Member Contributer Mohawk Posted June 16, 2016 Member Contributer Share Posted June 16, 2016 Yes CBR forks are a bit shorter than VFR forks, but many people have used them as is with NO adverse effects. The VFR has a very conservative geometry, so will be fine. But if you want the original geometry, then swap the stanchions as described above. Link to comment Share on other sites More sharing options...
2stroke Posted June 16, 2016 Share Posted June 16, 2016 19 minutes ago, Mohawk said: Yes CBR forks are a bit shorter than VFR forks, but many people have used them as is with NO adverse effects. The VFR has a very conservative geometry, so will be fine. But if you want the original geometry, then swap the stanchions as described above. Ok,but is it really the same diameter on both ? Link to comment Share on other sites More sharing options...
Trevor Posted June 16, 2016 Author Share Posted June 16, 2016 Sigh, you do not have to swap fork stanchions to keep the same geometry, the VTEC and VFR750 triples have IDENTICAL offset. All you have to worry about is height. So working on a 20mm difference in length, I plan to push the forks down 10mm, and have them lengthened internally by 10mm, therefore no height difference, and no geometry difference. Like I said this has been done many times before, it's a very common swap out. Link to comment Share on other sites More sharing options...
2stroke Posted June 16, 2016 Share Posted June 16, 2016 47 minutes ago, Trevor said: You do not have to swap fork stanchions to keep the same geometry, the VTEC and VFR750 triples have IDENTICAL offset. All you have to worry about is height. So working on a 20 mm difference in length, I plan to push the forks down 10mm, and have them lengthened internally by 10mm, therefore no height difference, and no geometry difference. Like I said this has been done many times before, it's a very common swap out. Post pictures of your front end swap ! Link to comment Share on other sites More sharing options...
Trevor Posted June 16, 2016 Author Share Posted June 16, 2016 Mine is not complete, waiting for F4i axle to arrive, then it goes to my Mechanic to be all fitted up, will take some photos then. Here however is a pic of the KR750 (4th gen) that zRoYz built, using all the same parts, I am just copying this bike. Again, there are no geometry changes here. The only time geometry changes is if you use sports bike triples with a smaller offset than VFR triples, like CBR/SP1 etc are 30mm vs the VFR being 40mm. Link to comment Share on other sites More sharing options...
2stroke Posted June 16, 2016 Share Posted June 16, 2016 1 hour ago, Trevor said: Mine is not complete, waiting for F4i axle to arrive, then it goes to my Mechanic to be all fitted up, will take some photos then. Here however is a pic of the KR750 (4th gen) that zRoYz built, using all the same parts, I am just copying this bike. Again, there are no geometry changes here. The only time geometry changes is if you use sports bike triples with a smaller offset than VFR triples, like CBR/SP1 etc are 30 mm vs the VFR being 40 mm. Great that you will take and post some Pictures ! KR750 , ...is that a Kawasaki with Honda front end ? Link to comment Share on other sites More sharing options...
2stroke Posted June 16, 2016 Share Posted June 16, 2016 Link to comment Share on other sites More sharing options...
Member Contributer JZH Posted June 16, 2016 Member Contributer Share Posted June 16, 2016 20 hours ago, VFROZ said: But how did you get the rebound adjuster screw to still reach the rebound piston for it to still be effective? I lengthened the outer damping rod and lengthened the inner adjusting rod at the same time, so the adjuster operates the same way as before. I was worried about the "surgery" coming apart, so I believe I used red Loctite. I should mention that lengthening forks in this way requiresthe use of donor fork parts. But it's easy to find "pretzeled" forks on eBay, and the internal bits I needed are usually usable even if the tubes are not. Ciao, Link to comment Share on other sites More sharing options...
Member Contributer JZH Posted June 16, 2016 Member Contributer Share Posted June 16, 2016 13 hours ago, 2stroke said: 1. Is the only difference the length ? ....what about the diameter ? 2. What brakes will fit and from what bike ? 3. Are the pictures from that fork rebuilding ? Diameter is different, but that's one of the benefits of swapping the forks! The newer NISSIN 4-piston calipers I'm talking about were used on the following bikes: CBR600F4, CBR600F4i, CBR600RR ('03-'04), CBR900RR ('98-'03) and VTR1000 SP1-SP2 (possibly others). Note that these calipers have used different piston sizes and different master cylinders (as well as brake disc diameters), so it is important to match the components carefully. I just bought another set of CBR600RR calipers/master cylinder for one of my front end conversions. Those pictures were from 1999, when I installed a set of VTR1000F forks on my 3rd gen VFR, but wanted to keep the geometry exactly the same as before. So, I got some replacement stanchions made (easy, as I lived near a company that made replacement stanchions!) and specified that they be exactly like the VFR stanchions, just longer. VTR1000F forks are the same OD (41mm) as the VFR's forks, so I didn't have to change the triple clamps. I used a 4th-gen wheel and rotors and the mudguard, calipers and master cylinder and axle from the VTR. (I later changed the calipers and master cylinder to CBR600F4 or F4i items.) Ciao, Link to comment Share on other sites More sharing options...
Member Contributer Mohawk Posted June 17, 2016 Member Contributer Share Posted June 17, 2016 On 16/06/2016 at 8:33 AM, 2stroke said: Ok,but is it really the same diameter on both ? VFR750 3rd/4th gen forks are 41mm. VFR800 5th gen 41mm. VFR800vtec are 43mm. CBR600F2/3 forks are 41mm, as are VTR1000. CBR600F4/F4i are 43mm, CBR600F4S & early CBR600RR are 45mm, as are CBR900. Link to comment Share on other sites More sharing options...
Member Contributer Mohawk Posted June 17, 2016 Member Contributer Share Posted June 17, 2016 23 hours ago, Trevor said: Again, there are no geometry changes here. The only time geometry changes is if you use sports bike triples with a smaller offset than VFR triples, like CBR/SP1 etc are 30mm vs the VFR being 40mm. Well that's NOT quite correct. There are 3 components to frontend geometry, they are offset, which is created by the triple T's, plus rake the angle of the forks measured relative to the Vertical & trail, the castor effect of the front wheel, which is determined by a combination of the offset+rake+wheel diameter. Manufacturers state in their literature the default dimensiosn they designed the bike to, these are often NOT correct when measured. But regardless, if you have a bike then you have these 3 measurements in use empirically. If you push the forks up through the T's then this alters both the rake & trail. If you pushed the standard forks up 20mm or fitted 20mm shorter forks then you have adjusted the rake & trail together by the same amount regarless. So there is a change in geometery when fitting the shorter CBR forks. That said the VFR's have a quite conservative geometery to allow for loading with a pillion & luggage, I'm sure you have all noticed how carrying a pillion changes the way the bike handles, its more to do with a more relaxed geometry than the weight. Weight on the rear, lowers the rear ride height which in turn increase the rake & trail (think chopper here) making the steering slower. Shortening the length of the front forks, or raising the rear of the bike (which has the same effect) makes the rake angle steeper & shortens the trail (trail being the self centering castor effect of the wheel) this makes the bike handle or rather change direction quicker, which is caused by the moment of precession. Precession (https://en.wikipedia.org/wiki/Precession) is what allows a bike to turn, the closer you bring this to the ideal angle the less effort it will take to steer, but conversely the less stable the bike will become & the more sensitive it will be to external forces deflecting the front wheel. On a sports bike the geometry is set closer to the ideal & thus making major changes to their geometry, leads to the much published "Tank Slapper" effect where the front wheel when light & hitting a bump, can slam from lock to lock. the VFR has a very conservative geometry, so can tolerate much larger changes, like a 20mm shorter front fork without becoming nervous, though you will notice the change when it comes to the effort required to steer the bike, this is a GOOD thing. Now just get on & get it done :) Link to comment Share on other sites More sharing options...
Trevor Posted June 17, 2016 Author Share Posted June 17, 2016 Wow, some quite lengthy explanation of my simple statement that still stands true and correct, there will be NO geometry changes to MY bike, which is what 2stroke actually wanted to know i believe? :-) As per my statement above, dropping the forks 10mm and lengthening them 10mm = 20mm, no change in either ride height, OR offset. It all works in my favor, given I'm a short ass and had lowered both front AND rear to achieve neutral handling and lower seat height anyhow. So to sum up yes you CAN swap forks with NO alteration to geometry if that is what your trying to achieve. Link to comment Share on other sites More sharing options...
Member Contributer Mohawk Posted June 17, 2016 Member Contributer Share Posted June 17, 2016 Ah well if you'd said you were short ass & had a lowered bike already Link to comment Share on other sites More sharing options...
Trevor Posted June 17, 2016 Author Share Posted June 17, 2016 Haha yes, but I still feel I could make these forks the right length with a standard rear, 20mm is not much to accommodate. The clip ons I bought save 10 mm already. Link to comment Share on other sites More sharing options...
Member Contributer JZH Posted June 18, 2016 Member Contributer Share Posted June 18, 2016 On 17/06/2016 at 10:09 AM, Mohawk said: VFR750 3rd/4th gen forks are 41mm. VFR800 5th gen 41mm. VFR800vtec are 43mm. CBR600F2/3 forks are 41mm, as are VTR1000. CBR600F4/F4i are 43mm, CBR600F4S & early CBR600RR are 45mm, as are CBR900. Did the USA get the CBR600F4S? Anyway, it's also 43mm, not 45mm. The ST1300 is 45mm. I was going to use the adjustable fork caps from the 600RR on my ST, but never got past buying the parts... Ciao, Link to comment Share on other sites More sharing options...
Trevor Posted June 18, 2016 Author Share Posted June 18, 2016 I had 600RR forks delivered by mistake, 45mm and very nice forks, I really wanted to use them but it was too hard to work out wheel/axle/calipers. Link to comment Share on other sites More sharing options...
2stroke Posted June 21, 2016 Share Posted June 21, 2016 On 2016-06-15 at 9:44 PM, JZH said: "Stanchions" are the chromed steel tubes. Basically, he's saying to take the CBR600F4i forks apart, and replace the CBR stanchions with your VFR stanchions. Then re-assemble the forks. You will then have adjustable forks that are the correct length for the VFR. On 2016-06-16 at 9:11 AM, Mohawk said: Yes CBR forks are a bit shorter than VFR forks, but many people have used them as is with NO adverse effects. The VFR has a very conservative geometry, so will be fine. But if you want the original geometry, then swap the stanchions as described above. On 2016-06-16 at 9:01 PM, JZH said: Diameter is different, but that's one of the benefits of swapping the forks! I'm lost here....1. Since the forks on the VFR are 41 mm how can I mix the parts with the parts from the CBR600F4i since it is a 43 mm fork ? 2. How to achieve the same suspension travel as on the VFR ?( 1994 - 1997 ) VFR750 Fork suspension travel: 140 mm Rake: 26.0° Trail: 100 mm( 2001 - 2006 ) CBR600 F4i Fork suspension travel: 120 mm Rake: 24.0° Trail: 96.00 mm Link to comment Share on other sites More sharing options...
Trevor Posted June 21, 2016 Author Share Posted June 21, 2016 The VTEC triple clamps are 43mm, and the same bearings, so that's why you have to change the triple clamps. For me my current forks are RAISED 10mm in the triples anyhow, so I will just not raise the new ones. Link to comment Share on other sites More sharing options...
Member Contributer JZH Posted June 24, 2016 Member Contributer Share Posted June 24, 2016 On 21/06/2016 at 9:48 PM, 2stroke said: I'm lost here....1. Since the forks on the VFR are 41 mm how can I mix the parts with the parts from the CBR600F4i since it is a 43 mm fork ? 2. How to achieve the same suspension travel as on the VFR ?( 1994 - 1997 ) VFR750 Fork suspension travel: 140 mm Rake: 26.0° Trail: 100 mm( 2001 - 2006 ) CBR600 F4i Fork suspension travel: 120 mm Rake: 24.0° Trail: 96.00 mm Sorry, I can see why my reply was confusing. He also said to buy VTEC forks and triples. Those are the same OD as the F4i, so you can swap the lower tubes. I should have referred to those VFR forks, not the ones you have now. If you use the VTEC triple clamps, rake and trail will still be related to the frame geometry, which will not change. Suspension travel is related to the forks, and there is essentially nothing you can do about it except make sure that the forks are tuned (i.e., springs and valving) properly. The F4i manages just fine with 120mm travel. (A suspension specialist might be able to increase travel 10-20mm, but I'm not sure it would really be necessary.) Ciao, Link to comment Share on other sites More sharing options...
Trevor Posted June 24, 2016 Author Share Posted June 24, 2016 Precisely, I am using the F4i forks "as is" because I like the front 10mm lower anyhow. If I wanted to correct this then yes they can be lengthened 10mm while I am having them resprung and valved, but it won't be necessary. Link to comment Share on other sites More sharing options...
Trevor Posted August 20, 2016 Author Share Posted August 20, 2016 So it's finally together! The CBR forks seem pretty good for my weight (65kg) felt like a new bike on the way home. Offset remains the same and even the steering lock works. Lost 6mm in height from before to after, so it turns right quick now! That's ok, as I plan to lengthen the forks 10mm and raise the seat height 4mm to get back to where I was before during the suspension rebuild. Seat height going up as the sidestand is a bit painful at the moment. As is sometimes the way the bit I thought would be the least problem has become the most, and that's brakes. Idiot Ebay Seller sent me an IDENTICAL Master Cylinder instead of an F4i one, so we ended up using mine as it looked pretty crud anyhow. The calipers still need a piston kit, and the fifth gen rotors are well ridged. End result is a long throw on the lever and a bit spongy. They are still stronger and smoother than before, you just need to grab a big handful of lever, vs a lighter touch. So plenty good enough for now, but long term I will either grind the discs, or maybe just get galfers, piston kit for the calipers, and fit a proper F4i master. All in all I'm well chuffed with the difference, and I haven't even rebuilt the suspension yet. Link to comment Share on other sites More sharing options...
Member Contributer JZH Posted August 20, 2016 Member Contributer Share Posted August 20, 2016 Looks good. Get the m/c swapped soon--you don't want to discover that your lever hits the bar just when you need maximum braking! Ciao, Link to comment Share on other sites More sharing options...
Auspanglish Posted August 20, 2016 Share Posted August 20, 2016 Looks good. Get the m/c swapped soon--you don't want to discover that your lever hits the bar just when you need maximum braking! Ciao, +1 Link to comment Share on other sites More sharing options...
Trevor Posted August 20, 2016 Author Share Posted August 20, 2016 All good, I have adjustable levers luckily so it worked out, but yes, shopping for the master cylinder now! Link to comment Share on other sites More sharing options...
Trevor Posted October 22, 2016 Author Share Posted October 22, 2016 Fitted the F4i master cyclinder today, brakes are now bloody awesome! Also had the forks revalved with 0.9 springs and 10 weight oil and the penske rebuilt. In the end I kept the 6mm drop at the front as she tracks like a bloodhound now and still nice and stable. All in all the project is done, with the result I wanted, excellent suspension, and awesome brakes, in fact it feels like a new bike to me. Link to comment Share on other sites More sharing options...
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