Topic: Contemplating a GSXR front end swap - few questions

[ncstatecamp]

so my old 72 cb750 has a few front end issues, rusty/pitted upper tubes, dented chipping fender, and more recently my upper triple mount cracked (chicago pot holes... yay!). Instead of replacing all these bits and pieces I'm contemplating doing a front end swap. I've read through a few threads, lots of info, and the swap seems pretty straight forward.

Correct me if I'm work but buy gsxr 600, 750 or 1000 front end, swap the steering stem with a conversion stem and bearings kit from cognitio moto (simple quicker way), bolt on.

Now for my questions.

1. Why do people always seem to put a harley wheel?

2. Anybody whos done this conversion, hows the ride, besides way better breaking, does the front end feel heavier, more cumbersome etc?

3. I believe there's been an issue with fork tubes running into the tank, any method around this?

4. Any reason I shouldnt do this?

[calj737]

There's a member in SoCal (cb750caferacerfan) who's selling an entire front end for this swap if you need a good, reliable source of some components.

As to your questions:

1. Why do people always seem to put a harley wheel? - They don't, some use the custom hub from CognitoMoto which laces to a spoke rim (up to 3.5" for the GSXR fork spacing). Those who use the Harley rim do so out of costs (Harley hubs are cheaper).

2. Anybody whos done this conversion, hows the ride, besides way better breaking, does the front end feel heavier, more cumbersome etc? - Excellent. Way more stable, silky (could well be the new tapered bearings contributing to this) and great braking.

3. I believe there's been an issue with fork tubes running into the tank, any method around this? - This tends to be cause by the reduced offset in the stem/fork tube and using clip-on bars with the GSXR top clamp. Cognito also makes/sells adjustable offset triples to restore a deeper offset (effecting rake/trail too) and even have riser clamps available as a model so you can run bars.

4. Any reason I shouldnt do this? - Don't if you're planning a restore or Concours bike  Do if you want a really nice upgrade to a vintage bike but prefer some of the advantages of modern brakes and handling. You can achieve some of this for less with a GL front end swap (larger forks, dual disc ready) a fork brace, and installing cartridge emulators. It won't be quite the same, but may be less expensive and still a very nice upgrade.

Here's a recent 750 from Cognito with the GSXR swap but stock rear:

[ncstatecamp]

Thank you very much for the direct answers! I usually get like 1 or 2 questions answered and then the thread goes on a tangent.

A few more questions if I may.

1. I dont really see anybody use a GSXR front wheel, which I assume bolts straight on with no mods, do they use a spoked sub for looks?

2. Nice! Exactly what I want to hear. So I currently have the tapered all ballz head kit, should I expect even smoother or similar?

3. I will have to look more into this. At the mention of the trail and rake, how does the front end bolted on with just the stem swap affect the rack?

4. Ha my bikes way off concourse so sounds perfect. I was thinking the GSXR front end just b.c parts are much more available then the GL, but if I were to go that route, any particular year set I should be looking for?

[slikwilli420]

There are a lot of geometry implications that go into this as well. Everyone raves about this conversion, but there is one way to do it right, and a thousand to do it wrong. Cognito Moto makes all the right parts for the swap, but personally I don't see the real need. Take a look at FunJimmy's project. He swapped a non-USD front end from an R6 onto his and it looks great, handles tons better and fits the vibe of a vintage bike. My personal opinion is that this is overkill for the riding 99% of people do and it has been done to death. If you want to be unique, a USD swap isnt going to get you there.

[ncstatecamp]

Im sorry I'm not sure I know what you mean by USD (united states dollar cant be right?). The reason I'm doing this if you read my first post is my front end either needs a full rebuild, using old tech/old parts or build it up using new stuff. I would custom machine my own stuff but atm I don't have access to a mill or lathe.

[slikwilli420]

Upside Down Forks. Lingo for the more modern front ends found on many new bikes. Fixing the old will be quite a bit cheaper than swapping over but if you want increased performance, newer can be the easiest route. If you need help with triple trees in a custom design (spread/offset), let me know.

[ncstatecamp]

Ahh gotcha, that makes a bunch more sense. Also PM sent.

[slikwilli420]

And replied to!

[calj737]

1. I dont really see anybody use a GSXR front wheel, which I assume bolts straight on with no mods, do they use a spoked sub for looks? - some do use the front GSXR wheel, but then have to deal with either a spoked, stock rear, or fab an adaptation for the rear swing arm of the GSXR to the CB to run the GSXR rear wheel. Or they run GSXR up front, CB in the rear. So, yeah, it's looks and easier.

2. Nice! Exactly what I want to hear. So I currently have the tapered all ballz head kit, should I expect even smoother or similar? Yes.

3. I will have to look more into this. At the mention of the trail and rake, how does the front end bolted on with just the stem swap affect the rack? There are some effects of reducing rake (smaller offset) in terms of steering, but it's truly difficult to say that they actually show themselves on the street. I've ridden quit a few GSXR swapped CBs, and I don't perceive any adverse effects. If I were tracking the bike, sure, I'd be more inclined to tinker with it, but for the street stock CB or stock GSXR works well in my opinion.

4. Ha my bikes way off concourse so sounds perfect. I was thinking the GSXR front end just b.c parts are much more available then the GL, but if I were to go that route, any particular year set I should be looking for? I'm not a GL guy, so I'm not a great resource for this. I believe they're fairly comparable in the overlapping years of the SOHC bikes, but you want the GL triples too (differ stork tube size and slightly different spacing).

[JWExperience]

I'm using the stock gsxr wheel with a cbr600 f2 rear wheel. They're 91-94 cbr600's I think. The spokes don't match but you can't really see the spokes on front due to the size of the rotors.
You may have difficulty with the cbr rear because your k swingarm is not as wide as my f swinger plus you would have to fab some extra for the rear brake master cylinder.
I'm not completely done with the rear on mine but it will only take a little tinkering with spacers and a brake stay.

Sent from my iPhone using Tapatalk

[ncstatecamp]

So looking at the Cognitio stem/triple kits, there are a varity of offset options. From my research increasing the offset would effect handling, though im not entirely sure how atm.

But increasing the offset would allow for the larger size tubes more room to turn without running into the tanks as soon right?

Opinions?

[calj737]

Correct

[ncstatecamp]

So what would it do to handling? I think quicker turning but less stable at high speed right?

Sent from my SAMSUNG-SM-G900A using Tapatalk

[ncstatecamp]

Also anybody know what's the cb750k offset stock?

Sent from my SAMSUNG-SM-G900A using Tapatalk

[calj737]

If you use the adjustable offset triples, you have the option of "slowing" your turning down from the stock Gsxr geometry, more towards the stock CB. You also can swap your rear swing arm (depending upon year/model of your 750) to a 550 swing arm. They're 1" longer on most cases which coupled with the adjustable tripled, lets you tinker with a combination of offsets you like.

There's no disputing the geometry numbers affecting the actual measurements, but having ridden a few CBs with GSXr swaps (non-adjustable triples) I personally don't detect any handling issues. I suspect many might not when riding on the street. On a track, dead right you can, but less likely for pedestrian travel.

[FunJimmy]

So what would it do to handling? I think quicker turning but less stable at high speed right?

Sent from my SAMSUNG-SM-G900A using Tapatalk

Motorcycle suspension and geometry is a science. Engineers design and specify a specific set of parameters to meet the performance requirements of the motorcycle. Those specifications differ widely between models. Cruisers, UJM, sport touring and Superbikes are all motorcycles but you wouldn't want the handling traits all mixed together.

Race Tech's Motorcycle Suspension Bible is one of the best recourses on suspension & geometry. Someone previously posted it on the forum but I can't seem to locate it. Highly recommended.

There's lots of readily available information on the topic. I posted a bit here:

http://www.dotheton.com/forum/index.php?topic=57497.msg651257#msg651257

[edwardmorris]

So what would it do to handling? I think quicker turning but less stable at high speed right?

Sent from my SAMSUNG-SM-G900A using Tapatalk

.........Race Tech's Motorcycle Suspension Bible is one of the best recourses on suspension & geometry. Someone previously posted it on the forum but I can't seem to locate it. Highly recommended......

Not the whole thing, but I'm guessing you're talking about this

http://forums.sohc4.net/index.php/topic,147787.msg1759065.html#msg1759065

[FunJimmy]

So what would it do to handling? I think quicker turning but less stable at high speed right?

Sent from my SAMSUNG-SM-G900A using Tapatalk

.........Race Tech's Motorcycle Suspension Bible is one of the best recourses on suspension & geometry. Someone previously posted it on the forum but I can't seem to locate it. Highly recommended......

Not the whole thing, but I'm guessing you're talking about this

http://forums.sohc4.net/index.php/topic,147787.msg1759065.html#msg1759065

Good find! Thanks

[Bikeriderz]

Very interesting info here, Thanks guys!!    I need to do fork seals, but I love the look of a modern, inverted fork setup on a vintage bike, I may have to start looking at boneyard forks....