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I'll start off by giving a light intro about the bike and the way this thread is going to go. The bike is a ’69 CB350 K0 that I picked up about 6 months ago. It ran fairly well when I got it so I cleaned it up a bit and rode it around all summer. It was a blast and I really fell in love with the old thing. Did I mention it's my first bike? I was in a little over my head at the beginning but I was able to quickly figure stuff out as I went.
So, I've been lurking around this forum as well as hondatwins and I've been intrigued by all the guys doing modern front ends on these old bikes. The drums on the front of the 350 were ok but I felt the need for more stopping power (some of you may argue that drums work great if setup correctly and I 100% agree).
I was able to pick up a complete front end off a 2005 gsxr600. I would say I jumped the gun a little on buying the front end because it sat in my apartment for 3 months (sorry to my wife) but I couldn't pass up the amazing deal.
I then read through Devin's (Speedbump/Cognito Moto) cb550 build thread and I immediately knew that I wanted to work with him to build the bike.
With that said, this thread is going to be a team effort. Devin and I will be updating this thread as often as possible to help keep everyone up-to-date on the build.
Plans for the build:
Modern front end
Ducati Monster S4R SSSA rear end w/ mono-shock
Heavy frame modification
Engine Rebuild
Electronic Ignition + all new electrics
Paint, seat, etc. details that we will figure out along the way
Here are some photos of the evolution thus far. Let me know if you guys have any questions.
I usually not a fan of the SSSA on these older tubular framed bikes, but for some reason I really like the way that looks. I think the shape of the tank helps a lot. Keen to see where this one goes as you certainly have some capable help in Cognito Moto.
Looking like a nice transformation Sailer, I'm definitely in to see how you end up modifying the frame to get the swinger and shock to work out. Once I get back to mine the upper shock mount and finding the right size rear wheel are on my priorities list for my '69 CB 350 SSSA project. What width rear wheel and tire are you running? I've been thinking about the older RVF400 18" wheels but I'd love to find a narrow 17" for better tire selection (4~4.5"). Can't wait to see the progress and finished product!
@neevo - Thanks! I'm with you on the bulky swingarms on the tubular frames. I also agree about the tank although we are still tossing around some different ideas for the tank. Tank TBD.
@1969Honda - The wheel is a 17x5.5. It's pretty damn wide but looks great from the back. The tire is a Shinko 009 Raven 160/60/17.
@xb33bsa - Yea good call, it's definitely going to be around 3" but we won't know for sure until the frame modification is complete. Since it's a relatively short bike to begin with, I think the wider rear tire will effect the handling more so than the 3" extension.
I'd love to hear some first hand accounts from people with extended swingarms on these bikes.
You also have about 2 inches less offset at the front, so the wheelbase may not be as long as you feared, but weight distribution will be very different.
what will you do to support the outside of the swingarm bolt? you have removed its support and added extra loads with the longer heavier swinger tire combo
Weight of swingarm and wheel is 40lbs for CB350 and 50lbs for Ducati. The mounting will done similar to how it is mounted on the Ducati with support to match.
This should be a fun project. I'm looking forward to the challenge and change of pace from my normal builds. I think that swing arm looks awesome with all the tubing and the mono shock to match.
I think we are still undecided on the tank but as the build moves on we will have clearer direction.
Unfortunately the backbone is not as stiff as one might imagine particularly in twist because it's relatively narrow. The outer frame rails and swingarm end plates do contribute on a stock frame.
@ Teazer, I'm curious as to what your thoughts would be to adequately hold to forces placed by a SSSA on the stock CB350 frame. I've got one underway myself that has been torn down in the build phase for 8 years now due to work and military service. On my project I've ground down, butt welded, and then over lap welded a piece of 1.5" wide 11 gauge strap all along the top and center post factory seams.
I then created new pivot bolt support brackets where the factory pivot bolt and foot peg mounts were located out of 3/16" plate in a c-channel shape and welded them in place (no pictures available at this time). Are there any other suggestions that you would recommend? I'm trying to stay away from the really wide stock triumph/ducati wheels and get my hands on a narrower rim 4~4.5 range if possible (rvf400, NSR250R, etc...).
Sorry if I'm hi-jacking your thread Sailer, but I figured since your at a similar frame stage to me with the same bike/frame concept we might as well try to keep the advice/opinions/ideas in one location for easy reference.
Think in terms of triangulation and adding Depth rather than thickness. So for example adding supports at the end of the swingarm help to double the strength as long as they are tied to something equally wide. On race bikes with twin shocks we can tie teh center spine to teh rear down tubes for added stiffness.
With a SSA, you may have to think about adding outer frame rails and tying that all together to get extra depth and triangulation.
So looking at Speedbump's rendering are you saying that you would add a couple of tubes coming up from the lower frame rails at an angle to meet with the swingarm pivot tube where it lools like there have been a few vertical braces added to the main down tube Teazer? I understand the triangulation concept from a stand point of triangle being the strongest geometric shape and transfering loads I'm just trying to understand why you would locate the vertex of the triangles for the best results I guess.
So looking at Speedbump's rendering are you saying that you would add a couple of tubes coming up from the lower frame rails at an angle to meet with the swingarm pivot tube where it lools like there have been a few vertical braces added to the main down tube Teazer? I understand the triangulation concept from a stand point of triangle being the strongest geometric shape and transfering loads I'm just trying to understand why you would locate the vertex of the triangles for the best results I guess.
you will need substantial outboard support just like the original cb350 frame had ,even more substantial because of the extra loads on it now with the longer swinger
Unfortunately that box section/engine mount is not as rigid as it might appear. Some years ago I gave myself a nasty fright following another guy on a CB77 racer. the back end was flapping about in the breeze.
Unless teh holes are reamed and super tight fitting mounting bolts used, the frame walks around the motor mounts with a stock bend swingarm and will act like a spring with a more rigid swingarm and grippier tire. That center section is too narrow to resist the twisting forces effectively. The wider the support, teh more resistance to twist, so adding tubes outside the swingarm pivots is a good idea.
you will need substantial outboard support just like the original cb350 frame had ,even more substantial because of the extra loads on it now with the longer swinger
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