CB750 K1 Valve Timing Question

[cbxman]

Nigel,

Just had another look at an emulsifier.  The small holes are at the bottom, not the top as mentioned in my last post

Sorry,

Jerry

[K2-K6]

I strongly suspect that Kiehin (and subsequently Honda) have the original arrangement as taper characteristics to track main jet volume flow throughout it's range to bring consistent aeration to the fuel delivery. I'm highly suspicious of uncontrolled actions to change things like this without the "director" understanding why it was this way in the first place.

I like the outlook and involvment mark has in these bikes, but things like this need to withstand significant scrutiny to offer validation.  I can't see the logical path to that decision (perhaps I've missed something) as the percentage change doesn't involve a step change, and if it did then shifting atomisation seems an odd answer. 

The statement of leaner mix making more temperature is fundamentally untrue and backed by research of far greater depth than we can bring here and shows to me a naive setting off point for further analysis. This a interesting topic in itself.

For interest, the clip statement a couple of post back about ethanol is from here https://extension.psu.edu/fuel-ethanol-hero-or-villain which appears to offer reasonable balance in topline discussion of that fuel supply.

Nigel.

[cbxman]

For interest, the clip statement a couple of post back about ethanol is from here https://extension.psu.edu/fuel-ethanol-hero-or-villain which appears to offer reasonable balance in topline discussion of that fuel supply.

Nigel,

Interesting article.  It is light on the downsides, like for "older machinery".  We all know how corrosive the use of ethanol can be and this must be our main worry.  However, I don't see that we have a great deal of choice.

Mark is suggesting a way of compensating for the "Leanness", but of course if you end up using variable E numbers, or none, then you may run rich.  I think in the states they are stuck with E10, so it makes sense to re-tune the engine somehow.

I have read that some people make a weak two stroke mix in their tanks, which is claimed to reduce the corrosive element of ethanol fuel.  Not sure of this as I am not a chemist.

Cheers,
Jerry

[K2-K6]

The combustion element, as with other effects, will obviously split opinion. I just can't see a difference of any significance that needs reacting to and principally because these era carburettor fed engines essentially run rich in greater error from the outset.

I agree with tentative exploration of running two mix "light" to asses if it affects/improves your own storage stability if using E fuels.

Two aspects that I feel could be considered. One is some residual oil may help in protecting the exhaust interior of these expensive systems, especially when used sporadically. Two stroke exhaust will generally not corrode internally from this effect, that could offer something significant to owners. The water vapour output from burning petrol has a sulphuric acid content (ultimately from sulphur content of fuel) which is the primary cause of corrosion within these mild steel systems, and something to consider at least.

Fuel stability is another aspect. It seems to me that premixed fuel does improve in keeping and corrosion effects in systems that use it, this is experience and not from outside reports. I have a number of smaller engines that seem to benefit in this way. One a Honda generator 4 stroke that has significant periods of non use that I've had oil mix in for about 8 years and never had to clean the system in any way. Usually run the carb dry with fuel off before storage, then it just starts again on re use.  It's been with a outlying type of oil though that's not in general use. From this I've been running same at 100:1 mix ratio in a petrol car to guage the effects there too, and with no detrimental characteristics in approx 10,000 miles. Notably this starts impeccably and runs without compromise, it's 32 yes old and  170,000 miles status.
Anecdotal, yes, but maybe of interest in using E 10. I use std fuel from local supermarkets and never enhanced product, they are high throughput though which can have a different effect on their own storage I understand. 
I've set some long term samples in glass jars too, this to try and judge longe term keeping dropout, water accumulated etc. Certainly in sealed containers the E fuel seems to keep without problems, but also with the oil appears less likely to give the micro corrosion on some carburettor components (that crystalline type accumulation that effectively impairs jets etc) and could be worth experimenting with for others.

Nigel.

[cbxman]

Nigel,

Interesting.

I think I might try a 100:1 mix with two stroke oil in the tank and have ride before I put her away in the autumn for the long winter snooze.  Same with the CBX.  I have a Suzuki GT550, so I have 2T oil handy.

Cheers,

Jerry