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Discussion Starter · #1 · (Edited)
As you might have read in my project thread I recently fitted the front end from a 1984 VF500F Interceptor onto my 1982 CB450SC. There were a couple of reasons I did this, mainly it was because I’m cheap and the CB needed a new front tire. Due to my own negligence I had a VF500 sitting around collecting back fees with the DMV, and after sitting outside for two years it wouldn’t start. Although the VF500 was a little far gone I had a brand new set of Bridgestone Battlax BT45’s in storage for it.

I figured I could swap an entire front end cheaper than I could buy a tire (ha!). Once the idea took hold I started to scour the internet to find out if it was possible, or if someone else had gone down this road. I found a lot of build threads involving fork swaps, but nothing directly pertaining to these two bikes. I used the All Balls fork conversion tool to find out if the VF fork was compatible. As luck would have it All Balls told me that the stem diameters we’re compatible. In fact, the bearings needed were the same ones I would need if I was simply replacing my bearings and keeping the stock fork. What I did not learn from their conversion page was stem length. Stem lengths are not very easy to find on the internet either. They may be out there, but I couldn’t find them. Without taking both bikes apart I couldn’t get a real accurate measure either. I did bust out a tape measure and took some rough numbers that made it seem like it’d work.

This was good enough for me to move forward. I ordered the needed bearings and made a list of what else would be needed. Because I planned to swap over the triple, forks, wheel and clip-ons the only thing I needed was new headlight brackets (but I did decide to get new brakes lines and wheel bearings too). I also replaced the master cylinder as the one from the VF had its cover screws stripped out by the PO and replacing it was more economical that fighting stripped screws and rebuilding it. Because this is my daily rider I waited and got everything in order so I could pull off the conversion in an afternoon.

When fork swap day came around I still wasn’t 100% sure that the VF stem was long enough but I got lucky. I tore down the front of the CB450SC and installed the new bearing races. Although I thought the top race was fully seated it was not, and this lead to the stem getting loose as the race worked its way down, I’m getting ahead of my self though. Once I had the CB front end removed I took the lower triple from the VF and checked the steering stops. The movement was pretty limited on the bottom stop, but the top stop had more than enough space. Out came the angle grinder with a death wheel and I cut down the stops on the frame. I took off about a ¼” from either side and checked again, this time with what seemed like enough room.
The rest of the swap was straight forward. Pack the bearings with grease, seat the lower bearing, put it all together. The All Balls bearing kit comes with a few washers of different thicknesses. For this swap I used the thinnest washer included with the kit under the lower bearing. The VF stem assembly had a spindle washer between the stem nut and the lock nut. The CB assembly did not have this and those parts wouldn’t fit when installed on the CB frame. My reasoning here was that the CB never had it in the first place so I would be OK to run without it on this new front end. After 2500 miles that reasoning seems sound.

The catalyst for the swap was being a cheapskate, but I also recognized the benefits of going from a single disc 33MM stanchion front end to a twin disc 37MM stanchion front end. The front is about 2 inches lower than before which coupled with the 16” front wheel (19” was stock) and twin discs has resulted in a much more surefooted ride that inspires more confidence in its handling and immensely improved braking. This has allowed me to get much more aggressive in the twisties. The brakes are so good now that when panic stopping behind a bus on the freeway a few weeks ago I lifted the rear wheel.
There are a couple of drawbacks however; at first I didn’t have the stem tight enough and the bike wanted to dive when cornering. A few turns of the wrench and that was gone. The more persistent negative attribute of the 16” front wheel is that it tramlines (pulls the bike into and along grooves in the road) way worse than before. This was really unsettling at first but I’ve gotten used to it and I just need to grab the tank with my knees and give it more throttle and it’s fine.

Overall I’m very pleased with the results of this swap. The bike inspires more confidence, stops better and can carry more speed through corners. If better handling and braking are what you’re looking for I recommend this swap or one similar.

Parts used:

Entire VF500F fork from tire to grips

All Balls bearing kit

I think the top nut I used was from the CB

Tools needed:

Metric socket/spanner set

Hook spanner (the one in your Honda tool kit works fine)

Angle grinder to cut down the stops

Hammer and punch to remove old bearing races.


TLDR; VF500F fork will fit no problem, here is how.

Put your CB/CM on the center stand and using a jack and some wood, get the front end off the ground.

Remove everything in front of the gas tank.

Remove upper and lower races using a hammer and punch.

Replace new races using the old races and a hammer to drive them in. Make sure they are FULLY seated.

Take your VF500F stem and remove the lower bearing and any washers.

Take the thinnest washer from the bearing kit, put it on the stem followed by the dust seal.

Drive the lower bearing onto the stem. (it helps to freeze the stem first)

Cut the lower steering stop using and angle grinder, hacksaw or file. You'll need to remove about 1/4".

Insert the stem into the frame.

set in the upper bearing.

Put on the upper dust seal.

Install part #5 (parts fiche just calls this "thread", its the bearing retaining nut) from the VF500F stem assembly

Install the VF500F top bridge.

Install parts #18 (washer) and #16 (stem nut) from the CB/CM assembly

Put the rest of the front end together.

You want the stem tight enough that there is slight drag when turning the bars with the front wheel off the ground.

Your CB/CM key switch will not fit the VF500F top bridge. I used a new key switch mounted on a plate bolted to the gas tank mount.

Your CB/CM fork ears will not fit the VF500F fork. I used aftermarket ones I was using prior to the swap.

Part #5 from here

vf500 stem.jpg

parts #16 and #18 from here

cb450top bridge.jpg

Cut the steering stops to look like this

20180106_142035.jpg

Now go ride it!

The CB450SC stem is 8 5/8"

The VF500F stem is 8 3/4"

CB forks are 31 1/2" long (axle center to fork cap)

VF forks are 31 3/4" long (axle center to fork cap)

VF clip-ons are 1 1/2" where they attach to the forks with 1/4" of fork above their retaining clips.

Fork swap resources:

https://www.allballsracing.com/index.php/forkconversion

Steering Stem Bearing Sizes list

After the swap your bike will resemble this (winding road not included)

20180310_162956.jpg

I'll be happy to answer any questions, take more measurements or load more pics if anyone would like me to do so.

I hope this is helpful to anyone looking at a fork swap.

EDIT: fork lengths added.
 

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How much shorter were the VF500F front forks compared to your original CB450SC forks & how does it handle now with them and the 16" front wheel at high speeds ?
 

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Discussion Starter · #3 ·
I would need to remeasure the fork legs themselves to be 100% accurate but the difference is only an inch or so. They sit lower because the fork legs protrude above the top clamp for the clip-ons to mount to. I will be able to measure them tomorrow for you. I've had this bike up to 103MPH (GPS speedometer) with this set up and its completely stable. It is not twitchy in anyway at high speed. Handling is comfortable and predictable. Whether its on the freeway or a winding road it is compliant and responsive.
 

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"This was really unsettling at first but I’ve gotten used to it and I just need to grab the tank with my knees and give it more throttle and it’s fine."

This doesn't sound like a very good situation. what happens if acceleration isn't an option?
 

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Discussion Starter · #5 ·
Where I ride, in the bay area, the highways often have deep groves that do not follow the lane. These want to pull the bike into them. This happened to me on my VFR700F2 (16" front), my VF500F and the CB450SC prior to the fork swap (19" wheel). With how light the CB450SC is the 16" wheel does want to follow these grooves more than before and more than the other two bikes I listed. Often my solution as I said is to hold the bike tighter with my lower body (I always try to keep a loose grip up top) add power and lean away from the groove. There are times when I am in traffic and accelerating isn't an option. When I can't add throttle I do the same thing, knees on tank lean away from the groove. The difference when I can't add throttle is that it will wiggle a bit more coming out of the groove. It can be unsettling but has never caused me to be afraid of crashing or thrown me off course. It's not that the bike is unstable, I'd equate it to rolling resistance. It is harder for a smaller wheel to overcome and obstacle. A good analogy might be the recent trend to 29er wheels/tires on mountain bikes, which have come to popularity because they can more easily roll over terrain. By going smaller I have made it harder to roll over the lips of the grooves. In all honesty it's far less troubling than when I rode bicycle in San Francisco on a road racing bicycle with 22MM tires and had to deal with street car tracks.
 
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Try raising the front tire pressure a couple of pounds, that may clear the rain groove problems. Cal Trans got really carried away on some sections of the freeway.
Save your ignition lock, they are in very short supply used and NLA new.
 

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Discussion Starter · #7 ·
I replaced my ignition lock months before the swap. My tail light was no longer working and I traced the problem to the ignition lock. For months I had to wiggle the bottom plastic bit to get my tail light working and it eventually quit all together. I'd even pulled it apart and cleaned the contacts. It hit the trash a long while ago.
 

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Discussion Starter · #8 ·
Try raising the front tire pressure a couple of pounds
Interesting you suggest raising pressure. I was actually thinking of lowering the pressure, I checked my tires temps (with my hand) after 10 miles of riding on straight dry pavement (as you suggested in another thread of mine) and I found the rear to be warmer than the front. My train of thought here was that a lower pressure would make a slightly larger contact patch and might raise the temp. Will a higher pressure overcome the grooves better because of less sidewall deflection?
 

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Discussion Starter · #9 ·
How much shorter were the VF500F front forks compared to your original CB450SC forks & how does it handle now with them and the 16" front wheel at high speeds ?
I busted out the tape measure today and I found the CB forks are 31.5 inches while the VF forks are 31.75 inches, both measured from the center of the front axle to the fork caps. the VF clip-ons are 1.5 inches tall with .25 inches of fork above their retaining clip. I have edited the original post to reflect this.
 
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Sidewall deflection can be a cause for the rain groove following. Softer tread area can also follow the grooves easier. Raising the pressure could correct either issue.
In checking tire temps it's not front vs. rear. It's center tread vs. tread edge of any given tire.
 

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Discussion Starter · #11 ·
Temps center and edge were pretty much the same. I really need to invest in a quality tire pressure gauge. I don't exactly trust the ones at the gas station.
 

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Temps center and edge were pretty much the same. I really need to invest in a quality tire pressure gauge. I don't exactly trust the ones at the gas station.
I like the ones that have a small round air gauge on them with a pressure release lever;they seem to remove less air from the tire compared to the long silver ones.
 

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Yep and you can use that pressure relief button to bleed down to your desired pressure after overfilling instead of filling/checking/filling some more...
I recommend one with a 0-60 psi scale, a 90 degree chuck for tight spots (16" Comstar rear) and a rubber boot around the gauge so it doesn't smack the ground too much.

Jerzee Customs - Tire Pressure Gauges
I've had the second one on this page for nearly a decade, bought it locally at one of the auto-parts chain stores for near $20 if memory serves.
 

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Discussion Starter · #14 ·
I purchased the second one in your link. Bought it from the same seller but from their eBay store. Shipping was cheaper that way. I'll get a chance to use it later today on my jeep, but first impressions are it's a quality piece. Thanks for the recommendation.

On another note, have you ever heard the saying "if you think it's the front it's the rear, and if you think it's the rear it's the front"? I can't remember where I heard this but it was in reference to race car handling. Anyway whoever said it was right. Over the weekend I had a Bridgestone Battlax BT45 installed out back in 130/90-R15 and the tramlining problem is virtually gone. I've only clocked about 250 miles on the new tire but so far things are looking better.

My old tire, a Shinko 712R was pretty flat in the middle from commuting. I suspect this was the cause of my problems. Time will tell.

I'll try to keep updating this thread and the original post as time goes on. I have yet to change the fork oil or play with the TRAC settings. I also want to measure triple clamp offset, rake, trail and wheelbase and add those figures into my post.
 
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