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1967 CB450K0 Black Bomber Rebuild - By Royhall
royhall:
Been recently having a play with the Black Bomber trying to get it to run lean instead of burning the plugs black and bore washing the cylinders. I cant believe it's 4 years since I finished this project and I still haven't got it right. It got itself dumped in the back of the garage for a while as it was peeing me off.
I have tried 500T carbs and 450K3 carbs all of which ran very rich. I decided it must be the silly expensive pattern air filters at fault, so have gutted out the folded paper element and replaced it with oiled foam. They were really restrictive as you cant even breath air through a single piece of the old element, it's like cardboard (usual crap quality pattern parts). That done, I have refurbished the original 14C carbs that were meant to be on a Bomber with the help of a few parts supplied by Ash. Fitted the carbs and refurbed air filters this afternoon and things appear to have improved some.
Unfortunately I have noticed another issue that I hadn't seen before. When fitting the plastic air filter boxes that have the rubber inlet fitted, only about a quarter of the air filter is being used as the rubber intake blocks the rest. So about three quarters of the air filter is breathing through a 1/4" hole, that cant be right. Can somebody with a Bomber please have a look if it's the same on yours. I may possibly run it without the plastic cover fitted as I think it's just a noise suppressor. That will allow the engine to breath through 100% of the filter element. Am going to give it a 10 mile run tomorrow and see what pans out. I can feel a dump it in the back of the garage moment coming on again.
mo goldie:
Hi Roy
I sure do know where your coming from with the problems with running rich. I went out on mine sunday as just fixed a left carb bowl from leaking for the 5th time. I have done everything from Flattening the float Bowl checking the float Hight, also tried allsorts of gasket seal,
anyway get back to the ride it was going Great for the first 5 miles then it started to splutter and nearly thought I was going to have to call out the Breakdown van. anyway I managed to get home... next day striped the left carb and found loads of the silicone all in the bowl and it blocked all the jets too ..... so after cleaning that all out and putting it in my Uatsonic for a deep clean put a very very thin layer of a new type of silicone on and left that over night and put it back on and went out for anther ride this afternoon and it was popping and banging a bit on that left side so pulled over tweaked the mixture screw and no more popping and it did all run fine..... I will take the spark plugs out tomorrow see what they look like ?
Getting back to what you say about the air filters ..... i did put a bit on a thread a while ago to say what I had done to mine, all the paper folds were so dirty I decided to cut them all out and put in Foam as well so all good there now,
Not thought about leaving the plastic box part out but yes might help with the rich running let us Know how it go`s without that on, also if it do make a lot of sucking sounds without that Ha
One more thing they seem to be one bike that Needs All the attention and one minute it runs lovely the next you think it is like an 60`s TV and need a slap to get the picture back ha..... well I must admit I do love riding it tho LOL ;D
McCabe-Thiele (Ted):
Yikes I admire the persistance of Black Bomber owners in trying to fix the rich running issues.
All that pain in taking carbs off repeatedly it would seem.
On my 400 before the rebuild I had my carbs off a couple of times - a task I hated so much with the bruising & cuts to my hands that happened every time.
royhall:
I ran the bike today for about 9 miles. It ran very well indeed so looks like I'm getting there. Looking at the plugs afterwards they are still black but it looks like burnt oil rather than soot. It's probably not done 100 miles yet so the rings are still bedding in, plus it's been stood for a good while. The white smoke from the exhausts has also now stopped so it does look like it's leened out a bit now. Time to give it some use and see how it goes.
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AshimotoK0:
--- Quote from: royhall on July 31, 2024, 03:26:52 PM ---I ran the bike today for about 9 miles. It ran very well indeed so looks like I'm getting there. Looking at the plugs afterwards they are still black but it looks like burnt oil rather than soot. It's probably not done 100 miles yet so the rings are still bedding in, plus it's been stood for a good while. The white smoke from the exhausts has also now stopped so it does look like it's leened out a bit now. Time to give it some use and see how it goes.
Sent from my Pixel 7 Pro using Tapatalk
--- End quote ---
Good news then Roy. I suppose you have to consider that loads of Bombers clocked up tens of thousands of miles each back in the day and must have performed OK ... once the initial 14C carb upgrade was done very early on. It's possibly just a case of getting a collection of decent carb parts and making up the best set you can, retaining Keihin brassware and making sure the piston/cap assemblies are in good order... i have seen loads that stick after 50 odd years of storage and abuse. Did you run it with the plastic air filter covers removed in the end?
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