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Old 24 October 2014, 23:34   #1
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Suzuki 2.5hp 4 stroke hesitating

Hi guys looking for some assistance to cure my Suzuki 2.5 hesitance issues.
It's a 2010 with no more than 15 hours on it.
It starts up and idles perfectly.
Problem is when you go from idle to rev up it briskly the revs die down. If you persist with the throttle it cuts out.
This is the case whilst in gear or in neutral.
To stop the engine cutting out you have to feed the power in very slowly.
Once the revs are up above idle, it revs up and down freely without fear of cutting out.
Any suggestions welcome.
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Old 25 October 2014, 02:57   #2
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I think its a well known problem with the suzi 2.5hp 4 stroke Kaman... I learned to live with it.. it just doesn't like fast acceleration from idle. It never lets me down once above that critical idle point.. which has to be passed slowly. It alweays starts first pull too..even after stalling if going to fast past that "flat point"

I heard rumours that there is a new carb with bigger jets on the later models but cant confirm. The dealer I got mine from said it was due to the strict emissions controls that these small engines have to comply with ?

Plenty discussions on the problem on the net.. example

DF 2.5 questions - Page 4 - Suzuki Outboard Forum

Please post back if you find a solution that fixes yours..I was a bit reluctant to try the bigger jet size in case no improvement. My Suzi 2.5HP 4stroke is now my Auxilliary engines back up because of this niggle
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Old 25 October 2014, 03:14   #3
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Cheers for that Gurnard.
The suzuki is a cracking little engine apart from that one little niggle.
I can live with it tho as like yours it is my aux.
I had a Johnson 2.5hp 4 stroke previous to the suzuki 2.5hp 4 stroke This was the exact same engine albeit it was coloured white as opposed to black and badged differently.
It didn't have a tell tale jet though - just the little breathers that expels splutters of ingested water.
However it never had this little niggle and revved freely without stammering.
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Old 25 October 2014, 04:27   #4
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Classic weak idle setting issue. On these more modern motors they try and stop you fiddling but you can find the idle mixture screw under a thin alloy anti-tamper cap which you can get out by drilling/levering. Also raising the idle speed a little can help.

I'm sure there will be someone on the net who's done this and uploaded images... I'll look in a while.

Edit: Here you go...



Same or similar model to yours?
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Old 25 October 2014, 08:28   #5
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Cheers fenlander.
The model in the video is identical to mine, even the year of manufacture.
Mines idles sweetly.
It just stammers when I pick up the revs too quick from idle.
Do you think altering the idle mix will resolve this stammer.
It's surely worth a try at least given that it's not too difficult a task to alter the mix.
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Old 25 October 2014, 08:34   #6
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Yes I think it will sort it. Happens that guy had idle running issues but he comments he needed to turn the mixture screw a full turn to get an improvement. Often more like half a turn will do it if you are just suffering a stutter.

It is just possible you have some dirt in the carb but getting that properly cleaned is more trouble than trying the idle screw. After all it is non-invasive and if it doesn't work you can put it back as it was (make a note of the screw's starting position and how much you move it).
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Old 25 October 2014, 15:43   #7
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The engine has had this issue since new so I don't think it's dirt in the carb.
I will give it a look thru the week and feedback.
I take it its anti clockwise to richer the mix?????
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Old 25 October 2014, 16:57   #8
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Yes unscrew it to make it a bit richer. I'd screw the screw right in counting the turns and making a note. Then put it back to how it is now and set the engine running in a tank (or tied up in the water somewhere) until warm (with most motors this would be in forward gear too). Then screw in the mixture screw until it hunts noting how many turns that is. Screw out until it hunts again a similar amount. Then set it in the halfway posn between the two points. Stop the engine and screw it all the way in noting the turns so you can compare with where it is now, then return it to the best mid posn. It will be interesting to see if the new mid posn is perhaps 1/4 to 3/4 a turn further out than originally.

If in this mid posn there is still a slight stutter when opening the throttle screw out about 1/4 turn and try again. As long as it will still idle nicely this will be fine.

I've had loads of small engines over the years that have needed the idle mixture setting up to stop this stall/stutter as the revs rise on the throttle. Stihl strimmers in particular, powered hedgecutters, chainsaws, outboards etc etc. This includes the used Mercury 15 2-stroke I've just bought and I assume the previous owner thought it was part of the engine's character but it was transformed by a part turn on the idle mixture screw.
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Old 26 October 2014, 03:20   #9
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No matter what enriching it up more will help, as it is going lean when you whack the throttle open.

I also like to run all tests under a load too. In other words connected to a boat in the water moving. With a motor that small a trash can is near enough.
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Old 26 October 2014, 23:48   #10
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Thanks for the input guys!!
I will get out to the garage in the next few days and try this experiment out on her!
I'm also in the midst of changing cars.
Gone is the Honda CR-V 2.2 diesel.
Looking at VW Tiguans and Touaregs.
The Tiguan looks like a winner to me.
Can tow 2.2 tonnes and returns almost 50mpg on an average extra urban outing!
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