Topic: CB750K Lowered suspension questions (some 360 twin eye candy)

[sethdhawkins]

Hello Gents!

I'm returning to my Cb750K project in full force after four years, two moves, and four vintage bikes (XS650, CB750F, CB175, and a CB360). I've learned a lot and am glad to be tackling this project again with more experience and a larger budget

Here's a pic of the finished 360 (rebuilt from the ground up with all work done by me):

There's a project thread over on DTT, if you wanna smell old spice and tears.

Anyway, I've been away on the tug with a heavy wallet from the sale of my XS650 bobber, which I've promptly relieved in the form of new parts for the 750! One of the purchases in question was -2" forks from Cycle X (which I understand are really only -1"?). I also have a set of progressive springs for this setup. Should I be cutting theses springs down, preloading them with a spacer, etc? The forks in question will be run in one of those billet top trees from Dime City that supposedly give another .5" of drop. I've done all this because, alas, I'm a short, funny looking fellow. I'm hoping that I'm correct in expecting about 1.5" in drop from stock height in the front end? Also, as far as rear shocks are concerned (don't worry about horrible, death-defying trail differences), I'd like to have an even stance forward to aft, and willing to have a little forward rake if need be; Do I have any options other than the 13-13.2" height shocks and those evil little 11.2" that cycle x sells? Anyone out there with roughly the same frontend drop, feel free to chime in.

Regards,

Seth

[sethdhawkins]

Alrighty, so after some more searching on the topic, I've decided to do what people do when they add a spacer, which is to cut the spring for the amount of drop and keep a little for preload. If I'm gonna chop off a chunk of the progressives, which end; tight wound or loose wound end?

[seanbarney41]

seth, how tall are you?

[sethdhawkins]

5'10" with a 29" inseam...I know, built funny

[seanbarney41]

5'10" with a 29" inseam...I know, built funny

I'm 5'10" with a 30" inseam, so yeah, I know you are built funny...the only thing I have trouble with, on a totally stock cb750, is backing up, and even that is not that bad...however my main rider right now is lowered in the front via 550 fork tubes(from aprevious owner) and progressive springs...so probably about the same set up in front as your plans.  I have stock shocks in back set at max pre-load.  This results in the trail being somewhat reduced but the bike is still quite stable.  I actually had cb900f shocks on the back at one time.  They are about an inch longer than stock.  Turn in was noticeably faster, and overall handling was twitchy, but I wouldn't say dangerously so.  Adding a steering dampener would have made that set up perfect imo...so, you have some wiggle room in the trail departement.  Also consider that a cafe or brat style seat could easily be 3" inches lower than the stock seat.  I would stick with stock length rear shocks unless you are really stuck on the look of a lowered bike

[sethdhawkins]

Thanks for the reply! That helps me some.

[Really?]

I've seen this bike around this site a lot.  Belongs to some chiq with short legs I think.

[bollingball]

Seth I remember when that bike was first posted. I think he built it for his wife. I need to do the same thing maybe not quiet so low. I am 6' with 32'' inseam. My problem is the PO put what looks like +4'' or +6'' tubes way to long.
 I wonder if you or I got the -3" tubes would they actually be 2" shorter. To make thing even worst mine had 10" ape hangers Do you or any one know what the stock tubes measurement for a 78 750K is?
Ken

[sethdhawkins]

My understanding is that stock fork tube length is 22 7/8" for a K model.

[bjbuchanan]

I'm the same height and inseam as you. I have on my 750k is 12.5~ shocks on rear and i dropped the forks through the triple tree about 3/4 inch and made my own bump seat

It's plenty comfortable for me and manageable. The height drops are good and don't adversely affect handling and the seat is the icing on the cake. For me, the stock seat where it bows outward a little is the killer and digs in to my legs. Now that the seat i made is straight and a little slimmer its all good

The shocks are from dime city cycles and all i did was plug there mm measurements in to an online converter

If you go with them they also have a nice progressive line too you can check out in a bunch of lengths

[JoeHip]

i've used the 2"under (1"under for F types i think) from cycleX
and shorter ikons to level the bike
had to shorten my progressive forksprings 1 3/4"
feels a bit choppy now so i'm thinking of thicker oil and maybe air support

[WhyNot2]

5 foot 9 inches with 30 inch inseam.


11 inch rear shocks and lower the fork tubes throught the top tree....roughly and inch or so.

[sethdhawkins]

JoeHip,

That's a shot after you dropped her? What length Hagon's are those?

Thanks for the useful info boys!

Seth

[JoeHip]

Sorry it took me a year to answer (slow internetconnection)

Pic is after dropping her
I think they are 11inch shocks