SOHC.co.uk Forums > CB350/400
A couple of "tune up" questions...
K2-K6:
Encouraging that there's improvement, always feels good getting progress too.
Do you know where you've now got the airscrews set at, absolute turns out from closed in other words ?
Have you gapped the spark plugs to maximum ? If so, then try them set tight to minimum specification gap to try it like that.
It maybe you'll need to lift the needles by one notch to get the fuelling just slightly richer at that problem point, getting the idle and main to attach together smoothly being the aim, to then give that linear response you're after.
Neither the idle tweak or needle lift change the overall jetting, but both tickle it up just a small amount to try and optimise around that shift point.
Mikep328:
I should have checked to see how many turns out each screw is now but I didn't. I started out with them at 2 and adjusted them individually to Max RPM/ then drop 100 RPM so don't know the current settings. But I'll check when I'm at the bike later this week.
I pulled the plugs and adjusted the gaps to .028" the other day. The plugs looked good color wise but they are not new plugs - center electrodes edges are not sharp like new ones. I've been meaning to install a new set. ;) I was trying to find NGK D8ESL - which are in the engine - but they don't seem to be available so I guess the DR8ESL is the one?
I'd rather not pull/disassemble the carbs again but needle height may need to be changed. FWIW, my BMW R1200RS had the same sort of stutter at a similar RPM range that was also annoying at low speed, trundling through town. It was cured with the installation of an aftermarket electronic device (forgot the name) that "fooled" the computer into enriching the mixture at low RPM. So pulling the carbs/raising the needles might be required... :(
K2-K6:
Understand not wanting to pull carbs off again ;D especially as you seem to be so very close to getting them exactly how you want.
There maybe a little room to tweak the airscrews again to just squeeze it a little more into range. They are a very precise carburettor, with just tiny little refinements needed to get them on song.
Something from the later PD carb instructions from Honda manual I think is useful, to go through setup and then record exactly where they are as result of this, to then act as baseline for all those parts in situ on that bike.
Something the 400 is affected by with it's modest torque, is that if you open the throttle and it can't easily increase rpm, it then prompts the rider to open more the throttle, which reduces the vacuum under the slide and results in going even leaner momentarily. The obvious stumble a result of this.
I feel it's correct to run as lean as practically possible as it just reduces unburnt fuel excess washing into engine oil. But there's a need to get enough in there to get the revs rising smoothly and up onto the main jetting phase without bogging it down into that annoying glitch.
Sounds very close, hopefully it'll give you what you need with a little more adjustment.
alfiembra:
[quote author=Bryanj link=topic=29801.msg288162#msg288162 date=1694197864]
Plywood is actualy 1440x1220 which just happens to be 8 x 4
[/quote]
Ahem 2440 or 2438.4 if you really want to a pedant like me :)
Bryanj:
I was having a bad day
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