CB450 Carb Issue

Doing that today. He wants to eventually go with a single tach/speedo unit any way. The main thing wrong with this bike is that it was stored under a tarp in PA by a would-be collector. Things go gummed up and a bit weather-beaten. Fortunately, the original owner seems to have taken decent care of it and there was almost not rust at all. What there was is on the chrome.
 
TripleKing said:
Doing that today. He wants to eventually go with a single tach/speedo unit any way. The main thing wrong with this bike is that it was stored under a tarp in PA by a would-be collector. Things go gummed up and a bit weather-beaten. Fortunately, the original owner seems to have taken decent care of it and there was almost not rust at all. What there was is on the chrome.
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Here is something interesting. I raised the needles figuring that it will let more fuel in when I crack the throttle (solving the miss/hesitation it was having off idle) and maybe giving it more fuel for higher RPMs at anything but full throttle, there by fixing the miss above 7500 RPM. Mission accomplished off idle, but by giving it more fuel by raising the needles, my miss is now just under 7,000 RPM. Could it be I am dumping too much fuel up top?

Currently, I have the needle clip at the next lowest setting (next to highest needle setting) out of five. It was in the middle. Dare I move it up to the second highest

My jetting is:

190 Main, 35 Pilot, 6DH7 Jet Needle, 2.0 Air Jet, 159 P-5 Needle Jet

The bike has original exhaust, but one of the previous owners removed the baffles and new (properly oiled) Uni filters.

Addendum: Lowered the needles and I don't get a miss/breakup at all until 8000 RPM. I had to re-tune the idle dramatically.
 
TripleKing said:
Doing that today. He wants to eventually go with a single tach/speedo unit any way. The main thing wrong with this bike is that it was stored under a tarp in PA by a would-be collector. Things go gummed up and a bit weather-beaten. Fortunately, the original owner seems to have taken decent care of it and there was almost not rust at all. What there was is on the chrome.
Click to expand...

My son and I took an 80 mile round trip to and from his first motorcycle safety course and the 450 ran splendidly. I road along on my very well-sorted 79 CB400T. His 450 gave my 400 a run for its money. He is very happy with my carb tuning.
 
That confirms that the low end is lean. If it were mine I would try larger pilot jets to see what that changes and then I would try 159 Q-0 needle jets, to see if that works.
 
TripleKing said:
My son and I took an 80 mile round trip to and from his first motorcycle safety course and the 450 ran splendidly. I road along on my very well-sorted 79 CB400T. His 450 gave my 400 a run for its money. He is very happy with my carb tuning.
Click to expand...

Good deal, should serve him well as long as he takes care of it. The more he rides it the better it will get.
 
Now to teach him how to maintain a vintage bike. Seems like many (not all) in his generation want to "plug and play) and turn the key and go.
 
teazer said:
That confirms that the low end is lean. If it were mine I would try larger pilot jets to see what that changes and then I would try 159 Q-0 needle jets, to see if that works.
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Yup, I have the airscrews open only 1/2 turn on the left carb and one turn on the right carb (as a mention previously, I jabe a problem with the pilot jets due to fuel sitting at a now defunct shop. I think that going up from #35 pilot jets to #40 (one size higher) might do the trick, but I may have to send to Sudco as they are stuck fast. If I raise the needle to the highest clip setting (lowest needle setting) that might completely cure my high-end problem. He rarely takes the bike over 6,000 RPM, always mindful that this is an old engine that sat for a decade.
 
Take the carbs off and remove the bowls. Then spray carb cleaner through the left pilot jet and then the right one and compare flow pattern/rates. try each drilling one at a time and compare sides. Repeat of the air passages and make sure that every intake or orifice is tested for comparison side to side. That should tell you whether it's a partly blocked jet or passageway.
 
HA, at 6k that engine is JUST getting into its power area, they run best at around 5-8 K. We were having that discussion about a 450 on another sight and a fellow that couldn't get this bike to accelerate on the high way. Turns out he was never getting over 5k on RPM and never really seeing the true power of the engine. They are HIGH RPM engines designed to do it, heck the points will probably float before you get to damage areas. Would I run mine all day long at 10k? No but at 7 or 8? Sure. I ring mines neck every time I get on it, it goes to redline in at least 1-3 gear if for no other reason than to clean the carbon out.

55 mph should prolly be done in about 3rd gear if you are looking to be able to maintain speed up hills. 5th should really only be used for 70 and above running and for saving fuel at 65. Don't be scared of that 40 year old engine I'm sure as hell not of mine and I've got prolly way more money in it since I built a bike from a literal trailer full of parts.

As for tuning, I like to use the time it takes to unwind, listen to some music, and to get away from the wife. Learning about the timing, cam chain tension, valve gaps, oil changes, lubing drive chains, changing fork oil, cleaning air filters, etc. will sure test his interest in it for sure.
 
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