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Messages - K2-K6
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3151
« on: April 23, 2019, 12:52:37 PM »
It's more likely reference to conrod bearing shells, as Oddjob points out, the main bearings have to align with crankcase indents for that part which orientates them for you. Although that hasn't in the past stopped people from torqueing the cases together with those gearbox location pins out of alignment with the machined holes  The 750 manual states "bearing pawls to front of engine" in section for assembly of conrod. I'd presume that during the cylinder power stroke the main thrust faces are the ones that have no interrupted bearing surface as presented to the crank during that phase, and so more resilient under load and keeping the oil film more complete at the maximum load site.
3152
« on: April 22, 2019, 09:58:50 PM »
I can't remember accurately Bryan, but thought I recall that Dresda used taper roller bearing arrangements to support their swingarm.
Those look like they could be with the aluminium outer providing a sleeving into the bearing bore to size them onto std Honda pivot bolt.
In which case to be ideal they should have a clamped distance tube between the two races.
3154
« on: April 22, 2019, 09:45:13 AM »
I crossed over with you there Steve so may seem slightly out of sync. My D is not showing smiley on Android tablet  Interesting to get electronic engineer view of it. As you say the lengthening of spark assists mechanical layout of combustion chamber. Combustion is often mistakenly viewed as single time event of explosion by people selling "high power" ignition systems. Reality is its a controlled burn with progressing stages. These engines have a fairly conservative design (evidenced by the total ignition advance being around 35 degrees) and rely on the squish area pushing unburnt mixture toward the spark location on approach to peak combustion pressure. Any lengthening of spark duration would be a welcome characteristic to facilitate this design. It follows that if they required suppression for their developing markets, USA etc, then the engine design would incorporate that element as a primary lead during development, making it logical that they should always be run with resistance to fit that specification. If you flip the analysis, and now remove resistance, the resulting shortening of spark duration should have a detrimental effect on completion of combustion burn. It can also lead to detonation.
3155
« on: April 22, 2019, 09:18:15 AM »
It's a much more intricate area than is readily given importance to I feel, and dominated by the bigger and fatter the spark, then the better it is stance. That seems more marketing huff and puff than based on factual engineering.
Do you mean with reference to the R&D specifically related to resisted ignition, or how resistance affects spark and ignition effects?
It may, by way of logical explanation be more relevant in the thread I was writing about detonation than isolated as it's really an extension of that field from an informative point of view.
3156
« on: April 20, 2019, 01:53:20 PM »
I feel these combustion chambers were researched and developed to use resisted ignition system.
It's often just referenced to radio interference, but it changes the length of spark which is intrinsic to combustion chamber design. I don't think they should be run without resistance.
3157
« on: April 20, 2019, 01:49:57 PM »
That gives an interesting look at the current status. No wonder it's smelling of petrol.
As you've said, something well out of range on no1, seems a bit of a gusher on that one. Although if it had any mis-fire on that cylinder it wouldn't help the unburnt fuel total.
Also appears to have idle jets 1 or 2 steps higher than needed, be interesting to see what numbers are in there.
looks like carb balnce is ok for 1,2,3 with 4 sitting slightly lower judging by the O2 readings.
Unless there's anything specific about valve clearance to give confirmed non std, then I can't see why normal tolerancing wouldn't be in place.
3159
« on: April 19, 2019, 07:30:12 AM »
There are surface finishes that have altered/additional friction reduction materials, but I don't think that's the case here.
As I understand it, it's the surface grind that leaves a structure to hold lubricant in very small quantities that allow the seal to move easily. A little like the inverse of a cylinder bore. There is a very very small loss of oil that you can just about see gathering dust over a period of time above the fork seal, almost undetected n volume.
They centreless grind the tubes to finish, it states on their info page. If you set up a tube in fixed centres to grind it, then any bend in the tube at all, or deflection from the grind wheel pressure, could result in the grind breaking through the chrome layer, but if centreless it just follows the surface and leaves the chrome layer at uniform thickness all round the tube.
The grind wheel material creates the desired final surface micro finish, if you run your finger nail up and down it you should by able to just hear the surface.
3160
« on: April 18, 2019, 05:52:42 PM »
It'll be interesting to see roughly where it is to give you a guide.
I know it's not run under load for those about to point that out, but it does give something to understand and work on.
3161
« on: April 17, 2019, 09:50:50 AM »
Undoubtedly specific knowledge would help here with straight numbers for jets if anyone has relevant experience.
In the past people have just assumed that things like this "just need jetting up " but the same carbs used for the smaller engine will have a greater volume of air going through them......... Which also takes more fuel from standard jets, so it's never as big a change as presented or believed.
You can usually smell an old bike or car ahead in a line of traffic currently as most engines don't kick out unburnt fuel, so it's very noticeable when you follow one that does.
A basic start view could be to get a reading from each pipe on MOT test equipment, HC (unburnt hydrocarbons) level will tell you straight away if it's really bad.
I know you'd not want to run it lean, but heading to bore wash levels is just as bad with people not seeing it as much of a risk.
3162
« on: April 16, 2019, 08:51:59 PM »
I know it's all a little experimental to find a decent setup, but if you're interested in addition to jetting you could try it with resistance plugs as well as plug caps.
I know that's counter to generally accepted views, but there's a possible benefit in how it ignites the mixture and could help with what you have here.
NGK 8 would also be a good start point.
3163
« on: April 16, 2019, 04:18:36 PM »
Can you pull each one in individually using the swing arm bolt, with a washer or spacer at the opposite side to pull against? Perhaps the bolt isn't long enough, but could be a possibility.
Or a carpenter's sash cramp to squeeze them in.
3164
« on: April 15, 2019, 08:58:58 AM »
I think generally over the years people just throw bigger jets at it, which heads towards the results described above.
To expand briefly, when Honda set it up it had a vacuum gradient (if that's the right description) with the airbox etc in place. This they matched with carb components to get fueling in the right range. Specifically the throttle slide cutaway and shape of the needle are designed to meter correctly with the prevailing vacuum.
When airbox is removed, the air flow now has a different shape of vacuum "mapping" for the same engine speed and airflow it had before.
Really what it needs is a throttle slide with a different cutaway, plus a change in form of needle to match it. As that's not going to happen in most situations you're left with trying to compensate with what you can change to try and bring back a parity of mixture over the engine response range.
Overriding is that the engine doesn't need to burn more fuel to work, it just pulls less fuel than it did because of altered vacuum. So it mostly runs leaner.
If you just put in bigger idle jets to correct low speed running it may fix that but shift the blend to main jets too rich, so you get a blubbery flat spot as you come up on the throttle, which you struggle to get rid of. If you up the mains, it may correct the top but not link to the lower, hence the steps in response.
You are in effect running into and out of ideal fuel mix ratio. Less than 10 parts air to 1 fuel will give you too rich, this generally gives you those "dead" flat spots as the plug won't reliably fire the mixture. So you can at least feel which way the error is.
More than 13.5 parts air (on conventional carbs) to 1 fuel will give you those lean "waffety" slow responses that just feel lethargic. This is usually because the combustion mix fires but fails to completely burn in its entirety. Mostly, you should be getting this, so trying to push it back towards correct range without overshooting straight out the other side to rich ratio, is what you're trying to get.
The answers usually don't conform to convention (as compared to book values) but by squeezing it with the adjustments you have, it can be reasonably set up.
Out of interest, what plugs and plug caps do you have in it?
3165
« on: April 14, 2019, 09:16:51 PM »
Subtle changes you could use to edge it towards better response would be, close the idle jet screws down to approx half normal setting, raise float height a couple of mm if possible, and lift the main needle jets a notch (move circlip down) to give more fueling across the whole range.
It should at least let you see if any improvement is made to running.
Try it across its rev range, then look at plug colour to see what you're getting.
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