A couple of "tune up" questions...

[Bryanj]

Most confusing thing in my currebt trade of HGV is up to 32 ton is english ton over 32 is metric tonne and 1,000 kg is not a ton

[Johnny4428]

This is certainly a drawn out affair. The transition from imperial to metric. My very first job on leaving school at 16 was working in a timber yard. After a shipment of timber to the islands the bings were all mixed lengths so first job was to sort all the timber into the correct lengths - 3.0, 3.3, 3.6m etc going up to 6.0m. It was great I very quickly learned my metric. Of course we always still referred to a 6 x 2” or 8 x 2” or whatever. So customer would come in and it would be marked as 2 x 4.8m x 6 x 2” rpos.

[Matt_Harrington]

About 20 years ago (?) they tried to force the TV & Monitor market to move metric. It failed miserably and screen diagonals still are measured in imperial.....

[K2-K6]

I disassembled the carbs/cleaned all parts thoroughly.   I reassembled with original brass, set the float levels,  and installed new (NJ) Orings and bench-synced the carbs.  On the bike with engine running each mixture screw functions properly, changing the idle as it is screwed in/out so I don't believe there is any issue with clogged passages, etc.  I'll richen the mixture slightly, as suggested.

I'll check the tappet clearance/adjust if needed - it was allegedly set properly by the shop tech prior to my purchase...

Something that may help in details. Often the great wide opinion out in internet-land is that the idle airscrew simply changes absolute mixture, when in reality these design change the "slope" of mixture leading up from lowest rpm to link into main jet response territory, which can be much further up in influence than many appreciate.

Thinking of a simple way to express it, thoughts like the following to expand a visual representation of them:- if you had a ladder to reach a second floor window of your house, you'd likely extend it to comfortably reach the sill, while leaving it at a decent angle for you to climb. Too steep and you risk it falling outward  too shallow and you risk it sliding down the wall in the opposite to before.

The airscrew adjusts both reach and slope to get the ladder to let you comfortably reach the window safely. If the ladder is too long to get into range, that would be the pilot jet too big and not let you get down below the guttering, too short and no chance of reaching the window the pilot jet being too small.

With all passages clean and correct brassware,  then it should allow you to trim that mixture slope until it attaches meeting all the requirements in blending  into the mainjet lower reaches and not give any discernible flat responses, rich or lean. It doesn't matter exactly where the screws end up (within reasonable amount of turns out range) but it will calibrate your carb, your airflow, your airfilter, at your altitude to bespoke tune the idle circuits as  Honda and Keihin designed it.

If you live in a bungalow, you're going to be mystified by this 

[Mikep328]

Went out today and checked the tappet clearance - they were .003"+ so I reset them all to .002"  Then I synced the carbs with a gauge set after first calibrating the set so that all gauges read the same when attached to the same cylinder.  I had bench-synced the carbs a few weeks ago and was pleased to see that they all cylinders were within a needle's width of each other.  I tweaked them so they read exactly the same though I doubt that a needle-width difference matters.

I richened the mixture by 1/8 turn on each carb but it was raining so didn't take the bike out to evaluate the change.  In the parking garage it accepted a quick throttle movement from idle with less hesitation than previously.

One thing that I was NOT happy about -  when I started the bike from cold there was visible smoke from the exhaust though it seemed to disappear after it warmed up.  Couldn't really tell the color but it smelled oily to me.  However, the spark plugs all look good color-wise with no sign of oil or fuel fouling.  My wife was behind me on her bike riding to Bristol the other day and she didn't mention seeing any smoke from mine.  I hadn't asked her to look for it but I'm sure she would have said something about it had she seen any smoke.  In any case, further evaluation is in order.

[Nurse Julie]

It may have been that you had just richened the mixture or it could be worn valve guides.

[McCabe-Thiele (Ted)]

If it's a relatively small amount of smoke when cold I would not worry about it unless you start using oil in any quantity.

I have found that older engines often give some smoke on start up sometimes due to oil that has found its way past valve guides whilst standing overnight.

Easy to panic and think the worst,

[TrickyMicky]

Went out today and checked the tappet clearance - they were .003"+ so I reset them all to .002"  Then I synced the carbs with a gauge set after first calibrating the set so that all gauges read the same when attached to the same cylinder.  I had bench-synced the carbs a few weeks ago and was pleased to see that they all cylinders were within a needle's width of each other.  I tweaked them so they read exactly the same though I doubt that a needle-width difference matters.

I richened the mixture by 1/8 turn on each carb but it was raining so didn't take the bike out to evaluate the change.  In the parking garage it accepted a quick throttle movement from idle with less hesitation than previously.

One thing that I was NOT happy about -  when I started the bike from cold there was visible smoke from the exhaust though it seemed to disappear after it warmed up.  Couldn't really tell the color but it smelled oily to me.  However, the spark plugs all look good color-wise with no sign of oil or fuel fouling.  My wife was behind me on her bike riding to Bristol the other day and she didn't mention seeing any smoke from mine.  I hadn't asked her to look for it but I'm sure she would have said something about it had she seen any smoke.  In any case, further evaluation is in order.

You mention that it was raining when you started the bike, meaning the air was quite moist, likely as not, it was steam from the condensation gathering in a cold exhaust. In my nearly days, this cost me a fortune in replacement exhausts (CB750),  as I used it for riding to and from work in all weathers, 5 miles each way so did not get hot.  As much as possible nowadays I do not start the 400 unless I'm going for a long enough ride to get its really hot. I'm still using the genuine Honda system that I fitted in 2006. If you say that someone following you did not see any blue smoke and it's not using oil between changes, I think I would just ride it. Stay safe. Mike.

[Mikep328]

Thanks Trick!  I asked my wife specifically today if she had seen any smoke at all from my 400 when she was following me on her motorbike and she replied, "absolutely not!"  So now my plan is to NOT worry about it!

[Mikep328]

We went out on a ride of around 30 miles today.  There was a substantial improvement in how the engine would accept opening the throttle so richening the air screws by 1/8 turn definitely helped.  I still have a rough spot - stutter - at around 1800-2000 RPM which continues to make in-town slow speed running at that RPM range a bit annoying.  I'd like to get rid of that...

[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  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