Honda CBR 1000F front preload adjustment and new springs / oil
 

I sometimes visit here and have made a couple of post but I thought I would give something back to the forum.

I also posted this yesterday in the German CBR forum as I live in Germany.

Hope this helps other CBRF owners..... as this really has transformed my bike.

Honda CBR 1000F front preload adjustment and new springs / oil

OMG !! What a difference, the change is totally amazing and actually words can’t describe how I felt after the final road test with all the changes and adjustments complete. It’s like a completely different bike with greatly improved stability and balance and with soooooo much more feedback about what’s going on underneath you.

Bike is a Honda CBR 1000F type SC24 with Dual linked brakes, year model 1999 and code FX,

I weigh 98Kg, 108Kg with all my winter riding gear on, 105Kg with all my summer riding gear on

I hope this write-up helps owners on this and other forums to maintain and keep these beautiful bikes on the road. I couldn’t find the information I wanted about how to add front spring pre-load and set the suspension up correctly on the CBR1000F, so I hope the week I spent removing / adjusting and re-installing my forks and the multiple hours of road testing will give other owners the confidence that they can do it to.

Initial problem:

So did the bike have a problem before I started, well yes and no, we all know the CBR-F bikes are heavy and the standard setup is way too soft and under sprung and if we are honest its true to say that they feel soft and bouncy and as the speed increases this gets worse. But for me there were 3 main areas or problems.

1) Occasional bottoming out on the front forks
2) Lack of feel from the front when braking hard
3) Nervous feeling on the front during turn-in and instability during mid-corner

Measurement of changes:

The bike was tested on the same 19Km stretch of road before and after each adjustment so that I could get a feel for what had changed, the road has a combination of slow ( 20-40Km ), medium ( 50-80Km ) and fast ( 90-150Km ) corners with a mixture of really poor road surface and a nice fast 5Km stretch of new freshly resurfaced road.

The process was really simple but time consuming, all I did was take my time and stop and make notes on how I felt and how the bike felt after each adjustment, and then I used this info as my measurement of a positive or negative change.

In addition to this the only data measurement I could record was corner entry speed. What I mean is this, on the 19Km stretch of road there is a really nice mixture of corners so I picked 7 of them to measure corner entry speed. All I did was to record the maximum entry speed at which I felt comfortable and safe. I then increased this entry speed by small (5-Kmph) increments until the bike felt nervous on the front and then I would stop and made notes. (See further comments under the Road test Sequence section below)

Why Wilbers? And why Progressive Springs and not Linear?

After quite a bit of initial research I had decided that I would install linear springs and not progressive so I emailed RaceTech and Sonic Springs both based in the USA and asked for help and advice about choosing the right spring rate. I received NO REPLY.

I then emailed Wilbers and Wurth here in Germany and asked the same questions, only WILBERS replied, so as Wilbers was the only company that responded to my enquiry I decided to go with them. Next I emailed the UK branch of Wilbers and eventually had several telephone conversations with their workshop boss (John) and we talked through the pros and cons of linear vs Progressive springs and air gap and preload settings.

I must say that we did talk about Linear springs and that if 70% of my riding was going to be at a very fast pace and if I was going to do some occasional track bike days then this would definitely be the way to go. I think that the linear spring would also provide the ultimate feel and a more stable balance when the bike is cranked over on the edge of the tyres…. But I just don’t ride like that anymore (well not that often). So hence we decided on Progressive and I decided I would take my time sorting out the preload to gain the maximum from the spring change.

Parts used:

Wilbers Zero Friction Progressive springs: 600-0177-00
Wilbers Zero Friction Fork oil 1L of 10W: 610-0110-00
Eni Fork oil 1L of 10W (used for fork flushing – cleaning)
10 x Preload spacer / washer: purchased from a hardware shop (in Germany Obi)

OEM / stock settings:
Image 002 / 003 and 004 show the standard OEM setting with the standard 50mm preload spacer.

Image 003 shows the OEM spring with the tight wound section of the spring at the BOTTOM of the fork. When you install your new springs you’re going to fit them the other way up.

Image 005 / 006 shows the OEM spring next to the Wilbers progressive spring. (Note the Wilbers spring length was 2mm shorter than the OEM spring length.

I did notice some odd things while dismantling the front forks, the oil condition was not that bad, yes it was a dark colour but not as dark or smelly as I thought it would be. (This was the first indication that perhaps the previous owner had already serviced the forks)

The fork oil level was also low, I measured approximately 186mm in air gap in the top chamber and I think the OEM setting should have been 172
Second strange thing was the second nut down on the damper rod, the smaller one that holds the preload top washer in place, this was loose… the left hand fork was a full 2.5 turns lose and the right hand one 1.25 turns lose. This of course would also equal less or reduced preload and would have contributed to the horrible soft bouncy front end I started with.

Last thing I noticed was that the OEM springs were mounted tight wound coil end downwards, I do not know if this is a stock setting or if someone had installed the springs incorrectly.

Removing the old fork oil:

I did not fully dismantle the forks or separate and remove the fork seals; I also did not use degreaser or a cleaner fluid to clean out the forks. Instead I used 1L of new 10w fork oil to thoroughly flush the system.

Basically I took the bike for 45mins ride before I started so that the oil would be warm, then I drained both forks and left them upside down for 30 mins. I then used an old hairdryer to heat up the fork tube base and poured in 250mL in each fork and then worked the damper rod up and down for 10 mins in each fork before again draining them. I repeated this process a second time to make 100% sure or the old oil was out.

Preload Spacer / washer:

Several forums mention that the front spring change is more tricky on the 94 year onwards bikes, but it’s actually really straight forward and easy to do, and if you are replacing the springs, fitting preload spacers is really simple.

The actual part I used was purchased from a hardware shop (Obi): Sold as 32mm x 11mm x 2mm but actually measure OD 31.8mm ID 10.6, thickness 1.8mm (See images 008 / 009 and 010). The final setting was 5 preload spacers / washers in each fork so you will need x 10.

See images 007 / 011 and 012 for the correct position of the preload spacers.
Image 012 shows the damping rod pre-assembled with 4 preload spacers (The final assembly was with 5 spacers)

Image 011 shows that the Wilbers spring installed with the tight wound section of the spring facing upwards / towards the top of the fork tube. This is the exact opposite of how I found the OEM springs which were mounted tight wound section facing downwards ( see image 003 ).

The OD and ID of the washers / spacer is absolutely critical as the ID must fit snuggly (but not tight) over the piston rod smooth surface and the OD must be wide enough to cover the top of the new spring but (not wider) than the OEM washers that sit (over and under) the OEM preload spacer.

Oil Level / Air Gap:

OEM air gap setting is approximately 172mm (I think)
Wilbers recommend an air gap of150mm
I tried 160mm / 150mm and 140mm

The final setting was 145mm, which I felt gave the best compromise
Please note that if you increase the air gap the damping will be softer, so if you want a slightly firmer feel you should decrease the air gap.

Setting the Sag Level:

After a lot of research and reading and watching a guy called Dave Moss from DMT on YouTube, it was clear that a general sag setting of 30-35mm on the front and 25-30mm on the rear was a good point to aim for with me in my normal ridding gear.

The initial sag settings I had before starting any suspension work was quite simply terrible. The front was 57mm and the rear was 41mm. in the past I had tried to increase the rear preload but once I got above 6/7 clicks in, the balance of the bike changed and was terrible, partly because at that point the rear was becoming over sprung and moving more weight onto an already soft and bouncy front.

SAG - Starting point: Front 57mm and Rear 41mm

But with all the changes to the front of the bike I was able to greatly increase the rear preload to match the front. One way to check is the bounce test… you need to stand 2/3M away looking at the side view of your bike, and then you need to helper who is about your weight and can bounce up and down in the middle of your bike while trying to spread the weight evenly between bars and seat.

What you are looking for is an even simultaneous compression of both front and rear suspension. To give you an idea, I could see a real difference when the rear preload was 7 clicks as it was always the back of the bike that started to compress first, but after adjusting that setting to 18 clicks you could see the whole bike compress as one unit…. It was amazing to see and even more amazing to test ride afterwards as it made a noticeable improvement.

SAG - Finishing point after suspension work and re-adjustment: Front 36mm and Rear 29mm

Road Test and Testing Sequence:

Road test 1:

New Wilbers springs and oil, air gap set to 150mm – no other changes – rear preload set to 7 clicks in. The bike felt immediately better especially under braking

Road test 2:

New Wilbers springs and oil, air gap set to 150mm – 3 preload spacers installed - rear preload set to 7 clicks in. (See image 007 showing correct position for assembly of the 3 preload spacers). This was a small step forward and I was just trying to achieve the correct sag level. Noticed the entry speed was slowly going up on the 7 test corners.

Road test 3:

New Wilbers springs and oil, air gap set to 150mm – 5 preload spacers installed - rear preload set to 7 clicks in. (See image 011 showing correct position for the final setting of 5 preload spacers). This gave me the sag level I was aiming for and the front end was feeling much better, but the bike felt a little unbalanced. Entry speed again feeling better as more weight comes of the front.

Road test 4:

New Wilbers springs and oil, air gap set to 160mm – 5 preload spacers installed - rear preload set to 7 clicks in. This gave a slightly softer feel to the front which I did not like especially when braking hard.

Road test 5:

New Wilbers springs and oil, air gap set to 140mm – 5 preload spacers installed - rear preload set to 7 clicks in. This was much better under brakes but while just cruising and taking it easy on the way home from the test route I decided it was just beginning to feel to firm.

Road test 6:

New Wilbers springs and oil, air gap set to 145mm – 5 preload spacers installed - rear preload set to 14 clicks in. The air gap is now set to 145mm which is the final setting and then I started looking at the rear shock to see if I could match the front. With an increase from 7 to 14 clicks on the rear you could really feel the back of the bike beginning to match the front, corner entry speed is going up especially on the faster sweeping corners…. I can’t quite believe how stable she feels now

Road test 7:

New Wilbers springs and oil, air gap set to 145mm – 5 preload spacers installed - rear preload set to 18 clicks in. This gave me almost perfect sag setting on the front and rear, which also confirmed what I was feeling on the test route. The bike is feeling really stable at turn in and mid corner which is something I thought would never happen on this big old heavy girl….and under heavy braking you have much more feeling for what the tyre is doing. Honestly it’s like a completely different bike.

Road test 8:

New Wilbers springs and oil, air gap set to 145mm – 5 preload spacers installed - rear preload set to 18 clicks in, – both front forks lowered ( dropped ) in the yokes by 4mm. (See image 013 showing fork tube lowering of 4mm). This was an interesting test, I didn’t think I would feel or notice any difference, but you can, the bike is even more stable in the faster corners and straights, but I think I can feel a decrease in the speed in which the bike turns in the slower corners. I’ve decided to leave things at this setting and I am going to wait until the local bike club goes out when the weather warms up and put a few more hundred Km on her and let everything settle.

Road test 9:

All suspension settings as Road Test 8 above but, with new brake pads installed (Lucas TRW MCB 658 SV pads) and a complete brake fluid change.

Road test 10:

As Road Test 9 above but, after the carbs have been stripped and cleaned (for a second time) I was trying to resolve a slow speed hesitation with throttle openings of 0 – ¼ throttle that the bike has had since I got her, the problem also got worse as the weather gets warmer, so in the summer it’s a real pain in the butt, But I think it’s finally fixed.
This second time of removing and stripping the carbs I paid a lot of attention on the slow running circuit, yes the Pilot jet and tube need to be free from blockages but I found that my problem was some of the tiny holes just under the throttle butterfly were blocked. Each carb has a small opening downstream of the butterfly which is the main fuelling directly from the pilot jet, BUT…. Just under the butterfly you will find 3 extremely small holes and these also seem to be part of the Pilot circuit. They are very difficult to get at to clean and almost impossible to test, but I found a very small wire that I managed to use to check the holes, and then used compressed air to thoroughly clean every airway I could kind.

I also decided that the mixture setting was wrong, the first carb rebuild I did I set the mixture to 2.5 turns out which seemed to be what most people use. But I think this is too rich, and having now set all mixture screws to 2.25 turns in I’ve noticed the bike starts better and may also have helped with the throttle problem above.

The End:

This has taken me ages to write-up so I hope some of you guys find it helpful and maybe you will not need to do all the installing / removing and testing I’ve done and just fit some preloads spacers when you change your springs and oil.
If you have any questions, just ask, I’ll do my best to help

Kind Regards
HondaDog - Carl

Ahhhh

Images.....

Anyone got a simple way for me to get the images up here so you can see what ive explained.

Any help and guidance would be great Guys
HondaDog

Hi , are you still active on this forum?

Hi Luke

How can I help ?

Or send me a PM

Carl

https://cimg5.ibsrv.net/gimg/cbrforu...1acca18018.jpg
Hi ,
I have just purchased a 98 model CBR1000F with 58000Km on the clock . I have booked in for service and tune up next week . I am getting what I can best describe as a "bounce" when I sit on a cruise speed . Going through the gears it is fine but when I sit on a speed it happens . I was thinking this was chain bounce so I have checked and there is a stack of movement up and down in the chain .I can feel a vibration in the hand grips as well . I will get the shop to put on a new chain and sprockets now as well.
I also thought it may be the front suspension and i googled a few things and came across your post . Very helpful . On checking there is some play in the suspension from when I am riding along and apply the front brakes . The suspension travels down freely before it starts to work . I have yet to check the pressures (air assisted suspension) . There are no fluid leaks that I can see . Just wanted to get your thoughts ?

spring rate? maybe You could send me the fotos yo guanacofilms@gmail.com?
 

Hi,
I'm in the process of rebuilding my std front end at the moment, looking to upgrade to suit my weight and keep the desired sag, I found this extremely useful and never seen such a detailed project undertaken with results to match.

Respect.

Guys - good thread - can I just confirm (for my 1996 CBR1000f) the fork oil air gap is measured with the
forks vertical, springs removed and top tube fully pushed down into the bottom slider ?

Thanks