PDA

View Full Version : hard tailing a cb question



REV
05-10-2010, 3:08 PM
with the help of some friends, im going to hard tail a stock cb. this isnt my frame, but it is a cb frame, so i figure i can use this as a reference.

attached is a pic of the cb frame, and a computer rendering of basically what im after., last pic is of what i hope the bike to basically look like when done, save for a few changes.

question is this: what do i have to keep from the stock front loop in order to mount the motor up correctly? ive seen some guys just using 2 rear motor mounts, and i think that the 3rd hole isnt a motor mount...

anyway, im worried about cutting too much stuff off, or having to redo the whole back bone of the bike. im going to start buy cutting the rear "triangle" off, where the old seat/fender went. them move the 2 side seat posts in to a point, cut off the horizontal brace so im left with roughly a diamond shape.

after that, i want to grind off that mount behind the neck, and smooth the neck as a hole.


is there any problems with that? and can any of you suggest a good way to keep the rear motor mounts but make the lower tubes flow back, instead of angle up? and can i run a single seat post instead of 2 on the sides? ive seen that a few times, just dont know how its done.


thanks!

bigdaddy
05-10-2010, 7:05 PM
you don't have to keep the stock front loop. hell, you can build anything if you have the time and resources. the middle hole in the rear motor mounts appears to be the swing arm mount. i found a pretty good website that showed how a guy hardtailed his xs. it was step by step stuff. pretty good too. i'd recommend keeping the stock front loop. cut just in front of the rear motor mounts (after you've made a jig for the rear mount holes) and then weld the rear part of the new frame on using slugs. the thing i hate about these frames is the stupid "three backbone" set-up. check out tc bros. they have a pretty sweet set up for the cb. i'm not saying you have to buy someone elses product, but the pics might give you an idea of what to do. their cb hard tail is much better looking than the xs hardtail kit they offer. it looks like they use the rear motor mounts for mounting the hardtail. kinda pricey, but nice looking. now, this is only my opinion, and i'm not engineer. i can't weld, and i've only screwed up one frame out of one that i've built. so it's totally okay if you don't take any of my advice. i can surely tell you what NOT to do if you're interested. good luck. here's a pic of the hard tail. they've got pics in their gallery of cb's as well.

http://www.tcbroschoppers.com/store/index.php?main_page=product_info&cPath=8&products_id=8

REV
05-10-2010, 7:37 PM
i looked into tcbros tail for a while. i almost went with it, but i saw that one area around the seat, where its square. i dont like that at all. but what they have is a good idea. im hoping to build something thats done one time, and never have to worry about dicking with it again. the tcbros looks like something id change later

MIKE47
05-11-2010, 6:37 AM
My preferred method is to chop them off at the end of the backbone straight section and extend it a bit. Then I chop off the rear loop side tubes where they straighten out. Then I build the tail from there with a single seatpost. I like the looped rear section (kind of BMX like and old BSA-ish) but it can be done the traditional way as well. I think this way makes the bike look a little "lighter" and less cluttered. I use the front motor mounts and the long bolt through the bottom then fabricate the rear mounts to keep 3 mounting points.

http://i130.photobucket.com/albums/p241/mikeypspix/IMG_0937.jpg
http://i130.photobucket.com/albums/p241/mikeypspix/IMG_1672-1.jpg

REV
05-11-2010, 1:52 PM
hot damn, its finally arrived!

needs some tlc here and there, brake attention, fork seals etc. i almost feel bad about cutting her up. almost. 1975 cb750f

JLeather
05-13-2010, 5:17 AM
If you're not into the "seat hump" of the TC bros kit you might wanna check out the kits from CycleOne manufacturing:

http://www.cycleonemanufacturing.com/id227.html

You cut the backbone a bit farther up ahead of all the seat-area nastiness, and the framerails ahead of the stock rear motor mounts. It slips over the stock CB tubing, very strong and no alignment issues. Comes with the new rear motor-mounts and all. Something to consider if you don't have the equipment to do it from scratch.

REV
05-13-2010, 11:40 AM
sweet. thats a little more than i wanted to pay, but for what it comes with, fuck it, ya know? looks good and is ready to rock, thanks!

luckystiff
05-13-2010, 12:42 PM
My preferred method is to chop them off at the end of the backbone straight section and extend it a bit. Then I chop off the rear loop side tubes where they straighten out. Then I build the tail from there with a single seatpost. I like the looped rear section (kind of BMX like and old BSA-ish) but it can be done the traditional way as well. I think this way makes the bike look a little "lighter" and less cluttered. I use the front motor mounts and the long bolt through the bottom then fabricate the rear mounts to keep 3 mounting points.

http://i130.photobucket.com/albums/p241/mikeypspix/IMG_0937.jpg
http://i130.photobucket.com/albums/p241/mikeypspix/IMG_1672-1.jpg

damn that looptail looks right. if i do a full custom built frame for one of the cb360s i've got it'll probably get a looptail provided one of the local(ish) frame guys is up to it. maybe it's my old bmx upbringing but i've always loved looptails...ken....

Brandon
05-13-2010, 1:33 PM
check out hillbillys wicked choppas on here he does good looking hardtails at a good price.

landman76
05-19-2010, 11:54 AM
Personally I think these a the best looking weld on's, not the cheapest though:
http://www.cycleonemanufacturing.com/id227.html

No hump where its grafted to the frame like some others I've seen.
A nice straight line from the neck to the axle plates.