78' CB750 Front Swap

Cody.linhart

Cody.linhart

Been Around the Block
Hello,

I picked up a complete front end from a 2001 Yamaha R1 and I'm planning on swapping it onto my 78' Honda CB750.

Does anyone have any resources or advice on how to keep as close as possible to the stock geometry of the CB750?

I was thinking of possibly using fork extenders if that would help any with any issues?

Thanks DTT!

Here are some pictures of part of the R1 front end. Needs a good scrub down but it's all there!

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Do you know the offset and lengths on the R1 front end? That's the first place to start on whether or not you'll be able keep the stock geometry. I suspect the rake on an R1 is much different than the CB750.
 
I'm not 100% sure. I wasn't planning on doing a swap but I came across this entire front end for a price that I couldn't walk away on. So, I guess I haven't ever researched too much about doing the swap before I started..

So get the offset and tube lengths and what's my next step?


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First thing is measure your stems. You may have to swap or machine stems, run a spacer or something else. If someone has done this swap, all the figuring out may have been done already, so search for that too. If'n the R1 stem works, then I'd get a tapered bearing kit from All Balls to do the swap to R1. Mock it up and measure your rake and trail. Before anything, you should know your comparative fork length, as shorter forks are going to drop your nose and alter your rake and trail. The R1 triple's offset will also likely alter your wheelbase if it's different. You're also likely going to a smaller rim size on the R1, so there's another number to figure out your drop.
 
Yeah I'll have to research to see if someone else has done it. I know De Bolex did it on a CB750 so it can be done. Thanks for the advice! I've got a long way to go on this haha.


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that does look really good; adds beef to an otherwise bony front end the CBs have.

i'd shoot them an email and ask about it.

i think joker machine or somebody makes something for conversions although it might be for gsxr front ends.
 
I agree! I'm planning on sending them a quick email so hopefully they'll be able to steer me right (pun intended)

I'm pretty sure CognitoMoto makes the conversion but it's extremely pricey. Does Joker machine have a website?


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it might be cognito moto...i don't know, i just remember coming across it recently as i plan to do a front end swap somewhere down the line.

you might be able to source your own parts from whatever the kits come with. that way you'll know what you need and why.

http://m.jokermachine.com
 
That front end on that CB doesn't have enough offset to make the CB rake work. If you go that route, you will have too much trail. You need a set of triples with a closer offset to what the stock bike has. I think that cognito incorporates that into his custom triples so while it may be pricey it would be worth it.

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I have the forks and complete triple tree from the R1. I should be able to get bearings and make it work.

Or to get closer to stock I could have my stem from the CB punched into the triple tree for the R1 correct?


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So I guess now that I have the frame completely stripped, the R1 front end all cleaned up and ready to go, what would you all recommend I do next?

I have some ideas but with this being my first build I want to make sure I'm doing this correctly.

Thank you all for your advice and help with this!


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Cody.linhart said:
So I guess now that I have the frame completely stripped, the R1 front end all cleaned up and ready to go, what would you all recommend I do next?

I have some ideas but with this being my first build I want to make sure I'm doing this correctly.

Thank you all for your advice and help with this!


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Click to expand...

any frame modifications you plan on doing i.e. adding detabbing, adding brackets, a tail hoop, etc.

now would be the time to get it blasted & powder coated if you want.
 
I would definitely be certain you get the r1 front end straightened out and be certain it works and you have the stance you want because you start chopping or welding, and definitely don't powder coat anything until you know for sure you have everything how you want it, I would get the front end squared up, then do a light mock up of everything to make sure it's stanced how you want it, then powder, paint, etc.
the last thing you want is to pay a bunch for powder and then figure out something doesn't fit, or is stanced the way you want it.


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Yeah I agree.

But, would it work to get close to stock dimensions if I had the stem punched from my R1 triple tree and replaced with my stem from the CB triple tree?

Or is there an easier or better way to get better dimensions?

There is always the "buy a new triple tree from Cognito" route but if there is a cheaper route I want to choose it.


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Cheap won't get you proper rake and trail
And neither will swapping stems, this will only make it easier to mount in the neck of the CB frame.

I don't the measurements but if this setup will have all the wrong geometry then you either have to get a prefabbed triples or use the CB stem in the R1 triples and then get the neck of the CB raked (cut the weld on the neck to the frame, have it set in a jig so it can be professionally welded back at the correct angle)

Either way this endeavour isn't cheap
And don't think that you can just stick it on there and hope for the best because th best is going to be shopping cart front wheel with your bike tossing you off
 
Just to clarify, the offset is the distance between the centerline of the steering stem and the centerline of the forks. Changing the stem will not have any effect on this measurement. This one is important because it directly affects the trail. Newer bikes have much steeper rake or less in terms of degrees. I believe the cb falls in the 27 degree range where newer bikes are around 24 and maybe below that. Older bikes had more offset in them to make up for the relaxed rake and keep the trail in a desirable range usually well below 4 inches. News bikes have much stiffer frames and can handle the force of the reduced rake angles so the need less offset.
Either custom triple clamps or serious frame mods are required to make your front end work.

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