Tomorrow I'm going to do a more extensive ride to see how the bike does under a variety of conditions. I've organized a ride for April 17th with about 10 other people, and I'm going to do a 'dry run' of it -- about 150 miles round trip. This should give a good idea as to how the bike does with the 30 rear sprocket (though I have forewarned John that I might want to go back to the 32). The bike did seem to provide the most 'thrills' with that 32 sprocket, but I'm just not sure about the extra revs on the highway. We'll see!
Plus, I also made a point to wash and re-oil the K&N filters, just in case they were dirty and somehow restricted performance (though they looked okay to me). The only other thing the bike needs at the moment is a good cleaning!
Japan Meets BritainG-Man, Correct on all points and nicely explained.
Fuels slope is the way that the A:F changes over the rev range. As Revs increase, so does the air speed through the carb and air has less density than fuel so it can change velocity faster. That tends to lead to a condition where the mixture gets leaner as revs rise or in some carbs it gets richer as revs rise. Designers fit air jets to balance the flow of fuel and air over the whole rev range. In some situations a carb may have the right main jet for WOT at say 4000 rpm but that same main jet at 8000 may be too big or too small. If that's the case, a typical fix is to change the air jet. 4 strokes typically have a main jet holder with holes in it AKA an emulsion tube and the size of the air holes changes the fuel slope. Vince at 15:30 (or 16:32) one tooth at the front is the same obviously as two on the rear. That rule of thumb is because many bikes run 15:45 or 3:1 and that's where that old rule came from. G-Man, I suspect that you may be right about valve float, but it's not just about spring poundage and reciprocating weight, though they are very important. Cam shape is also a factor especially as it passes over the nose. Float occurs when the valve is accelerated fast and as the cam passes over the peak, the valve may still be traveling away from the cam and it comes crashing back onto the cam (well the rocker arm does). I have not done a detailed work on a stock CB cam but some aftermarket cams have excessive acceleration and jerk causing valve float and damage. A dyno run won't fix any of the above, but it will show what the HP actually is and what revs it peaks at. If it peaks at say 7,700 then something is not working the way it should. If it peaks at say 9000 then it may just need to be geared down to take advantage of the power curve. And if it runs fine and Vince is enjoying it, it really doesn't matter in the grand scheme of things. That's the problem with chasing perfection. The closer you get the farther away it seems. Teazer
Thanks for those thoughts. I left cam profile out of my post because I understand that Vince is still using the standard cam. Lighter valve caps reduce reciprocating inertia so the valves should be able to follow the profile better. Not really looked in detail at a CB cam to see what techniques Honda used to design them. Jerk (or rate of change of acceleration) is, as you say, a problem with some simple cam profiles and can be designed out. I used to be able to do the calculations on cam profiles but that was a long time ago... :-) I enjoy reading your insights. G '60 C77 '60 C72 '62 C72 Dream '63 CL72
'61 CB72 '64 CB77 '65 CB160 '66 Matchless 350 '67 CL77 '67 S90 '77 CB400F
One thing I had definitely been 'chasing perfection' with is the chain guard, strange as it may sound. I've had chain guards fracture at least three times, and yesterday while I was cleaning the bike, I discovered that this one fractured again (at that curved piece that goes behind the shock). I have finally cried 'uncle' with these chain guards -- this particular one (a thicker repro) had been reinforced every which way - but obviously not in certain spots! So, what I've decided to do is to take an old one that I have, and cut it to make it a very short chain guard (so that it's only going slightly beyond those two fixing points towards the front sprocket). Plus, I'm just going to 'paint it black', as they say. Very very frustrating indeed.
Today is my ride day, so we'll see how it does under a variety of conditions, and I'll decide whether it'll be the 30 or the 32 rear sprocket. The rush of acceleration from the 32 is awesome, but I'm not crazy about the higher revs on the highway. The 30 has less acceleration, but it feels great on the highway. So we'll see..... I feel like Homer... duh!All I can say is..... if I'd known half of the stuff I've learned since joining the 305 Forum a year ago, I'd have been hard to beat back in the day.
If neither the 32 or 30 seem right, maybe a 31- Sprocket Specialties now appears to be Sprocket Specialists, and they list 28 to 71 tooth sprockets:
http://www.sprocketspecialists.com/spro ... cts/page-4
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