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I'm having trouble with my 74 CB 450 after the engine rebuild. For some reason I can't get the bike to DTT. Wide open throttle in top gear won't go over 80mph. I've had the bike up to 105 before so I know the bike can do it. The timing is dead on correct and the carbs are pretty close to perfect adjustment now. The bike has plenty of power up untill that point and then it just seems to run out of power doesn't miss or anything it just feels like the horsepower to air drag ratio equalizes and it just can't do it. Any Idea's what happened to my top end horsepower? 150 main jet 38 idle jet. bored out to 484cc. bike seems a tad lean judging by the plugs when you shut it off running down the highway at 80 but not extreme.
Is there a restriction in the fuel delivery part. If it doesn't run any different at lower speeds, you have a few choices: Plugged exhaust, plugged intake, no fuel. You could have weak spark. Have you tried backing out of the throttle? Will it speed up at part throttle but not full?
I really babied the motor for the first few hundred miles. then just switch to driving averagely no real hot roding. This is the first time I've really gotten on it hard. I Changed the oil about 5 or 6 times during the break in period. All that was done to the engine was pistons, rings and reseating of the valves. The engine just seems to hit a brick wall at 80 mph 4th or 5th gear doesn't make any difference it just won't climb any higher. I've put about 800 miles on the bike so far. It feels like it has plenty of power under normal driving conditions I can get the front wheel off the ground. Its just when I try to top it out on the highway.
well I think I got it figured out. My carbs aren't perfectly synced just yet but the main problem was a little clutch slippage combined with my messed up wrist. I wasn't thinking and accidently put oil in it that had friction modifiers in it. I changed the oil thismorning and took it out and got it up to 95 then I let off of it cause it wasn't a very long stretch. I tried to hit the ton on it right before i changed the oil and i've got a messed up right wrist it doesn't bend back very far. I dont think i was cranking on the throttle hard enough lol. but when I hammered it I noticed it slipped a little. I changed the oil and it stopped slipping. Left plug still looks a little lean. Right plug looked perfect. Any advice on richening up that left side at WOT.
So tweek the float a little to let the level be a little higher in the left bowl? how much difference would that make? The left plug looks pretty grayish white when I checked it so i want it to be richer. the right plug had a slight brown to it so it seemed ok. Could the carbs being out of sync on the throttle cable cause one to run leaner? I'm not 100% sure if they are perfect. I just adjusted them by watching to see that they were opening at the same time.
Unless you installed vacuum ports, that is the only way you can sync them.
And yes, I meant to just raise the float a bit to make it richer, if that is what you want it to be. The other options are to change the jet size or start messing around with the needle. Raising the float is free and you can always put it back if you don't get the outcome you wanted.
I don't know how much of an effect it would have. These carbs are black magic to me. It was just a thought.
So would slightly adjusting the throttle cable to make the carb open up a little more or a little less in relation to the other carb effect the richness of the cylinder if the float doesn't quite get it there? Anyone know for sure which way I would have to go with it or if it would make any difference at all?
So would slightly adjusting the throttle cable to make the carb open up a little more or a little less in relation to the other carb effect the richness of the cylinder if the float doesn't quite get it there? Anyone know for sure which way I would have to go with it or if it would make any difference at all?
You do have a manual right?
the OEM manual has a good write up about how to set the carbs
Rich and lean is controled by the jets
a motor will seem to run lean or rich due to the floats not being set right but that is a by product of the floats being wrong not letting the jets do thier jobs
Well there is a special machined finish on the piston an top cap mating surfaces. If those get messed up or really dirty, then the vacuum piston doesn't function properly.
So this raises the question, are mikunis that important of an upgrade on the 450s? I can understand getting away from the diaphragms on the 350s, but not on a street only 450. Sorry for derailing the thread
yeah surprisingly This bike came with the original owners manual tucked underneath the seat. I haven't had too much problems with these Keihin Carbs but I think I'd rather have the Mikuni's. I've got 150 main jets in my carbs right now. Where could I get some jets slightly bigger to try out? Looking on Ebay I see a lot of 130's 145's and 150's but nothing else.
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