Gsxr front swap

[tmtrebor]

Basically what year do I want to buy if i want to throw a GSXR front end on my cb750. Sorry, I wrote that from my phone in a meeting so I didn't forget when I got to my desk.

I'm looking at a newer front end off a GSXR (2012 I think) with Brembo calipers and controls for $900 (clipons for $1100) and a 2003 front end off a GSXR 750 for $500.

I was hoping someone would have some info on the difference in sizes to match with the rear wheel and bike.


*updated to match my second post. I was in a meeting and this was a placeholder.

 

[VonYinzer]

I'm not entirely sure what you're asking here...

 

[tmtrebor]

Basically what year do I want to buy if i want to throw a GSXR front end on my cb750. Sorry, I wrote that from my phone in a meeting so I didn't forget when I got to my desk.

I'm looking at a newer front end off a GSXR (2012 I think) with Brembo calipers and controls for $900 (clipons for $1100) and a 2003 front end off a GSXR 750 for $500.

I was hoping someone would have some info on the difference in sizes to match with the rear wheel and bike.

 

[clem]

I obviously don't know everything and don't pretend to but while tires sizes are important there are a few more things that you may want to look into when doing a swap. Comparable wheel travel, damping characteristics, spring weights are a few. Check the dry weights off all motorcycles involved and see how they compare. You don't want a bike that is worse than what you have now. I started a thread in this the suspension section to layout all of the troubles of just slapping a random suspension to a motorcycle and trying to get it to work well....that may take a while to complete. Don't forget about rake and trail too.

 

[tmtrebor]

I obviously don't know everything and don't pretend to but while tires sizes are important there are a few more things that you may want to look into when doing a swap. Comparable wheel travel, damping characteristics, spring weights are a few. Check the dry weights off all motorcycles involved and see how they compare. You don't want a bike that is worse than what you have now. I started a thread in this the suspension section to layout all of the troubles of just slapping a random suspension to a motorcycle and trying to get it to work well....that may take a while to complete. Don't forget about rake and trail too.

Good to know.

I was speaking with a shop here and they made it seem like the things you needed to worry about are wheel size and weight of bike. They mentioned gsxr front ends swapped easily onto the cb750, so that's what I've been looking at. Is this not the case?

 

[focusinprogress]

that's said mostly just because that's the most plentiful and readily available front ends.

Cognito moto makes a lot of parts based on adapting GSXR forks to the CB's, though you'll pay a bunch for them.

people do just get conversion bearings from allballs to get the GSXR forks and triples mounted, but the trail is way off and there's little to no steering feedback and it ends up with twitchy handling.

there's also the issue with wheel....if you run the gsxr wheel you obviously don't have much to worry about other than tire circumference, but you certainly won't make up for bad triple tree offset in tire size if you're using GSXR triples so it's kind of moot.

Best case is a 19" front wheel and tire combo adapted to the GSXR forks and 45-50mm offset triple trees.

 

[irk miller]

Personally, I'm not a fan of the GSXR swap on the a CB750. Regardless, you have to look at which model forks they come from. They come in 2 different offsets- 30mm and 32mm, and 2 different lengths- 720mm and 738mm. The 1000s are actually the shorter fork.

 

[VonYinzer]

End of the day...

Are you after the looks of a USD fork or actual performance upgrades? Which is really more important to you?

 

[tmtrebor]

End of the day...

Are you after the looks of a USD fork or actual performance upgrades? Which is really more important to you?

Looks and performance. Problem is this. I have a 78 cb 750 with a shitty front brake and forks that need a rebuild.

The dual disc looks sick, and I ride about 30 miles at a time max. The caliper is at a shop currently, and they are trying to charge me 200 for a rebuild / new puck. This could go towards the front end with nicer looks / performance. Ride height may need to be adjusted and whatnot, but the cost of the front end (minus the wheel).

Price is not necessarily a problem, as I've put way too much time into this thing now lol. I want it to look super nice.

 

[focusinprogress]

if you're wanting to keep the stock front wheel, you'll be limited to a single disc anyhow.

Is your front wheel spoked or a comstar/mag?

 

[Tune-A-Fish]

Personally, I'm not a fan of the GSXR swap on the a CB750.

And why I used the 07-08 R6 forks 25mm offset 210mm spread 745mm tall >< mm's for preload

 

[tmtrebor]

if you're wanting to keep the stock front wheel, you'll be limited to a single disc anyhow.

Is your front wheel spoked or a comstar/mag?

It's spoked. Do you want it? I want to get rid of it. I thoroughly enjoy this look :

 

[focusinprogress]

if it's spoked why not keep it? or, dmable44 has an older 6-bolt hub spoked wheel that would support dual disc with a custom axle/spacers and custom rotor adapters if you want to keep the spoked look on inverted forks. Or, you can spend big money and buy a Cognito Moto hub that fits the gsxr front end and laces up to stock honda rim, using GSXR bearings, spacers, axle, and rotors all bolt-up.

 

[Tune-A-Fish]

SOHC or DOHC year?

 

[tmtrebor]

if it's spoked why not keep it? or, dmable44 has an older 6-bolt hub spoked wheel that would support dual disc with a custom axle/spacers and custom rotor adapters if you want to keep the spoked look on inverted forks. Or, you can spend big money and buy a Cognito Moto hub that fits the gsxr front end and laces up to stock honda rim, using GSXR bearings, spacers, axle, and rotors all bolt-up.

I'm actually looking into this now tbh... the main problem is that's literally double what i have in the bike (including cost). But, again, costs isn't a huge driver, but it's still one of those "do i really want my fork to be more than double the bike" kinda thing. Then I have to offload the controls and whatnot, which I guess i'd have to do anyway... it is an option though.

 

[clem]

I started with a GSXR 600 rear shock for $16.00. I'll have to dump about another $300 into it for re-valving and a new spring maybe even a longer shaft. So that's $316 right there, throw in the $100 front end + axle then new springs, oil, possible new damping at about another $150 to $200. So what started out as a $116 venture can possibly more than triple in costs. Now my original forks were totally rusted and I chose to dump the rusted rear twin shock setup but you can see how it escalates. I forgot to mention the new front and rear calipers to go along with the rest of it. I'm not trying to discourage you but just bring up what it might take to pull it off. It sounds like you want the bike to work well so I'm sure you'll do the research. I just don't want to be on pins and needles begging my bike to turn in the turns and stay straight in the straights.

 

[surffly]

End of the day...

Are you after the looks of a USD fork or actual performance upgrades? Which is really more important to you?

THIS!

Honestly if you are asking the questions you are right now then you really are in over your head to think about doing this from a performance point of view.

You have a vintage bike, but are paying a shop to get a caliper working?
And then the thought was to swap a whole front end to avoid learning how to fix a caliper?
Really?

At the end of the day there is a crazy amount of math that needs to be done and lots of things to look at and think about to make a suspension change work. Saddly many are jerking off to pipeburn and want to play this dress up game. These are the people that talk about how easy it is to just "swap" or slap on a GSXOEPSPSST front end and be done. Most of them wouldn't even know a good running bike.

Also you have not talked about what the rear wheel would be.....

Screw costs.
Stuff cost money. This is not a hobby to be on a "budget" with.

 

[focusinprogress]

I'm actually looking into this now tbh... the main problem is that's literally double what i have in the bike (including cost). But, again, costs isn't a huge driver, but it's still one of those "do i really want my fork to be more than double the bike" kinda thing. Then I have to offload the controls and whatnot, which I guess i'd have to do anyway... it is an option though.

the issue with that logic is it's more often "cheap" to get into a vintage bike than not.....with the understanding that repairs, maintenance, upkeep WILL almost always exceed the cost of admission to this hobby.

So, basically....you can either just spend $60 on bearings from all balls to toss a complete factory-assembled GSXR front end on and have it look fancy but ride like shit, or you can spend money to get progressive springs and gold valve emulators in your stock forks with new seals and fluid with the rebuilt caliper...install a steel braided line and new master cyl, or you can spend a bit more money than that to get a GSXR front end on there in proper fashion which will be a massive upgrade in all departments....so much so that if you ever grab all of the lever on the front brakes you're more likely to bend the frame then to exceed the capability of the brakes.

 

[tmtrebor]

THIS!

Honestly if you are asking the questions you are right now then you really are in over your head to think about doing this from a performance point of view.

You have a vintage bike, but are paying a shop to get a caliper working?
And then the thought was to swap a whole front end to avoid learning how to fix a caliper?
Really?

At the end of the day there is a crazy amount of math that needs to be done and lots of things to look at and think about to make a suspension change work. Saddly many are jerking off to pipeburn and want to play this dress up game. These are the people that talk about how easy it is to just "swap" or slap on a GSXOEPSPSST front end and be done. Most of them wouldn't even know a good running bike.

Also you have not talked about what the rear wheel would be.....

Screw costs.
Stuff cost money. This is not a hobby to be on a "budget" with.

OK, let me be a little more clear on this. The mechanical stuff is not the issue. I've tore the entire bike/engine down as a project and rebuilt it pretty easily although it took a while due to MBA/work promotions). I've done very extensive car work, never anything bike related outside my mountain bikes. The problem was sourcing the correct caliper rebuild kits and bleeder screw. I went to bleed my brakes and the bleeder sheered off in the caliper, tried an easy out / torch to no avail and then drilled it out. Problem is... I had no idea what size the original bleeders were. To make it easier, I took it to a shop to help source the stuff, they didnt have it in, said they'd do it all for me no problem and give me a new piston. It's been 3 weeks and I'm still waiting. That was outside the scope of my original question, so I didnt feel the need to post it.

As for the good running bike, again, the bike runs fine as is, minus the front brake, but looks like ass. Once I get done with my quarterly stuff I'm going to post a post build thread going into stage 2. The guys at the shop were just telling me options I think. I start looking and see something I like. So, have I done this before? No. But I have swapped forks and whatnot on mountain bikes (obviously I'll be going a LITTLE faster than 25 mph on this fork...) so I understand the effect on geometry and how that impacts handling slightly. That's why I'm asking questions.

 

[tmtrebor]

the issue with that logic is it's more often "cheap" to get into a vintage bike than not.....with the understanding that repairs, maintenance, upkeep WILL almost always exceed the cost of admission to this hobby.

So, basically....you can either just spend $60 on bearings from all balls to toss a complete factory-assembled GSXR front end on and have it look fancy but ride like shit, or you can spend money to get progressive springs and gold valve emulators in your stock forks with new seals and fluid with the rebuilt caliper...install a steel braided line and new master cyl, or you can spend a bit more money than that to get a GSXR front end on there in proper fashion which will be a massive upgrade in all departments....so much so that if you ever grab all of the lever on the front brakes you're more likely to bend the frame then to exceed the capability of the brakes.

and this is what I wanted to know. Like I said, I dont mind buying extra stuff, I just literally have no one that I can talk to about this. The shop has pissed me off a bit, no one I know rides bikes (outside of dirt/mountain) and I'm kinda doing it all from the "I've tore my car down and rebuilt it so I can buy a bike that doesnt run and build that into a fun toy."

The only problem I see right now is, if the performance is not there, why should I drop an extra 1800 on a front end that I can do myself? It seems like there is a performance issue outside of just "stopping better," which I was not aware of. What is the difference here?