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Vintage drag bike project, DOHC CB450

oldschool

Well-known member
Joined
Feb 12, 2022
Member Number
652
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Location
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I realize drag racing is not a big thing here but hopefully there are a few who will appreciate this effort. I have a much longer thread with more details at vintagehondatwins.com so this is a synopsis in pictures. If anyone is interested in seeing the full thread it's here: https://www.vintagehondatwins.com/f...)-Budget-drag-bike-project-DOHC-450-of-course

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At first I considered using a CB360 swingarm for the extra 2" of wheelbase it offered, but it required opening the axle slots for the larger rear axle. Then this happened

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I was given a CB650C after the salvage yard took what they wanted from it.

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Weirdly modified 450 swingarm on top of the CB650 swingarm, which is much beefier and longer allowing the use of much stouter parts - bigger axle, sprocket drive flange and wider 16" Comstar wheel

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Forks cleaned of corrosion and painted hammer silver

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Hideously corroded front hub cleaned up and quickie painted (spokes mostly taped off)

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Checking chain alignment

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Slightly out of order but you get the idea

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Clutch cover literally had mud dauber nests in the oil passages from the centrifugal filter

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Sorry, not upside down at my forum :lol3

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This engine led a rough life

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JB Welded some 6mm nuts on the backside for the rotor cover screws, this bike will be running total loss so the entire alternator is removed
 
Planning on running tubeless with that Comstar?
Pretty sure it's tubeless now based on the valve stem in place and yeah, if it is then I will. I might put a couple of screws through the rim into the bead on each side to keep it from slipping, depends on how good the traction is and how low I end up running the pressure in it. I used 2 on each side of the WM3 rim I had on my 450 drag bike in the early '70s and it was plenty to hold a 4.00-18 Avon slick.
 
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Used the old PVC inside the tubes trick to shorten the forks, still has about 2" of travel. Cheap Chinese clip-ons in place

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Tank mounts turned, threaded and welded in

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Road sign bought from an indoor flea market in Pickens SC to use for the tach bracket

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Suzuki shift lever for the rear brake pedal

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I had a few pieces of links with heim joints laying around, found a good one for the pedal connection but it was 6x1.25 thread and my old cheapie tap and die set only had 6x1.5 in it, so I re-tapped the .236" ID to 1/4-20 so I could use the 1/4-20 die on the rod
 
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Found a 20 amp LiFePO4 battery for the total loss ignition, dimensions were perfect for the Yamaha Venture Royale battery box I found on eBay. Originally mounted the tabs under the forward factory rear fender brace but it sat too low and would have caused drive chain clearance issues, so I had to fab a bracket to mount it on top.

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I'll be using an ignition power kill relay for shifting, testing the late model Honda throttle/switch assembly for the best through-circuit to use. Chose the pair that turned off the headlight during cranking so the starter button will activate the relay and break ignition power

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Mounted the lighted main toggle switch and made the harness, soldered and heat shrunk every terminal and connection

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Cut a small plate for the condensers and shift relay, wrapped the harness with self-bonding silicone tape. Mocked up the coil mounts until appropriate spacers could be found.

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The LiFePO4 battery holds 13.5 at rest after a full charge

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Gotta represent my longtime friend and welder/fabricator Mike who helped me on my red 450 build and only weeks later had a stroke in late 2017. He rode and won often in the over-50 motocross class at local tracks and his lifelong number was 5. And a tribute sticker for my father, without whom I'd never learned enough mechanical and fabrication skills to even be doing this stuff.

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My machinist friend told me I had to buy some Moon eyes for the tank. Done.

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Fabbed up a basic chain guard just in case any tech inspection expects to see one. Heavier gauge and weight than I'd have liked but it was laying around, and I've gained more weight over the years than this will add to the project

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Leftover brackets from the unused legs to a HF parts washer that lives on a table, finally got some use out of them

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Plenty of clearance to the sprocket studs
 
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Throttle cable installed, routed and test-connected to one of my new 36mm Keihin PWKs

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Spacers acquired, condensers mounted, wiring ready to connect to the points wires and nylock nuts tightening things up

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Both coils came with the same color wires so I sprayed a little blue on the right coil's points wire. Additional ground wire to ensure solid connection frame to harness

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All cables in place. Roller waiting for an engine

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My local riding buddy, a big drag race guy, donated a couple of modestly-priced tires to the cause (he knows I'm a broke-dick)

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:D :D :D
 
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