Fork Maintenance

[PieEater]

This years Winter project will be fork maintenance. I've had the bike about 5 years now and feel as if the damping is not as good as it was when I first bought it so am thinking the oil has had it. I've never been unhappy with the forks performance until recently and when I had help setting them up a couple of years ago was able to discern a difference in each adjusters setting so I'm assuming that they have had some work done on the internals but won't know for sure until I open them up.


I'd appreciate any guidance / hints / tips from those that have undertaken a stripdown & rebuild of the forks - other than oil & seals will I need to purchase any other parts / tools / fluids, what oil is recommended, if I find the springs are OEM should I replace them and if so what with, is it worthwhile renewing springs anyway if they are at least 5 years old? If it helps I weigh 23st and have more weight over the front than stock via a jack-up kit, height adjustable shock and having the forks through the yokes by ~12mm, riding style is fast on minor A roads (lots of bends and not the best road surfaces - so forks are working hard).

[mhowse]

You will require a tool of some sorts to replace the oil seals should be doing more than oil and spring change, many like myself have found suitable alternatives and much cheaper from a plumbing supplier for a diameter that fits round the fork stanction to tap new seal in.. Plus worth spending a little extra for quality seals that have a more compliant rubber than harder rubber type cheap ones. so you not have to do the strip down again for another 5 or more years.

Also depending on your mileage it may be worth considering re-newing the top and bottom fork bushes again I did mine at 45K miles though mine did not show much signs of wear to the teflon coating which could of been down to regular fork oil changes, got my bushes from brooks suspension. may as well do the dust seals at same time as save in the future, a small amount of tape  round top of stanction will protect new fork seal when slipping it onto the stanction, myself I smear a little red rubber grease onto new seal also to aid fitment you could just smear a little new fork oil, you will also need some sort of measuring stick to help measure new fork oil level  I use a ruler and move 10mm up the measure from bottom of ruler so that I can see when the level is nearly correct, and wrap a cable tie at the correct measure of the rule so it rests on the top of the stanction and prevents whatever you choose to measure with does not vanish into the stanction you are filling with oil not something you really want to happen ... , will make more sense when you come to do the job.

I did once try 10w fork oil but found this way to harsh for my liking and now only use 5w .

My choice was to change springs to hyperpro and made a noticable difference so worth thinking on new springs which ever make you choose to go by.

A tip when commencing work is to slacken the allen bolt at the bottom of each fork leg before slackening off the yoke clamps and should they spin and not release a suitable shaped broom handle when you have removed them will stop the offending rod within the fork from spinning allowing you to remove bottom allen bolts this also aides when you refit and tighten the bottom allen bolts....not too complicated a task and with winter time to take it slow and do the job well. there is a good link somewhere and sure others have their own tips and tricks for making the job simpler.
Also woth noting all you settings before hand so you have a base set up to return to when competed  along with measuring how far down the rod the nut on rod within fork is that the top rebound/preload adjustment /cap sits on you will see this when you get to point of removing fork cap.

[PieEater]

Thanks a lot for the advice and for taking the time to type it up.


I'm looking at K-Tech's linear springs though they don't seem to do any for the Fazer past 10.0N and according to a couple of online calculators I need 11.0N for my weight, I've emailed K-Tech to see if they do any higher rated springs but if anyone knows where I could get some I'd be interested to know. Also K-Tech list the seals (Fork & Dust) as well as the bushes (Guide & Slide) would these be OK or should I go with OEM?

[sadlonelygit]

D Faulkner springs can make you up custom springs for your 'generous' proportions.
the problem you will find however is the amount of rebound you will need to control the forks as you will now have BFO springs bouncing the bike back.
i had 1kg/mm springs and 5W oil with the standard air gap and i felt the rebound was right on it's limit.
10W oil might be enough but then compression damping may be compromised.
it's a black art this suspension shit.
only special tool needed is a tape measure for rebuilding forks (11mm of thread on the damping rod req'd)

[nivek24]

D Faulkner springs can make you up custom springs for your 'generous' proportions.
the problem you will find however is the amount of rebound you will need to control the forks as you will now have BFO springs bouncing the bike back.
i had 1kg/mm springs and 5W oil with the standard air gap and i felt the rebound was right on it's limit.
10W oil might be enough but then compression damping may be compromised.
it's a black art this suspension shit.
only special tool needed is a tape measure for rebuilding forks (11mm of thread on the damping rod req'd)

can i ask what is the (11mm of thread on the damping rod req'd) i have just changed the oil and seals in mine and i screwed the top adjuster down as far as it would go then nipped the nut to it.
i did unscrew the adjuster off, before i stripped it down.
have i done it wrong! should i have screwed the top adjuster down 11mm then nipped the damper rod up.
kevin

[sadlonelygit]

distance of bolt 2 from top of threads. it sets the rebound rod in the correct place!

[nivek24]

thanks for the diagram , think i better strip mine back down and check what mine is set at then.

[PieEater]

I've heard back from K-Tech they also recon that 11.0N would be too much (thanks SLG), so it looks like I'll be going with their 10.0N linear spring.

I'm leaning towards 7.5w oil rather than 5w as I think slightly heavier oil would be better suited for a heavier rider, or is this mistaken thinking? K-Tech supply Motul fork oil, will I be alright with this if I end up ordering everything (springs / seals / bushes) from them?

Has anyone got any experience of K-Tech's parts (seals and bushes) vs OEM parts, haven't yet priced these up so not sure what the price difference will be or if the quality is any different?

I'm looking at following the Haynes manual for disassembly / reassembly if anyone has any addendums to the information or alternative guides I'd appreciate the info (i.e. Mr Haynes tells you to remove the carbs for a valve check when you don't have to).


/Update - Chris from K-Tech is recommending 10w oil for standard internals.

[Tmation]

I had my forks uprated, including heavier springs, by K-Tech about 9 years ago. Massive improvement in ride quality and never had any problem with them. I had the forks service by MTC 2 years ago and everything was still in good condition.


Go with their recommendations for oil etc.

[sadlonelygit]

for a 300lbs rider, you would need 10.846315789473685 n/m as the ideal spring rate.

that's simple physics, not pushing anyone's product

i had the 1kg/mm springs and being 7st lighter thought they were just right...........

give MHR in calne a tinkle and see what he says, being an independant

[ricknz]

Timely thread... I'm doing the same work... have everything to hand (new bushes, seals, dust caps and 9.5 KTech springs)... just umming and arring about the KTech piston kit.

[PieEater]

So I've ordered 10.0N linear springs, bushes, seals & 10W oil from K-Tech...Anything heavier would have meant bespoke which would most likely mean more £££ and a problem if I did ever need to sell the bike.

[ricknz]

I've ordered the KTech piston kit... I sent my cartridges to someone here in NZ but to cut a long story short I have them back (return to sender from their postbox!) and have told them to send me the kit so I can fit them myself... anyone have any experience with this? Or is it better to send them to someone local to fit them for me? I have most tools, but nothing too specialised.

[Falcon 269]

Hi Rick

Unless you have prior experience of suspension tuning work and the necessary tools and skills to go with it, I suggest you look for a specialist to do this job.  I don't think it's as simple as swapping out old parts for new, put it that way.

You could, of course, e-mail K-tech and ask their advice.  They're very helpful folks.

[ricknz]

Yup I thought as much - I'll give the guys at ktech a bell and see what they say - and search for some people local. What do you think would be a good price to get these fitted to the cartridges? Then I'll multiply it by 4 for NZ! Regarding an earlier post about the distance of the thread showing - my records show both forks were at 14mm!

[ricknz]

Here is the piston kit alongside my fork cartridge... someone must have had a go at this... I've seen a post on yamahafz1oa so may take a scoot there...

[Smurfbud]

If not on here, maybe someone has done something similar on U-tube ??