Honda-SOHC

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Looking at this arrangement that you don't usually see opened like this.  Lorenzo crashed his Ducati moto gp bike and made a real mess of it this morning which allowed a view into something that's generally covered.

It uses an airbox,  the top of which is to rhs of picture. Intake bell mouth which are retracted and extended to affect engine combustion, they raise and lower on that frame which also has the fuel injectors travelling with them.
Interesting that with all the ecu control available and virtually unlimited R+D resources, it still has to use something that is fundamentally the same as our old road bikes to make the inlet system flow properly. 
If they need this stuff to run properly,  then how difficult does that make it look to strip off the original Honda kit from these SOHC and have a realistic shot at getting them to run without glitches.

http://www.yeoldecycleshoppe.com/roadtestlibrary/2017/4/10/1970-honda-cb450-road-test

Interesting write up with some technical details from contemporary road test of 1970.

Site is live so you can look up other bikes on there too.

Nigel.

https://www.classicsmallmotorcycles.com/honda-over-350cc.html

I've not seen this before,  maybe others have. Some interesting bikes.

Just noticed that the photobucket pictures that have been blanked on forum like this, after requiring payment for the service, still appear in images searches on Google. So if anyone has no original access to photos they may want then it's just possible you can find a copy.

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This one was on here some years ago but still stored by then Goo men I presume.

Alright,  I know I " go on about it" but been looking at why I feel detonation can easily occur on this engine given the right / wrong conditions.

As others pointed out you normally associate lean mixture with something like this,  which is not obviously the case if jetted properly,  you'd have thought?
A characteristic of slide carbs is that you can create it with how you ride,  even if setup is correct.
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Above should be a dyno trace that Jensen has kindly shared of his 400 Four running in 4th gear with throttle rolled open in that one gear to build the power curve you see in top traces.

The really interesting bit is the lower trace,  left scale is mixture with rpm along the bottom. It's obvious from that peak leading up to 4000rpm that it's running toward an over lean condition. Complete burn is considered to be 14.7 parts air to 1 part fuel. Most engines won't get that close. During acceleration you'd expect closer to 12 to 1 to make it move,  with cruising state in between the two.
It's not a wrong setting on here,  just characteristic of running from low rpm to high in one gear which is needed for the dyno plot.

What it does is the vacuum the engine draws at low rpm with throttle wide open cannot match the flow the carb venturi is making,  resulting in loss of vac on the main jet,  and so less fuel than ideal is pulled from float chambers ( it's this bit that PD carbs fill in with accelerator pump,  clever a?)  you can't jet your way out of it as the carb and main jet is almost fully open. It's really a failure of slide carbs used in this way and what would be termed "lugging " the motor in high gear.

In addition,  the ignition advance reaches max around 3000rpm and quite early for full load application ( more suited to cruising on light throttle to give good economy)  so in that lean peak area you've also got probably too much advance for a short period.

Put those conditions together,  perhaps riding along into a headwind,  fith or sixth gear,  trying to keep up speed at lowered rpm and you've got classic detonation. Riders with experience would recognise it's not pulling properly,  but if the circumstances are held like that without the engine accelerating through that, it will most likely detonate. It'll only take a few minutes like that to start the destruction of the pistons and rings.

You can't jet it differently,  it's just how you ride it. They need to be revved if you want them to go.
You've either got to back down the throttle or drop gears and spin it to higher revs.

I hope that I may get some help with part numbers for Honda bikes I don't know,  for example handlebar switch # 35150-187-601 which is a rhs assembly with switch,  throttle and cable brake lever bracket built in.

Can anyone identify the bike from this?

And also is there a resource that I can look up various numbers from, mostly from 70's and 80's I'm guessing.

Thanks it advance for anyone's help.

Nigel.

Looks like there could be something of ineterest here on Sunday 27th July and also a bike autojumble.

I don't know what it's like as I've always missed the dates before but may get over there tomorrow to have a look, it's near Gatwick airport so not too far for some of those on here.