cb1100F fork change

[barryadam]

Thanks NIls.

After reading every single thread I can find on fork conversions for a 1979, I have a couple of questions.
When going to 39 mm forks, do the Prolink triple clamps have the same geometry (trail / offset) as the 1979 originals?
Is the rake difference between the 1979 and Prolink only in the frame head tubes ?
If the Prolink triples and forks are used with 1983 CB1100F wheels and rotors, and 1982 CB750 twin piston calipers and brackets, will the rotor spacing and caliper mounting be in alignment to work?
For the above combo, which axle, the Prolink or 1100F? I assume 1100F speedo drive and custom spacers will be needed.

[Don]

We need to get Dave McMunn to comment here - He's done several 39mm conversions (including mine) and is really familiar with which pieces work with each other

The 39mm triple trees from a ProLink keep the rake and trail the same as stock when used on an early model and they're perfect since the instrument mounting tabs are the same as an early model. THe fork tubes are the same length as your 35mm ones, so you can stick with clip on handlebars - There are some Honda Interceptors which used 39mm clip-on bars about the same size as early model Sportkit bars . . . . they show up on eBay from time to time

viewtopic.php?f=24&t=4805&hilit=interceptor+bars

If you don't really care for the clip-ons, you can use the shorter 1100F forks and devise some new way to mount your instruments. The calipers and hangers from a 900F (probably 750F as well) work on the ProLink forks to give you the double piston front brakes - You can slide a complete 2.5 inch wide 1100F front wheel with rotors into this setup. If you use the 1100F 18 inch wheel, you'll need to lower your stock '79/'80 fender half to three quarters of an inch to make it look 'right' but this is easy to do by drilling new mounting holes in the fender brace. I have seen some guys who go to the trouble of grinding away the ProLink reflector mounting bosses so as to keep the reflector up higher where it is on a stock early model. I think that's probably worth the trouble . . . . personal preferences apply of course

For an '80 model, the complete 1100F rear end is a pretty simple bolt in - Everything fits . . . . swingarm, caliper and mount, trailing arm, wheel/rotor and the nice chromed chain guard. All you need is a 104 or 106 link chain. On the '79, you'll have to do something about the CBX's smaller swing arm bolt. Dave had a matching bushing machined when he put it all on my bike, but some guys just enlarge the holes in the frame and the rear sets to accomodate the 1100F swingarm bolt

The ProLink/1100F upgrades really turn a CBX into a much nicer rider - Nearly a 'night and day' difference in my personal experience

Don

[barryadam]

Thanks Don.
I'll have to keep an eye out for 39 mm Interceptor bars.

I appreciate you adding some details like that.
I've decided on all the major conversion parts - just need to source a few more items.

Barry

[johnod]

Thanks Don.
I'll have to keep an eye out for 39 mm Interceptor bars.

I appreciate you adding some details like that.
I've decided on all the major conversion parts - just need to source a few more items.

Barry

I,ve collected the parts for the same change, I found a set of bars on Ebay, unfortunatly, I can't remember what from, they may well have been interceptrr bars, they came with a spacer about a 1/4 inch that can be insalled or not by the looks of it, below the clipon. They are about the same hieght as the sport bars which is what I have. About the only difference I can see is the sport bar has a slight offset in the casting putting the actual handle part slightly closer to rider, the "new" bar lacks that step.

[NobleHops]

We need to get Dave McMunn to comment here - He's done several 39mm conversions (including mine) and is really familiar with which pieces work with each other

The 39mm triple trees from a ProLink keep the rake and trail the same as stock when used on an early model and they're perfect since the instrument mounting tabs are the same as an early model. THe fork tubes are the same length as your 35mm ones, so you can stick with clip on handlebars - There are some Honda Interceptors which used 39mm clip-on bars about the same size as early model Sportkit bars . . . . they show up on eBay from time to time

viewtopic.php?f=24&t=4805&hilit=interceptor+bars

If you don't really care for the clip-ons, you can use the shorter 1100F forks and devise some new way to mount your instruments. The calipers and hangers from a 900F (probably 750F as well) work on the ProLink forks to give you the double piston front brakes - You can slide a complete 2.5 inch wide 1100F front wheel with rotors into this setup. If you use the 1100F 18 inch wheel, you'll need to lower your stock '79/'80 fender half to three quarters of an inch to make it look 'right' but this is easy to do by drilling new mounting holes in the fender brace. I have seen some guys who go to the trouble of grinding away the ProLink reflector mounting bosses so as to keep the reflector up higher where it is on a stock early model. I think that's probably worth the trouble . . . . personal preferences apply of course

For an '80 model, the complete 1100F rear end is a pretty simple bolt in - Everything fits . . . . swingarm, caliper and mount, trailing arm, wheel/rotor and the nice chromed chain guard. All you need is a 104 or 106 link chain. On the '79, you'll have to do something about the CBX's smaller swing arm bolt. Dave had a matching bushing machined when he put it all on my bike, but some guys just enlarge the holes in the frame and the rear sets to accomodate the 1100F swingarm bolt

The ProLink/1100F upgrades really turn a CBX into a much nicer rider - Nearly a 'night and day' difference in my personal experience

Don

I'd add a couple of minor things to this post - if you're using the stock CBX wheel in the 1100F swingarm you will need to shorten the left side wheel spacer by 6mm and you will need to shave the right side swingarm collar by 1-2mm so the dust caps will fit. As Don said, go find Dave McMunn's wisdom on this topic, he is far more fastidious than I with stuff and will help you get it perfect. Also: at 106 links my (18" stock) rear tire contacted (and trashed) my rear fender. At 104 (with a bobbed fender), it's fine.

N.

[Don]

To continue the discussion, Dave and I did some playing around with the front end on my '79 a couple weeks ago

I switched from the ProLink 39mm front end to one from a Canadian 1100F and I'm very happy with the results

The ProLink setup is quite an upgrade - The difference when you ride the bike hard will be immediately noticeable. The front end is much less flexible and the forks are very compliant . . . . great ride even over the roughest of roads. My only real problem with that setup is the really excessive nosedive you get under hard braking. If you're using even 50% or so of the braking power you'll compress the forks just about all the way . . . . and then if you hit any sort of bump while you're braking and cornering hard, the excitement will really begin!! I tried adding some air to the forks to improve things and they did behave better with 7 or 8 pounds of air in them. Many guys will tell you the early models don't need air because the front end is so much lighter than on a ProLink, but my opinion is you'll need to do *something* to get things even close to right - Maybe slightly heavier fork oil, maybe a longer spring spacer to firm things up a bit, but I quit messing with mine when I found that a Canadian 1100F front end would fit . . . . because it comes with the TRAC ant-dive setup which Honda used successfully on many, many bikes, right up and into this decade - My ST1100 uses TRAC and it squats under hard braking hardly at all compared to my X with the ProLink front end

I only have about 500 miles on the new 1100F front end, but it's a *huge* improvement over the ProLink setup, IMO. You have adjustable compression dampening with the knobs on the top of the forks and you have 4 levels of screwdriver TRAC adjustment on the bottom of the forks. The '1' setting is almost no anti-dive and the '4' setting is almost no dive at all, so the '2' or '3' adjustment is probably what you need, depending on your weight and whether you ride 2 up or not - The '2' position with the upper compression dampening set on '1' is about perfect for me, riding by myself

The 1100F upgrade is at least as much better over the ProLink forks as they are above the stock setup. The major advantages are:
1.) A beefy (and good looking) built-in factory fork brace
2.) The stock '79/'80 fender fits perfectly by just enlargeing the stock holes - You have to drill new holes about 3/4 inch up to make the fender work with the ProLink forks
3.) The compression adjustment is really nice - You don't need air nor do you need to mess with mixing custom fork oils or playing around with spring shims
4.) The TRAC system is . . . . incredible!! - You can grab a big handful of your new dual piston brakes and still have suspension left to handle those unexpected road irregularities you run into when you least need to encounter them

The only disadvantages that come to mind is maybe the complexity of the system or the extra unsprung weight - But the system works so well that you won't notice anything is any heavier . . . . if anything, it makes the bike feel lighter

The Canadian setup we bought came with aftermarket fork tubes by Frank - http://www.frankmain.qpg.com/ - If you can't find a Canadian 1100F front end, you could just buy a set of the US version forks and then get yourself a set of the longer for tubes from them. You would have to add a longer spring spacer to make up the difference in length and you'd need to have a welder add an appropriate extension in the middle of the top adjustment rods, but both would be easy enough to do. Find a set of US version lowers for $100 or so and rebuild them and add the new tubes

You can use a stock ProLink tripletree and everything will fit - We used a lower 1100F clamp, the ProLink upper and steering stem . . . . it all fit together perfectly

I predict you'll really like the 1100F front end . . . . but if you don't, I think you'll find plenty of eager buyers wanting to buy it from you if you take it back off ;)

Don

[EMS]

Sign up on Glenn's CB-F site and ask for a set of forks from a CB1100F. You should be able to get a set there for a decent price. Those guys take them out of their Fs all the time and replace them with better stuff