Suzuki 4 stroke problem

[duggie12]

Hi fenlander, sorry I feel like you are becoming my personal mechanic!
Is setting the idle 'mixture' the same thing as setting the idle screw? There is something in the manual about setting the idle screw. See attached.

On another search I read something about the df 2.5 hp having an anti tamper idle screw where you would have to drill a bit of the carb to access it, but there is no mention of that in my manual.

[Fenlander]

Well it gives a break from varnishing floorboards and oars... heady work in 30deg kneeling over trad solvented varnish!

Yep I meant the idle mixture screw. What does it say in the manual to set it... can't see "attached".

Some do have a thin alloy or plastic plug which usually just needs a drill to start then a self tapper and pliers to remove.

Even if I think it's set incorrectly I'd always first wind all the way in counting turns until it stops. Make a note so you can get back to that posn if needed.

Most OBs (under 25hp for sure) benefit from the idle mixture and speed being set while in a water container in forward gear so they are set up to cope with prop drag.

[duggie12]

Oops forgot to attach

Here it is

Thanks

[Fenlander]

OK so that's just the speed which does help if on the higher end of the range... but can you not see an idle mixture screw or its plug??

Edit: Just looked back at that carb parts link I gave above... unless they have left it off the diagram on purpose it seems they may have deleted the idle mixture which you could adjust on models at least to 2005.

If it has been deleted then all you can do is set the idle speed up to max of the stated range in gear in a tank.... and only then think if you needed any new gaskets for a proper seal.

[Bern Hanreck]

May just be worth mentioning , as it has caused problems before.......my suzy 5hp auxillary was giving me lots of trouble at the start of this season and it turned out that the 15 year old quicksilver fuel hose had completely broken down ( possible reaction to ethanol in fuel ? ) , and the thin inner layer had separated from the outer hose , and was breaking up into small pale brown chunks . I had the symptoms of poor starting and rough running and at first suspected all the things that you are checking.

[duggie12]

Do you think the cover for the mixture screw is to the left and down a bit or the star head screw ?

[duggie12]

This is from a 2005 manual, but I think it covers my 2011 model.

[duggie12]

Low mid speed

[duggie12]

Pretty sure this is mine

[duggie12]

Low/mid

[duggie12]

Tried the engine in the bin again just there. Seems to be okay but just makes a 'bang/pop' every now and again from the carb/air intake area - the noise doesn't seem to be coming from the exhaust

[Fenlander]

Yep that's the classic lean mixture as you come off idle effect.

That plug looks promising... I'd pull it out and see... what could go wrong!

[duggie12]

I'm sure this is a stupid question - but how far do I drill?!

[Fenlander]

Just enough to pierce, it's probably only 1-2mm thick. Then get a self tapper in it to get pliers on.

[duggie12]

Sorry fenlander I'm not sure I'm getting this!

Am I putting a self tapping screw into the alloy cover, then pulling the cover off via the screw/pliers, to access the mixture screw hiding behind the alloy cover?

Thanks

[Fenlander]

Yep that's it, effectively you are scrapping the cap which does not need replacing.

[duggie12]

Do you think i can I carefully drill out the whole cover? I don't think I have any self tapping screws, but I could take a trip to screw fix later if need be !
Thanks

[Fenlander]

You will have something on the car under the bonnet where you can borrow a screw... something like clip or whatever self tapered to the inner wing... nothing crucial though!!

Or a woodscrew like on an interior door hinge.

[duggie12]

You are right, it is there mixture screw is accessed!

Now what ? :-)

[Fenlander]

OK...

First screw it in counting turns until it bottoms out gently. Make a note of this and return it to the existing position. Then in a bin of water get it warmed up idling in forward gear. If it isn't keen bring up the idle speed with the linkage screw just enough for it to continue idling OK.

Then turn in the idle mixture screw until it just starts to hesitate and note how many turns that is from fully screwed in. Then turn out the idle mixture screw until it starts to hesitate and find out how many turns out from fully in that is.

Set it to a position half way between the two which should be the ideal... sometimes they pick up from idle best just a fraction screwed out from the halfway point.

If during this mixture setting it improves the running enough to make the idle too high back the speed screw off to a normal idle and go through the procedure again.