Topic: How to tackle converting front end forks, rear wheel swap?

[fastbroshi]

   I saw this bike on ebay, and it got me thinking, how the owner went about it.  How is this tackled first?  It looks like the rear sprocket is about the same size, but I doubt it's spot on.  If it's close, how do you get it spot on?  And what measurements are needed to do this. 
  As far as the front goes, I guess he just hacked the neck off of the donor and welded it back on?  Would you have to replicate the original's rake and such to get it to handle safely?  I've been wanting to convert my '76 550 to cafe and this just throws some more ideas into my head.  This one started out as a 550 as well.  For those of you with answers, feel free to be as pedantic as possible. 

Tim

[ProTeal55]

Those are pics of that crazy Ebay bike...
Very sick indeed....

I am sure he either welded on the neck of a newer bike, or found a newer front end that would
adapt to the CB neck. Either way is possibile. I would think chopping the neck would be easier, but you would have
to insure the rake,trail,etc are all the same. You could increase the rake at this point, but you would take away from the
handling a bit by doing that...
OHIOCAFERACER has a bike on his site with a late model GSXR front end on it , and looks killer. I would get ahold of him
and see what all was involved in the swap. I believe user CD811 also has a newer sportbike front end on his CB project as well...

[Faust]

I can't enlarge the picture enough for a really close view, but, those look like '77-'78 550 forks with a dual disk conversion.

[fastbroshi]

Nope, it's the entire front end off of a late model Suzuki SV650.  The owner said he kept all the stock controls.  Been trying to contact him on this topic.

[Lumbee]

...u guys have probably seen cd811's bike...

http://www.sohc4.us/forums/index.php?topic=3036.0

he has a GSXR front end...I saw the bike in person this weekend...very nice...anyway I got some specifics on how he did it.  He said he pressed out the stems of each triple tree, then bolted the 750 stem into the GSXR tree, and it bolted right up.

...as far as rear wheels go...you should look into a 90's FZR 600 rear wheel...it will line up, though you will need to cut spacers.  When it comes to modifing a rear wheel that will fit a 750 first and foremost it will need a [reletively] skinny hub.  That will allow u to line it up...after that its just a matter of spacers, and then modifing a brake to fit.  The FZR rear wheel is also doable do to the brake set up...the brake caliper actually acts as a spacer on the right side, so all u have to do it fab u'r stabilzer bar, and break pedal and u'r in there...

[Lumbee]

...couldn't resist...here I am with Carls bike...

[Sam Green Racing]

Did you get to ride it ?

[ProTeal55]

CD811 has a great scoot, always been a fan of it....

[cbjunkie]

aaaagh! you guys suck! i hate you for being able to even think about a ride...

have you ever seen A Christmas Carol where the kid licks the flagpole? that's my ass on my bike this past weekend...

cbj

[ProTeal55]

  I am right their with ya , todays high temp was 4 

[Lumbee]

nah...I didn't get to ride it.  I was up in Arkansas picking up a 77 Super Sport, so a bunch of guys from hondachopper.com got together.  Carl was the only one that was man enough to brave the temps.  Only in the 50's...but chilly for the south..   

[dusterdude]

lumbee,is that fzr wheel a 17 inch?

[cb(r)]

well I am in the process of doing the same thing with a '74 550.  I have a cbr hurricane 1000 front with the 1000's rims on front and rear.
the front end I just took all measurement from the original's neck and cut the new neck down about 1.75''  then had it welded up.  I did have to make an alignment fixture for welding.  you also need to put witness marks on linearally (if that is a word)  to keep neck straight and aligned.  just a safe measure.

the cb and cbr threads and bearing diameters were the same so I just used original ball bearings.  the lower cbr triple tree stops had to be cut and moved as well because of lack of turning radius.  I also made a new upper tree to accomadate new gauges.  but not necessary.  you can adjust the rake by sliding forks up and down as you know. 

as far as the rear, I am using original cb swingarm and 1000 sprocket (44 teeth). strictly TT bike.  the three things I think you need to know there is first a major one.  the distance from the centerline of the new rim to the centerline of the new sprocket has to be very close to the same distance on the original bike.  if not, you will either have tracking probs  or chain alignment probs.  the second prob was get wheel to fit in swingarm so I had to cut down the cush drive and make a bearing insert to relocate the bearing and seal deeper in the wheel so it would fit into swingarm. so far so good.  the last wheel prob will be spacers.  I have not gotten there yet.

I am currently working on the rear wheel right now.  this is taking some time  and still in R&D so I have no real specifics.  one thing that I just notice last night is that I have to put rear caliper behind rear shock. another relocate project. I hope to mount the wheel by next week.
 there are other options that are easier.  using other bike parts. like the hurricane 600 rear wheel distance is a closer match up to the original 550. I really wanted to keep everything in the honda family of parts.  also I wanted a big honda.  good luck with your project!

[Lumbee]

...not sure on the size duster...the wheel I have is from a 95 FZR 600.

[ohiocaferacer]

Thought i'd pop in here and help if I can......

I have done a complete front end swap on the lastest project bike....a 1970 Honda CB340 twin. Using the entire front end components from a 1998 Suzuki GSXR750. Originally, I thought I could just find some taper roller bearings to fit the diameter of the gsxr stem and the frame head of the cb350 and just slide the front end into place.......couldnt find anything close. What I had to do was take the gsxr lower triple clamp and the cb350 lower clamp......press each of the stems out using a hydr. press....then take the cb350 stem and press it into the lower gsxr triple clamp. Amazingly, with almost 30 years difference between the 2 models....the stem bases are the same diameter. Also....the steering stop on the cb frame had to be cut off and a new one welded in....to give proper turn radius.

Now....I know some of the cb500/550 inline fours......the lower triple clamps have the stems welded at the bottom. You can grind the weld off the underside of the triple clamp and then press the stem out. This should allow you to press it into another lower triple clamp with the same diameter lower stem, if you need to use larger fork tubes. I dont think I would advise the  cutting and welding of stems. This is such a major stress point in the geometrics of the frame....that I dont think i'd risk snapping a weld and loosing a front end.

For my rear end set up.....I used a rear wheel, spacers and brakes from a 1991 Yamaha FZR600, but with the CB350 stock rear axle(same dia. as fzr) and axle adjusters. This is a tight fit in the cb350 swingarm....but just makes it. The rear rim size is an 18"x3.5"...and with a max rear tire size of 130(width). Set up in this configuration, the rear tire will line up perfectly with the centerline of the frame......but the sprocket will not line up with the countershaft sprocket. To fit this issue......you will have to mill the crush drive to recess the sprocket about 1" deeper into the drive. I have used laser levels and measurements(double check and double check)...but the easiest way I have found to get the measurements is to clamp a piece of very very straight 1" wide flat sheet stock to the countershaft sprocket...have it lay across the crush drive and scribe it.

Currently, i'm using the cast alloy mag wheels.....but i'm gonna have some spoked wheels built to keep a somewhat vintage look.

Heres a pic of the bike after it was mocked up:

http://www.ohiocaferacers.com/cb350rr-right150.jpg


http://www.ohiocaferacers.com/cb350rr-rear150.jpg

....and later fitting the tank and welding in a new steering stop:

http://www.ohiocaferacers.com/tankside2-150.jpg

There are a ton of pics and info on the build at my website.
Later,
Greg
www.OHIOCAFERACERS.com

[paulages]

excuse the ignorance here (never tried swapping front ends before)...is it impossible to find a modern front end with the same fork tube diameter and triple tree spacing? stupid question i imagine, or this topic would be unfolding a bit differently, but i'm just curious if these two specs are the main considerations in such a swap, or if there is something esle i am missing.   

[ohiocaferacer]

Most of the modern bikes fork tube(smaller tubes) are around 41mm...maybe as small as 39mm and the older CB Honda's had fork tube sizes of 33mm, 35mm or 37mm. So....finding a modern twin disc setup with smaller forks is difficult.

Plus.....just the "WOW" factor of the more impressive bigger fork tubes.......IMHO makes it worth swapping out.

Greg
www.OHIOCAFERACERS.com

[Lumbee]

...I can see your question about tube diameter.  If they are the same then you could simply continue to use a stock tree, and just add the new forks. As far as trip. tree spacing...not sure I follow there.  Even if the spacing is the same, I don't know that that necesarily means the stem lenth is compatiable.  And you still have to consider the bearing diameters...

[dusterdude]

depending on the size of the new tubes,how bout the possibility of boring out the trees

[ProTeal55]

Good question duster, would it be possibile to take a set of bone stock CB triple-trees and bore
them out to accept late model, bigger diameter fork legs ? Would enough material be left
to give strength to the tree's ?

Seems as this would be allot easier way to do the swap...

Anyone ?

[Lumbee]

...not only no, but hell no!!!  Stock honda trip/trees are weak to begin with...at least I know the cb750's are.  The rings that tighten down on the forks are known to snap if you tighten them to much.  Besides the fork rings are only a few MM worth of material.  Like someone mentioned above most new sport bikes are 40mm +...so vintage stock honda trees are not even close enough to this size to try and make it work.

[ohiocaferacer]

Have to agree with GLum on this one also....no way would I bore any material out of a stock steel cast lower triple clamp. Those things are so brittle....if you were to create a stress fracture while boring it(internal fracture)....reassembled it....then it broke..that would be nasty.

I had posted a few days ago and I think someone had posted it also....that if you want to keep a nice vintage setup with dual discs, one of the common things to due is put a 1975-77 Goldwing frontend on the older CB Honda's. Alot of the CR750 vintage race guys are using this setup and seems to be a really nice option.

Greg
www.OHIOCAFERACERS.com

[paulages]

by triple tree spacing, i was referring to lateral spacing---as in the distance between the fork legs. it seems that for a stock triple tree to work with a different setup, this distance would also have to be identical.

[cd811]

I thought I smelled someone talking about me...lol
like the great said, the swap I did was fairly straight forward...just swapped stems basicly.
why use the old trees when you can update??
the old trees worked great but basicly SUCK
with the gsxr trees I got a wide front-end made of good quality stuff.
now the wheels are another story...I wanted 16's front and rear, so I founf these on a 88 yam radian(600)...the front just spaced up with diffrent bearings with gsxr axle ...now the rear needed new spacers, new brake linkage and anchor on radian axle on 3inch stretched honda swinarm...no easy task but it can be done!!!!!!!!!!
I later found out that honda made a nighthawk that had 16's front and rear that might have made my job easier.

[ProTeal55]

I was just asking about boring out the stock trees, glad I asked 1st 

CD811---->
What year GSXR front end did you use for the swap ?
So all you did was take the stock CB stearing stem and press it into the
new GSXR trees ?

I was thinking, if people are doing this swap with sportbike front ends, would it be possibile to say , swap a front
end from a late model Honda shadw to a CB ? Would it just be the same press out old , press in new procedure ?
I ask because then I could retain the spoke wheel. Maybe even do a VTX front end