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Carbs Install

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Martin6:
Hi,

As mentioned in a previous topic, Im looking into why my new 750K6 is reluctant to tickover and run, particularly no.4, along with a stiff throttle that won't return on its owm. The ignition / timing looks ok. Plugs will be replaced.

I've removed and cleaned the carbs and fuel lines. I found 2 things;
-Floats were set at around 30mm above the bowl rim. So maybe it was lean? I've put it to 26mm and will watch out for leaks!
- I was unable to see through two of the slow jets (one was no.4). Hopefully, now all clean.
I'm not familiar with Keihin, nor multi carbs set ups. Im used to single Amals!  At this stage, I only cleaned what I could get to from the float bowl without dismantling them from the gantry system. I'll replace the fuel, the tank is very clean.

I'll crack on this morning. A couple of questions:

I know the carbs were not synch'd prior to taking them off. Is there a good method to getting a base setting on all 4, before re-installing? I have vacuum guages for once it's running (that will no doubt, be fun and games!).

The issue with the throttle not springing back remains a mystery. Cable run is smooth arcs. They were a little, very slightly, stiff.  I don’t think this was the issue. I've flushed them through with silicon lube. They are now nice and light. Off the bike, the throttle movement on the carbs gantry is very stiff. Im not able to shift it manually. On the bike, once the cables were removed, they did operate and spring back. The springs look ok. Should I be lubricating something, or easing any clearances? Is there perhaps a 'usual cause' for this?

Thanks, Martin

Johnny4428:
Hi Martin, I’ll give it my best shot until someone that has more knowledge comes along. With the idle adjust screw backed off to ensure fully closed sliders, viewed from the intake side of carbs use a plastic WD oil delivery tube or similar ad Nurse Julie suggests and set each slider in turn to get uniformity accross the four. This is the tried and tested bench sync method which can be tweaked with bike running and a vacuum sync.
The carb throttle stiffness, have you disconnected throttle return spring to see where the problem lies? Make sure all clean and no binding with the air intake sliders.

McCabe-Thiele (Ted):
A very basic thought is the twist grip nice and free, the one on my 500 was quite stiff when I removed the twist grip the tube was split causing binding.

K2-K6:
Accurate bench synchronisation of the carbs is easily as good as later "gauge" methods, they don't hold superiority over diligent setting in the first place. Once you have set them off the bike, made sure that you can close the slides fully by turning down the master tickover screw (the big one that controls idle rpm ) confirmation that you can modulate right down to zero on the carb bank, then that's good enough to run.

It holds advantage in diagnosis too, in that if there's fault of ignition or jets impaired/worn then it allows you to see that error rather than chase your tail by adding inappropriate adjustment to carb balance.

Worth stating the purpose of any multi carb balancing, that is to ensure the slides and hence air volumes are the same under full load, it's not a method for trimming idle smoothness, just coincidental that the idle should be smoother when the slides are set at parity.

Individual cylinder denand AT IDLE is emphatically set by adjustment of the low speed mixture circuit AFTER the slides have been correctly set. There's clear information and routine in Honda's manual that describes this schedule.

Martin6:
Thank you. All very encouraging  :)

The WD40 spray tube suggestion, im thinking all adjustment just done with what the manual calls the 'adjuster screw' above the top of each carb?

I checked the handlebar throttle tube, the action seems fine. That's all back together awaiting carbs to connect up the cables. Before connecting the cables, pushing on the 2 large U shape castings on the gantry, it seems to open and spring closed OK. Maybe just needed the cables lubing. I'll try it, before I get new cables.

Edit: With the master tickover screw fully out, all slides are fully down, as I raise the tickover screw, the slides all seem to start moving in unison. A WD40 straw is a fraction too large to fit into the cutaway on the intake side. I'll adjust the tickover screw to allow that and start the bike from there. Just have to get them back on now!

Cheers, Martin

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