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Honda CB450 Cafe Racer

8000 Views 27 Replies 8 Participants Last post by  Stickystuff
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After nearly ten years of getting pushed aside it’s finally time to finish this Honda CB450 cafe racer project. I bought this non-running, mostly complete 1972 Honda CB450 K5 back in 2010 to give myself something to tinker on and get better acquainted with motorcycles in general. At the time I had a 2008 Suzuki SV650 and a 2008 Triumph Bonneville T100. Neither of which needed me taking them apart to see how they worked.

The tank and side covers had been painted several times, it was missing it’s original seat, and although it was a low mile bike, it had endured a hard life. I later discovered that the frame was bent which further attests to the abuse it had suffered at the hands of its previous owners. I was able to track down a titled, straight frame from a 1973 K6 on eBay to replace the bent one so technically this is now a 1973 CB450 even though the majority of the parts are from the original K5.

As many of us do with our first project bikes I immediately started ordering a slew of parts and chopping tabs and brackets off of the frame (the bent one) without having a solid plan. Ultimately I settled on a cafe racer style bike as my target. At the time I was watching Cafe Racer on Velocity and reading Cafe Racer magazine so I suppose it was inevitable. The following year I bought my 1974 CB360G and quickly lost interest in the CB450 project. Afterall, the CB360G was a complete, running bike that I could jump on and tear around the back roads with. So, the CB450 sat for several years while my collection grew and pushed the CB450 further and further back in the garage.

A few years after that I decided that I lacked the motivation to finish the bike and passed it along to my brother. We tinkered with it a bit but then it continued to sit and collect dust in his garage. Which brings us to the present. With the CB77 restoration complete, I needed a project. Ideally one that wouldn’t cost me a pile of money. So the CB450 cafe racer is back in my garage and with a little luck, and a little of my brother’s money, the kids and I are determined to complete this project and get it back on the road by next spring.


Getting ready for the 5 hour drive home.



First look after unloading it. I stuck latex gloves between the filters and carbs to keep the rain out on the drive home.



To my amazement the bike fired right up. I always drain the carb bowls when putting bikes away for any length of time and this one was no exception. We had also fogged the cylinders.



We've settled on a seat from Tuffside. Here is a quick Photoshop mockup. I have no idea what color the tank will be. We're miles away from that step.

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Here's a quick project update. The Tuffside seat I ordered arrived last week. I'm very impressed with the quality and workmanship. I had heard good things about the seats in the past but had never seen one in person. The rear hoop that was on the frame already was setup for a BCR tank and seat combo which is about 4.5 inches longer than the setup we're working with now so the hoop needs to be shortened and angled up about 12 degrees to follow the line of the new Tuffside seat. I took advantage of the cool, dry evening we had here in SW PA yesterday and got started on the modifications. Weather permitting, I'll tack the modified hoop in place this evening and move on to the the mounts.













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That seat looks nice. I like the look. It's hard to go wrong with a CB450/500. They make great looking cafe racers.

They look so good, that I adopted a CB450 tank for my CL450 scrambler. Much nicer look!
Where will your battery live?
It will either go in a tray under the front half of the seat or under the seat bump. Plenty of room with either option, it will just depend on where we mount the other components.
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Progress has been slower than I'd like but that's the way it goes sometimes. I ran into a bit of trouble trying to modify the frame hoop to follow the "egg" shape of the Tuffside seat's tail end. My first attempt failed as you can see in the video below but fortunately I had the hoop on the original bent frame to give it another try with. The second time around worked out much better.






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Hey folks, Just a quick update, mostly pics, on the CB450 project. I've got the seat mount and hinge setup basically complete. One of my favorite things about these older Hondas is the flip up seat to access the battery, etc. so I figured why not make a similar setup for this project as well. The weight of the rider will supported by several rubber pads and the whole thing will be held in place by 2 quick release latches.



Mocking up the electronics tray out of wood.



The actual tray is made out of 16 gauge steel sheet. It took me 2 attempts to get the dimensions just right but it was a pretty straight forward process. I cut it out with an angle grinder and then made the bends with a vice break.



Checking for fitment. The battery can fit in either the tray or under the seat hump. I'm leaning towards the seat hump just to keep things from getting too cramped.



Lots of masking tape and paint stir sticks used in this project.

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Quick update on the CB450 project. I got the hinged seat mount and latching setup worked out and installed. I also built the electronics tray and mounted that. Next up is the battery mount and then on to the rearsets.










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Small but important steps this week. I worked out the location of the rearset mounting points. The tabs were welded to the frame and then I mocked the mounting plates up with some wood scrap (which quickly broke) and then in 1/4" PVC. Once I get all the linkage squared away I'll make the final plates in 1/4" steel.






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It took quite a lot of trial and error but I think we finally have a solid solution for the rear brakes. I didn't want mess around with bending the brake rod and trying to make that work, it seemed like that would flex too much and make the rear brake considerably less effective. I thought about trying DCC's cable conversion kit but with the cost of the kit plus shipping it was a little pricy. I'm also not a huge fan of cable operated brakes. Fortunately the way the rear brake pedal mounts on the CB450 frame makes it quite easy to work with.

Here's what I came up with:














I'm waiting on a return spring that I ordered. It may or may not work. I'll let you know either way.
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As promised, here's the update regarding the return spring. The first one I ordered ended up being too big but it worked as proof of concept. It was off of a VW of some sort and I had just guessed at its size based on a photo in an eBay listing. I should have known better. I ended up ordering a handful of different springs from from my favorite supplier of any random thing I can think of: McMaster-Carr. I should have started there as they have their spring sizes broken down exactly as I needed. I ended up using a "Torsion Spring, 120 Degree Angle, Left-Hand Wound, 1.342" OD" (Part number 9271K928). The winding is important because it determines what side the legs are on.

I welded on a tab to keep the spring in place and I'm going to bend and trim the spring legs to ensure it doesn't work its way out of place.



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The cold weather has really slowed down progress lately but I did manage to get the rearset mounting plates done. I cut them out of some scrap 1/4" steel plate that I had. I rough cut them with an angle grinder and then did the finish work with a file. It was quite a bit of work as you can see in the video but the result was worth it.








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Finally! Back to work on this project. We moved back in February so the months leading up to that were consumed with finding a house, packing, moving, etc. so no time for bikes. After the move there were (and still are) endless projects and repairs to be done around the house but I think I'm finally at a point where I can start sneaking out to the garage again for more fun projects. My first task, which should have been a relatively easy one, was to mount the Dunlop D404 tires that had been chosen for this project. The front went on fine but the rear tire refused to seat properly after numerous attempts. Ultimately I accepted defeat and we order a different style tire. According to Dunlop's website the tires are meant for much narrower wheels which seems odd since they are such fat tires. I think it's a combination of that and my relatively limited experience with mounting modern tires on older wheels. At least that's what I'm telling myself. Oh well, we all know that things rarely go according to plan when modifying these old bikes. I'm just happy to be wrenching again!


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What size did you go with on the rear? I have the 110/90/18 on my 78 CB400a With the Comstars. I like these a lot so far.


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This one was a 120/90/18. Wider than stock for sure but the main issue I had was actually getting the tire to seat on the rim.
This project is still fighting me at every step. I suppose there's nothing to do but press on.

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I'm going to make an effort to post more pictures going forward, I realize that not everyone wants to sit through my rambling videos. Hell, I don't even want to sit through them sometimes. I started on the new exhaust today. I had the headers made by a company called J&D Tube Benders a few years back. I provided them with the design and specs and they made me 3 sets (6 headers total). The flanges and collars were machined by friend of mine out of 1/4" mild steel.









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What do you guys think about this setup for the mufflers? I was thinking about doing a 2-1 like I had done before, but just for fun I dug these out of the parts bin and to be honest I'm really liking the look.









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