a_morti

Hi all,

I am a newbie here to pick your technical brains.

I have a Honda CB-1, my second one now after having my first for 6 years, deciding to "move up" then 3 years later after 2 fireblades and a 955i daytona, deciding I want another CB-1. I am going to upgrade from the single disc sliding caliper forks, to VTR forks. I know VTR forks are not the best out there, but they:

• have the right caliper mounts
• were available cheaply
• have some adjustment (CB1 forks have none not even preload)
• allow me to keep my triple trees
• allow me to use the CBR400 front wheel that I want to use for that great Honda six-spoke effect. The wheel is the same as a VFR750 94-97 front.

Anyways, my questions relate to the original forks. I have sourced a bent pair very cheaply. I will have the forks in bits, and naturally will replace all seals and bushes with Honda OEM. I will be shortening the fork by 15mm by using my own stanchions, and shortening the spacer to suit. Are there any well-known CHEAP mods I should be doing while the forks are in pieces? What's the recommended oil weight and air gap? I weight just 150lb, and the CB-1 is probably slightly lighter than the VTR. I read that VTR spring are a little light, but think that would likely cancel out.

I plan to use a full brake set up from e.g. CBR929,954,600RR. These are later calipers than the VTR with bigger pistons.

Thanks in advance,

Aaron

a_morti

My CB-1:



A picture of another CB-1 with VTR forks:


The forks I bought for £25 delivered (messy, but hopefully the bottoms are recoverable):

Stumpy

Pm hawkrider he has the answers you are looking for.

Thomas

Tweety

Actually the only worthwhile mods to the stock forks is to swap the springs for the correct weight and replace the valving & shimstack...

But some simple guesswork and math says the weight difference is 23 Kg between the VTR and CB-1... Weight bias is roughly the same, so little over 50% of that is on the fork, ie ~12 Kg... You weight 68 Kg and the VTR forks are optimal for around 45-50 Kg on the VTR... "Add" 12 Kg to that number and by estimation they should be good for 57-62 Kg on the CB-1...

I'd say that's close enough to what you are looking for... That means that for normal road conditions, the OEM springs and valving will be on the soft and comfortable side but decent enough... Not for ***** out roadracing though...

For brakes, I'd look for the 954 or SP2 caliper & M/C since they have slightly smaller pistons than the others (929 & SP1 are the larrgest)... Ie still a lot larger than the VTR's and CB's but given the "soft" fork they should be easier to modulate while still giving you more than ample stopping power...

For all the tech specs (airgap, oils spec), plus some valuable step by step for assembly go download the service manual, I have it linked here www.tweety.se/links.php

Keep in mind to set the adjustments correct before assembly, most people forget that and end up with the adjustments frosen and need to do it all over...

a_morti

Sounds perfect, I am not about *****-out riding anyway these days. If I were, I wouldn't be riding an '89 400! The rear shock is a replacement unit from Hagon which has preload and "damping" adjustment, so I should be able to get it all to match nicely.

I will have a look at your link, could be very useful and has already given up "air gap 130mm, fork fluid "honda suspension fluid"" which I think I remember is just ATF?

I take it you mean that e.g. I have to ensure the adjuster is lined up? I have had some 96 Fireblade forks apart before, and more by luck than judgement I got the forks back together correctly. I think it's the old addage, slow and steady wins the race, I am usually ok at remembering how things came apart.

Thanks very much for your help!

Tweety

Actually it says "Pro-Honda Suspension Fluid SS-8" which is 10W according to spec... So any good quality fork fluid of 10W should be a good replacement...

As for the adjusters... Well, yes and no... It means you need to set the rebound rods the same, or your adjustements are different for the different legs and could end up completely wrong if you are unlucky... Here's a quote from when Hawkrider/Greg explained it a while ago...

Another solution is to not disasemble it completely... But that's up to you...

a_morti

I think I understand, and I am sure it will all become clear.

Due to the job I am doing swapping bits between forks, and replacing all seals and bushes, I will have to take everything apart. I look forward to the smell of old fork oil with enthusiasm!

Tweety

Yeah, I forgot... Your fork internals are also bent...

Ooohhh yeah! The smell of rotten eggs are a nice way to clear your sinuses...

lazn

Fork oil smell isn't as bad as supercharger oil.. Found that out last weekend.

1971allchaos

Yeah, lazn I agree with you, I thought toastie supercharger oil had to be the worst smell, Then i opened up a 8.8 Chrysler limited slip Third member with 2k-plus miles on the clicker, and a screaming bearing...
Just ain't a way to describe....Yuck.....

Tweety

Well... try fork oil that should have been swapped some 10 years ago and now have separated into three distinctive fluid layers... I was very close to vomiting, trust me... And the clothes I wore still stink despite being washed...

lazn

The thing with supercharger oil (and probably other high performance oils too) is that it is largely made of animal fats, it literally rots after enough time and then gets burnt from heat..

8541Hawk

And why do you think the term "Fish Oil" is used for stock suspension fluid......

But I'm with Tweety on this one. Until you experience the fork oil spuge you can't really image how bad it can be....

JamieDaugherty

Stock might be 10w, but it's best to use 5w. Don't use the SS stuff, go with the Honda Pro Oils 5w in the black bottle.

While you are in there about the only thing that I would suggest is getting rid of the float on the shim stacks. By that I mean there is a 12mm shim against the face of the valves instead of a 17mm one. That shim holds the rest of the shim stack away from the valve, thus "floating" it. Take that shim out and place it into the rest of the stack where it fits (the stack should taper evenly from 17mm to the 8.25mm clamp shim). This doesn't come close to matching the performance of aftermarket valving but helps, and it's free!

Good luck!

nath981

+1 I tried ATF when I didn't have any 5w and ended up getting rid of it. I think it varies but ATF can be as much as 15w. .....5w is good IMO....more responsive.