Vfr750 owner gate crashing :-)

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Renevator
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Joined: Thu May 17, 2018 10:59 pm

Vfr750 owner gate crashing :-)

Post by Renevator »

Hi guys

I'll be honest. I joined this forum to see if any of you have wisdom regarding upgrading the standard VTR forks.
I have a VFR750 FR that I want to fit with firestorm forks, essentially to benefit from VTR, 954, sp2 etc calipers.
I've decided this option because it keeps the geometry as close to std as possible, unlike using 954 or sp1 forks, but it does limit me to just rebound and preload adjustment, even with having the forks rebuilt.
Just wondering if any of you have improved the adjustability of the std forks, I.e, added compression adjustment, etc.
Also, if anyone has a pair of std VTR forks for sale I'd be very interested.
Thanks.
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fabiostar
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Re: Vfr750 owner gate crashing :-)

Post by fabiostar »

get rogered :eek2 :eek2 :eek2 .. now by that i mean the best mod for VTR forks seems to be getting Roger Ditchfield at Revolution Racing to work his magic on them. :thumbup: .

welcome along by the way. :thumbup:
the older i get,the faster i was :lol:
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Watty
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Re: Vfr750 owner gate crashing :-)

Post by Watty »

fabiostar wrote: Mon May 21, 2018 8:15 am get rogered :eek2 :eek2 :eek2 .. now by that i mean the best mod for VTR forks seems to be getting Roger Ditchfield at Revolution Racing to work his magic on them. :thumbup: .

welcome along by the way. :thumbup:
Roger can also work magic on Viffer forks!!
SH#T HAPPENS!!!!!!!!
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Watty
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Re: Vfr750 owner gate crashing :-)

Post by Watty »

fabiostar wrote: Mon May 21, 2018 8:15 am get rogered :eek2 :eek2 :eek2 .. now by that i mean the best mod for VTR forks seems to be getting Roger Ditchfield at Revolution Racing to work his magic on them. :thumbup: .

welcome along by the way. :thumbup:
Roger can also work magic on Viffer forks!!
SH#T HAPPENS!!!!!!!!
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Watty
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Location: Barnard Castle, Co. Durham.

Re: Vfr750 owner gate crashing :-)

Post by Watty »

Hello from another Viffer owner :thumbup:
SH#T HAPPENS!!!!!!!!
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popkat
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Re: Vfr750 owner gate crashing :-)

Post by popkat »

Another VFR owner here and I have VTR forks on one of mine, It's not an FR it's an FJ do different model, and it's a race bike. My advice would be to speak to Richard at Maxton, see what they can offer for your current forks and for VTR forks, depending on how much you want to spend, they can make cartridge kits with rebound and/or compression, I'm sure they will advise which fork option of the two is best to go with.

If you just fit a pair of stock VTR forks I don't think you'll be too impressed, they have really soft springs as standard, If your looking for better brakes yes they are 4 piston but do tend to need a big squeeze, also the VFR brakes twin pot can be very good with braided lines and the right pads.


.
http://www.bidefordmotorcycles.co.uk
2014 CRMC Post classic Superbike champion.
2014 CRMC Post classic senior production champion. On a Suzuki Katana 1100
My bikes, Firestorm, Suzuki GSX-s1000 Katana, VFR800Fi. Projects, 1986 popup Katana, 3 XJ600’s
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Cadbury64
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Re: Vfr750 owner gate crashing :-)

Post by Cadbury64 »

I have had VTR forks on my VFR, and I did all the re-springing and re-springing myself using RaceTech parts. I'm happy to share what I found. My recipe involved 0.9kg/mm straight-rate springs, 15mm preload, Gold Valves in both the compression (most important) and rebound (nice to have) position, 5 weight oil @ 130mm (I think, would have to check).
2017 MT-10SP, 2019 Vespa Primavera 150
Renevator
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Joined: Thu May 17, 2018 10:59 pm

Re: Vfr750 owner gate crashing :-)

Post by Renevator »

Thanks for the replies folks.
Cadbury64 - thanks for that info, very interesting. I'd like to know what you hunk of the end result and why you went that route as opposed to a USD config. I kno a lot of folk do, but I feel, for the road, it spoils the ergonomics of the VFR. Track is a different proposition of course.
Re Maxton, well I still have my Maxton shock from a previous VFR, and the reworked forks, but there's no adjustment on them.
I'm curious. How does one introduce adjustments that aren't there on a standard fork? I always thought you had to have the actual physical after on the forks to start with if a specialist is going to improve that.
There's a guy next to where I work who's a top notch specialist, so I can get home to rework whatever forks I decide to fit.
I'll have a look at Revolution racing and see if Maxton can fit some GP20 cartridges into a set of firestorm forks....if I can find any decent ones.

Thanks again.
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Cadbury64
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Re: Vfr750 owner gate crashing :-)

Post by Cadbury64 »

My path to modified VTR forks in my VFR was partly to upgrade the brakes (VTR fork lowers play nicely with opposed 4-piston calipers from CBR954s and others), to de-link the brake, and to add some external adjustability for rebound damping, for a minimum cost. I already had modified damper parts and springs in the VFR that I swapped into the VTR fork. I bought some "lightly crashed" VTR forks and used the tubes from my VFR with the VTR lowers and internals. I kept the stock bars, triples, wheel, axle and guard (with homemade adapters). Had I put USD forks in, I would have needed to change lots more parts. For road use, 41mm diameter forks are acceptably stiff for my tastes(but don't get me started on 37mm 1986 VFR750F forks, what were they thinking?).

All forks can be adjusted either externally (with a screwdriver) or internally (by swapping or modifying parts). Most important is getting the right spring rate to suit your weight, then adjusting the damping to suit that. External damping adjusters work by adjusting a bleed port that bypasses the shim stacks, but all cartridge dampers have a form of bleed port that can modified if needed, and the shim stacks themselves (which are assemblies of spring steel washers that are pushed away from the oil ports by the flowing oil) can be changed to make them stiffer or softer.

Where the VTR (and VFRs) forks are weak is the HMAS piston design which uses relatively small oil ports behind the shims; these introduce a degree of harshness on bigger hits that can't be tuned out. Aftermarket pistons like Gold Valves use much bigger ports and relay wholly on the shim stacks to create resistance, which means you can tune the damping force to suit individual tastes, and they tend to be more forgiving on large bumps.

You can of course alter the shims stacks on the standard pistons if you want, and for the rebound side that is not such a bad proposition, but I wouldn't suggest keeping the standard compression pistons.

There's nothing magic about USD forks that will give them better damping properties but they are stiffer than RWU forks. AFAIK most Honda's from the 90's and 2000's use a common 20mm cartridge and piston size and so you can mix and match the parts; as examples, I have reworked ST1100, 99 VFR800, 97 VTR1000 and 2000 CBR600F4i forks with the same basic damper parts.
2017 MT-10SP, 2019 Vespa Primavera 150
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popkat
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Re: Vfr750 owner gate crashing :-)

Post by popkat »

For VFR forks Maxton would have to fit a cartridge kit, this can have rebound damping at the top, they make new fork caps. they can give you compression adjustment too but this is usually not so easy to get to the adjuster, In my experience Maxton set them right in the first place so having rebound will be good enough. If you fit firestorm forks then they can fit a piston kit, this is much cheaper than a cartridge kit as it just replaces the piston inside the standard cartridge and offers a greater degree of adjustment and better to start with. there are other alternatives of course, there's K tech but their piston kit is a very old design and after having it in mine would not use that product again (forks felt solid and no adjustment range). that's not to say I won't use K tech as their newer stuff is top notch.. other places do re-valves, MCT is one that springs to mind, but as I said earlier Maxton for me have always got it spot on, I've tried others but always gone back to them.



.
http://www.bidefordmotorcycles.co.uk
2014 CRMC Post classic Superbike champion.
2014 CRMC Post classic senior production champion. On a Suzuki Katana 1100
My bikes, Firestorm, Suzuki GSX-s1000 Katana, VFR800Fi. Projects, 1986 popup Katana, 3 XJ600’s
Renevator
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Joined: Thu May 17, 2018 10:59 pm

Re: Vfr750 owner gate crashing :-)

Post by Renevator »

Great amount of info there, many thanks Popcat and Cadbury64.

Regarding the VTR lowers, could my local suspension guy take the Internals of my VFR forks and simply swap over the lowers, or is more needed. And in your experience, would this result in any change in length of the complete fork assembly.
I'm thinking, maybe as an interim step I could get some VTR lowers and swap the Maxton VFR fork internals into that, and then aypt a later date get some more adjustment built into this set up. I can then benefit from the 954 brakes immediately. I still need a VTR axle and front mudguard, and 14mm master cylinder, from an ST 1100, I understand. And possibly need to buy longer brake lines?
By the way, Fabiostar, do you still have those forks for sale? Saw them the other day but can't reply on that forum until I've got my post count to 50. Bit cheeky asking here of course :plainsmile .

Cheers guys, all very helpful.
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Cadbury64
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Re: Vfr750 owner gate crashing :-)

Post by Cadbury64 »

As far as I know, all the 20mm cartridge innards should be swappable, certainly I know the parts in my VFR800, VTR1000 and ST1100 all use a common diameter and thread size for parts like fork caps, damper rods, bottom bolts, sealing washer, seals and bushings, and rebound and compression valve bodies. If Maxton parts use the same dimensions I bet these will swap straight into the VTR lowers.

The overall fork length extended is dictated by when the bottom of the fork inner tube engages with the top-out spring on the outside of the cartridge, so If you use your VFR tubes and cartridge tubes, they will end up exactly VFR length when using VTR lowers. You should be able to use the VTR caps and rods with adjustable rebound, with the VFR cartridge, VTR lowers, and end up with a completely VFR-stock length.

For a stock looking master (to match a VFR integral reservoir) you can get a CBR600RR part from 2003 (to 2004?); this is the perfect size match to a stock CBR954RR.
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Renevator
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Re: Vfr750 owner gate crashing :-)

Post by Renevator »

Cadbury64, that's brilliant, thank you so much for this info 👍
Not gonna have much time to ride let alone rebuild for the next few weeks but that definitely gives me what I need to know to make the swap.
Thanks.
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