vintage race CB350 - last 10% is the hardest

Re: della corsa CB350

The SL350KO brace appears to be a frame brace to take side stand loads. No side stand anymore therefore brace not needed I suppose.

Did some more work to fit the rear hoop section. Cutting, grinding, shaping, etc. It's getting closer. I did some more trimming to the fiberglass solo seat so it kicks up a little at the rear. Need to fill in turn signal holes then shape hoop a little bit more before I tack it in place and verify final fitment. Once I'm satisfied then I'll weld it for real.













Also today I scored a good deal on a used Ohlins steering damper. Now I can start figuring how I'm going to mount it. Hoping to do a top mount or front mount. There's not much room between the tank and the head tube so I might have to build something off the front fairing probe I'm fabricating.
 
Re: della corsa CB350

Hey man, nice work.. Love the thread..

So where exactly do you find these "..readily available..." 35mm SL350 Trees bro.. You got a secret hook-up I need to know about..? I have searched for weeks now, I know the 1972 SL350K2 trees are the ones that are the 35mm variety (according to other references), but I cannot find a set anywhere..? The only ones I can find are the smaller, single pinch bolt kind..

Hook a brother up man..!
 
Re: della corsa CB350

UnionJackMotoCo said:
So where exactly do you find these "..readily available..." 35mm SL350 Trees bro..
Such is the nature of building old bikes. The parts are everywhere when you don't need them but the moment you decide you gotta have one they're nowhere to be found! Keeping searching eBay (SL350 tree* in Motorcycle Parts and select the check box that emails you daily when new items match your search) and be patient. Lots of small shops out there parting out UJMs. Or try Baltimore Cycle Salvage.
 
Re: della corsa CB350

ohiocaferacer said:
Nice build.....looking forward to seeing the finished bike.
Greg

Thanks! Yeah, me, too! Your build was a big source of inspiration to me. I hope that one day soon we'll actually get to race against each other.
 
Re: della corsa CB350







Turn signal holes plugged. Welded front side and back side. On to the next step...




I filled the little notch at the rear of the frame. All of this is in preparation for fitting the rear frame hoop.




Shaved the friction steering damper bracket that sits just behind the head tube. I may end up mounting the new hydraulic steering damper there.



Scored a used Ohlins steering damper locally for $80. Cleaned up well with #0000 steel wool. Now I need to figure out how to mount it to the frame. It has relatively short stroke as it was meant to be top mounted across the front of the tank à la Kawasaki ZX-10R.
 
Re: della corsa CB350

freedomgli said:
Such is the nature of building old bikes. The parts are everywhere when you don't need them but the moment you decide you gotta have one they're nowhere to be found!

How true brother.. I think I have a lead on a set from a member of HondaTwins, another forum I'm a member of.. I just started building a CB350 racer myself, like literally 3 weeks ago.. Got a thread going over there, "so you wanna be a road racer huh..?".. I could transfer it here to I suppose..
 
Re: della corsa CB350

I only get to the workshop one day a week at most so progress is slow. Here is what I accomplished this past Saturday.


Shaved the battery box and side cover frame tabs. Things are looking much cleaner now.


Added this sheet which will serve as a platform for the tank mount (I'm probably on my 4th or 5th tank mount design iteration here) and place to hide away electronic ignition ECU, fuse box and alternator regulator/rectifier.
 
Re: della corsa CB350

UnionJackMotoCo,

I'll have to check out your build on Honda Twins. I am a member there also but mostly just try to help answer questions. I have another build thread over at caferacer.net. It's hard keeping up to date with documenting it. Bikes aren't built on the internet, they're built in the garage. I just wish I could get out to the garage more often!
 
Re: della corsa CB350

Rear tank mount bracket design #5 is about 90% complete. The 4 holes for affixing the bracket it to the large flat surface I welded to the frame are slightly off. It's hard to transfer the pattern precisely from the bracket to the flat surface with so little room to work. So now I'm going to enlarge the 4 mounting holes a little bit and use backing washers for the pop rivets to help ensure dimensional accuracy. Ultimately, the tank mount will allow me tool-less quick release with R-clips.

Also ordered the CR750 fairing and belly pan so I can fit them to the frame and make whatever bracketry is needed.

And these awesome billet aluminum race parts for the CB350 arrived from Cappellini Moto. Prodotto in Italia. I'm going to add spring hooks to my exhaust pipes and do away with the split collar arrangement.
 
Re: della corsa CB350

Front part of seat mount is done. Still need to finish the back part. It's a little tricky because of the curve in the seat pan (presumably for rear tire clearance) and because the seat is so far back and so short I need to make sure it's well supported to withstand my weight.

Also added stainless steel spring hook to CB350 exhaust pipe in precisely the correct location to put 3/8" preload on the swivel end beehive spring. I used a hose clamp to hold it in place so I could tack weld it. Then I removed the hose clamp to finish welding it.



Not too shabby considering this is my first time welding stainless steel.

 
Re: della corsa CB350

Did you order those flanges straight from Cappellini Moto, or is there a US dealer?
 
Re: della corsa CB350

ndromb said:
Did you order those flanges straight from Cappellini Moto, or is there a US dealer?
I got them from eBay seller valtermotousa. His prices were very reasonable considering the €MSRP on the Cappellini Moto website. Just beware that you must contact the eBay seller FIRST about combining shipping on multiple items. I foolishly got stuck paying 200% more than I should have for shipping when I bought multiple items at the same time. The seller stuffed all the small parts into the same flat-rate USPS Priority box and he kept the change!
 
Re: della corsa CB350

neevo said:
Where did you get your SS bends, collars etc?
I didn't make the exhaust myself, I just added the spring hooks. Chris Fiaccone made it for me a few years back. But I'm certain he purchased all the materials from Burns Stainless.
 
Re: della corsa CB350

In other news, the seat mount is finally done and the rear hoop is welded on the frame. It turned out awesome. I shaped the flange so there is a smooth transition from the stamped steel section to the tubular section. I just need to shape the seat profile a little bit for a really tight body line along the rear hoop that has a slight kick up.

Next up is making the left side frame mount for the steering damper and then getting the frame stripped and refinished so I can start reassembly.
 
Re: della corsa CB350

hmenzies said:
Cool build.

Thanks, man! I've been super busy lately but I got a couple of minutes to play in the garage this weekend.


Trying to figure out where to locate the mounting points for the Öhlins steering damper. There's not much room for error as you don't want the steering damper to limit travel and act as a steering stop. My original plan was to mount the damper body to the frame down tube. Although there is a threaded hole conveniently located on the right-hand side of the lower triple clamp, I was going to mount the other end of the damper to a split collar affixed to the left fork leg. Theoretically, this would allow me to adjust the damper with my left hand while maintaining full throttle with my right hand as I race down the straightaway.

However, I've been advised to flip the steering damper 180° with the body mounted to the fork leg and the rod end mounted to the frame as it is safer to the rider in a crash scenario. So I may go back to mounting the damper to the right hand side. Unfortunately, there is no room for a top mount setup like on modern bikes given my frame/tank. But there might be room to do a front mount steering damper depending on how the fairing probe works out.


Here you can see the seat mounts and rear frame hoop. Because the tank is so long the seat has to be short. The fiberglass seat pan has a raised feature towards the bum stop so I bent some flat iron to mimic that shape and provide the needed structural support. Fiberglass is strong but because the seat has been shortened so much this lightweight racing fiberglass isn't quite stout enough to support all my weight without some reinforcement in key areas!

I'm using 4 button head socket cap screws to secure the seat to the frame. They thread into floating metric nut plates riveted in place. These floating captured nuts allow for some misalignment, which makes assembly/service easier. Some rubber grommets and strip of old radiator hose provides some vibration dampening.


Rear frame hoop will provide convenient place to push the bike when loading onto trailer or in the event I need help with a bump start.





I shaped the rear stamped steel section for better visual flow to the tubular section for the rear frame hoop. Then I seam welded it. The bike was originally spot welded in most places so I've gone over the entire bike and seam welded it for strength.

You'll notice the ends of the rear frame hoop are open to the elements. I'm debating whether I should close them off and/or whether I should drill a drain hole so water doesn't get trapped in that section.
 
Re: della corsa CB350

And yes, I realize the forks are on backwards. Just mocking things up now. I will put them on the right way when I do final assembly.
 
Re: della corsa CB350

Bespoke racing parts made for the Honda CB350K in the UK by Jon Sunter have arrived.

www.sunterhonda30.co.uk

Months of research, one e-mail inquiry and a prompt reply, followed by an international wire transfer, 15 nail biting weeks later and I am rewarded with some very trick bits! And I must say, it was well worth the wait!

I am duly impressed. The apparent build quality of these parts is outstanding. I'm a handy guy in the workshop but I could not have built anything that looks so nice. It's almost a shame the parts are going on a lowly Honda CB350 instead of something a bit more exotic and worthy!

Jon Sunter is a true gentleman for putting up with all my e-mail messages and the inherent hassle of dealing with international customers. I feel really fortunate that craftsmen such as him exist to supply this niche market and I would not hesitate to recommend his business to others.


Front Fairing Probe - Stage 4

Front fairing probe for mounting fiberglass bodywork to Honda CB350 race bike. Includes lugs for mounting rev counter bracket, fork lock stops with nylon ends, front aluminum extension with upper fairing mounting frame, front locking washer, safety pin and aluminum rev counter bracket.


Front Fairing Probe - Stage 4


Front Fairing Probe - Stage 4


Front Fairing Probe - Stage 4


Rear Top Fairing Mount

Fits standard Honda CB350K frame. Made of 6082 aluminum alloy. Includes cross bar, frame mounting tabs, 2 x tapered outside washers and countersunk bolts that are screwed into short extensions that stay attached to fairing, 2 x R-clips for quick release. Fully adjustable to suit most any fairing.


Rear Top Fairing Mount Detail


Fairing Belly Pan Mount

Fits standard Honda CB350K frame. Rigidly fixes the rear belly pan in position.


Fairing Belly Pan Mount


Front Mudguard

Very lightweight fiberglass construction. White gelcoat ready for sanding, primer and paint. Requires only minimal preparation for finish. No pin holes.


Clutch Pushrod Seal Retainer

High crankcase pressure can cause the clutch pushrod seal located behind the countershaft sprocket cover to become dislodged and cause a major oil leak. This aluminum keeper device prevents that from happening. No one besides me will ever see this part but it sure is pretty, though! Combined with a vented oil filler cap I should have no worries.


Swingarm Bushings

Replacement swing arm steel bushes for standard swing arm. Made from EN36, hardened and ground to size. These are aftermarket replacements for Honda part numbers 52141-268-000 and 52141-286-000, which are no longer available new anywhere as far as I am aware. Mine were all corroded and pitted so I'm very thankful I found these new replacements to take the last bit of compliance out of the swingarm pivot!
 
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