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750c3 carb setup

Posted: 04 Sep 2017, 16:19
by knight
HI all,
glad your back!
Does anyone know the reason why one of the four carbs spits/hicups on tick over only?
me thinks blocked idle jet maybe,not sure of mixture setting either,if carbs have to come off im gonna wait till winter comes :(

Re: 750c3 carb setup

Posted: 05 Sep 2017, 22:54
by hugojose
...you could try draining them and then priming,,,,, may flush any debris.....You could try synchronizing see how it looks. It is also possible to open the top, and/or removing the bowls, if tensioner is removed, without taking the carbs off.

Re: 750c3 carb setup

Posted: 06 Sep 2017, 11:24
by Freddy
knight wrote:HI all,
glad your back!
Does anyone know the reason why one of the four carbs spits/hicups on tick over only?
me thinks blocked idle jet maybe,not sure of mixture setting either,if carbs have to come off im gonna wait till winter comes :(
The first thing I'd do is check the valve clearances and compression. Need to do that anyway (valve clearances) so no wasted effort. Then you can rule out mechanical and by the sound of it unlikely to be electrical. So then at least if you do have to pull the carbies of you know your in the right area.

Never tried it on a Zephyr, but common practice to maybe clear a blocked carby on a car 'in the good old days' was to remove the air cleaner, engine running, open the throttle fully and as soon as the revs really pick up stick the palm of your hand on the carby top. Creats a massive vacuum pull. Lift you hand off just before the motor slows enough to die. Let it splutter and then rev up again, repeat. Do that 3 or 4 times. Worked in a lot of cases. How would you do the same thing on a Zephyr? Get something to block off the air intake. Maybe a piece of stiff cardboard.

If you see bits of foam rubber spitting out the exhaust (the air cleaner) you know you got a good vacuum clean going (just joking). Worst that can happen is it'll do nothing.

Re: 750c3 carb setup

Posted: 07 Sep 2017, 15:00
by knight
Hi Guy,s
Thanks for reply,s
I should have explained more, first i checked valve clearances all ok then i changed coils,spark plugs ran seafoam through carbs have ran for about 400 miles

then tried balancing carbs to find carb 2 spits/hicups every 30seconds or so,it only happens on tickover when starting from cold when warm seems to smooth out a

bit, she pulls like a train when giving some wellie :D just slight hesitation on pick up,will try ideas/check carb diaphams, its such a pain as the bike is a great fun ride just this niggling problem,thanks again for your help 8-)

Re: 750c3 carb setup

Posted: 07 Sep 2017, 22:26
by Freddy
knight wrote:Hi Guy,s
Thanks for reply,s
I should have explained more, first i checked valve clearances all ok then i changed coils,spark plugs ran seafoam through carbs have ran for about 400 miles

then tried balancing carbs to find carb 2 spits/hicups every 30seconds or so,it only happens on tickover when starting from cold when warm seems to smooth out a

bit, she pulls like a train when giving some wellie :D just slight hesitation on pick up,will try ideas/check carb diaphams, its such a pain as the bike is a great fun ride just this niggling problem,thanks again for your help 8-)
Things I'd do ......
Replace the air filter with a genuine Kawasaki filter. Don't forget to oil it (ok I'm stating the obvious)
Check that all other aspects of the intake are in good working condition, and set-up exactly the same as it left the factory. That includes replacing the roam rubber that raps around the white plastic noise dampener in the air cleaner lid intake. Guarantee it'll be a crumbling mess. It does affect running. Make sure no one has pulled out the quite large rubber block (noise dampener) that should be in the center of that white frame.
Set the idle mixture screws to 2 1/2 turns. A little difficult to do in the bike, but I find the small flat-blade screw driver tip out of a set of electric screw driver bits to work ok. Doing it when the engine is cold is MUCH easier not burning your hands. The hardest one I find to get at is the inner left, and removal of the front sprocket guard does make it much easier to get at if struggling.
Can you get non ethanol fuel where you live? Mine definitely ran worse on it the occasional time I've been forced to use it. It's easy to buy non ethanol fuel here in Australia.
Only use 91 RON or equivalent fuel.

Could someone have replaced the factory jets at some time?

Think that about all the intake related things I've found over the years that affect running. Other than that, pulling the carbies off and a good clean and set is probably the only think left. Don't worry if you haven't done that before, its not as bad as some make out (well maybe the first time till you figure the 'technique').

Re: 750c3 carb setup

Posted: 08 Sep 2017, 13:15
by knight
Thanks again Freddy for your vast knowledge on carb issues,
Your right iv never tackled a bank of four carbs before,only twins, your advice is priceless i will work my way through the process this weekend,all the best :)

Re: 750c3 carb setup

Posted: 08 Sep 2017, 19:37
by Richard
knight wrote:tried balancing carbs to find carb 2 spits/hicups every 30seconds or so,it only happens on tickover when starting from cold when warm seems to smooth out a
bit
I wonder, why this 30 seconds? Could be just the amount of time needed to empty a carb bowl when the engine is running. If so this could be related with the fuel shut off valve (float valve) or a sticking float or something...

Just an idea though ;)

Re: 750c3 carb setup

Posted: 09 Sep 2017, 15:13
by knight
Cheers Richard,
I think you might have had a bright idea :idea: