly two hours to separate the bastard leg
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gavcarter
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PostPosted: 07:40 - 30 Jun 2014    Post subject: Reply with quote

Vincent wrote:
0.000mm out of true is about right Thumbs Up

I've never heard of any tolerances for fork stantions, I thought they were either straight or bent Question
There may well be a limit........I'm just not aware of one.

What diameter are they? 41mm?


Yes 41mm, Will have to try and find a proper honda manual for it or something.
Haynes just say to have run out check by honda dealer.

I would assume a minute amount of bend is acceptable as they eventually bend ( just ever so slightly ) from heavy braking - although they usually end up so badly pitted by then that no one notices as they get changed.
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gavcarter
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PostPosted: 07:50 - 30 Jun 2014    Post subject: Reply with quote

Wow that was easy! I did not expect to find one that quick, here is URL incase its any good to anyone https://www.cbrextreme.com/file/down/F3manual.zip

Apparently your allowed up to 2.0mm radial and axial on the front wheel and 0.2mm on the forks, so they are within limits.

Thats good news to me because it saves a lot of ££ Laughing
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barrkel
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PostPosted: 09:09 - 30 Jun 2014    Post subject: Reply with quote

Any bend from braking won't be asymmetrical though.

Sideways bend that puts the front wheel out of alignment with the rest of the bike affects handling, making left turns different to right turns.

Didn't take much bend at all for my old SH300 (post-highside) to be affected, can't have been more than 1mm out on the stanchion. Was barely measurable but the handling was fixed when the forks were swapped for my new SH300; handling was fixed permanently when stanchions were swapped out.

Scooters with their narrow tyres and quick steering are extremely sensitive to it though.
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gavcarter
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PostPosted: 10:45 - 30 Jun 2014    Post subject: Reply with quote

this is probably the reason for the service limit, honda will have came up with 0.2mm has enough effect to make it feel weird.

I forgot to half my measurements aswell so the original bend will have been around 0.8mm and is now down to 0.05mm

the left fork got done this morning, no faffing on, stripped seal and clip and chucked on oven hob for 20 min, one slide popped oil seal, next one brought bushes out, was much easier to do when warmed through.

This leg had about 0.3mm of bend which ive managed to squeeze down to 0.03 ish, will put up in show and tell later, i find it interesting if no one else does.

Front wheels all true ( or well within spec at least ) but bearings rattle like mad so they will be changed....
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stickybackbob
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PostPosted: 15:18 - 30 Jun 2014    Post subject: Reply with quote

gavcarter wrote:
Wow that was easy! I did not expect to find one that quick, here is URL incase its any good to anyone https://www.cbrextreme.com/file/down/F3manual.zip

Apparently your allowed up to 2.0mm radial and axial on the front wheel and 0.2mm on the forks, so they are within limits.

Thats good news to me because it saves a lot of ££ Laughing


Cheers for the manual. Just bought a rough one of these to play with Smile
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gavcarter
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PostPosted: 17:09 - 30 Jun 2014    Post subject: Reply with quote

Play with or work on?
Ive had a pig of a day getting the dog bones off the swing arm, had to bake the swing-arm over the gas hob to bray the bolt out as the the spacer is seized on to it
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stickybackbob
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PostPosted: 20:55 - 30 Jun 2014    Post subject: Reply with quote

gavcarter wrote:
Play with or work on?
Ive had a pig of a day getting the dog bones off the swing arm, had to bake the swing-arm over the gas hob to bray the bolt out as the the spacer is seized on to it


Definitely to work on for now. Just started into it and found the previous owner was telling some porkies about it's state. Running gear seems ok apart from a bald front tyre. Pity the same can't be said for the carbs Smile
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