Honda Izy running rough

RichD1 · 10 Apr 2021

My Izy has a choke position on the throttle control. It's a 2007 model. Yes, fuel tap is fully on but it is very stiff. I got fuel to run out the tube which goes on the carb before reattaching it. Been using an aerosol can of carb cleaner but don't have access to an air line. Have to make do with mouth pressure. As far as I can tell I can hear no air leak on the inlet gaskets.

Richard

Burnerman · 10 Apr 2021

The fuel taps are usually stiff as hell but they do loosen up with use.
It's really best to shift that emulsion tube but if it's impossible, look at the carb face air cleaner side....see the small bleed hole to the side below the main venturi?
Squirt carb cleaner in there.
Izy carbs have a pilot jet too which is supposed to be sealed and non adjustable but give us a close up pic of the carb top and I'll tell you how to shift it.
John

RichD1 · 10 Apr 2021

Hi John, at the moment I'm a tad despondent after giving it what I thought was a good clean. The gardener needs to mow the grass at the mother-in-laws in the week so will probably leave it till next weekend. Hopefully I'll have a bit more enthusiasm then. I'll attach some pics then.

I have removed the screw above the idle jet and was able to put a small piece of wire down through it and was able to see it through the hole on the air filter side. Also the carb cleaner went through easily.

BTW, what does the little sprung twist lever just right of the throttle stop? It can turn through 90 degrees.

Richard

Burnerman · 10 Apr 2021

If its the part I think you mean, its the pilot jet adjustment......it has a leaded cap on a screw which can only be turned a few degrees? It has limited adjustment to minimise pollution but on occasion it has to come out.
To do this, I cut the lead peg off which allows the needle to unscrew - its usual setting is 11/4 turns from fully in.
John

Keithmac · 11 Apr 2021

As John has pointed out it may need pilot air screw adjustment.

The petrol you put in now is not the same as it was back in 2007 so you'll need to richen it up imho.

RichD1 · 11 Apr 2021

Burnerman said:
If its the part I think you mean, its the pilot jet adjustment......it has a leaded cap on a screw which can only be turned a few degrees? It has limited adjustment to minimise pollution but on occasion it has to come out.
To do this, I cut the lead peg off which allows the needle to unscrew - its usual setting is 11/4 turns from fully in.
John

When you say 'cut peg off' do you mean the bit that stricts movement to a 1/4 turn?

Richard

Burnerman · 11 Apr 2021

Yes - if you prise the entire cap away you are left with a screw with no slot

which can complicate things!
I saw the nib off with a junior hacksaw which allows the whole thing to be unscrewed. When I'm done I apply a blob of paint just to lock it in place.
The jet itself is under the brass philips headed screw alongside.
John

Keithmac · 11 Apr 2021

There's a few motorcycles like that, I've wound the screws out with a pick and then cut a slot in the top so next time it's easily adjustable.

RichD1 · 14 Apr 2021

Having thought a bit more about this hunting problem. If the emulsifier tube is gummed up on the cross holes surely this would make the mixture run richer rather than causing a starvation.

What if I added some fuel treatment that is used in cars for cleaning up the fuel injectors?

Richard

Harry Bloomfield · 14 Apr 2021

RichD1 said:
Having thought a bit more about this hunting problem. If the emulsifier tube is gummed up on the cross holes surely this would make the mixture run richer rather than causing a starvation.

No, I would expect it to cause weak running or starvation.

RichD1 · 15 Apr 2021

I still can't see it. Could you explain how that works please?

Richard

Burnerman · 15 Apr 2021

The purpose of the emulsion tube is to aerate and mix the fuel that passes through the main jet heading up to the venturi..
In usual circumstances the emulsion tube admits air from some of the drillings and adds some fuel from others....the fuel passages are extremely fine and difficult to see - it's a blast of compressed air that's needed to sort that, with luck.
The carburation is in three stages - at least on a more complex carburettor system.
1) The idle stage, where most of the fuel passes through the idle jet, and aerated with an air bleed passage;
2) The intermediate stage where the emulsion tube helps to deliver fuel into the venturi when not on full throttle;
3) The full throttle stage where the idle jet and emulsion tube are largely redundant.
However, who can say of the accuracy of this when applied to simple carbs by Honda or Briggs and Stratton are anyone's guess!
Anyway Rich - to get your carb performing again the emulsion tube and idle jet do need to have to come out - the chances are the alloy corrosion, which will surely be there to some degree is interfering with things.
Pattern carbs are available at a fraction of the Honda price, of course.
John

RichD1 · 16 Apr 2021

Thanks for the explanation John, I think I understand.

Anyway, I took the mower back to let the gardener use it and he says that it now runs well after having it running for about 40 mins. So maybe it was reside that had gummed up over the winter lay-up and petrol running through it has done the trick. I'll keep an eye on it and when I've got a spare moment I'll take it apart again.

Thanks for all your help guys.

Richard

Burnerman · 16 Apr 2021

You’ll notice the izy has a drain plug on the float chamber, so you can use that or run the engine with the fuel tap off when you want to lay the machine up in the future.
Pleased it seems to be behaving!
John

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Honda Izy running rough

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