Longjohns 1973 CB350G Build

[longjohns]

well i picked up this cb350 a couple of days ago and while doing research on the bike i found this site. im VERY new to the bike scene. just getting into it so im going to need a lot of help with this build. the bike is a 1973 CB350G. from my research the only difference is mine has front disc brakes.

i have an "el poquito" tank and seat being made as we speak.
as far as the motor goes i just want the damn thing to run right. it needs the carbs synched i believe. thats what the previous owner tells me. i only started it up once then started to tear in.

anyways here are some pics...

at the previous owner...

with me a day later...

do you see these little cracks?? anything to be worried about? i was going to weld a bead over it then sand it smooth. what do you guys think??

 

[coolatula]

Those are going to be very nice pieces from Benjies.

Don't know about the crack without actually looking at it. If if was on the tail end past the shock mount I'd say don't worry and weld it,but that is on the inboard side. Can't tell from the pics if it would be a structural concern or not. May just be that top plate or could be the tube frame underneath is cracked or broken away causing the top sheet metal to crack? Have it checked out by a certified welder and if need be they could fix it and weld in one or more plates/gussets to make sure it doesn't happen again in that area.

Good luck!

 

[Roustabout]

My 350 race bike cracked in the same spot on both sides. I welded it up with no issues. It's common practice to weld up the spot welded seams where the stamped members are joined to stiffen things up. The bracket that connects the swing arm pivot to the outer frame rail (also doubles as passenger peg mount) is another spot that people weld up. I actually cut the passenger peg bracket off and used the 2 threaded holes to mount my rear set bracket. For extra support people tie the outer rail just above the swing arm pivot to the frame spine. Another spot to check is the lower down tubes where they cradle the engine. They can rust from the inside out from water getting down there. Give them a few good taps with a hammer to check for holes.

 

[longjohns]

so you guys grind down the seams then weld it up? i might look into that tomorrow.

 

[coolatula]

so you guys grind down the seams then weld it up? i might look into that tomorrow.

Yes,Honda only spot welded their stamped frames just like the car manufactures did/do. That is not the best or strongest route to go so people grind them and fully weld the seems to prevent the sheet metal/sheet metal to tube welds from coming apart and to strengthen the frame/make it more rigid. A lot of guys box in the hollow areas of the sheet metal also(see Benjies Honda 350 they built).

Bracing and gusseting in areas where they are known to flex also helps the handling. Too much chassis stress/flex in corners is why a lot of older bikes wallow/move around in the curves and can't be ridden to their potential. Too much suspension flex just adds to this instability also. That's why a lot of vintage bike owners replace the swing arm bushings/shock mounts with needle bearings/bronze/Derlin plastic bushings etc. Kawasaki H2s were know to have a LOT of power and absolutely scary high speed handling and frame flexing.

 

[Canuck Plumber]

I did a bit of MIG on my frame and the metal isn't the best to work with so be really careful since it seems to be in front of the shock mounts.

 

[longjohns]

yeah im gonna grind it down and see how bad it is. all i have is a mig as well so i dont think i wanna jump straight into the seams yet.




****what does everyone think about running toggles instead of the normal switches on the bars? im thinking of running toggle for:

-headlight (off-low-high)
-signal lights
-kill switch
-starter button
-horn

i was thinking it would be pretty simple to run the wires out of the headlight to toggles mounted to the plate the ignition is mounted to. anynone do this? i want to clean up the handle bars since im going to be running clip-ons.

 

[Canuck Plumber]

Depends on what kind of toggles. Could be really cool. You were thinking of putting them on the frame somewhere?

 

[longjohns]

well the plate that goes on top of the risers where the ignition is. thats where i might put it.

** question: i was installing the new clutch perch and i noticed that the clutch was tight. when i pulled the clutch with some force i heard a snap and the cable is loose. when i pull the cable i can see it moving on the other side.. so i dont think the cable snapped. but i cant get inside until i take one of the stripped screws off.

my question is, is there anything in there that the cable mounts to that could have snapped and made the cable go loose? or could it have just been the cable end? and is there oil inside the cover that the clutch cable connects to?


here are some pics.. the bars are just for mock up. i bought some clip ons that im waiting for and i also threw the seat and tank on for shits and grins....

 

[longjohns]

so i finally got the cover off to see whats inside. i really have no idea what im looking at. any help would be great. when i push the clutch lever it comes out fine but wont retract. the spring seems to be fine. also when i opened the cover this small peice fell out. it looks like it was cracked off something but i cant find another peice in there... here are some pics.

 

[Tim]

I don't know what the 1/2 pipe is there, but as you can see the rod just in front of the sprocket is what gets pushed on by the cam mechanism at the end of the clutch cable. It goes through the engine to the other side to expand the clutch plates.

Do you have the parts manual for the bike? Nothing like exploded diagrams of the parts to see what makes what work.

By the looks of it, the problem could be gunk buildup in the cam mechanism, the clutch rod could be sticky where it goes through the engine etc. Pull and push on that rod - does it move freely?

 

[longjohns]

well today i was bored so i decided to dent up my tank with some knee cut-outs. i think it came out alright considering the fact that it was my first time everdoing it. still needs some bondo though. what do you guys think? i ordered up stuff from benjies but im also going to keep the original stuff for when my wife wants to ride sometimes... might as well make it look good!

 

[chrisf]

so you guys grind down the seams then weld it up? i might look into that tomorrow.

I did this on my CL350, but you have to be cafefull. As you grind the seam down, it begins to split, making welding it very difficult. What I did was grind a spot completely out, then weld in a bridge in a couple places. I'm specifically talking about the spine. Though a laborous process, I would grind out 1/8" WITH A FLAPPER WHEEL, then run a bead with high heat, making sure to get very good penetration. Then sand it down to just above where the weld penetrated, then repeat.

You could also try just fusing it with a TIG.

Where the pressed sheet metal meets to tubes (i.e., on the neck), I just welded it in with the MIG set on pretty high heat. If you go to the www in my profile, scroll way down the page to see how I did it.

--Chris

 

[zixxerboy]

pulling the clutch lever will push out the mechanism under the cover. the retraction comes from the clutch spring force which is transferred throught the rod in front of the sprocket. does the rod move freely? i believe that rod can be pulled right out from that side

knee dents - how much mileage is lost on a tank? I always figure I don't have enough range as it is (200km)

 

[longjohns]

I did this on my CL350, but you have to be cafefull. As you grind the seam down, it begins to split, making welding it very difficult. What I did was grind a spot completely out, then weld in a bridge in a couple places. I'm specifically talking about the spine. Though a laborous process, I would grind out 1/8" WITH A FLAPPER WHEEL, then run a bead with high heat, making sure to get very good penetration. Then sand it down to just above where the weld penetrated, then repeat.

You could also try just fusing it with a TIG.

Where the pressed sheet metal meets to tubes (i.e., on the neck), I just welded it in with the MIG set on pretty high heat. If you go to the www in my profile, scroll way down the page to see how I did it.

--Chris

after looking at your build it really makes me want to tear my bike all the way down and clean it up. its not too hard but i want to get it running before i tear down. your bike looks great!

there is a guy at work with new 2008 ducati sport classic and i cant wait to get my bike going to show up that bike! it is a sexy bike though...

about the welding. i might do the same with the four inches at a time at high heat. from looking at the frame it seems like there will be a pretty good gap when its ground all the way down. i might leave a very small gap some i not trying to bridge the two sides.

 

[longjohns]

i started stripping paint off the tank so i can start the bondo and to also see the conditino underneath. it looks pretty good. i also too the risers off the bike so i need to find a place to put the ignition switch. where is everyone putting theres? most of the stuff i have done is wiring. so as far as i can tell up to now the wiring is good. i have no way of telling if the tach or speedo are working because i havent tried to start the bike yet. anyways here are some pics.

 

[dcmspikes]

I did this on my CL350, but you have to be cafefull. As you grind the seam down, it begins to split, making welding it very difficult. What I did was grind a spot completely out, then weld in a bridge in a couple places. I'm specifically talking about the spine. Though a laborous process, I would grind out 1/8" WITH A FLAPPER WHEEL, then run a bead with high heat, making sure to get very good penetration. Then sand it down to just above where the weld penetrated, then repeat.

You could also try just fusing it with a TIG.

Where the pressed sheet metal meets to tubes (i.e., on the neck), I just welded it in with the MIG set on pretty high heat. If you go to the www in my profile, scroll way down the page to see how I did it.

--Chris

this is a little late, but couldnt you clamp the across the tube maybe underneath it and the grind. then maybe it wouldnt open up before you weld it back together?? seems to me like that would be simple, but i havent tried it

 

[longjohns]

yeah that is what im going to do when i get started on that point. i just want the motor to get running as of right now. then i will deal with stiffening up the frame.

 

[904cafe]

i just found this one... great looking bike, already made some good progress cosmetically! i can def see where you are going with this and i like it! woot to the smaller bikes ;D

 

[burntblacktoast]

WHOA SLOW DOWN. i just registered to say a few things. First of all that whack you heard in the left side primary cover means that your clutch adjustment is wayyy off. Probably happened when you took the lever off the perch. It can be rectified so dont worry too incredibly much. It does require a lot of small adjustments to get it just right. it needs to be just right. go to caferacer.net, do a search for cb clutch actuation and you will get some results. trust me, they helped me with the very same problem you have now with there adjustment procedure. do a search first or they will probably give you a hard time, thats just what they do there. They are smarter than you. that thing that fell off looked like a chain link roller, get a new chain. And clean the gunk. Another thing, why was it necessary to bash in the tank if you have one being made? It can be very easy to get tired with a new project when you dedicate precious resources to cosmetics only to have a bike that does not run. Start with the mechanical and structural, don't butcher the electrical, then procede to cosmetic and asthetical. And you will never be able to show up a Brand new Ducati with your cafe'd honda, sorry. i love my 70cb 350 but, sorry.