SOHC.co.uk Forums > Project Board
1967 CB450K0 Black Bomber Rebuild - By Royhall
royhall:
Hi Mo.
Yes they are a 500T carb experiment that so far is not going too well. Hopefully removing the air cut off valves will cure the problem. Just re-looking at the advice that Ash sought on Facebook, and I'm not sure I agree with what was said. They mentioned that the cut off valves introduce extra air on the over-run to stop exhaust popping, that's not my understanding. I'm fairly sure they introduce extra petrol to enrich the mixture past the point of ignition so it cant burn in the exhaust header. Hence my running rich problem, and why I'm removing them. Will find out once the jobs done and the weather allows a run out.
On the other point about the tank. Bombers don't have a cross pipe to level the fuel, they just use the braking and accelerating of the bike to slosh the fuel to the other side. Typical 60's Honda.
mo goldie:
Hi Roy
Thanks for that I thought having that blanked off bolt in the tank was it should have had a crossover pipe of some sort to get the fuel over the other side of the Tank where the Tap is,
oh I got some carb kits from wemoto and have put them in so hope they ok as some things did look different to the old ones, and the old ones things like the needles were bent so did Not know where to go to get some originals ones...... don't know how she will run with the new ones as they had needle clips so I have put them on the middle position.
Ashley
did get back to me about the rectifier and said the one I put on the link was good to use.... how all go`s well with that too....can`t try it all out till my cases come back from the sprayer.
AshimotoK0:
[ Guests cannot view attachments ]
--- Quote from: royhall on February 14, 2024, 02:52:09 PM ---Hi Mo.
Yes they are a 500T carb experiment that so far is not going too well. Hopefully removing the air cut off valves will cure the problem. Just re-looking at the advice that Ash sought on Facebook, and I'm not sure I agree with what was said. They mentioned that the cut off valves introduce extra air on the over-run to stop exhaust popping, that's not my understanding. I'm fairly sure they introduce extra petrol to enrich the mixture past the point of ignition so it cant burn in the exhaust header. Hence my running rich problem, and why I'm removing them. Will find out once the jobs done and the weather allows a run out.
--- End quote ---
This is what Cycle World said about the carbs in 1975 (plus the whole article if anyone is interested in the CB500T itself).
[ Guests cannot view attachments ]
[ Guests cannot view attachments ]
royhall:
Thanks Ash. According to that article the removal of the air cut off valves shouldn't make any difference to the rich mixture problem the bikes suffering as it only occurs over 4000 rpm. At least I was understanding it's operation correctly. The removal of the diaphragm housings are done now and I am about to check the float heights are correct then I can reassemble the bike and test what has changed. If nothing has changed, I may end up looking for some decent 450 carbs after all.
Sent from my Pixel 7 Pro using Tapatalk
royhall:
Just been studying the schematic of the diaphragm housing and my plan to remove and blank the ports wont work. Without the housing the slow running circuit will not flow air. It appears that the housing will have to go back on with the diaphragm in place to hold the spring plate open, but blocking the vacuum tube will keep the system locked in that position. Either that or a much more powerful spring to prevent the diaphragm moving. This is all too complex to be worthwhile so I am on the lookout for a good pair of CB450 carbs. Shouldn't have tried this in the first place really, I would rather the bike was ready for spring than be in the garage with some experimental nonsense going on. Plus running as rich as it has been will eventually trash the engine.
Ash. Putting that aluminium disk in wont work either as the plate valve behind will stay in the over-run position and be horribly over rich all the time. You just need to blank the small port above that disk with a piece of rubber the same diameter as the o-ring, then reassemble the valve as stock with the diaphragm in place. That's job done.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version