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Idle and Starting Set Up

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mgy66:
Hi,

Following on previous post to get better understanding on the right carb set up. I have a K1, big bore 830cc. Pilot #40, Main 110, air screw at 2.0.

I went through a carb balancing procedure (using 4 gages) and setting the readings at 150 Hg/mm.

I ended up with adjuster screws fully turned to lowest position, while in the Haynes it recommends to keep 1.8mm between the stopper nut and the tip of the adjuster screw. The idle is holding up for few secs but I need to rev up at red light or it would fade and stall.

Also, for my understanding does anyone know if the adjuster screw move only the throttle valve or is it both the throttle valve and the needle together?

Another question on my settings is the 26mm floater position. Can I get confirmation it is 26mm when the floater is up (floating valve closed)? Would a higher position overflow the carb or would foul the plug (assuming it is not high enough to reach the top of the carb to prevent closing of the valve nor the bowl gasket as I would notice leakage at the gasket).

Many thanks,
Marc

hairygit:
The adjuster moves both. Are you running standard pipes ( 4 into 4)?  I seem to recall that K1 with std pipes should be 120 mains, but I'm sure someone will tell me if that's wrong. Raising the float height may well cause the carbs to flood, better to lift the needles by 1 notch will give more fuel for any given throttle opening.

Sent from my X5 using Tapatalk

mgy66:
Hi,

I am running 4 in 4 standard but I think I have no bafle at the end of the pipe. I also have velocity stacks but I tried as well standard air box without being able to get a steady idle between 1000 rpm to 2000 rpm.

If I go with moving the needle up via the pin, has anyone tried to change the pin set up in situe, I.e carbs on the engine? Is there an easy access from the top of the carbs?

It seems that my starting problems come from gas not accessing the chambers despite new slow jets. Few supporting symptoms are:

- I usually.need to open up the idle screw at cold start taking the risk to foul the plugs. I can run a battery load without any succes otherwise. No need to say the choke is totally useless;
- My starter is actually a can of carb cleaner that I spray like a full on the velocity stacks.

Rather than changing the needle height pin, do you thing using a bigger slow jets, say #42 instead of #40 could help?

Thanks...

Spitfire:
120 mains rings a bell from my CH750K1 days, it had a 900cc conversion, a standard airbox with no filter inside, and at various times 4 into 4 and 4 into 1 exhausts, the carb was standard settings apart from the needle which was up one notch if I remember correctly.
Here's a chart


Cheers

Dennis

mgy66:
Thanks for these inputs.

From my reading, I thought the main jets were not so critical for start up and idle. Once in run, it may not be the most performing set up but it does run.

The issue is really the start up and idle. wrt to the start up, spraying carb cleaner into the inlets is a great solution until I get to understand how I should set my carbs. The idle is more tricky and other than running at 2000rpm or setting the idle screw lower and keep rev'ing at redlight I have not any solution.

I think I need to go a step beyond and dismantle all the carbs for a good and long ultrasonic bath... I think despite having brand new slow jets somehow not enough fuel reach the cylinders at low/start rev.

Any suggestion on what ultrasonic bath and product I should be considering? How long I should leave the carbs into the bath? Wrt to my former question on the 26mm floating position, can you confirm it is 26mm when the valve is in close position (i.e. floaters are up in their bowls)?
Thanks,
Marc

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